C O N T R I B U T I O N T O G E O C H E M I S T R Y

o f t l i e

K H E T R I C O P P E R B E L T ,

I > i s t . R A J A S T H A N (IndiA).

B Y

M O H A M M A D Z A F A R

M. Sc. (Chemistry), M , Sc. (Geology)

Assistant Chemist, G . S. I.

T -

Thesis Submitted for the Degree of

Doctor of Philosophy in Geology

At The

Aligarh Muslim University

A L I G A R H , INDIA.

1971

CONTRIBUTION TO GEOCHEMISTRY OF THE KHETRI COPPER BELT,

DISTRICT JHUNJHUNO, RAJASTHAN, INDIA

Mohammad Zafar

Department of Geology, Aligarh Muslim University, Aligarh, India

A B S T R A C T

The Khetri Copper Belt, which extends for about 80 km from Singhana

(28°06' : 75®53*) in the north to Raghunathgarh (27°39' : 75°2r) in the south,

falls in the Rajasthan State. Stratigraphically, it is a part of Delhi System,

the subdivisions of which are known as Ajabgarh Series (predominately rargilla-

ceous group) and Alwar Series (predominately arenaceous group). There is a

major strike fault running almost along the contact of these two series. I^iere

are intrusions of granites, pegmatites, dolerites, etc., into these metasedi-

mentary rock series which have been intensely deformed into doubly plunging

folds and affected'by a number of secondary reverse and normal faults. The

regional strike of both the rock series is NE-SW and dip varies from 30® to 70®

towards north-west.

Mineralization of copper has largely been at or near the contact of

lower Ajabgarh Series with the upper Alwar Series. Comparatively, the former

rock series played a greater role as a host rock than the latter. The chief

centres of ore deposition have been the innumerable fractures in the shear zone

which runs parallel to the main fault. Field evidence indicates that some of

the secondary faults served as the channels for ore fluids.

The important ore mineral of copper in the deposits is chalcopyrite

which is also frequently associated with pyrite and pyrrohotite in varying

proportions. The predominant host rock of the copper deposits in the Madhan-

Kudhan and Kolthan copper mines is garnetiferous quartz-chlorite schist. The

«

- 1 -

- 2

wall rocks show some evidence of alteration due to sericitization, silicifi-

cation, felspathization, biotitization and chloritization.

The present investigation is mainly concerned with the distribution,

geochemical behaviour and significance of certain trace elements in rocks, it /•

some rock-forming minerals, ores^ as well as residual soils of the outcropping

rocks of the copper belt. Petromineralogical studies have been very helpful

to confirm the identity and nomenclature of the various rock types.

About 250 selected samples have been analysed by Atomic Absorption

Spectrophotometer in order to determine the traces of the metals like Cu,

Pb, Zn, Ni, Co, Cd, Cr, Li and Ag in them. Additionally, five different samples

of igneous rocks and four of metamorphic rocks are analysed following the

conventional chemical methods for quantitative determination of all the fourteen

major constituents.

The chemical evidence coupled with field and petromineralogical studies

reveals that the granite, which occurs at Gotro, a village close to Madhan-

Kudhan copper mine, is intrusive. Further, the original nature of the different

metasedimentary rocks and also of the basic intrusive has been determined with

the help of variation diagram and A C F diagram.

Lithologic or stratigraphic control over the ores has been ruled out for

lack of any evidence. However, there are some positive evidence to believe that

the ore deposits have been largely controlled by the structure of the host rocks.

The granites being poor in mafic minerals are generally depleted in

copper content while the granite gneisses having a greater proportion of mafic

minerals^ record relatively higher values. This is an important indication that

the concentration of copper in these rocks is directly related to the proportion

in which the mafic minerals occur in them.

The schists generally have a higher concentration of trace elements

than the other rock types of the area. The separated pyrrhotite from the ores

is more nickeliferous than the coexisting chalcopyrite. Analytical results of

the separated mineral fractions of granites and granitic rocks as well as of

the host rocks show that the trace metals concerned are generally concentrated

in the ferromagnesian phase. The felsic group (quartz plus feldspars) generally

shows Insignificant traces of these metals except Pb which is usually high in

- 3

the pink granite gneisses. Further, the trace raetal distribution in the

bulk rocks is compared with their separated mineral fractions and it has been

pointed out whether the trace elements are associated with the silicate phase

or the sulphide phase.

Dispersion aureole of the individual trace elements in a particular

rock group and residual soil is shown with the help of geocheraical variation

diagram. Primary and secondary dispersion patternjof Cu, Pb and Zn have been

compared and a scheme of their relative mobility has been proposed.

The isoconcentration maps of Cu, Pb, Zn, Ni and Cr have been prepared

to show clearly the areas of low and high concentration of these elements in

the rock samples of the belt. When the weight percentages of Cu, Pb, Zn and

Ni in granites and the host rocks are plotted separately in triangular and

rectangular diagrams, the concentration trends of the ratio of elements in

the two rock groups shows striking similarities. This is a valuable evidence

in support of genetic relation between those trace elements which commonly

occur in granites and the host rocks.

The nature of concentration trends of certain trace elements, as

stated above, and the data showing general depletion of copper in the granites

and enrichment of the same metal in the separated hornblende and biotite

fractions also have some useful bearing on the geochemical relation between

the productive copper deposits of Khetri and the neighbouring intrusive granite

of Gotro.

C O ^ S T T R I B U T I O N T O G E O C H E M I S T R Y

o f t K e

K H E T R I C O P P E R B E L T ,

I > i s t . Jli.TumLjl:xi«:i.«, R A J A S T H A N (INDIA)

B Y

M O H A M M A D Z A F A R

M. Sc. (Chemistry), M . Sc. (Geology)

Assistant Chemist, G. S. i.

Thesis Submitted for the Degree of

Doctor of Philosophy in Geology

At The

Aligarh Muslim University

A L I G A R H , INDIA.

1971

T1183

r II

C O N T E N T S

CHAPTER I INTRODUCTION

i) Location, extent and communication ii) Physiography, drainage, etc.

iii) Scope of work and statement of problem i'v) Brief history of the copper deposits v) Ancient mining

vi) Prospecting, mining and reserves vii) Sampling and preparation of samples

viii) Acknowledgements

CHAPTER II PREVIOUS WORK AND GE01X)'SY

i) Brief review of earlier investigations ii) Stratigraphic position

iii) Structural setup iv) Uetamorphism v) Ore deposits

a) Occurrence b) Mineralogy and composition c) Form and shape

iv) Control of ores

a) Lithological b) Stratigraphical c) Structural

1 1 2 4 5 6 6 8

10

12

12 22 24 25 27

27 29 29

30

30 31 31

CHAPTER III UBORATORY METHODS OF STUDY ... 34

i) Systematic analyses of rock samples for major elements by conventional chemical methods ... ... 34

ii) Separation of minerals from rock samples 37

iii) Trace element analyses by Atomic Absorption Snectrophotometer ... 40

CHAPTER U OCCURRENCE, LITHOLOGY, PETROMINERALOGY AND PETROCHEMISTRY OF ROCKS ... 44

i) Occurrence and lithology ... 44

1. Intrusives a) Granites and granitic rocks 44 b) Pegmatites and quartz veins 47 c) Basic dykes ... 48

- 1 -

- ii -

2 . Metamorphics

a) Quartzites ... 49 b) Schists and phyllites RO c) Carbonate rocks ... 52

ii) Petromineralogy ... 53 ili) Petrochemistry ... 68

CHAPTER V Gi:XKE!iISTRY AND DISTRTBDTION OF TRACE EtEMENTS IN ROCKS, MINERAI^ AND SOILS 72

i) General statement ... 72 ii) Interpretation of results P8

CHAPTER VI GEOCHEMICAL DISPERSION OF TRACE EL£?.:ENTS 109

i) Geochemical variation diagrams for primary and secondary dispersion aureoles 109

ii) Comparative study of primary and secondary dispersion patterns of Cu, Pb and Zn 125

iii) Trace element isoconcentration maps 130

aiAPTER VII SIGNIFICANCE OF TRACE ELEMENTS

i) Concentration trend of some trace elements

ii) Geochemistry as appli^ed to the Khetri copper ores

CHAPTER VIII SUMMARY AND CONCLUSIONS

137

137

14]

146

REFERENCES ...

EXPLANATION OF P U T E S

APPENDIX

152

1?9

-iii-

LIST OF TEXT FIGURES

Facing paqe No,

1 A1 SF diagram

2 Variation diagram

3 ACF diagram

4 Histograms of some trace elements in granites and granitic rocks, quartzites and schists and phyllites.

5 Histograms of some trace elements in Khetri copper mines samples'and other rock types.

6 Histograms of some trace elements in the residual soils of granites and granitic rocks, quartzites, schists and phyllites and other rock types.

7 Histograms of some trace elements in the separated mineral fractions of granites and granitic rocks.

8 Histograms of some trace elements in the separated mineral fractions of host rocks.

9 Variation diagram showing relationship between Cu, Pb, Zn, Ni, Co and Cr contents of the bulk rocks and their separated mineral fractions in granites and granitic rocks.

10 Geochemical variation diagram for primary dispersion aureoles of various trace elements in granite and granitic rocks.

11 Geochemical variation diagram for primary dispersion aureoles of various trace elements in quartzites

12 Geochemical variation diagram for primary dispersion aureoles of various trace elements in schists and phyllites.

13 Geochemical variation diagram for primary dispersion aureoles of various trace elements in Khetri Copper mines samples.

68

70

RO

93

96

100

102

105

112

115

117

120

- IV -

Facina page

14 Geochemical variation diagram for secondary dispersion aureoles of Cu, Pb and Zn in the residual soils of granites and granitic rocks, quartzites and schists and phyllites. ^22

15 Variation diagram for primary and secondary dispersion pattern of Cu, Pb and Zn in granite and granitic rocks and their residual soil samples. 125

16 Variation diagram for orimary and secondary dispersion pattern of Cu, Pb and Zn in quartzitic rocks and their residual soil samples. 126

17 Variation diagram for primary and secondary dispersion pattern of Cu, Pb and Zn in schists and phyllites and their residual soil samples. 32*7

18 Variation diagrams for Cu-Zn-Pb in granite and granitic rocks and host rocks with copper ores. l^T

19 Variation diagrams for Ni-Cu-Zn in granite and granitic rocks and host rocks with copper ores. l^P

20 Variation diagrams for Ni-Cu-Zn-Pb in granite and granitic rocks and host rocks with sulphide ores.

_ V -

LIST OF TABLES

Table 1 Table of formations present in Delhi System (Heron. A.M., 1923), It P.

Table 2 Stratigraphic succession of Khetrf Copper Belt, Rajasthan, as proposed by Roy Chowdhury and Das Gupta (1965)^ |8 p.

Table 3 Analyses of roclcs from Khetri Copper Belt, Rajasthan

Table 4 Analyses of residual soil samples from Khetri Copper Belt, Rajasthan

Table 5 Analyses of the bulk rock and their separated mineral fractions of pranite and granUic rocks, Khetri Copper Belt, Rajasthan.

Table 6 Analyses of the host roclcs and their separated mineral fractions, Khetri Cooper Belt, Rajasthan.

Table 7 Chemical analyses of rocks from Khetri Copper Belt, Rajasthan. (Major elements).

(Tables 1 and 2 are in the text and tables from 3 to 7 are in the appendix).

- V i -

LIST OF MAPS

] Location map

2 Trace element isoconcentration maps

a) Copper b) Lead c) Zinc d) Nickel e) Chromium

3 Schematic geological map of the Khetri Copper Belt (Northern part), Hajasthan.

4 Schematic geological map of the Khetri Copper Belt (Southern part), Rajasthan.

(Map No. 1 - in the text, maps 2 to 4 - in the pocket),

LOCATION MAP

Chapter - I

INTHODUCTION

Location. extent and communication

Some of the important localities of geological interest which

lie on this belt are Singhana (28°06' : 75*^53' ), Khetri Nagar

(28®4'15" : 75°48'30" ), Khetri (28®0' : IZ^Al' ),and Babai (27°53' :

75°46' ) in the northern part and Satkui (27^49* : 79°35' ), Dhanaota

(27®44M5" : .75°30' ). Chappoli (27®44' : 75°36') and Saladipura

(27°38' : 75°31' ) in the southern part of the belt.

p

The area under investigation is included in toposheets Nos.44 /12,

M

16 and 45 /9, 10, 13. of the Survey of India and extends over a distance

of about 80 km from Singhana in the north to Raghunathgarh in the south.

Khetri Nagar happens to be the present chief copper mining district.

It is situated about 150 miles SW of Delhi and approachable through Gungaon

and Narnaul by a good road.

Most of the above mentioned localities within the copper belt are

interconnected by metalled roads and frequently buses ply through them.

The copper workings of Madhan-Kudhan and those of Kolihan are separated

from one another by a road distance of about 10 km.

- 1 -

- 2 -

Physiography, drainage._sl£,.

The Khetri copper belt is a part of the Delhi System which forms

the northwestern extension of the Aravalli mountain range (see Heron,1923).

The Delhi System is composed of two series of rocks namely Alwar and

Ajabgarh .

The Aravalli range occupies the north-western part of the Indian

Peninsula. They "are now the remnants of once great mountain ranges of

tectonic origin" (Krishnan, M.S., 1968, P. G ). According to Pascoe, E.H.

(1950, p. 253) the range, which played the most important role in the

history of Peninsular topography, was the Aravalli. Here the rocks are

highly disturbed with the axes of disturbances more or less parallel to

the direction of the chain.

The entire Aravalli range is characterised by a general NE-SW

trend commencing from Champaner ( 22°33':73°24' ) in Gujarat at the head

of the gulf of Cambay to near Delhi. It runs across Rajasthan placing

Bikaner, Jodhpur and Jaisalmer on the west and Udaipur and Jaipur on the

east of it. Auden, J.B. (1933) observed that the Aravalli rock forma-

tions appear to continue northeastwards into parts of sub-Himalayan zone

of Tehri-Garhwal. Near Delhi, they form sub-surface ridges bordering the

Punjab plains. The southeastern part of the Aravalli range bifurcates,

one limb turns eastwards and merges into the Satpura range in Central India,

the other limb probably continues southwestwards upto the islands of

Laccadives and Maldives in the Arabian Sea. The prominent exposures in

the north are high quartzitic ridges of Khetri, about 1(X) miles north of

Jaipur.

- 3 -

The Alwar quartzites generally form high ridges while the Ajabgarh

Series of rocks present a low lying topography. The high ridges are generally

interrupted by sand dunes which are formed from the disintegrated material

of the parent rocks, taken away by wind and deposited elsewhere. At places

these ridges ar.e found rising prominently from the plains of the region which

is widely covered with sand. The elevation of the crest of the ridges

sometimes attain 3,450 feet (Raghunathgarh). There are well developed

ridges at Kho (3,212 fefet) and at Khetri and Bagor where the elevation of

the Alwar quartzite is over 2,000 feet from the mean sea level. The well

known forts of Khetri and Bagor were constructed on these quartzites. At

Babai and Gurha-Ponk, the quartzite ridges are very prominent and extend

for several miles.

The Ajabgarh series of rocks are represented by a few rounded, low-

lying outcrops often strewn with boulders of the same rocks.

There is no major river in the area. Only two seasonal rivers,

viz., Kantli and Kharkhar serve as the drainage of the area in the rainy

season. The rivers flow along the natural depression formed by the high

ridges occurring on either side. The annual rainfall in the area is low

and varies from 20 to 22 inches. The seasonal rains from the southwest

monsoon wash the area from June to September. May and June are the hottest

months in the region when the day temperature sometimes rises upto )I6°F

(46.6°C). In cooler months of December and January the thermometer records

minimum temperature of about 47°F (18.3°C). Sometimes winters have

occasional showers.

There are scattered bushes and shrubs in the area. The predominant

- 4 -

vegetation is Euphorbia plant which grows on the hilly terrain and slopes.

Snake, scorpian and goira are common. Panthers are rare while deer

are main inhabitant of the jungle.

Scope of work and statement of problem

For the last two decades a greater attention has been paid to the

Khetri copper belt by the Geological Survey of India, Indian Bureau of

Mines, National Mineral Development Corporation and other workers attached

to several scientific institutions of India. Some of the investigations

have been published and from which it is evident that many of the earlier

workers have given considerable attention to the geology, lithology, structure,

metamorphism, mineral paragenesis and economic potentialities of the belt.

Attempts were also being made to throw some light on the genesis of the

copper ores of the area.

A review of the published literature indicates that practically no

attention was given to apply the knowledge of geochemistry in the earlier

investigation of the area. Therefore, according to a plan worked out, the

present project was undertaken with a view to study the geochemistry of the

Khetri copper belt. Through trace element studies of rock, mineral and

residual soil samples, aided by petromineralogical work, an attempt has been

made to gather a knowledge of the geochemical dispersion of certain trace

elements in the belt and also to bring out the geochemical relation between

the various rock groups and the associated trace elements. Further, an

attempt has also been made to trace the source of the copper deposits of

the belt.

- 5 -

Brief history of the copper deposits

Certain localities in the Khetri copper belt had been the places

of considerable interest to ancient miners who have left evidence of past

mining and smelting activities in the form of many abandoned old working

pits, cuts, trenches, huge slag heaps and mine dumps.

Nothing is known about the exact period of ancient mining activity.

Ain-e-Akbari (p. 194, No. II), written in 1590 A.D., is perhaps the earliest

record in which the existence of copper mines at Singhana, Udaipur and

Babai was mentioned. Singhana and Udaipur are reported to have copper

coinage mints also in those days. Two mints, one at Singhana and the other

at Khetri existed upto 1869, which were later closed down by the British

Government in India. Silver coins were minted once in the name of Mohammad

Shah Alam (1759-1786, A.D.).

According to the Rajasthan Gazetteer (Vol. II, p. 160) and Imperial

Gazette of India (Vol. XXII, p. 435), the copper mines in this area did not

work regularly from 1872 to 1944. Some efforts were made by several private

concerns to take up the mining work during 1923-1927. It was the Jaipur

Mining Corporation which carried out some significant mining work during

1944-55.

' In March 1957 the Indian Bureau of Mines carried out drilling and

prospecting systematically and had submitted an Interim Report in August,

1958. Based on the recommendati ons of the above report, exploratory mining

tvas taken up in February, 1959. In 1961 Western Knapp Engineering Company,

SanFransisco, U.S.A., were appointed as consultants.

- 6 -

Ancient mining

Ancient raining deserves appreciation of the skill which the old

miners possessed. Although in those days there was no dynamite to blast

the rocks yet they developed a technique to break them by alternate heating

and sudden cooling. Fire wood used to be burnt for heating the rocks. On

the third day the miner used to descend the mine vjith chisel and hammer,

a small basket tied round his waist and resting on his knees and a 'diya'

on his head. Probably rope ladders were used as conveyers. Hie workman was

skilled enough to bring back only copper ore with him. Some old workings

still have ancient wood plumbing arrangement in the form of a ladder to

facilitate the movements of the worker during mining. The collected ore was

then powdered to proper grain-size using 'Ghuns'. Later on the ore was

reduced by mixing it with cowdung, followed by drying and roasting.

The roasted ore was then transferred to the smelting furnace which

was made of fire-clay. The ore was mixed with charcoal and flux alternately

and heated for about 12-14 hours. The flux was called 'Reet'. The molten

copper was then transferred into suitable containers and allowed to cool.

It was then ready for the market.

The work of mineral exploration and prospecting in the area has

received momentum in recent years. According to Chandra Chowdhury (1968),

93, 111 meters of drilling and 11,800 meters of exploratory mining have

already been done. The annual target of copper metal from Madhan-Kudhan

miner is 21,000 tonnes and the daily output target of copper ore is 8,000

tonnes. The annual target of Kolihan mine is 10,000 tonnes of copper metal

* 'diya' = An earthen oil lamp.

'Ghuns' = Big hammers

- 7 -

and daily output target of ore is 1,600 tonnes. The site selected for the

smelter plant is near the Madhan-Kudhan mine. It is proposed to transfer

the ores from Kolihan mine and nearby places to Madhan-Kudhan by an aerial

roapway which is under construction. The daily outnut of ore dressing and

floatation mills at Madhan-Kudhan is expected to be 4,600 tonnes of con-

centrates per day. These two copper mines are now being developed by the

Hindustan Copper Limited, a Government of India undertaking. It is expected

that the mines would start production by 1972-73. Further exploratory work

in the neighbouring areas is being carried out by the Geological Survey of

India.

The exploratory work at Satkui is also being completed recently. A

total of about 4,249 metres (Hore ^ a i - t 1968) have been drilled in Satkui

with good prospects of copper ores. Prospecting is in progress near

Saladipura area for pyrite deposits (see Muktinath ^ a j . . , 196R).

The proved reserves (Sikka et, y.. 1966) in the Madhan-Kudhan and

Kolihan mine sections are 7,84,90,000 tonnes averaging 1% Cu, 0.02 OZ/tonne

Au, 0.53 OZ/tonne Ag upto a depth of 800 meters, with an average width of

7.5 meters. The indicated reserves are 1,01,30,000 tonnes averaging

2.29% Cu, 0.032 OZ/tonnes Au and 0.069 OZ/tonne Ag, 0.0165% Ni, 0.0157% Co

upto an average depth of 400 meters.

The latest available determination of the grade and quality of

copper ores (Chandra Chowdhury, 1968) are summarized here.

The average grade of copper from Madhan-Kudhan Mine is around 0.8

to 1% and Kolihan Mine, 1.5% initially (i.e., the first three years) followed

- B -

by 2.2 - 2,4% subsequently. The grades of ores are classified as follows:

Very low grade ore 0.5 - 0.65 % Cu

Low grade ore 0 . 7 - 1 . 2 % Cu

Medium grade ore 1 . 5 - 1 . 8 % Cu

High grade ore 2.9 - ^.2 % Cu

In the central block of Kolihan mine the grade goes upto 3.5 to 5%

of Cu. The sulphur content varies from 3 to 8%. The concentrated ores

gave a value of 25% copper and 3)% of sulphur.

Pyrite-pyrrhotite deposits of Saladipura contain 22.5% to 40%

sulphur and the estimated reserve of iron sulphides are 115 million tonnes

(Muktinath et. aj^. 1968), Sphalerite, which is commonly associated with

pyrite and pyrrhotite, has no economic importance on account of its low

zinc content (less than 1% Zn).

Samples were collected on a square grid pattern at one km intervals

for rocks and the corresponding residual soils. The sample spacing was,

however, reduced on the outcrops of granites and granitic rocks. Care was

taken to follow the grid lines as far as possible. When more than one sample

from an outcrop was collected (dykes, contact rocks, veins, etc.) other than

that which falls on the grid points, they were properly numbered. As far as

possible only the fresh and unweathered rock samples were collected. The

residual soil samples were collected by scooping with a spoon after removing

the cover layer completely from the soil.

About 2 kg of rock sample and 500 gms. of residual soil sample were

collected from each grid point. Rock samples were stored in new cloth bags

- 9 -

while soil samples, in plastic bags which were sealed in the field to avoid

contamination.

Using 'fi' for rock samples and 'S' for corresponding soil samples

the collected samples were numbered similarly as

from the different grid intersections.

In the northern part of the area there is a metalled road (connecting

Singhana in the north with Babai in the south) which was taken as the base

and the grids were numbered in accordance with the position west and east

of the road. In the southern part of the belt (i.e., from Satkui in the

north to Saladipura in the south) numbering of samples was done locality-wise.

Preparation of samples

The rock samples were crushed in a Jaw Crusher to smaller pieces.

After coning and quartering the chips were transferred to a portfelain mortar

and pestle for coarse powdering. Coning and quartering was repeated. Final

powdering was done in an agate mortar and pestle.

The powdered sample was then passed through a fine linen cloth

stretched on a wooden frame. The oversize particles were again ground in

an agate mortar and sieved until they all passed through the cloth and

attained a size of 100 to 120 mesh.

- 10 -

Acknowledgments

It is a privilege of the author to record his sincere gratitude to

Dr. S.H. Rasul, B.Sc.(Hons.), M.Sc.(Ca].), Ph.D.Tech.(Sagar), C.P.G.(U.S.A.),

F.A.A.Sc.(U.S.A.), of the Department of Geology, Aligarh Muslim University,

Aligarh, for introducing the research topic, inspiring supervision and

encouragement by helpful suggestions at a]l stages of the research and in

the preparation of this thesis.

The author is deeply grateful to Professor F. Ahmad, M.Sc., Ph.D.

(Alig.), M.Sc.(Tasmania), F.N.A., Head, Department of GeologyAligarh

Muslim University, Aligarh, for his immense interest, advice and encourage-

ment which helped bring the study in the present form. Sincere thanks are

also due to Mr. Woman Ghani, I-ecturer in Geology, AHgarh Muslim University,

for his warm hospitality, numerous useful suggestions and active help during

the period of research.

The author is particularly thankful to Mr.G.C.Chatterjee, Ex-Oirector

General, Geological Survey of India, for granting leave for study and

permission to work in the Central Chemical Laboratory of the G.S.I.,Calcutta,

to Dr. A.N.Chowdhury, Chief Chemist. G.S.I, for his interest and providing

many laboratory facilities and to Dr. A.K. Das, Chemist, G.S.I., for the

assistance in trace element analyses. Sincere thanks are also due to

Dr. A.P. Subraraaniam, Deputy Coordinator, Air Borne Mineral Survey, New Delhi,

for kindly providinq facilities to work in his chemical laboratory at

Faridabad, Haryana, where trace element analyses of some samples were done.

The cooperation and help extended by the chemists of the Air Borne Mineral

- n -

Survey is also gratefully acknowledged.

The author is extremely grateful to Mr. S.M. Mathur, Director,

Geological Survey of India, M.P. Circle, Bhopal, for his personal interest,

encouragement and all the kind words he has spoken to the author during

the course of this study. The author is also indebted to Dr. D.B.Sikka,

Mining Geologist, Planning Division, N.M.D.C., for permission of field work

in the area and to collect samples from underground workings. A special

word of thanks is due to my old friend Mr. Syed Irfan Hosani, Geologist,

Hindustan Copper Limited, Khetri, for his cooperation and providing many

facilities during field work, and to Mr. Syed Akhtar Husain for h 's help

in giving the finishing touches to this thesis.

Sincere appreciation is due to the Staff Members and Research Scholars

of the Department of Geology, Aligarh Muslim University, Aligarh, for

sympathetic cooperation. Thanks are also due to Mr. Mashhood Alam Raz for

careful typing of the manuscript and to Mr. Salimuddin Ahmad who has done so

nicely all the final drawings in this work.

The author gratefully acknowledges the tenure of a Research Scholar-

ship of the University Grants Commission, New Delhi. Financial assistance

by the Geology Department, A.H.U., Aliaarh, is also gratefully acknowledged.

In the end it now remains for the author to make acknowledgements

and record gratitude to his w'fe for her patience and cooperation throughout

this research work which this brief sentence is woefully inadequate to express,

Chapter - II

PREVIOUS WORK AND GEOLOGY

Brief review of earlier Investigations

Hacket, C.A. (1881), who first studied the geology of the Central

and Eastern Aravalli region of Rajasthan, dealt in some detail the geology

and structure of the presently known Khetri Copper Belt. He also briefly

stated the occurrence of some economic minerals in the area.

He found that "between Khandela and Khetri, the range again expands

and near Raghunathgarh attains to an elevation of 3,4S0 feet above sea

level, but a few railes north of Khetri at Singhana, the range may be said

to terminate, for north of that are only a few broken narrow ridges rising

abruptly from the plain, and which terminate near Dadri, about 40 miles

north of Sin^ana". He further stated "the Aravalli range, becomes more

important both in elevation and breadth", in the Khetri area. He correlated

the rock groups of the area with the rest of the Aravalli system and

observed that comparatively these rocks have very few granitic intrusives.

The main rock types reported by him are gneisses, schists, limestones and

the Alwar quartzites forming the peaks of the hills in the area. He found

that in the north, near Singhana, the Aravalli hill range was connected

with the Alwar hills by the hills in Torawati. In the southern end, the

hills extend upto Jaipur and further beyond. The highest peak in the

- 12 -

- 13 -

Khetri area reported by him is located in the range of Alwar quartzite

on ivhich the old Khetri fort was built.

He also mentioned in his report that the famous old copper mines

at Khetri and Singhana are situated in this portion of the range, the

former occurring in the schists and the latter in the quartzites.

The credit of the first systematic geological survey of the Aravalli

region goes to another pioneer worker, viz., Heron, A.M. (1923). Earlier

it was Bose, P.N. (1906) who made some casual remarks on the geology and

mineralisation of this area. Heron (1923) made a more detailed study of

the geology, structure and lithology of western Jaipur including the

Khetri Copper Belt and also studied the copper deposits of the • area

(Khetri Copper Belt) from the economic viewpoint. Further he suggested a

classification of the rock types known in the region. (Table 1).

Heron (1923) at places found it difficult to clearly demarcate

between the Alwar and AJabgarh Series because of the close resemblance

of their structural and lithological characters. Generally, the Alwar

group of rocks formed higher ridges while the Ajabgarh group occupied low

lying and irregular hills. The anticlinal structure is very clear at the

south-western end near Babai and extends from Gurha-Ponk (27°5o' : 75°41')

for about 26 miles south-westwards upto Sangrua (27®25' : 75°22').Gurha-Ponk

happens to be the highest point (3,350*) in the belt.

Heron (1923) described the Alwars as a group of largely thin-bedded

quartzite with micaceous laminae, some broader zones rich in mica and a

- 14

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- 28 -

few brown and black limestones. They are usually fine-grained, reddish,

yellow or grey in colour and softer than the typical Alwars occuring

elsewhere in the region. He also found that the width of the Alwar

outcrops abruptly decrease where granites intruded into them.

He also introduced Ajabgarh rocks as white and reddish, thinly

bedded and micaceous flagstones with slates dipping regularly to north-

west. They are not much metamorphosed and almost free from igneous intru-

sions. The main ridges located about ten miles from Singhana, have an

elevation of over 2,000 above M.S.L. where the ancient forts of Khetri and

Bagor were built.

Heron (1923) gave a brief account of the igneous intrusives in the

Delhi System and broadly classified them into the following:

1. Epidiorite Sheets and veins

2. Granite bosses

3. Pegmatite veins.

He preferred the terra epidiorite for the basic intrusive rock

instead of amphibolite which is generally used. He also pointed out the

significance of the granites occurring all over the belt and their possible

role in the copper mineralisation. He also found an extreme modification

of the pegmatites in the form of quartz tourmaline vein rock in which

tourmaline crystals are often zonally arranged. His work was largely based

on field observations which gave a firm footing to the later workers.

Soy Chowdhury and Das Gupta (1965) divided the main rock types of

the area into sedimentary, metamorphic and intrusive rocks of Precambrian

- 16 -

age and followed broadly the classification of the rocks suggested earlier

by Heron (1923) and added some new rock types in order to make it compre-

hensive. The Alwar Series is characterised by arenaceous rocks while the

Ajabgrah Series by argillaceous rocks. They found that the contact between

the two series was gradational and at places anthophyllite-cumraingtonlte

bearing rocks resulting from metasomatism attendant with mineralization

were well-developed. They recognised a distinct group of intrusive rocks

consisting of amphibolites (metamorphosed dolerites), granites and the

related rocks (mainly synkinamatic replacement), in addition to some

younger basic dikes (Post-kinematic) which were least disturbed tectonically, r

They attached some genetic importance to the granites for copper minerali-

zation although the rocks are not prominently exposed in the area.

The regional strike of the metamorphic rocks is roughly NE-SW and

dip at angles varying from 30° to 70®, generally towards west. They are

folded into anticlines and synclines plunging south-^westerly. There is

also a series of major doubly plunging anticlinal folds, the cores of

which are occupied by the Alwar quartzites.

The authors also found in the area various types of faults such as

transverse faults, strike faults, reverse faults and lateral faults and

observed that some of them served as conduits for the transportation of

mineralizing solutions.

The grade of metamorphism is higher In the northern part of the

belt where it is in the proximity with granites and is rather low where

- 17 -

there is no granite. Generally the grade of metamorphism decreases from

north to south.

According to them copper is distributed in a variety of rock

types such as schists, quartzites, phyllites, etc., instead of remaining

confined to a single rock type i Shear zone fractures jSf fault planes

were found to be the favourable loci for mineralization. They also held

mineralisation responsible for a large scale iron-magnesia metasomatism

producing anthophyllite-cumraingtonite, chlorite and biotite schists.

Other effects contemporaneous to mineralization were sericitization and

silicification.

The primary sulphide minerals in order of abundance and also in

paragenetic sequence are pyrite, pyrrhotite and chalcopyrite. Pyrrhotite

gradually decreases towards the south and at Dhanaota it is totally absent.

They believed in the hydrothermal origin of the copper deposits.

The generalized tentative stratigraphic succession as given by

Roy Chowdhury and Das Gupta (1965) is presented in Table 2..

Several other earlier workers have also made some substantial

contributions which are briefly outlined here.

Crookshank (1948) and Arogyaswa m y (1949) gave a brief account

of the geology, structure and economics of the Khetri Copper Belt. Both

of them described the occurrences of copper in metamorphic rocks and

enphasized the necessity of prospecting the area in detail.

- IR -

TABLE - 2 Stratigraphic succession as proposed by Roy Chowdhury

and Das Gupta (F/65)

( Ankerite-Chert, Quartz veins ( ( Younger basic dikes

Intrus Ives ( ( Granites, pegmatites, quartz veins, etc. ( ( Older basic rocks

Delhi System

Ajabgarh series (about 1300m)

( 6. Quartzites, phyllites, schists, etc. ( ( 5. Marbles, calc-gneisses, etc. ( ( 4. Various types of schists and phyllites

Gradational Contact

Alwax Series (about 1300 m)

3. Amphibole quartzites, amphibole gneisses, marbles, etc.

2 . Arkosic quartzites, quartzites with intercalated phyllites and schists .

1. Phyllites and schists

Base not exposed

- 19. -

Based on thin section studies of some metamorphic rocks containing

traces of copper minerals. Deb (1948) pointed out that usually the carbonate

minerals form superficial encrustation in the secondary enrichment zone

of most of the metamorphic rocks. He found sulphide minerals to be in a

highly disseminated state and occurring only in the amphibolites and

garnetiferous quartzites. The same author also noticed that the degree of

metamorphism was less intense in these rocks as compared to the older rocks

of the Aravalli System.

Later some of the officers of the Geological Survey of India

investigated the area in a greater detai1,.major part of which is in the

form of unpublished reports. Chandra and Aditya (1956) mapped some parts

of the area and submitted a report on the future prosoects of exoloration

of copper ore. Roy, B.C. (1958), while working on the economic geology

and mineral resources of Rajasthan and Ajmer pointed out that the deoosits

are worth exploring. Roy Chowdhury, Prasad Rao, Venkatesh, Ramienger and

Das Gupta (1962) studied the geologic potential of the belt. They made

many useful recomtnendations on the test drilling and prospecting for copper.

Das Gupta (1964) also attempted to demonstrate the close relationship between

deformation, grade of metamorphism and mineralization. He indicated that

in the northern part of the belt, mineralization took place under meso-

therraal while in the southern part under epithermal conditions. He

believed that the ore forming fluid was initially rich in iron, precipita-

ting magnetite and later in copper and sulphur leading to crystallization

of sulphides.

- 20 -

Vcrma and Patni (1962) also discussed the copper deposits of

Khetri and pointed out that the mineralized zone comprised a system

of fracture-filled linked ore veins which are flanked by disseminated

sulphide in the brecciated wall rocks. They assumed faults to have acted

as feeder channels and shear fractures and foliation planes as ore

receptacles. The authors described that the deposits represented high

temperature hydrothermal replacements and the mineralising solutions were

thought to have been derived from the pre-mineral intrusion of Erinpura

Granite. Verma and Krishnanauni (1963).while contributing to the origin

of copper deposits of Khetri indicated some important factors which control

the copper mineralization. They also described the distribution of minor

elements in the sulphide minerals and their correlation with the temperature

of formation of the ores. They regarded mineralization to be epigenetic

and assumed it to have occurred under raesothermal condition. The minera-/

lizing solutions appear to be connected with the late stage of emanations

from the granitic magma.

Mukherjee, A.D. (1966), studied some ore minerals from the Kolihan

section and reported first the occurrence of valleriitey^ackinawite,

ilmenite and rutile from the deposits. He also discussed the structural

and textural features of the ores and suggested the probable nature of

physico-chemical environment during the mineralization. He also outlined

a probable paragenetic sequence of the ore minerals.

Rao and Rao (1968) carried out ore microscopic examination of

metallic minerals in some detail. They pointed out the structural

- 21 -

variance of ore minerals and observed the occurrence of intergrowths of

other sulphide minerals in them. On the basis of textural study they

indicated the presence of at least two generations of sulphides, the

dorainent minerals being piyrrhotite and chalcopyrite in both generations.

They also observed that the textural features indicate a high temperature

of formation of the deposit.

Muktinath, Natarajan and Mathur (1968) described the occurrence

of zinc in shear zones near Saladipura in the southern part of Khetri

Copper Belt. They found the shear zones to be rich in pyrite and pyrrhotite

with small amounts of sphalerite, chalcopyrite and galena below the

gossans. The authors found that sphelerite was chiefly associated with

pyrrhotite carrying about 1 % of zinc which might be extracted as a

by-product.

Recently Das Gupta (1970) reported a massive pyrite-pyrrhotite

deposit at Saladipura where a steeply plunging anticline localised the

mineralization. The core of the anticline is formed of amphibolite in

which the sulphide ores occur. He found the deposits to be compos^ed

essentially of pyrrhotite with a subordinate amount of pyrite and a

silicate gangue. The author remarked that chlorine metasomatism

was responsible for altering plagioclase and part of hornblende into

scapolite. He also pointed out that the Fe of the Pyrite and pyrrhotite

has been derived from the pre-existing iron rich silicates and oxides.

- 22 -

Strati graphic Position

The stratigraphic nomenclature of Delhi System was first intro-

duced by Heron (1923). It includes the rocks of the Alwar Series and

Ajabgarh Series, a part of which is exposed in the so-called Khetri Copper

Belt, Bajasthan.

The stratigraphic position of the Delhi System in Rajasthan was

given by Krishnan (1968) as follows:

Vindhyans of W. Bajasthan

Malani suite of igneous rocks

Delhi System

Raialo Series

Aravalli System

^Banded gneissic complex and Bundelkhand gneiss. Archean

The rocks belonging to the Delhi System extend from near Delhi

in the north, through Ajmer and Mewar to Idar and Palanpur in the south.

They overlie the older gneisses and schists and at places the Ralalos

with a great unconformity which Heron (1917) named as Eparchean interval.

They are overlain by the lower Vindhyan system unconformably. Between

the Aravallis and the Delhis or Raialos Heron (1923) described, "a violent

and very clearly seen unconformity which has been traced in a general way

for over 300 railes"(see Pascoe, 1950)" .

The Delhi System has been placed in the Purana group of the Indian

stratigraphy and includes all the Precambrian rock formations occurring

23 -

between the Eparchean unconformity and the Cambrians. However, this

classification has not been much favoured by the Indian Geologists in

recent years.

The rocks of the Delhi System differ from the other late Precanbrian

formations of India in having suffered extensive folding and intrusion of

igneous rocks. They also show intense and widespread metamorphism in the

central and southern parts of Rajasthan similar to that of the underlying

Aravalli System. The resemblance inthe rocks of these two systems is so

striking at places that their true identity becomes difficult.

The Delhi System has been correlated with the Dharwar System of to

Mysore, but there is a difference of opinion as regards/their lithology,

degree of metamorphism and an unconformity which separates the two. At

the same time the Alwar quartzites of Bajasthan do not have any equivalent

in the Dharwar rocks.

The age of the Delhi System is widely taken to be Algonkian. It

has further been confirmed by the radioactive age determinations of some

samples of uraninite from Bisundni, Ajmer, Merwara (735 m.y.) dnd monazite

from Soniana, Mewar State (Age ranges from 700 to 865 m.y.) which were

found in the pegmatites occurring in the Crinpura granite intrusions

(Aswathanarayana, 1964). This may be true only when it is accepted that

the Erinpura granite belongs to Delhi age. The pegmatites and Baialos

do not have any radioactive mineral and thus radiometric dating was not

possible in these cases as yet.

- 2.4 -

Recent investigations by Crawford (1969) on the basis of radio-

metric dating (Rb-Sr method) indicate that the Delhi System is much older

than that it was earlier believed. The age of the Berach granite which

intrudes the Delhi System has been determined to be 1,650 m.y. He

correlated the Delhi System with the Gwalior lavas whose age was found

to be 1810 ±200 m.y.

A brief summary of the geological structure of the area is

presented hereunder:

The rocks of the area have undergone intense folding and faulting

due to which its structural history became complicated. There are a number

of elongated NN£ and NE-SW doubly plunging anticlinal folds throughout

the area. The regional strike of the formations is NE-SW. Their dips

vary from 30° to 70® towards west or east. The cores of the folds are

occupied by the rocks of Alwar Series. Micro coaxial folds are also

developed on the limbs of the major doubly plunging folds.

The intense folding is accompanied by numerous faults and disloca-

tions. There is a series of transverse, -oblique and strike faults.

Transverse faults are frequent. These are indicated by the occurrence

of fault breccia, slikens ides and displacement along the fault planes.

This was particularly indicated where felspathic quartzite displaced the

overlying magnetite-haematite band as it is in Madhan-Kudhan Section

- 25 -

(Map3iJ,4). According to Boy^ Chowdhury and Das Gupta (1964) strike

faults are located either at the contact of the Ajabgarh and 'Alwar Series

or along the contacts between different lithological units.

In the Madhan-Kudhan section the mineralized zone has been dis>

placed by faulting and accordingly, they are some post«-mineralization

faults. Therefore, they cannot be regarded as channels for hydrothermal

solutions. According to Roy Chowdhury (1965) the development of sub-

parallel shear zones in association with the major faults is common and

is more important than the faults themselves from the point of mineralization.

Although the rocks have been subjected to an intense deformation,

some of the primary sedimentary structures are well-preserved in some

rocks. The felspathic quartzite of Alwar Series and sericite quartzite

of Ajabgarh Series show current bedding and gradded bedding. Bedding

strike is from N25® to N70° dipping northwesterly and the dips of the

beds vary for obvious reasons as they depend on the position of folds and

faulting. Ripple marks are also present in these rocks. Some quartzites

(massive and magnetite-haematite quartzite) and brecciated rocks occurring

at the contact of granites and conglomerates are however exceptions.

MgtapiQrphjsji

Metamorphism has resulted in much mineralogical and textural

rearrangement in rock units. The mineral assemblage of the argillaceous

rocks is garnet, chlorite, kyanite, staurolite, andalusite and amphibolei .

This mineral assemblage reaches to quartz-albite-epidote-almandine

- 26 -

subfacies (B 1-3) of the green-schist facies (Turner and Verboogen,1962)

and to the high grade amphibolite facies. These minerals indicate progre-

ssive regional metamorphism with Increasing temperature. The mineral

assemblage in the arenaceous rocks is simple. Amphiboles, chlorite and

epidote are the common associated minerals suggesting relatively lower

grade of metamorphism.

Chloritization of garnets (garnetiferous quartz-chlorite-schist)

and sericitization of andalusite (biotite-andalasite schist) indicate

retrograde metamorphism.

The grade of metamorphism is higher near the granitic rocks and

low away from them. Large scale felspathization of quartzites in the

vicinity of granites indicate contact metamorphism. Andalusite bearing

rocks occur near amphibolites indicating the possibility of their forma-

tion due to the intrusion of basic rock.

According to Roy Chowdhury and Das Gupta (1965) metamorphism is

accompanied and followed by metasomatism resulting in the felspathization

of schists in Jasrapura, Babai and Kotri, and scapolitization of amphibo-

lites (see Das Gupta, Chakravorty, 1962) in the area.

The predominating iron-magnesia metasomatism of quartzites and

schists is represented by anthophyllite-cummingtonite and chlorite in

the northern portion of the belt. These processes are connected with the

wall rock alteration and superimpose the products of regional and thermal

metamorphism.

- 2-7 -

The host rocks of copper are intermediate metamorphic rocks

represented by garnetiferous quartz-chlorite-schist, biotite schist,

amphibole schist, etc. High grade metamorphic rocks (amphibolites) are

not good host while low grade metamorphic rocks (quartzites and phyllites)

welcomed the ore mineralization very well.

ar£_Dgpo&jUs.

Occurrence: The sulphide ore deposits of Khetri have been reported to

occur all along the belt running from Singhana in the north to Raghunath-

garh in the south. In most places their presence was indicated at the

surface by the occurrence of gossan consisting of oxidized ores of copper

and iron having stains of malachite and azurite, boxwork of lenticular

limonitic or red ochre bands. Realising the economic importance of the

ore deposits, the ancient miners sank innumerable pits which could be

seen even today scattered all over Singhana which is also known as the

ancient smelting and marketing centre of copper in the area. Most of

the present day prospecting is guided by the location of ancient working.

The names of the localities in the northern part of the area where

prospecting and some mining for copper is in progress are Peeliwali

(28°4'15" : 75°48'45" ), Ghatiwali, Madhan (28°4'15" : 75®48'30" ).

Kudhan (28°4'15" : 75°47'25" ), Masjidwali (28°4' : 75°48' ), Duradum-

wali (28°4'15" : 75°4'45" ),Kolihan (28°r : 75°44' ), Khetri

(28° : 75®47' )^Akwali (27®56' : 75®46' ).

The Hindustan Copper Ltd., a Government of India undertaking, holds

- 2'8 -

mining and prospecting lease in most of the above mentioned localities.

Copper is also being prospected at Satk;ui (27°49' : 79°35' ),

Dhanaota (27®44'45" : 75°30' ) and Charana (27^42* : 75°25' ) in the

southern part of the area.

Exploratory work is still in progress at Saladipura (27°38' :

75"3r ) where a promising pyrite deposit has recently been located.

Copper has mineralized both the Ajabgarh and Alwar Series of

rocks, but the extent of mineralization is relatively wide in the

former series. The mineralization, however, is not confined to any

particular rock type of either of the two series. Local as well as

regional shift in mineralization is not uncommon in this area.

In the northern part around Madhan-Kudhan section, although the

chief host rock is garnetiferous quartz-chlorite-schist, yet others such

as garnetiferous amphibole-chlorite-schist, amphibole quartzite are also

mineralized to some extent. The chlorite^schist continues to be the chief

host rock in the Kolihan mine though garnetiferous biotite-schist,

andalusite-schist, phyllites and amphibolites also have some indications

of copper mineralization.

Passing further south, the occurrence of copper has also been

reported from the biotite-fschist and phyllites occurring around Akwali.

There is a marked change in the nature of host rock at Satkui and

Dhanaota in the southern part of the belt. Here the quartzites and

phyllites are the chief host rocks. A few schistose rocks (chlorite and

- 29. -

biotite-schists) are locally mineralized around Dhanaota. At Saladipura

biotite-quartzite, biotite amphibole-scapolite quartzite, carbonaceous

phyllites (Muktinath, 1968) are the host rocks for pyrite-pyrrhotite

deposits having insignificant amounts of sphalerite, chalcopyrite and

galena.

and Composition : Pyrite, pyrrhotite and chalcopyrite are the

primary sulphide ores present in order of abundance. The paragenetic

sequence of the ores was first determined by Roy Chowdhury and Das Gupta

(1965).

According to the compilation work done by Sikka and Chatterjee

(1966) the mineral assemblage and paragenesis of the Khetri Copper deposits

are as follows

Mineral Assemblage

Copper minerals

Paragenesis

Other Minerals

Associated gangue minera Is

Chalcopyrite, cubanite, bornite, valleriite, tetrahedrite, cuprite and tenorite.

Pyrrhotite-pentlandite-pyrite-chaIcopyrite Cubanite-velleriite-meinicovite

PyiYhotite, pyrite, sphalerite, pentlandite, cobaltite, uraninite, magnetite, ilmenite, rutile,molybdenite, arsenopyrite, raramels-bergite, millerite stannite.

Quartz, chlorite, biotite, calcite, scapolite, muscovite, sericite, zircon, garnet, amphiboles apatite, andalusite, cordierite, sideroplesite.

Form and Shape : Much information was gathered from the old stopes, bore

hole data and underground working to evaluate the nature of the ore bodies.

Since the ore control criteria are not dependable, the true form and shape

- 30 -

of the ore bodies remain confusing. A general assessment on the basis

of the above knowledge reveals that the ore shoots are lens-shaped dipping

steeply towards the west. Where such occurrences are frequent they are

usually arranged In an en-echelon pattern and occasionaly displaced by

transverse faults.

The mineralization also occurs in the form of impersistent

stringers, disseminations, veins and veinlets, blebs and patches, replace-

ments, etc.

Individual ore shoots vary in length from a few meters to 200-500

meters. Their plunge depends on the nature of the host rock. Usually it

varies from 10° to 40° south-westerly or north-westerly in the northern

portion of the belt. Little is known about the form of ore bodies in the

southern part of the belt because of the fact that no regular prospecting

work has yet been done in this area.

Control of Ores

The exact nature of control in the belt is still dubious as it

is not possible to say conclusively whether or not the ore-deposits have

lithological, stratigraphical or structural controls.

Litholoqical - There is no lithological control in the belt in a true

sense. As stated earlier that there is a shift in the mineralization

from schistose rocks to quartzites, phyllites and amphibolites. The shift

cannot be attributed to the parent composition of the metasediments which

are found to have had different chemical compositions. The present author

- 31 -

recorded the original sediments by plotting the determined analytical

results of phyllite, quartzites, epidosite and amphibole-schists on ACF

diagrams. They are found ito be clays and shales and greywackes. It is,

therefore, evident that the distribution of sulphide ores has not been

controlled by the lithology of the host rocfcs.

Stratiqraphic - Since the mineralization is not restricted to any particular

horizon there appears to be no stratigraphic control on the ore-deposits.

In the northern part of the belt the contact zone between Alwar series and

Ajabgarh series is believed to be the probable site of copper mineralization.

Towards south around Akwali the mineralization shifts from the contact zone

to the overlying phyllites and schists of the Ajabgarh series. At Satkui

and Dhanaota the younger Alwar quartzites as well as the phyllites of the

lower Ajabgarh series are chiefly mineralized.

According to Hore gt al.. (1966) the mineralisation at Satkui is

localized along a major strike slip fault developed at the contact of

massive hard quartzite and soft phyllitic quartzite of Ajabgarh Series.

Roy Chowdhury and Das Gupta (1965) are of the opinion that this

progressive shifting of the zones of mineralization higher in the sequence

was not possibly due-to any broad stratigraphic control but due to inter-

communicating structures in different formations.

Structural - According to Roy Chowdhury et. al» (1965)the chief structural

features controlling the ore localization in the area are the normal and the

- 32 -

reverse faults. Fractures and shear zones which were developed as a

consequence of major folding and faulting are also the important structural

features controlling the mineralization. Fault zone fractures played more

important role than the fold zone fractures. Moderately dipping shear

zones are richly mineralized while steeply dipping shear zones are barren

except those which run parallel to the fold planes. Roy Chowdhury et a_l.

(1965) have made important observations that the fractures and shear zones

sub-parallel to the main faults, were the favourable sites for deposi-

tion of ores whereas the faults themselves were the main conduits of

transportation of mineralizing solutions. In support of their observations

they agreed that in some cases the ore shoots were located at the point of

intersection of shear zones and faults.

But they also stated that there are cases where shear fractures

do not show mineralization although they run parallel to the mineralized

veins. These were believed to have been developed by late deformation

contemporeneous to the period of mineralization. The author observed that

at places shearing was of low intensity but the host rocks were richly

mineralized (Hadhan-Kudhan section) while the poorly mineralized foot

wall quartzites were intensely sheared.

The schistose rocks are generally rich in copper. Cleavage planes

of the schistose rocks which run parallel to the bedding are highly

mineralized. Mineralized quartz veins run parallel to the strike of

foliation. Roy Chowdhury £t al^. (1965) observed that most of the trans-

verse faults are post-mineralization but there are pre-mineralization faults

- 33 -

sC- also Which are later than the strike fault. It is interesting to note

the pre-mineraliz9tion transverse faults which intersect the main shear

zones are richly mineralized (Madhan-Kudhan section). But it is also

true that all faults are not mineralized across their intersection. At

places there are also some transverse faults which have displaced the

ore bodies (Madhan-Kudhan section) indicating that they are post-rainera-

lization faults. Such faults have also been located at Dhanaota. These

post-mineralization transverse faults are invariably barren. In the

Madhan-Kudhan section some of these barren transverse faults were inter-

sected by later quartz-veins and basic dykes.

The folds do not show significant ore control. Smaller folds near

the fault zones are mineralized while larger folds are barren.The nose of

the folds and the axial zones are poorly mineralized.

The fault breccia in the Kudhan mine section is barren while the'

brecciated marble near Satkui is mineralized. Joints (Saladipura) and

tension fractures have played but minor roles in controlling mineralization.

Almost all joints in the fault zones show slikensides with or without

mineralization.

An interesting observation was made both in the Madhan-Kudhan and

the Kolihan sections where the host rocks were found to be largely

mineralized in the hanging wall but beyond it there is a barren massive

quartzite probably serving as a barrier to ore-fluids.

Chapter - III

LABORATORY METHODS OF STUDY

of yocfc samples for nrntrtr elements

bv conventional chemical methods

The analyses was carried out in order to determine fourteen major

constituents in igneous and metamorphic rocks. The elements determined

and the procedure followed are summarized below:

Total water (HgO +) was determined with the help of Penfield tube

at 8 0 0 ^ - 9 0 0 M o i s t u r e was determined by taking a known weight of the

sample in a platinum crucible and heating it upto llOX in an oven.

Silica : Each sample was fused with anhydrous sodium carbonate

(1:6 ratio by wt.) in a platinum crucible. The fused mass was cooled

and dissolved in 1:1 HCl. Double dehydration was done and the solution

was prepared in HCl (1:1). Filtered and the residue was Ignited in a

platinum crucible at 900°C and weighed. Silica was determined by hydro-

fluorizing the acid insolubles.

The residue left after hydrofluorization was fused with potassium

pyrosulphate, dissolved in HCl (1:1) and the solution was added to the

original stock.

RgOg were determined by precipitating the hydroxides with ammonia

in the presence of NH^Cl. The precipitate was filtered and then dissolved

- 34 -

- 35 -

in HCl and reprecipitated by ammonia. Filtered, ignited initially at

900°C and finally heated to red hot on a blast burner (about 1,100®C).

Necessary correction for platinum of the crucible (dissolved during

pyrosulphate fusion) was made by precipitating it (Pt) with HgS from

acid solution. The precipitate was then filtered, ignited and weighed.

Total iron (FeO + oxides were determined by titrating a

known aliquot against KgCrgO^ (N/20) solution after reducing it by silver

reductor.

Ferrous iron was determined by taking fresh sample in a silica

conical flask. Silica was hydrofluorized and the solution was prepared

in COg atmosphere. Boric acid was added and the solution was immediately

titrated against standard (N/20).

Titanium oxide (TiOg) was determined colorimetrically by developing

colour by HgOg in the presence of HgSO^ and H^PO^. The percentage trans-

mit tance was measured spectrophotometrically.

Manganese oxide was also determined colorimetrically by converting

it to permanganate and measuring colour intensity spectrophotometrically.

Calcium oxide was determined from the filtrate left after the

precipitation of hydroxides in RgOg determination. Precipitation was done

in highly ammoniacal solution by oxalic acid solution. The precipitate

was dissolved in HCl and reprecipitated. The final precipitate was

filtered, redissolved in HgSO^ and the warm solution was titrated against

standard solution of KMnO^ (N/IO).

- 36 -

Magnesium oxide was determined from the filtrate- left after

calcium determination. Magnesium was precipitated by dihydrogen ammonium

phosphate solution in alkaline medium. Dissolved, reprecipitated, filtered

and ignited in a muffle furnace at 900°C.

Alumina (AlgOg) was determined by subtracting the weight per cent

of the oxides of iron, titanium and manganese from that of R^^^g

Alkalies (KgO and NagO) were determined by taking fresh sample in

a platinum crucible. Silica was removed by hydrofluorizatlon. Hydroxides

were precipitated and a pinch of ammonium carbonate plus a little ammonium

oxalate were added. The volume was made up and left for 3-4 hours.

Filtered and the alkalies were determined with the help of E.E.L. flame-

photometer.

Sulphur was determined by carefully fusing the sample with sodium

peroxide (1:6 ratio by weight) in a nickel crucible and taking the mass in

water. Filtered and precipitated as BaSO^ by BaCl^ solution (10% solution)

in acidic medium.

Carbon-dioxide was determined by absorption method. A known

weight of the sample was decomposed by orthophosphoric acid in a nitrogen

atmosphere. The liberated carbon dioxide was absorbed In already weighed

ascerite tower and D^tube. Increase in weight in ascerite tower and

0 . tube determines the quantity of carbon'dloxide present.

- 37 -

Separation of minerals from rock samples

Ten different samples of granites and granitic rocks from different

outcrops of the belt were selected to separate their ferromagnesian and

felsic mineral constituents. The ferromagnesian minerals commonly are

biotite, hornblende and chlorite, epidote ,tetc. The felsic

group essentially includes quartz and feldspars.

Six samples were selected from three varieties of rocks (amphibole-

quartzite, garnetiferous quartz-chlorite-schist, garnetiferous quartz-

biotite-schist) which host the copper ores at the Madhan-Kudhan as well as

Kolihan mines. "Oie minerals separated are garnet, biotite, hornblende

and chlorite and magnetite. Felsic group comprised of quartz and a little

of feldspars.

Six samples of copper-iron sulphide were taken for the separation

of pyrite, pyrrbotite and chalcopyrite. Pyrrhotite and chalcopyrite were

further separated as pure mineral fractions. Pyrite,u on account of its

occurrence in small quantity (Kolihan samples), was omitted for final

purification.

Initial treatment - Thin sections of the selected rock samples were examined

under the microscope to identify their mineral constituents, grain size,

the nature of grains, inclusions and their parting distance. The copper

ore samples were examined under ore-microscope.

Sample preparation - For the purpose of magnetic separation -fiO to -120

and upto +200 mesh grain-size was used. Sometimes still finer powdering

was necessary, particularly in case of garnet which on account of its fine

- 38 -

inclusions of quartz needed finer powdering to decrease the number of

foreign grains.

The powder was first stirred with distilled water in a beaker to

remove adhering dust particles. Washing was repeated till the layer of

water above it became clear. Then the sample was dried in an oven at 110®C.

Magnetite was removed with the help of a strong hand magnet by

wrapping it in a tracing paper and combing it over the sample powder

repeatedly.

Separation bv Frantz Isodynamic Magnetic Separator

Principle - The principle of the isodynamic magnetic separator depends on

the relative magnetic susceptibilities of minerals.

The powdered sample was run through the separator repeatedly (3 or

4 times) increasing gradually the amperage after each run until about

95% of a mineral fraction appeared in the magnetic side. This range deter-

mined the magnetic susceptibility of the mineral. Remaining impurities

were removed by repeatedly passing the last separated fraction at a slow

rate. Where necessary (e.g., garnets) the last fractions were further

powdered to still smaller grain-size and the operation was repeated.

Separation of minerals - A little of powdered granites was taken and

magnetite was first separated by hand magnet. Then the magnetite free

powder was transferred into the hopper. The forward slope of the magnet

was kept at 20° and the side slope at 10-15°. 0.8 ampere current was

passed and the vibration was kept at medium range. Biotite, hornblende

- 39 -

and chlorite, and epidote fell on the magnetic side while quartz and

feldspars fell on the non-magnetic side. Then the ferromagnesian minerals

were taken for separating them from one another. The current was increased

gradually from zero ampere. Biotite was separated at 0.5 ampere. Horn-

blende and chlorite were difficult to separate and therefore separated

together at 0.8 ampere on the magnetic side. Epidote was separated at

a current value of less than 0.8 ampere. The separated fractions were

passed several times to get maximum concentration and purity. Quartz and

feldspars were collected together on the non-magnetic side at a current

value of 0.8 ampere.

The powdered host rocks were run through the instrument individually

and the mineral separation was done effectively in the same manner as above.

Garnet was magnetically separated at 0.4 ampere on the magnetic side. The

bigger crystals of garnet were handpicked before fine grinding.

Chalcopyrite containing pyrrhotite were treated differently.

Pyrrhotite being highly magnetic was first separated by a hand magnet and

finally the sample was run in the magnetic separator at a low current.

Pyrrhotite adhered to the sides of the chute and was removed by putting

off the current. Chalcopyrite was collected on the nonmagnetic side.

Panninn nf t. e concentrated fractions - A foolscap size paper of ordinary

thickness was stretched and kept sloping at 30°. Then the sample was

sprinkled. One end was kept holding and the other left free. The paper

was then slowly tapped on the sides. The mineral fractions moved down

under the influence of gravity. Lighter ones moved faster than the heavier

- 40 -

ones and thus, separated. This was particularly effective in case of micas.

Separation by heavy liquids - Bromoforra (sp.gr. 2.85 to 2.90 at 20®C) was

used for further concentration of heavy minerals. The desired specific

gravity was obtained by diluting bromoform with alcohol. Sometimes the

finer fractions were subjected to centrifuging.

Pure separation - The separated fractions of sufficiently high purity were

checked under the binocular microscope or mounted on a glass slide to

identify the combined fractions. Final separation was done by hand picking

using a forcep and a brush under the binocular microscope. The purity of

the sample was estimated by mounting it on a slide and point counting.

Trace element analyses bv Atomic Absorption Spectrophotometer

The application of Atomic Absorption Spectrophotometer to the

analysis for various elements particularly those present in traces has

got momentum in recent years. It was first described in 1955 by Walsh,

Alkemade and Milatz. Since then it became an important Instrumental

technique of analyses. It has got less chemical interference and Inter-

pretation of results is simple.

Principles - Its principle is opposite to emission spectros-copy. When a

substance is volatilized in an arc or a flame it gets ionized. Some of

the electrons of the atoms of metal get energized and jiwnp to higher levels.

When they fall back to lower energy levels, they emit light energy of

specific wavelengths which are characteristic of the elements present.

Only 1-5% of atoms get excited while the larger percentage remains in

- 41 -

so-called ground state. These atoms in the ground state are capable of

absorbing light of the same wave-length as that emitted if they were

excited. The absorption is measured electrically which determines the

quantity of the element present. The Atomic Absorption Spectrophotometers

used for the present investigation are Perkin-Elmer (303-model) and Jarrel-

As h mode 1.

Decomposition of sample and preparation of solution -

One gram of the sample was weighed in a platinum basin (100 ml.).

A few drops of double distilled water were added followed by the addition

of 5 ml. of perchloric acid and 20 ml. hydrofluoric acid. The basin was

kept on an electrically operated hot plate at low temperature for slow

evaporation for 5-6 hours. When copious fumes of perchloric acid continued

and the mass became viscous, the platinum basin was removed from the hot

plate and allowed to cool. Again 2 ml. of perchloric acid and 5-8 ml. of

hydrofluoric acid were added. The basin was again kept on the hot plate

at low temperature. When the mass attained condition as before, the basin

was removed from the hot plate and cooled. The sides of the basin were

washed with double distilled water. 5 ml. of perchloric acid was added

and the basin was heated till perchloric acid fumes started coming. Cooled

and diluted to about 20 ml.

Filtered through Whatman (No. 42) filter paper in a 100 ml. volu-

metric flask. Washing was done with warm distilled water for 5-6 times.

Cooled and the volume was made up to 100 ml. r. The sample solution was

ready for feeding to the instrument.

- 42 -

Preparation of Blank - A blank was prepared along with each set of

the samples following the same procedure as adopted for sample solution.

Preparation of standards - Stock standard solutions of 1000 ppra. were

prepared for each element of interest. Further fractions of 0.1 ppra.

to 100 ppm (as desired) were prepared by diluting the stock solutions.

The acidity of the solutions was maintained to 5% in all cases using

•perchloric acid.

Some modifications were made in the case of determination of

silver and lithium. For silver, the solution was made up to 100 ml

with 7% of ammonium acetate and 0.1 gm of KCN was added to it. For

lithium 50 ml of the solution was taken and 10 ml of sodium chloride

solution (equal to 500 ppm of Na) was added and the volume was made up

to 100 ml.

Soil samples were digested in a mixture of HCl and HNOg (2;1)

and the solution was prepared for analyses by Atomic Absorption Spetro-

photometer.

1) There are no spectral interferences as the monochromator allows

the line of the wave length chracteristic of the cathode.

2) There are no chemical interferences. The elements sought are

simply to be dissociated from its chemical bonds. No excitation is

required. A little difference in the temperature of the flame would have

- 43 -

negligible effect on the results.

3) Since the number of atoms involved in absorption are more than

95%, the analytical results are of great precision and accuracy.

4) The instrumentation technique is simple.

5) Most of the elements can be determined from a single solution.

6) Major elements can also be determined with equal accuracy but

it needs more care in preparation of sample and dilution,

7) Calculations are easy.

Chapter - IV

OCCURRENCE. LITHOLOGY. PETROMINERALOGY AND PETROCHEMISTRY

OF ROCKS

The rocks of the area have been divided into the following two

major groups.

1. Intrusives

Granites and granitic rocks Pegmatites and quartz veins Basic dykes

2. Metamorphics

Quartzites

Schists and phyllites Carbonate rocks

Occurrence and litholoav

Granil;:QS and granitic rocks - These rocks are further classifi^ed into:

a. Pink granite and granite gneises b. Grey granite and granite gneises

c. Ajilite

a) Pink granite and granite gneisses - Pink granite is comparatively abundant

in the area with colours varying from light to deep pink. It is a coarse-

grained rock and shows gneissic banding at some places.

In some cases augens of potash feldspars are distinctly seen. The

rock comprises mainly of potash feldspars, quartz and some ferromagnesian

minerals, viz., epidote, hornblende and biotite. In the gneissic variety

the ferromagnesian minerals are usually concentrated in the darker bands,

and schlieren.

- 44 -

- 45 -

b) Grey granite and qrainite gneisses - The grey granite is a light coloured

rock and has only a few occurrence in the area. They are medium to fine-

grained rocks composed mainly of plagioclase feldspars and quartz with some

biotite as the ferromagnesIan mineral. The gneissic variety is of two

types — one with amphibole as the predominent ferromagnesian mineral and

the other with biotite. The augen structure is mostly found in the latter

variety.

c) Aplite - The aplite is fine-grained and light pink in colour. It

comprises mainly of potash feldspars and quartz with a little of amphibole.

For the sake of convenience the description of the granites and

granitic rocks has been oresented sectortvise as follows:

1. Gotro sector - There is an outcrop of pink granite southward from

Gotro village which extends upto 3 km beyond which it is covered under

alluvium. Occasional veins of quartz (see Plate I Fig. 2 ) measuring

from a few inches to three feet or more wide and several feet in lateral

extent are found cross-cutting the granite. The contact of the granite with

the surrounding felspathic quartzite is not sharp. A brecciated rock occurs

at the contact of granite with felspathic quartzite (see Plate IV Fig. 1 ).

The granite is dotted with a dark green amphibole and epidote which

are also concentrated along some of the joint partings and give rise to

schlieren structure (see Plate IV Fig. 2 ).

2. Nizampur road sector - There is an isolated small outcrop of pink

granite at Nizampur road. The outcrop is strewn with big and small boulders

of granite and is surrounded by quartzites.

- 46 -

It is a mediura-gralned rock more or less equigranulgr having biotite

as the chief ferroraagnesian mineral

3 . Gorwala sector - Between Gorwala-ki-Dhani and Tihara-ki-Dhani, there are

several small exposures of pink granite-gneisses which presents a low lying

rolling topography. Its contact with quartzites is not clear as a large

part of the outcrop is covered under alluvium or residual soil.

Biotite which is present in noticeable amount is arranged in bands

to give gneissic appearance.

4. Biharipur sector - There is prominent outcrops of pink granite covering

a considerable area south of Biharipur. Small quartz veins often occur in

the granites having a cross-cutting relation. Its contact with the quartzites

is also not distinct.

Biotite is the main ferromagnesian mineral. Occasionally the rock

is foliated.

5 . Chappoli sector - There is an extensive occurrence of pink granite

gneisses and grey granite and grey granite gneisses near Chappoli. Several

prominent outcrops are found in the east of Chappoli near Mandaora and

south and southwest of Chappoli.

Near Mandaora the outcrop of granite is bounded within the curvature

of an arcuate quartzite ridge due to which its contact with the latter is

easily made out. Near the contact zone the granite is altered and brecciated.

The rock is generally coarse-grained but becomes fine-grained near the

contact with quartzite. Joint planes in both fine and medium grained granites

have some iron oxide coatings due to supergene deposition and action of

- 47 -

surface water.

Udaipur sector - In the east of Udaipur there is a small outcrop of

grey granite gneiss in contact with quartzite. It is intruded by minor

veins of pegmatite which are disposed almost parallel to the gneissic bands,

(see Plate IV Fig. 3 ).

The rock is dark coloured medium-grained. The main ferromagnesian

mineral is amphibole which is segregated in distinct bands.

7 . Saladipura sector - South and southwest of Chappoli particularly west

of Saladipura, several outcrops of pink and grey granite gneisses generally

occur a3 low lying exposures. They are medium to coarse-grained rocks

and have augen structure at places. The size of the augens in pink granite

gneisses varies from 0.2 mm to 1 cm. (see Plate V^ Fig. ] ).

The outcrops cover large areas and are lenticular in shape. They

are covered with big boulders. Their contact with quartzites is sharp in

the southwest of Chappoli.

The pink gneisses have augens of potash-felspars and a little of

biotite. The grey gneisses have amphibole and biotite .>as the main ferro-

magnesian mineral.

a

Pegmatites - Pegmatites occur only at/few places in the belt. They vary

in their mode of occurrence and also in mineral composition.

Northwest of Madhan-Kudhan mines there are a few small outcrops of

pegmatites intruding the quartzites. One pegmatite vein was found to be

about 20 feet wide and about 200 feet long. They are mainly composed of

quartz, feldspars and tourmaline. Muscovite is present only rarely. In

some cases the crystals of tourmaline are very well developed and are usually

- 48 -

of big size. There are instances of tourmaline measuring upto 10 inches

also in length and having perfectly developed prismatic faces. Sometimes

slender crystals of tourmaline are arranged in a radiating fashion in some

outcrops, (see Plate V, Figs. 2 and 3).

A distinctive feature of this pegmatite is that it has been folded

which becomes apparent by the arrangement of tourmaline, quartz and feldspar

crystals (see Plate VI, Fig.l ). In some specimens tourmaline and quartzo-

felspathic minerals are segregated along bands. Schorl rock also occurs in

the vicinity of the pegmatite veins.

Good exposures of pegmatites are also found near Papurna. They are

tourmaline-free» white and pink pegmatites. The pink variety is devoid of

rauscovite, while in the white variety muscovite is scantily present.

Near Chappoli there is a vein of pegmatite in mica schist. It is

rich in mica but poor in tourmaline.

Quartz veins - Almost all the rock types of area have quartz veins of

varying dimensions. In the mineralised zone these veins have traces of

sulphide ores indicating that they are of post mineralization age. Sometimes

the veins are several metres in length and vary from a few centimeters to a

metre in width. The larger quartz veins are more frequent in the northern

part of the belt and are found associated particularly with the granite

of Gotro. (see Plate I, Fiq. 2).

Basic dykes - The entire area of the Khetri copper belt shows a number of

dolerite dykes. Their occurrence is more prominent near Papurna and Babai

where they assume considerable dimensions. Some smaller dykes are seen near

- 49 -

Gotro village, SE of Madhan-Kudhan mines section. Such smaller dykes are

usually found all over the belt. They are more common SW of Chappoli and

also near Udaipur in the southern part of the belt. The rock is dark

coloured and fine-grained. There are certain dolerites having porphyritic

structure, (see Plate VI, Fig. 2).

Ouartzites - Quartzites are the predominating type' of rock of the belt.

They show distinct variation in mineral composition. Accordingly, they

have been classified as follows:

]. Feldspathic quartzite 2. Amphibole quartzite 3. Magnetite-haematite-quartzite 4. Massive quartzite

5. Sericite quartzite

This classification is to be applied in a broad sense as there is

a lateral gradation of one type into another. At a few places some of the

primary sedimentary features are still preserved in them. *

The felspathic quartzites are widely distributed particularly in

the northern part of the belt (see Plate I, Fig, 3 ). Their colour

varies from buff to light pink. Compositionally they range from ortho- to

arkosic-quartzites which are usually medium to coarse-grained. Infrequently

they have well-preserved ripple marks and current beddings. Occasionally

a few quartz veins are also found in quartzites. Starting from its contact

with granite near Gotro the felspathic quartzite grades into amphibole

quartzite on its western side.

The felspathic quartzite near the Madhan-^Kudhan mine is associated

with a thih bed of magnetite-quartzite which is faulted repeatedly across

its strike (see Plate II, Fig. 1 ).

- 50 -

The massive quartzite is thin bedded and is one of the widely

occurring types of quartzite of the belt. Its largest outcrops are seen

around Bahai and Gurha-Ponk.

The rock has colours varying from grey, creamy white to light pink,

Fine to medium-grained texture is common.

Sericite quartzite is thin bedded and occurs largely at the top of

the quartzite formation in the northern part of the area. It extends to a

considerable extent south of Madhan-Kudhan section and further upto

Kolihan. Occasionally the ripple marks are preserved in the quartzites.

Schists and Phvllites

This group of rocks shows a wide variation in mineral assemblages.

The distribution bears relationship with the structural and geological

set-up of the area.

Schists - The following types of schists commonly occur in the area:

1. Garnetiferous quartz-chlorite schist

2. Garnetiferous quartz-biotite schist

3. Garnetiferous anthophyllite-cumraingtonite schist

4. Amphibole-biotite schist and amphibole schist

5. Biotite-muscovite schist

Others of minor occurrence are biotite, muscovite, quartz and

chlorite schists.

Garnetiferous quartz-chlorite schist, one of the host rocks of

copper ores, forms the foot wall of the mineralized zone. It is the chief

rock type of the Madhan-Kudhan mine section^ (see Plate TT Fig.2 ).

- 51 -

The schists strike N 30°E to N 50°E and dip 40* to 65® due north.

A few transverse and strike faults are recorded. They also show folding

and jointing on a minor scale. They overlie amphibole quartzite with which

they have a gradational contact.

The schist is greenish in colour mainly due to the abundance of

chlorite. Garnets are of variable size (0.1 to 1 cm in diameter) and have

a tendency to concentrate along the planes of schistosity. In a few cases

they form irregular but distinct bands with some parallelism to the

schistosity. (see Plate VI 6 H I . Figs.. 3 & 1).

The garnetifetous anthophyllite-cummingtonite schist resembles in

lithology with garnetiferous quartz-chlorite schist. Garnets show more or

less similar lithological character as in the case of garnetiferous quartz-

chlorite schist.

The garnetiferous biotite-schist occurs mainly in the Kolihan mine

section. The rock is dark coloured with reddish garnets of variable sizes.

Biottte is the predominating flaky mineral and quartz is present in subor-

dinate amount.

Amphibole biotite-schist shows a wide mineralogical variation mostly

due to the variation distribution and type of amphibole. Quartz, biotite

and feldspars form the chief mineral constituents. Garnet is present but

in a few rocks.

The amphibole schist has anthophyllite-cummingtonite as the predo-

minating type of amphibole. The amphibole is light greenish in colour and

occurs in the form of fibrous or lamellar crystals. Feldspars occurs in

minor amounts. The rock is found in the Madhan-Kudhan section.

- 52 -

Biotite-andalusite schist is a dark brown coloured coarse-grained

rock. Flakes of biotite occur in abundance. Some large prismatic crystals

of andalusite range in size from 2 to 3 cms in diameter and 8 to 10 cms in

length. Most of the crystals have a preferred orientation. Cross section

of andalusite crystal shows inclusions of some carbonaceous material in

the central part while a vertical section shows a continuous thread of carbon

all over the crystal length, (see Plate VII,Fig. 2 ). The rock has good

exposures in the Kolihan section and in the southwest of Khetri. It was

found to occur mostly in the vicinity of epidiorite dykes.

Phyllites - Textures of phyllites are present in the northern part of the

area, near Madhan-Kudhan and around Kolihan mines. They overlie garneti-

ferous, quartz-chlorite schists. The rocks are grey to dark grey in colour

and frequently puckered (see Plate VII, Fig. 3 ). Cleavages are parallel

to the bedding laminations. Phyllites are highly folded with a general

NE-SW trend of their fold axes. The beds dip at 45° to 75° due NW. Occasional

bands of quartzite and carbonate rocks also occur as inter layered.

A river valley cuts across a large part of the phyllite formation r

near Madhan-Kudhan and runs in NE-SW direction parallel to the fold axis.

The exposures are highly weathered.

Carbonate rock - (Impure Marble) : Carbonate rocks of mainly impure marble

type are distributed all over the belt but not in any significant amount.

Their outcrops are found in lowlying areas generally interbedded with the

schists. Araphibolization is a common feature in impure marble (see Plate H .

Fig. 3 ). Commonly the amphiboles form lath-shaped and bladed crystals of

dark green colour. The colour of rock varies from greenish grey to dark grey

- 53 -

depending on the proportion of amphibole present.

The c?rbonate rocks occurring in between the Madhan-Kudhan.Kolihan

and Akwali mines are appreciably rich in amphiboles while those belonging

to the southern part of the area, viz., south of Chappoli are poor in

amphibole.

PETROMINERALOGY

Pink granite and granite gneisses

The chief mineral constituents in the order of decreasing abundance,

are feldspars (potash-felspars predominating), quartz, amphibole, epidote,

biotite and opaque minerals while in case of gneisses^biotite predominates.

Mineralogy

1. Quartz - Colourless, anhedral crystals, weakly biref-ringent and

having wavy extinction. The anhedral crystals of quartz are partially

enclosed in feldspars (plagioclases) and generally they have inclusions of

fine particles and also of epidote. In some grains sutured contacts are clear,

2. Feldspars

A . Potash-feldspars - Microcline and perthite are the chief felds-

pars.

Clear microcline anhedral crystals with characteristic cross hatched

twinning (M. type) and extinction angle on (001) is from 15° to 17°. The

microcline megacrysts are traversed by fine-grained veins of ground-mass

material (see Plate VTII.'Fig. 1). It encloses quartz and other feldspar

grains partially along the borders. In a few cas'es the phenocrysts are of

microperthites. The microcline-microperthite contact is indistinct. Islands

of quartz occur in optical continuity with perthites. Veins of epidote are

- 54 -

seen along fracture planes. Micrographic intergrowth commonly present

(see Plate IX, Fig.] )

B . Plaqioclase-feldspars - Plagioclase feldspars are less abundant

as compared to potash-feldspars. The crystals are lath-shaped with extinction

angle on (001) zone from 0° to 18*' indicating albite-oligaclase composition.

The plagioclase crystals show two types of twinning. One on a very

fine scale (lamellar) which is often patchy and a second, somewhat coarser

of albite type (see Plate VII];Fig. 2 ). The latter type of twinning is

characteristic of bigger plagioclase crystals. Some of the plagioclase

crystals display X-carlsbad twinning. In the case of granite gneisses the

plagioclases display extinction angles of about 12° on (010) zone which

indicates that it is albite. The bigger crystals are irregular with inclu-

sions of epidote and quartz concentrated along the border zone. Clouding

of plagioclases is a common feature. Feldspars show fracturing along

cleavages. Bigger crystals sometimes show deformation and dislocation of

twin compositional planes (see PlateVIII.Fig. 3 ). Where microcline pre-

dominates, plagioclase,if present, is usually oligoclase.

3. Amphibole - Light pale green prismatic, with two sets of perfect

cleavages at 120°, moderate biref-ringence and extinction angle ( Z ^ C ) =

12° to 15°.

It is distinctly pleochroic. The pleochroism scheme is as follows:

X = Pale green

Y = Bluish green

Z = Greenish blue

Absorption scheme : Z > X

- 55 -

The amphibole is, therefore, of hornblende type. Hornblende commonly

alters into epidote. The alteration is more pronounced along the borders

of the crystals .

4. Biotite - Tabular crystals, strongly pleochroic from very deep

greenish brown to pale brown. Pleochroic haloes are present. Bird's eye

structure is characteristically present. Some of the biotite flakes are

seen enclosed by plagioclase.

Sphene - Rhorab-shaped crystals of light broivn colour, weakly pleo-

chroic from colourless to light brown, showing high order white interference

colours.

Interference figure - biaxial positive.

Frequently it occurs in association with epidotes. In some cases

it is partially enclosed in feldspars. In the granitic gneisses it occurs

in close association with biotites.

6. Spidote - Generally equidimensional and markedly pleochroic from ish-

y e M o w to yellow/green colours. Their relief is high and high birefringence.

Interference figure obtained is biaxial negative. Two varieties of epidotes

have been identified.

a) Pistacite - Showing pleochroism and high order interference colours.

b) Clinozoisite - Almost colourless. Interference Figure - Biaxial

negative.

Epidote crystals are enclosed in potash-feldspars. It is commonly

associated with hornblende. Frequently it surrounds hornblende crystals so

completely that islands of unaltered hornblende in epidote may be seen.

- 56 -

The leached borders of hornblende in contact with epidote indicate their

alteration into the latter.

Cordierite - Colourless crystals and are usually big and anhedral.

Abundant inclusions of flaky minerals (see PlatelX, Fig, 2 ). Simple

twinning and zoning are distinct in some cases. Optic figure - biaxial

negative.

Minor accessories

Garnet - Garnet occurs as almost colourless and roughly rounded

grains. Tt is isotropic and is generally surrounded by biotite flakes.

2. Zircon - Crystals are colourless, prismatic with high relief and

interference colours. The crystals are length slow. They are commonly

present and generally occur as inclusions in biotite.

3' Tourmaline - Tourmaline crystals are prismatic and light grey in

colour. They are markedly pleochroic from colourless to light pink. Extinc-

tion is parallel and the interference figure is uniaxial negative. The

variety is schorlite.

Fluorite - Fluorite crystals are almost colourless and euhedral.

It has distinct cubic cleavages and is optically isotropic.

5. Calcite - It occurs as colourless, spherulitic grains showing

double refraction.

Opaque minerals - They are commonly iron ores which occur in rela-

tively greater quantity in granites.

- 57 -

Qisv-^.

They are light to dark grey in colour, medium to fine-grained.

The chief mineral constituents are feldspars and a subordinate quantity

of quartz. Lineation and schlieren were observed frequently. Hornblende

and biotite are the main ferromagnesian minerals. Iron ore grains are

present in small amounts.

Quartz - Anhedral crystals with minor cracks are present. It is

present in varying amounts and size. Most of the grains show wavy extinction

and other evidences of crushing and deformation. Dusty inclusions are also

present. They are largely surrounded by feldspars. Contacts are sutured.

Potash-feldspars - Microcline and perthite are the main feldspars.

Crystals are anhedral. Extinction angle on (001) varies from 16 to 18°.

The augen gneisses have feldspars as the predominant mineral. Per-

thite is the chief feldspar of augens. Some rounded quartz inclusions are

present in optical continuity. Microcline at places surrounds perthite

grains and shows patchy and M-twinning (see Plate VIIT, Fig. ]), The contact

between microcline and micro-perthite is not sharp. Clouding in feldspars

is not common.

Plaqioclase-feldspars - Albite-oligoclase are in smaller quantity

than the potash feldspars. The crystals are subhedral, lath-shaped with

equal extinction angle on (010) zone varying from 3® to 18®,

The crystals show lamellar as well as X-Carlsbad twinning. Some of

the plagioclase crystals have fractures along the cleavages. Clouding of

plagioclases is seen. Inclusions of quartz and ferromagnesian are present.

- 58 -

Amphibole - The chief amphlbole present is hornblende.

The pleochroism scheme of amphibole was determined in a number of

thin sections. It is as follows:

X = light brown

Y = Brownish green

Z = Deep brown. *

The angle Z\C varies from 17° to 21° showing it to be a hornblende

variety. The crystals in most of the cases are arranged parallel to the

foliation planes (see Plat6 TX, Fig.3 ).

Biotite - Flaky crystals of biotite are generally arranged parallel to the

foliation planes. The crystals show distinct pleochroism from pale yellow

to deep brown. Pleochroic haloes around zircon are present in a few cases.

Bird's eye structure is characteristically present.

Accessories - Minor accessories are opaque minerals (ores),sphene, zircon

and apatite.

Basic dykes

The basic dykes are metamorphosed dolerites and the chief mineral

constituents are amphibole, epidote, plagioclase, feldspar and minor quartz,

sphene and opaque ores. The term epidiorite has been used for them (see

Heron, 1923). The relict of porphyritic and ophitic textures present in

them (see Plate Fig. 2 ) indicating that they were doleritic before

metamorphism.

Amphibole - The amphibole found is an almost colourless variety of hornblende-

uralite. It is weakly pleochroic and contains needles of green amphibole.

Some of the crystals are strongly pleochroic (X = Pale, Y = green, Z = blue)

- 59 -

colourless crystals of epidote of clinozoisite variety are frequently seen.

They are formed from the alteration of feldspars. Som6 intensely altered

feldspars are still visible. Comparatively fresh plagioclases form pheno-

crysts and show zoning (see Plate X, Fig.2 ). Symmetrical extinction

angle of 30° indicating labradorite composition. Acid andesine shows

extinction angle of 22" and forms the ground mass. Quartz is mostly inter-

stitial and present in low amounts. Sphene forms the common accessory mineral

but in some cases its proportion is higher but never exceeds the accessory

limit. Opaque ores are seen distributed in all the sections in varying

proportions.

Pegmatite - Thin section study of the pagmatites of the belt shows varia-

tion in mineral composition. The pegmatites from the northern part of the

belt show feldspars, tourmaline, quartz and flaky minerals as their main

constituents. But those from the southern part of the belt are more or

less devoid of tourmaline.and the flaky minerals are also less at most of

the places. The mineral constituents of the pegmatites in general are

plagioclase-feldspar, potash-feldspar, quartz, tourmaline, mica and opaque ores,

Feldspars - Plagioclase feldspars are more abundant than the potash

feldspars. The plagioclases are usually lath-shaped crystals with extinction

on (010) zone from 0° to 16° indicating albite-oligoclase composition. They

show lamellar and X-Carlsbad twinning. Some of the plagioclase crystals

show clouding.

The potash-feldspars are less common. The microcline shows distinct

cross-hatched twinning. Extinction angle varies from 16° to 18°. Inclusions

of quartz are present.

- 60 -

Quartz - Quartz is present in subordinate quantity and is usually surrounded

by the feldspars.

Tourmaline (schorlite) - Tourmaline is present in varying sizes. The

crystals are prismatic and usually grey in colour. Strongly pleochroic from

light yellow to deep blue. Some of the tourmaline crystals show distinct

zoning (see Plate X, Fig, 1 ).

Muscovite - Muscovite occurs as colourless flaky mineral. Where present

it is usually arranged in a regular pattern.

Opaque ores are present in smaller amounts.

Quartzites - The petromineralogy of all the types of quartzites has been

presented collectively.

The chief mineral constituents are quartz, feldspars, amphibole,

sericite and opaque minerals.

The optical characters of individual minerals are mentioned below:

Quartz - The size of the quartz grains varies in different varieties.

Some of the grains show distinct wavy extinction. The bigger grains are

often rounded to subrounded and enclosed in a sericite matrix. They also

show a little deformation and some recrystallization. Minute inclusions of

apatite are frequently present.

In magnetite-haematite quartzite, quartz has innumerable inclusions

of opaque minerals. Some grains are fractured and show strain shadow effect.

Quartz in this rock is medium to fine-grained and generally shows mosaic

texture. Some clear vein-quartz of microscopic size, completely free from

magnetite or any other inclusions, were noted in quartzites. The vein-walls

are lined by continuous layers of iron oxide.

- 61 -

In some cases there are angular to sub-angular fragments of quartz.

Quartz porphyroblasts are rare (see Plate X, Fig. 3 ).

Feldspars - Feldspars are next to quartz in order of abundance. In some

cases feldspars are in minor amounts while they are in appreciable amount

in feldspathic quartzite. Both soda-lime feldspars and potash-feldspars

are present.

Plagioclases are usually small and occur as tabular crystals. They

show characteristic twinn ing. Most of the plagioclase crystals give

extinction angles on (010) zone varying from 3° to 16° which indicates that

they are albite to oligoclase. Where there is a predominance of oligoclase

albite becomes less. They are cloudy due to partial kaolinization.

Among potash-feldspars, perthite is common. It occurs as anhedral

crystals. Microcline is present in smaller amounts.

Amphiboles - The amphiboles are hornblende and actinolite types,of

which the former is more abundant.

Hornblende - Pleochroism scheme

X = light greenish

Y = Brownish green

Z = Deep greenish brown

Z A C varies from 17° to 21°.

The formeris generally prismatic. The crystals are somewhat oriented.

Some inclusions of quartz are present.

Actinolite - In a few thin sections amphibole of actinolite variety

was identified. It generally occurs as radiating needles and is enclosed

within the quartz crystals.

- 62 -

Sericite - Sericite is the common constituent of sericite-quartzite

which is one of the predominating rock types of this group. It is scaly

and light pink to greyish white in colour.

Minor accessories - Among the other accessories the following minerals were

identified. Biotite, tourmaline, opaque minerals, chlorite, epidote,

muscovite, sphene, zircon, etc. Their relative abundance varies according

to the composition of the rock.

The petromineralogical characters of the schists have been described.

The rocks, in general, have well developed foliation. Flaky minerals,

like chlorite and biotite are oriented parallel to sub-paralel to schistosity.

Garnets, wherever present, are arranged along the planes of schistosity. The

schists have lepidoblastic or neraatoblastic texture according to the shape

and orientation of the minerals.

Mineralogy - The grpin-size of quartz varies from medium to coarse-grained.

Most of the quartz grains in the schists were deformed as indicated by their

wavy extinction. Quartz is also present as inclusions in some ferromagnesian

minerals.

Garnet : Garnet shows marked variation in shape and size. It occurs as

xenoblasts as well as idioblasts. It varies in size from 0.1 cm to 1 cm in

diameter. The mineral is pinkish in colour and,probably, of almandine

variety. Inclusions of quartz, etc., are present. Three types of garnet have

been recognised; They are as follows:

Garnet I (see Plate XI, Fig.l ) - Xenoblastic, with 'S' arrangement of

- 63 -

inclusions. It was formed during earlier metamorphism.

Garnet 11 - Highly sheared and fractured garnet with parallel crack, filled

with chlorite. It shows alteration to chlorite (penninite variety).

Garnet III (see Plate XT, Fig.2 ) - Idioblastic in shape with rounded

and oriented quartz inclusions. Formed, probably, from the recrystalliza-

tion of garnet I and II (see Das, 1966).

The garnet porphyroblasts in a few cases show many helicitic inclu-

sions mainly of quartz, arranged in layers (oriented) and in continuity,

with the planes of schistosity of the rock. Such type of crystals may or

may not have undergone rotation. The shape of some of the garnet me1;a-

crysts is like 'S' which distinctly shows that they are rotated crystals.

The quartz inclusions are also arranged in a similar pattern (*S') which

is very apparent under the crossed nicols.

Due to rotation of garnet crystals some of the fragments are separated,

The spaces in between the fragments is occupied by chlorite of secondary

origin. It is also filled up by a deep brown, somewhat anisotropic, oxide

of iron. Some micaceous minerals are also arranged around the garnet

crystals. This in addition to the pattern of inclusions, indicates rotation

of garnet during its growth due to shearing movements.

In some other cases euhedral garnet porphyroblasts present no

evidence of rotation. The inclusions of quartz in them, also, do not have

any definite orientation. They have been altered into chlorite, biotite

and some epidote retrogressively without showing any evidenee of rotation.

Chlorite - Chlorite is light yellowish green in colour with inclusions

- 64 -

of quartz. Typical "Berlin blue" interference colours characterise them.

Some finer lamellae impart oranqe-red interference colours. They are flexured

and crenulated.

Chlorite is mostly concentrated along certain planes and around the

garnet porphyroblasts. The bands are highly folded. These bands indicate

planes of differential movements in the rock and it is along such planes

that garnets have undergone rotation.

Chlorite is studded with brownish patches of iron oxide and black

opaque minerals which are widely dispersed. It swings around the lenticles

of quartz wherever < pres-ent.

Amphiboles - The amphiboles present are anthophyllite-cummingtonite

and hornblende.

i) Anthophyllite cumminqtonite : They are almost colourless, needle-

like and weakly pleochroic (see Plate XI, Fig. 3 ). TWinning is poly-

synthetic. They have positive optic sign. Extinction is inclined.

ii) Hornblende : The pleochroism schemes of the amphiboles determined

in various thin sections are as follows:

I TI

X = Pale to light brown X = Yellowish

Y = Brownish green Y = Green

Z = Deep greenish brown Z = Greenish blue

The angle Z / \ C varies from 18® to 22°.

The optical characters suggest that the amphibole is a normal hornblende

type. The crystal aggregates are also acicular and oriented parallel to

the foliation plane. They are also enclosed within biotites and sometimes

- 65 -

grade into them. Bigger crystals show strain effects.

Biotite - Biotite crystals are flaky in habit and show a preferred

orientation. Pleochroism is from pdle to very deep brown.Pleochroic haloes

and zircons are present. Occasionally inclusions of sphene are present. In

some cases biotite (of amphibole-biotite schist) appears to have formed

subsequent to hornblende and opaque ores as the biotite encloses these

minerals.

In biotite-muscovite*schist, biotite occurs in abundance and shows

some dusty inclusions particularly in the. central part of the crystals.

Feldspars - Plagioclase feldspars are present in biotite schist and

araphibole schist. They are twinned en albite law and distinctly zoned. The

shape of the optic figure suggests a large value of 2 V. The extinction

angle on (010) zone varies from 10° to 15° giving albiclase composition, A

number of untwinned feldspars (plagioclases) are also present with clear

zoning. In zoned crystals the inner zone is generally of oligoclase compo-

sition and the outer one of albite. They have some inclusions of quartz and

amphiboles.

Andalusite (Chiastelite) - Andalusite of schists, are porphyroblastic

with moderate relief and two sets of prismatic cleavages. Their birefrin-

gence is low and extinction is parallel. The crystals are length fast and

their cross-section shows carbonaceous inclusions regularly arranged in the

form of crosses, which are characteristic of the chiastolite variety. Inclu-

sions of flaky minerals, like muscovite, sericite, etc., are distributed

throughout the crystals. They alter into chlorite, •

- 66 -

Muscovite - It occurs as a few flaky crystals, arranged in foliation

planes. They are generally colourless and of small size.

Opaque minerals are disseminated throughout the rock. In some cases

they are euhedral in shape and are present as clots.

Other mineral accessories are zircon, sphene and tourmaline.

Phyllites - A brief description of the mineral constituents of the phyllites

is given as follows:

Quartz - Quartz is common and generally fine-grained (0.05 mm to 0.5 mm)'.

The grains are somewhat elongated the longer direction being parallel to

the foliation. They usually show wavy extinction as a result of strain.

There are occasional inclusions of sericite and muscovite (see Plate XTT,Fig. 1),

Feldspars - Feldspars are next to quartz in abundance. Plagioclase

feldspars being more common,occur as tabular and lathshaped crystals and

show characteristic albite twinning. The extinction angle according to

M-Lavy's method varies from 12° to 15°. Some of them are strained.

Among flaky minerals, biotite, sericite and chlorite, show a linear

arrangement. Contortion of bedding planes in the rock is apparent by the

arrangement of these minerals.

There are a few grains of prismatic crystals of tourmaline, with

dusty inclusions arranged in the core. Its pleochroisra scheme is: 0 = brown,

e = light reddish to colourless.

Absorption <-0 > E It was thus identified as schorlite.

Opaque minerals occur in appreciable quantity in the form of fine

bands on the microscopic scale.

- 67 -

Carbonate rocks

The chief minerals in order of abundance are calcite, dolomite,

amphibole and opaque minerals.

Carbonate minerals

Calcite and dolomite show characteristic twinkling and glide twinn-

ing in a few cases. The texture (composite) is crystalloblastic with fine-

to medium-grained size,

Amphibole - The amphibole present is tremolite. It has bladed crystals

which are of variable sizes. The basal section fehows two sets of prismatic

cleavages. Pleochroism is feeble from colourless to light greenish. In a

few crystals green colour is more pronounced but the greenish tint is non-

uniform. The C Z angle varies from 15° to 17®. Inclusions of opaque

minerals are present. The mineral is sometimes replaced by carbonate

minerals along the fracture planes.

The opaque minerals are present in negligible quantity. Chlorite,

mica, etc., form the minor accessories.

T E X T F I G . N O . l Al S F DIAGRAM

- 68 -

PETROCHEMISTRY

Granites and granitic rocks

The petrochemistry of granites and granitic rocks has been studied

and the nature of these rock typos has boen indicated, (see rsKt r-vj. (),

Samples are selected from different rock outcrops occurring in the

area. They include granite, microgranite resembling alaskite, diorite and

pink granite gneiss. These were analysed for all the fourteen major consti-

tuents. The analytical data were recalculated as percentage values for

plotting on Al SF diagram as proposed by Osdnn (see Johannsen, 1962), where

S = Si02

Al = Al^Og

F = CaO + FeO + MgO - C

C = (AlgOg - A)

The total of S + Al + F = 100

The diagram shows that the points for granite (pink), microgranite

and diorite of the northern part of the belt fall in the igneous field while

the point for granite gneiss (pink) of the southern part of the belt falls

outside the igneous field. This indicates that granite of the northern part

near Gotro village is an intrusive igneous rock. The granite gneiss of

the southern part appears to be of non-magmat-ic origin.

50 60 70

P e r c e n t S j 0 2

T E X T F I G . N 0 . 2 VARIATION DIAGRAM

- 69 -

Metamorphic rocks and dolerite

An attempt has also been made to study the petrochemistry of meta-

morphic rocks and one dolerite sample of the area. Firstly, the variation

pattern of different oxides with respect to SiOg has been considered and

secondly, the weight percentages of different oxides are plotted on A.C.F.

diagram for determininq the original nature of the rocks.

Five rock samples were selected and analysed like granites and

granitic rocks. The samples include quartzites, schist, epidosite and

dolerite. The determined analytical results were taken up for the two-fold

study.

Variation pattern of oxides in metasedimentary and igneous rocks

when plotted against silica (SiOo);

The variation pattern of different oxides was studied in order to

determine the chemical behaviour of major elements in various rock types.

The oxide percentages were plotted against SiOg percentages graphically and

the observations made thereby are summarised below.

The SiOg percentage varies from 39.71% (epidosite rock) to 83.62%

(quartzite). It was observed that generally where silica (SiOg) was low

(39.71fo), the percentage of CaO (22.05%), kl^O^ (20.97%) and FepOg (10.70%)

were high while the contents of the other oxides were invariably Idw. Where

silica was high (81.83%), alumina (AlgOg) continued to be relatively higher

(8.31%) while the other oxides were generally having low values. In the case

of garnetiferous quartz-chlorite schist, AlgO^ and ^6203 were appreciably

higher as compared to the other oxides. The dolerite sample was found to

have relatively higher content of AlgOg, CaO and MgO.

l A

^ « ^

^ r - ^ /

y I I B

/ \

/

2 J^ /

• Sample

T E X T F IG .N0.3 A C F DIAGRAM

- 70 -

It was observed that the variation pattern was not simple and the

oxides did not form smooth curves when plotted against silica percentages.

Thus, they do not appear to have been derived from the common parent

material. It indicates the possibility of more than one suite of original

material which recrystallised and gave rise to the present rock types.

Analytical results plotted on A.C.F.diagram to indicate parent material(segT-f.g.sj

The petrochemistry of these rocks was further studied on A.C.F. diagram

with a view to trace out the original nature of the existing rocks. The

A.C.F. diagram was developed by Eskola (see Winkler, 1965), which allows

the representation of many rocks of not too unusual composition and having

an excess of silica. The diagram is divided into different areas, each of

which represents the area of a particular set of original material from which

the corresponding rocks have been derived. The specifications of each area

are as follows:

lA - Al-rich clays and shales

IB - Clays and shales either free of carbonate or containing upto 35% carbonate. Between arrows: marls containing 35-65% carbonate,

II - Greywaekes

1 - Ultrabasic rocks,

2 - Basaltic and andesitic rocks.

The analytical results were plotted on A.C.F. diagram after recal-

culating the percentage values of oxides where:

A = (AlgOg) + Fe203 - (Na20) + (KgO)

C = (CaO) - 3.3 (PgOg)

F = (MgO) + (MnO) + (FeO)

- 71 -

The total, of A + C + F = 100%, as they are expressed in terms of

molecular percentages.

The points fell on different areas in the diagram and the parent

material recorded with its help is shown below:

S.No. Sample No,

1

2

3

4

5

HR3M

FR.T 4

MR W

NR3E

Existing metasedi-mentary/igneous rock

Amphibole quartzite

Garnetiferous quartz-chlorite schist

Epidosite

Felspathic quartzite

Dolerite

Parent material recorded

Greyivackes .

Clay and shales free from carbonate.

Clay and shales containing upto 35% of carbonate.

Clay and shales free from carbonate.

Basaltic or andesitic rocks

The above observations are in confirmity with the previous results

available from the oxide variation diagram which indicates that the original

materials of these rocks were of more than one kind.

Chapter - V

GEOCHEMISTRY AND DISTRIBUTION OF TRACE EIEMENTS IN ROCKS.MINERALS AND SOILS

General statement

The general recognition of the trace elements is not of recent

origin. Earlier workers particularly, in the beginning of the 20th

century, have emphasized the significance and the distribution of trace

elements in geological materials. Washington (1913) while! discussing the

distribution of the elements in the earth's crust, described that the

minor elements iwere not only related to the rock types but also to the

major elements constituting the rock. Vogt (1918) and Buddington (1933)

pointed out certain complications in the distribution of the trace elements.

In recent years, vast knowledge has accumulated regarding the

geochemistry of the trace elements. Colossal work is being done on the

distribution of trace elements in igneous rocks and their geochemical

behaviour during the fractional crystallization of magma. Goldschraidt

(193T), one of the pioneer workers in the field of geochemistry, has made

certain useful observations regarding element distribution in rocks and

minerals and proposed a geochemical classification of the elements based

on their chemical affinity. He observed that the elements indicated

preference to enter into an iron phase, sulphide phase and a silicate

phase, and classified them as siderophile, chalcophile and lithophile

elements respectively. Shand (1947) proposed the term thiophile

- 12 ^

- 73 -

substituting the terra chalcophile. Goldschmidt (1937) found that the dis-

tribution of the chemical elements in these phases depended on the

electronic configuration of their atoms. Further, he assumed that mutual

replacement (diadochy) of ions in magmatic minerals was purely ionic. He

explained certain interesting interionic relationships on the basis of

ionic radii and charge. In fact, the concept of ionic radius was first

given by Bragg (1937), who found that when two ions come closer to each

other, a repulsive force is generated and which prevents them to come

closer than a certain limiting value of interatomic distance. He defined

this effective distance as a characteristic radius of each ion.

A con^jrehensive study led Goldschmidt to propose three basic rules

governing the distribution of elements in rocks and minerals. The first •

rule is based on his own observation while the rest two were derived from

inverse square law of electrostatic attraction applied to ionic lattices.

Recent advances in geochemistry revealed that the Goldschmidt's rules

needed modification. Greater emphasis has now been given on the signi-

ficance and the nature of chemical bonding. According to Fyfe (1951),

partial covalent bond in zinc compounds brings certain departures from the

laws governing isomorphism. Ramberg (1925), Shaw (1953) and Ahrens (1953)

were of the opinion that chemical bonding could explain for most of the

geochemical relationship of elements during crystallization.

Ringwood (1955a) used electronegativity as "an indicator of bond

type in minerals and rocks". The concept of electronegativity was

originally given by Pauling (1955), who defined it as "The power of an atom

- 74 -

in a molecule to attract, an electron unto itself". Pauling (19<}6) stated

that when two atoms of similar electronegativity are joined by a bond, it

would be a covalent bond. But when there is a difference in electronega-

tivity in the two atoms, the shared electron will be pulled closer by the

atom having a higher electronegativity. This results in creating an ionic

component into the bond. When the difference in electronegativity is

greater, the bond will be more ionic.

Ringwood (1955a), following Fyfe (1951), applied electronegativity

to the distribution of trace elements and proposed the following rule:

"Whenever diadochy in a crystal is possible between two elements

possessing appreciably different electronegativity, the element with the

lower electronegativity "will be preferentially incorporated because it

forms a stronger and more ionic bond than the other".

The rule satisfactorily applies to such cases in which the difference

in the electronegativity is more than 0.1.

Ringwood (1955a) also favoured the use of ionization potential,

suggested earlier by Ahrens (1953) and Goldschmidt (1954), as a possible

replacement of electronegativity criteria.

Ringwood's (1955a) modifications to Goldschmidt's rules was

criticised by Curtis (1963) and others because they found it difficult to

explain the behaviour of elements when ionic radius and/or charge and

electronegativity act in opposition. Nockolds (1966) also felt this

difficulty and pointed out that "bond length to oxygen may play an equally

important part and need consideration also".

- 75 -

Further, the distribution of elements in a crystal structure"

during the fractional crystallization is also governed by the geometric

arrangement of atoms (see Krauskopf, 1967). «

The geochemistry and distribution of individual elements has been

discussed in the foregoing description in the light of the above cited

work.

Copper iji rock$ and mineyals

Copper is a strongly chalcophile element. It occurs chiefly as

sulphides. Small amounts of copper have also been reported from the

silicate phase. Buddington (1927) reported that traces of Cu were commonly

associated with diorites. Sandell and Goldich (1943) observed that Cu has

a greater tendency to be enriched in the basic igneous rocks. According

to them acid igneous rocks have about l/lO of Cu content as compared to

the basic igneous rocks. Rankamar; and Sahama (1950) stated that Cu largely

occurred as sulphide in most igneous rocks. Wager and Mitchell (1951) have

experimentally shown that during the earlier stages of crystallization of a

basic magma, copper being free.would be incorporated in the silicate minerals.

Wager ^ ai. (1957) found chalcopyrite in the lower layered rocks at

Skaergaard.

The granites and granitic rocks of the Khetri Copper Belt have Cu

content varying from 10 to 48 ppm (20 ppm, Vinogradov, 1962). The higher

concentration is generally in the gneissic variety. The quartzites, schists

and phyllites in general show anomalous values particularly those near the

mineralized zone. The dolerites also have indications of copper mineralization

- lb -

and show values varying from 10 to 445 ppm (B7 ppra, Turekian and Wedepbhl,

1961). The separated ferroraagnesian minerals show preferable concentration

of Cu as compared to felsic minerals.

Copper is the chief element of ore complexes. The chemistry of its

being accommodated in the silicate phase, and later concentrating in the

residual magma is discussed below.

It is well known that copper has a strong tendency to concentrate

in residual magmas and precipitate as chalcopyrite. The reason being that

during the crystallization of a magma Na^ (0.98A°) in the plagioclases

comouflages Cu^ (0.96A°). Similarly in the ferromagnesian minerals, F e ^

(0.74A°) camouflages C u ^ (0.72A°) although both the univalent and divalent

I I

copper have ionic radii less than the respective elements, Na and Fe .

Goldschmidts' rules fail to explain such a behaviour.

Bingwood (1955a) explained this anomaly on the basis of electronega-

tivity. He compared the electronegativity of Cu^ (1.8) and Na^ (0.9) and

pointed out that Cu^-0 bond would be weaker as compared to the Na^-0 bond.

Similarly in the case of Cu"'"'" (2.00) and Fe"*^ (1.65), the Cu-0 bond would

be weaker as compared to the Fe^^-0 bond. Therefore, as a rule the elements

forming stronger bonds with oxygen will be preferably incorporated.

Copper in residual soils

The geochemical behaviour of copper during the formation of residual

soils is not well worked out. Generally the copper contents in the residual

soils are less than the parent rock.

- 77 -

It is also known that among the ferromagnesian minerals which are

the chief host for Cu, biotite is usually more resistent to chemical

weathering than hornblende (see Goldschmidt, 1954). It also indicates

that the ferromagnesian minerals formed at a higher temperature are more

susceptible to chemical weathering than those formed at a lower temperature

(see Krauskopf, 1967).

Residual soil samples of Khetri in case of granites and granitic

rocks and schists and phyllites generally show higher content of metal

than the parent rock while in case of quartzites the case is reverse. This

anomaly has been discussed in the foregoing pages where a comparative study

of the primary and secondary dispersion patterns has been made.

Lead in rocks and minerals

Lead was found to concentrate mostly in the acid igneous rocks.

Sandell and Goldich (1943) found that the acid rocks have twice as much

lead as the basic rocks. Hevesy (1931) reported that the lead content in

normal granitic rocks is six times greater than that of gabbros and similar

rocks. Goldschmidt found 5-50 ppm of Pb concentrating in normal granites.

According to Wedepohl (1956) and other workers, among feldspars, microcline

in pegmatites often shows maximum lead concentration. The enrichment of

lead in the late syenite differentiates has also been reported by some

workers. Apatite is a good host and generally has upto 50 ppm. of Pb. The

radiogenic Pb usually remains associated with its parent elements.

Lead has a controlled dispersion in all the samples of the belt and

- 7B -

the values range from 10-126 ppm. Among igneous rocks in general, pink

granites and pink granite gneisses gave values upto 85 ppm (20 ppm,

Vinogradov, 1962) while dolerites record upto 69 ppm of Pb (8 ppm,

Vinogradov, 1962). Quartzites, schists and phyllites both from and away

the mineralisation zone show a limited range of dispersion of Pb. Even

the sulphide ores do not record abnormal values. Ferromagnesian minerals

show enrichment in Pb. The felsic group (quartz + feldspars) also gave higher

values.

Pb is a chalcophile element and an element of ore complexes. The

factors governing its capability to crystallize as sulphide or enter

into the silicate phase are discussed below.

Generally it is the belief that Pb preferably occurs in the

potash feldspars (5-50 ppm) of silicate rocks. Goldschraidt (1937) was of

the opinion that lead could possibily replace K , Sr , Ba and to some

extent C a ^ also. Since the ionic radius of Pb (1.20A°) is smaller and

the charge is higher than K (1.33A®), obviously Pb can replace K^ from

early formed potash-minerals (see Goldschmidt, 1954). But other workers,

viz., Rank'sma and Sahama, 1949; Nockolds and Mitchell, 1948 suggested

that Pb could not enter potash lattice as efficiently as k"* but could

concentrate in the residual magma.

Ringwood (1955a) qualified these observations by explaining them

on the basis of their electronegativity as follows:

The electronegativity of Pb is 1.8 while that of k"* is 0.8. The

Pb-0 bond is therefore, more covalent and thus weak as compared to K-0 bond

- 79 -

in potash-minerals. Therefore K^ enters with relatively greater ease into

potash-minerals while Pb concentrates in the residual magma.

It is therefore evident that primary lead exists mostly in the

sulphide state on account of its great affinity towards sulphur. Either

it may occur as a primary sulphide mineral, viz., galena or formed by the

interaction between the Pb present in the silicate lattice of feldspars

and the available sulphur compounds.

Lead in the residual soils - Not much is known about the geochemical

behaviour of lead during the process of weathering of silicate rocks.

Whatever information is available about the behaviour, of the metal, it is

largely from its association with the sulphide ores. It is, however, known

that lead sulphide in the zone of oxidation changes to Pb SO^. Frequently

Pb COg is also formed by its reaction with available COg.

The soil samples of the area under study,in general, show low values

of dispersion of Pb than the rock samples. Its geochemical behaviour

during chemical weathering has been discussed in the foregoing chapter of

dispersion patterns.

Zinc in rocks and minerals

The occurrences of zinc in rocks and minerals in the form of

sulphide and silicate have been reported by s ^ ^ j ^ l earlier workers. Clarke

and Washington (1924) reported a value of 40 ppi^^^Zn in the upper

lithosphere. Newhouse (1936) did not find any sphalerite in the igneous

rocks. Sandell and Goldich (1943) found that the concentration of zinc

I

in a basic rock was twice as much as in an acid rock. Lundegaordhs(1948)

- 80 -

investigations show that zinc concentrates in granodiorites in preference

to gabbros and granites. He also found out that zinc was closely asso-

ciated with the amount of biotite in granitic rocks.

Zinc in the granites and granitic rocks of this area has dispersion

values upto 82 ppm (60 ppm, Vinogradov, 1967) except in a few cases. Quartzites

have less Zn content than the schists and phyllites. The various rock samples

from the Khetri copper mines show normal values for Zn while the sulphide

ores have higher content. Dolerites in general record values upto 340 ppm

(130 ppm, Vinogradov, 1962). Among mineral fractions, ferromagnesians are

found to be the chief hosts of Zn,

Zinc is a chalcophile element and an element of ore complexes. It

forms sulphides and also shows a tendency to enter into the silicate

lattice. Its geochemical behaviour in both the cases is discussed as follows:

The ionic radius of zinc (0.74A°) is very much similar to those of

the elements in the iron-magnesian group. It is, therefore, expected that

zinc should be able to replace M g ^ (0.66A°) and F e ^ (0.74A'') contents of

all such mafic minerals. Investigations have shown that olivine and

pyroxene have distinct traces of zinc, while higher concentrations were

recorded in amphiboles (200 to 2,000 ppm) and biotites.

It is now known that high co-ordination exists when zinc is bonded

to fluorine (see Ahrens, 1964). Further it was observed that amphiboles and

biotites have some water and fluorine. Ahrens (1964) pointed out that it

might be due to the presence of fluorine in these minerals that zinc co-

ordination tended to be octahedral and it replaced Mg and Fe easily,

- 81 -

resulting thereby concentration of zinc.

The concentration of zinc in the residual magma was explained by

Ringwood (1955a) on the basis of electronegativity. The electronegativity

++ ++ of Zn is 1.7 while of Fe is 1.65. Obviously more of zinc than Fe will

be concentrated in the residual magma. Zinc sulphide has also a marked

capacity of capturing traces of other metals. the

Zinc in the residual soils - Little is known about/geochemistry of zinc in

the process of chemical weathering. The present knowledge is, however,

largely based on the weathering of primary rocks in the oxidation zones

of zinc ore deposits. The products formed are usually sulphates and to a

certain extent, carbonate of zinc.

The geochemical behaviour of zinc in the residual soils of the area ,

under study,shows that during chemical weathering it is generally more

affected than Cu. Its details have been discussed in the foregoing chapter

of dispersion patterns.

Nickel and cobalt in rocks and minerals

The distribution of nickel in rocks and minerals was first studied

by Vogt (1923). According to Clarke and Washington (1924) the igneous rocks

were found to have 0.001 per cent of Co and 0.02 per cent of Ni. Newhouse

(1936) found that femic rocks have more sulphide minerals than salic rocks.

Later Sandell and Goldich (1943) determined Co:Ni ratio as 3:10 for upper

lithosphere, while Goldschmidt (1958) gave a ratio of 4:10. Wager and

Mitehell (1951) investigated ferromagnesian minerals of early crystallisation

to be enriched in Ni. Nockolds and Mitchell (1948) while working on some

- 82 -

Caledonian plutonic rocks, confirmed the observation of Vogt (1943) that

N1 has a tendency to concentrate In the early magmatic differentiates.

Turekian and Carr (1960) found that Cr and Ni were generally higher in

early-formed pyroxene crystals than in the later ones in a particular

extrusive or intrusive cycle.

Cobalt was reported to be usually concentrating in the ultrabasic

rocks. Sandell and Goldich (1943) generally found the granites to have

less than 1 ppm cobalt. Their observations were largely based on the

granites from Minnesota. Nockolds and Mitchell (1948) found the value of

Co to be below 15 ppm in granites and granodiorites. Lundegaordh (1945)

and Du Rietz (1955) found the values of Co to be varying from 50 to 200

ppm in some ultrabasic rocks of Sweden. Turekian and Carr (1960) on the

basis of their investigations on Stillwater complex, found Co to be follow-

ing very closely only Mg in granitic rocks.

The sulphide minerals generally accommodate an appreciable amount

of Co and it enters with greater ease in pyrite and pyrrhotite than chalco-

pyrite (see Gavelin and Gabrielson, 1947). An interesting observation was

made by Hegemann (1943) who observed that the amount of Co in the sulphides

was directly proportional to the degree of metamorphism of the sulphide

deposits.

The granites and granit ic rocks of the area show a maximum dis-

persion of 60 ppm of Ni (8 ppm, Vinogradov, 1962) and 8 ppm of Co (5 ppm,

Vinogradov, 1962). The granite gneisses in general give higher values for

- 83 -

both the elements. Dolerltes have values ranging from 18 to 140 ppra

(130 ppm, Turekian and Wedepohl, 1961).

In the separated mineral fractions of granites and granitic rocks

and host rocks of copper ores, both Ni and Co show concentration in the

ferromagnesian phase. The separated sulphide ores have anomalously higher

values for the Ni and Co contents. Ni was found to be essentially concen-

trated (upto 621 ppm) in the pyrrhotite. The Ni/Co ratio in the separated

chalcopyrite and pyrrhotite fractions is 1.23 to 1.49 and 1.5 to 1.70

respectively.

Both the elements show a consistency in their dispersion and are

generally associated with the copper ores. Thus they may be used as

indicator elements of the regional geochemical background in the area under

study.

In igneous rocks, the Co and Ni are usually present in the silicate

structure. In the absence of any sulphide mineral, the silicates usually

host all the Co and Ni contents of a rock and Co content in the granitic

rocks increases at the expense of Ni (see Goldschmidt, 1958).

Generally, it is believed that the ionic radiiti of Ni^^ (0.69A®)

and Co^"^ (0.72A°) being very near to those of Mg"*^' (0.66A°) and Ft^(0.74A°),

either Ni or Co or both should be able to replace one or both of the latter

metals. Goldschmidt (1944) suggested that Ni is likely to be enriched in

the Mg-bearing minerals because Ni-0 bond is stronger than Mg-0 bond on

account of its more covalent nature. But the idea did not sustain the

criticism of Ringwood (1955a) who stated "that the effect of increased

- 84 -

covalent bonding is to weaken the bond". He (1955a) pointed out that since

2+ 2+ the radius of Ni is smaller than Fe , the former could substitute the

2+ latter and further Fe-0 bonding is weaker than Ni-0 bonding and Fe is more

2+ 2+ mobile than Ni. This may render Fe to be easily substituted by Ni .

Earlier Ahrens (1953) attempted to explain it on the basis of his

field function concept. He suggested that "when competing for a site in

2+ 2+ a growing crystal Ni is likely to arrive and perhaps enter before Fe

2+ 2+ and Mg because the positive field about Ni is greater than that associated

with the other two ions".

Co has generally been found to be concentrated in the mafic minerals.

The ionic radii of Co^^ (0.72A°) and Fe^\o.74A°) have such a small difference

that a close relationship between these two elements should exist. But

there is a little variation in Co/Mg ratio as compared to Co/Fe ratio as

one passes from basic to acid rocks (see Carr et.ai., 1961). Thus a linear

relationship between Co and Mg was envisaged. The same authors also reported

that the Co content in high-calcium granites was generally high (6.6 ppm)

and low in low-calcium granites (0.88 ppm).

Chromium in rocks and minerals

Usually the ultrabasic rocks have a high concentration of chromium.

Wager and Mitchell (1945) found 1,000 gms/ton Cr in olivine from a gabbro-

picrite. Lundegaordh's (1946) investigations show that Cr has a tendency

to be enriched in forsterite-rich olivine. The fayalite-rich olivines were

found to be deficient in Cr. Nockolds and Mitchell (1948) while working

on some Caledonian plutonic rocks, found Cr to be concentrated in the early

- 85 -

differentiates of the magma. Carr and Turekian (1961) found that the

biotites in granitic rocks were good hosts for Cr (190 ppm). They also

found that the magnetites separated from high-grade metamorphic rocks from

the Adirondacks as well as phyllites have less than 3 ppm Cr.

Chromium generally has a low dispersion in the granites and

granitic rocks of the belt except in d few cases where the value is as high

as 90 ppm (22 ppm,Carr, ^ aj,!. 196lO.Dolerites give anomalous values up< to

580 ppm (170 ppm, Turekian and Wedepohl, 1961). Quartzites record lower

values as compared to the schists and phyllites (upto 245 ppm). The rock

and ore samples from mines and the separated mineral fractions do not have

unusual dispersion. Ferromagnesians show relatively higher concentrations.

Chromium has been taken as an element of the regional geochemical

background because of its chalcophile character and regularity of dispersion

in the area. The chemistry of its ionic replacement is discussed belmv.

It has been generally observed that Cr is preferably incorporated

in the silicate phase. Its chalcophile character cotnes into play only when

oxygen is either low or absent (see Goldschmidt, 1958). It occurs as an

oxide as well as silicate in igneous rocks.

3+ 3+ 3+ According to Goldschmidt (1958), Cr may replace Fe and Al

diadochally. Wager and Mitchell (1951) found that Cr "*" (0.63A®) was

3+

camouflaged by Fe ( I48O) during fractionation of magma. Therefore, high

concentration of Cr in the ferromagnesian minerals cannot be explained on

the basis of simple ionic radius. Ringwood (1955a) observed that the smaller

3+ 3+ electronegativity of Cr (1 . 6 ) than that of Fe (1.8) might be responsible

- 86 -

for such a behaviour. Carr and Turekian (1962) observed a good correla-

tion between Cr and Mg contents in a granitic rock. Further, they found

that Cr contents in high-calcium granitic rocks were 12 to 22 ppm, while

in low-calcium granitic rocks were 3 to 4 ppm.

Cadmium, lithium and silver in rocks and minerals

These elements do not show any significant dispersion quantitatively

in the samples of the Khetri copper belt. Their geochemical behaviour has

been briefly described here.

Cadmium - The geochemistry of cadmium is not studied much by the research

workers. It has a strong chemical affinity for sulphur. Sandell and Goldich

(1943) found that absolute amount of Cd is higher in gabbroid rocks than in

granites. Cadmium is usually present in sphalerite crystals. It has been

investigated that in the early magmatic sulphides the amount of Zn and Cd

are low. These two elements go to the late differentiates and form subs-

tantial consituents of late crystallizing ore fluids which intrude the

neighbouring rocks in the form of apophyses. Cadmium could not be esti-

mated in the rocks of the Khetri copper belt because of its low traces.

Lithium - Lithium is an alkali metal but in many respects it follows Mg.

The Li:Mg ratio shows a steady increase in the late crystallizing rocks

and minerals. Strock (1936) who made a careful study of this ratio for

various igneous rocks suggested that this element could be used as an index

to the stage of differentiation reached by a rock. During fractional

crystallization the concentration of Li ions increases in the liquid

phase while that of Mg ions decreases and thus favourable conditions for

- 87 -

Li to enter into early crystallizing ferromagnesian minerals. The element

is more enriched in the granitic rocks than syenites and nepheline syenites.

Generally the granite gneisses of the Khetri copper belt show little

content of Li. Schists and phyllites also have limited dispersion while in

quartzites it is not detectable. Dolerites and the mine- samples also have

insignificant traces of Li.

Silver - The geochemistry of silver is known considerably. It is found to

be more connected with the gabbroid magmas than with granites and highly

siliceous rocks. In the case of hydrothermal sulphide deposits Ag, pre-

ferably concentrates in chalcopyrite than pyrrhotite. Its presence and

qualitative assessment indicates the chemical history of the deposit

particularly as regards the temperature of crystallization. It is therefore

used in the present study as an element indicating stage of mineralization.

All the samples of the Khetri copper belt have low traces of silver

which could not be estimated by the Atomic Absorption Spectrophotometer.

- 88 -

Interpretation of Analytical Data

Rocks and ores

The worlf is based on the analyses of granites and granitic rocks

(25 samples), quartzites (31 samples), schists and phyllites (27 samples),

rocks and ore samples from the Madhan-Kudhan and Kolihan. mines (23 samples),

dolerites (8 samples), amphibolites (4 samp3es), pegmatites (3 samples) car-

bonate rocks (3 samples), etc. for trace elements viz., Cu, Pb, Zn, Ni, Cd,

Cr, Li and Ag by Atomic Absorption Spectrophotometer (Perkin-Slmer, Model

303). Additional determination for Co was done from the samples of granites

and granitic rocks and also those from the Madhan-Kudhan and Kolihan mines.

Eighty^two residual soil samples of various groups of rocks, viz.,

granites and granitic rocks (21 samples), quartzites (20 samples), schists

and phyllites (25 samples) and a miscellaneous group (16 samples) consisting

of dolerites, pegmatites, amphibolites, carbonate rocks, were analysed for

determining the traces of Cu, Pb and Zn, by Atomic Absorption Spectrophoto-

meter (Jarrell and Ash).

The analytical results are plotted on histograms on ppm ranges for

rock as well as residual soil samples. Tlie pattern of arrangement of the

samples in the figures, the epithets used and the points observed to arrive

at certain generalizations are the same in both the cases.

The background values for granites and granitic rocks have been

taken from other workers. For metamorphic rocks and the copper mine samples

- 89 -

the values have been calculated from the determined analytical data as has

been discussed in Chapter VI.

The sample numbers in the figure are arranged according to their

location in the Khetri copper belt. The first sample was taken from the

extreme north while the last sample from the extreme south of the belt.

The epithets used in the interpretation are listed below. They

connote the following order of relative abundance of elements. The same

terminology has been used in Chapter VI:

1. "Insignificant" Below the limit of sensitivity of the instrument.

2 . "Poor /Low/Depleted" Much lower than the background value

3. "Marginal" Within a close range of background value.

4 . "High/abundant/ Much above the background value.

enriched"

5 . "Anomalous" Distinctly above the threshold value.

6 . "Highly anomalous" Many times higher than the background value.

Rocks and ores (see Text Figs.4 & 5).

Granites and granitic rocks :

1. There is a general depletion in the Cu, Cr, and Li content and

enrichment in Pb, Zn, Ni, while Co, Cd and Ag have insignificant values.

2. Cu is rarely high (38 ppm). Dispersion of Cu in the granite gneisses

of the southern part of the belt is relatively higher than in the granites

of the northern part of the same belt.

3. Nl, Zn and Pb show abundance as compared to their respective back-

ground values. Their concentrations are relatively hioh in the oranite

gneisses ©f the southern part of the area.

- 90 -

4. The values for Co in granites vary from 3 ppm to 8 ppm which are

quite significant as very little of Co content was reported from the

granites of other places.

5. The samples having high Cu content have ordinarily higher values

for the other trace elements as well.

6. Pb and Zn show antipathic relationship with each other. Frequently,

where Pb records a high value (70 ppm), the value of Zn becomes correspond-

ingly low (26 ppm), and where the value of Pb is comparatively low (15 to

25 ppm) the value of Zn is usually high (95 to 200 ppm).

7. Ni and Co also have antipathic relationship. Where the values of

Ni are 10 ppm, the values for Co are as high as 8 ppm. Similarly where

the value of Ni is high (42 ppm) the value of Co goes down (3 ppm).

8 . Cr gives anomalous values in the case of two samples of the northern

part of the belt. Samples having higher Cr contents show enrichment in Zn

and Ni but rarely in Cu.

9 . Li is confined to a few samples of the granite gneisses only.

There was no distinct inter-relationship among these trace-elements.

Generally Ni and Co show antipathic relationship, Cu to some extent has

sympathetic relationship with Zn. Pb and Zn also show antipathy in some

cases.

Ouartzites

1. There is a general enrichment in Cu, Pb, Ni and Cr, and depletion

in Zn, while Cd, Li and Ag have insignificant values. All the above trace

elements show scattered dispersion all over the belt.

- 91 -

2. Cu gives very high values (770 to 1160 ppm) but only in a few

exceptional cases. Where cu shows anomalous values, Pb is also high (36

to 44 ppm) whide Zn remains low (20 to 21 ppm). Ni and Cr are either low

(except in one case) or absent.

Where Cu is low or insignificant, Pb and Zn are usually low while

Ni and Cr show appreciable enrichment.

3. The samples of the northern part of the belt, particularly the

amphibole quartzites, show enrichment in Cu and Pb contents and depletion

in Zn, Ni and Cr. On the other hand the samples of the southern part of

the belt (mostly felspathic and massive quartzites) show comparatively low

dispersion of Cu and Pb and enrichment in Cr, Zn and Ni (in order of increas-

ing abundance). There are, of course, a few exceptions to this generalisation,

4. Commonly Pb and Zn .have antipathic relationship, and the value

of Pb concentration is anomalous (74 ppm), Zn is either low (20 ppm) or

insignificant ( < 5 ppm) and where Zn content is high (89 ppm) the value

for Pb becomes low (12 ppm).

5. A sample of amphibole quartzite collected from the quartzite ridge

of Singhana recorded anomalous values for Cu, Pb, Zn, Ni and Cr. It,

however, appears to be an exception.

6. Ni and Cr showed sympathetic relationship in a number of cases,

7. Li in general is insignificant. Only two samples recorded a value

of 12 ppm.

8. Serioite quartzite (pieaJc quartzite> was found to be barren of

any mineralization.

- 92 -

It is evident from the above observations that the trace elements

concerned hardly have any inter-relationship among each other. In some

cases in which Pb and Zn have antipathy Ni and Cr have sympathetic

relationship.

Schi?t$ gnd phyllit^g

L. Generally, Cu, Cr, Pb, Ni, Zn and Li show a general enrichment (in

order of decreasing abundances), Cd and Ag occur in insignificant amounts.

2 . There is a greater abundance of Cu in the schistose rocks than in

the phyllitic rocks. In both cases where Cu is high (125 to 750 ppm) the

value for Zn is low (30 to 57 ppm),Pb is appreciably constant (30 to 46 ppm)

because the fluctuation in values is little. In some cases where Cu is

low (15 ppm) Cr is exceptionally high (245 ppm) and so is the case with

Ni (90 ppm).

3. Generally Cu occurs in greater abundance in the rocks of the

northern part of the belt than those occurring in the southern part barring

only one sample in which Cu is high (750 ppm).

4. Chlorite-schists and mica-schists show exceptionally high concen-

trations. Andalusite-schist also records higher values of Cu (55 ppm),

Pb, Ni and Cr.

5. To some extent Zn and Ni and distinctly Ni and Cr show sympathetic

relationship.

6. Except Cu (to some extent Zn also) none of the trace elements show

selective enrichment in a particular part of the belt. Zn has appreciable

enrichment in the samples NW of Saladipura (90 to 160 ppm).

KHCTRI COPP€R MVCS SAMPLES ICMieoMcrc

1000 500

300

2 00

1000 900

4 00

2 500

i

SampM NO*.

MTMTECTAILI

l e X T FIG. NO. 5

- 93 -

7 . Ni and Cr are more concentrated in the schists and phyllites than

in the quartzites and granites or granitic rocks.

8. Li shows appreciable dispersion in the biotite-schists. But in

general its dispersion is low. Ni and Cr show sympathetic relationship.

Cu has antipathic relation with Zn.

Zn gives higher values NW of Saladipura. Cr show enrichment in the

northern portion of the belt. Ni and Pb have a distinct dispersion all

over the belt.

tOl£ttl_copa.ejL-i!LLtLeg sgmp Igg

The samples include several types of schists and quartzites (host

rocks), amphibolites, dolerites, etc. Some of the ore samples and separated

chalcopyrite and pyrrhotite samples have also been analysed for elements

other than Cu. Copper being exceptionally high in certain cases has been

shown along the full length of the histograms.

1. There is a general enrichment in Cu, Co, Ni, Pb and Cr in the

decreasing order of abundance. Zn occurs in appreciable amounts while Cd

and Ag have insignificant values.

2 . Schists have significantly abundant of Cu content (3^0 ppm). Co,

Ni and Cr are also present in abundance in these rocks.

3. The quartzites have poor concentrations of Cu as compared to schists.

Quartzites have high Co content particularly, the amphibole-quartzite /

(Co, 216 ppm).

4. Phyllites are generally low in Cu (75 ppm) but relatively enriched

in Pb, Ni, Cr and Co. Zn is appreciably low (25 ppm).

- 94 -

5. The amphlbolltes have very low dispersion of Cu (20 ppm) but

indicate higher concentration of Ni (55 ppm) and Pb (45 ppm).

6. Dolerites are relatively high in Cu (45 ppm) and so is the case with

other trace elements as well.

7. The copper ore samples generally have higher concentration of Zn

(250 ppm), Ni (235 ppm) and Co (360 ppm). Cr and Li give poor dispersion

values (15 ppm and < 1 0 ppm, respectively).

8. Commonly, the samples of host rocks with Cu are having higher

contents of Cu give higher values for Ni and Co and low for Zn.

No assessment could be made of the inter-relationship of elements

because of a wide variety of rock types obtained in this section.

Dolerite

1. The samples show general enrichment in Cu, Zn, Ni and Cr content

while Pb and Li are marginally higher.

2 . The values for Cu vary from 10 to 445 ppm showing its higher dis-

persion in the northern part of the belt.

3. Zn does not show any sector of preferential concentration and the

values range from 48 to 340 ppm.

4. Ni contents do not show wide variation (18 to 140 ppm) while Cr

contents have values varying from 10-580 ppm.

5. Both Cd and Ag lie below the sensitivity limit of the instrument

except in one sample.

- 95 -

Pegmatites

1. Pegmatites do not show any abnormal concentration of Cu. The lowest

value obtained is 10 ppm from pegmatites near Papurna and the highest value

is recorded from the pegmatites SW of Chappoli (90 ppm). A sample from

pegmatite vein NW of Madhan-Kudhan mines gave a value of 29 ppm.

2 . Lead content appear to show direct relationship with copper because

the samples having high copper values also show higher dispersion of lead.

3. Zn, Ni and Cr appear to be inversely proportional to Cu and Pb

content.

4. Cd, Li and Ag show values < 5 ppm.

Amphibolites

1. Amphibolites show low dispersion of Cu except in one case in which

the value is 45 ppm.

2. Pb has a consistent dispersion in almost all the samples.

3. Zn values range from 40 to 175 ppm showing a general enrichment.

4. Ni has values almost directly proportional to zinc. The values

range from 30 to 130 ppm.

5. Cr shows poor dispersion except in one case (190 ppm). The values

range from 10 ppm to 190 ppm.

6. Cd, Li and Ag have values < 5 ppm.

Carbonate rocks

]. The values for Cu vary from 10 to 65 ppm. There is no significant

concentration.

ppm lOOO 900 400

2 «« A O 100

O R A N I T E A N D GRANITIC ROCKS

- 1 1 1 . .

RESIDUAL SOIL SAMPLES

OUARTZITES SCHISTS AND P H Y L L I T E S OTHER SOCK T Y P E S

K Z

» o o soo 400

3 500

Ui < 200 X »oo

so 2»

lOOO 900

400

>oo I too

•!••••••••• -rnmAmmrni

i m i h i H L i N M i l i •Ssa-!* giS

T E X T FIG. N O . 6

- 96 -

2. Pb and Zn values appear to be dependent on each other and show

general enrichment,

3. Ni shows variati on from 32 to 66 ppm.

4. Cr has dispersion values ranging from 70 to 100 ppm.

Residual Soils (See Text Fig. 6 )

Granites and granitic rocks - In general, Cu, Pb and Zn show a low dispersion.

Rarel]/^, the Cu content is high and touches a maximum value of 168 ppm. Samples

having higher Cu content usually show depletion in the content of Pb and Zn.

Similarly where Cu gives low values (16 ppm), Zn is usually high (45 to 77

ppm) and Pb is usually low (6 to 13 ppm).

Frequently Pb is more affected by the change in the Cu content and

has a closer antipathic relationship with Cu than with Zn. The relationship is

between Pb and Zn/rather uncertain and, therefore, it does not lead to any

firm generalization.

Sometimes where Pb is high (38 ppm),Zn also records high value

(63 ppm) and on the other hand, where Pb is low (9 ppm), Zn gives high

values (76 ppm). Similarly, where Zn falls to a low value (21 ppm), Pb is

either absent or records a low value (9 ppm). Such departures from any

definite pattern lead to generalise that Pb and Zn relationship is anti-

pathic in some cases and sympathetic in others.

The figure clearly shows that the samples on the left hand side

(i.e., northern part of the belt) give relatively higher values for Cu than

the samples on the right hand side (i.e., southern part of the belt). Further

it was observed that the samples collected from the western margin of an

outcrop had relatively higher values.

- 97 -

Ouartzites - The samples show marked enrichment particularly in the C«

content.

There is a general enrichment of Zn while Pb has a low dispersion

except in one sample of the southern part of the belt (44 ppm).

There is a wide variation in Cu-content. The values ranged from

12 to 610 ppm. Commonly the samples having higher Cu-content (377 to 610

ppm) give relatively low values for Pb (9 to 20 ppm) and Zn (50 to 53 ppm).

Where the value for Cu is low (16 ppm) the value for Zn is usually high

(82 ppm).

Pb and Zn do not show a clear relationship. The values of Pb came

down to as low as 5 ppm while Zn shows appreciable and almost uniform dis-

persion all over the belt. Cu show antipathic relationship with Zn.

It was found that Cu is anomalously high in the samples of the

northern part of the belt.

Schists and phvllites - Schists have higher dispersion in the northern part

of the belt. Phyllites also show appreciable concentration of Cu.

There is a general improvement in the concentration of all the three

elements. Cu shows anomalously high values to a maximum of 1436 ppm where

the values for Cu are higher (364 to 1436 ppm), Pb and Zn have relatively

low values. But such a relationship was not frequent. It was also true

that some samples having a fairly high Cu content (106 ppm) give high value

for Pb (53 ppm) and moderately high value for Zn (45 ppm). Further the

samples having a low Cu content (18 ppm) have higher values for Zn and

Pb (59 and 77 ppm respectively).

- 9B -

An antipathic relation exists between Pb and Zn in the samples

recording low Pb content. But in some other cases where the value for

Pb is high (46 pptn) Zn is generally high (71 ppm).

The samples distinctly show a higher concentration of Cu in the

northern part but it gradually decreases in the schists and phyllites of

the southern part of the belt. The values of Pb are comparatively high

but It has not conceYitrated in any paxticulax part of the belt.

Residual soils of other rock types

The residual soil samples of other rock types include soils of

dolerites, pegmatites, amphibolite and carbonate rocks. A general quantita-

tive assessment is made in the following way.

There is an appreciable concentration of all the three elements in

the samples. Cu gives appreciablly high values sometimes as high as 702 ppm.

Where Cu gives high value (702 ppm) usually the value of Pb is low (9 ppm),

where Cu is low (13 ppm), both Pb and Zn have higher values (63 and 65 ppm.

respectively).

The dolerites have exceptionally high Cu value (702 ppm). Pegmatites

do not show any enrichment. The amphibolites have comparable Cu content

(30 ppm) though rarely the values of Zn are high (73 ppm). Carbonate rocks

clearly show enrichment in the Zn content (106 to 142 ppm).

Based on a comparative study of the residual soil samples of granites

and granitic rocks, quartzites, schists and phyllites and the other rock

types, an overall picture of the trace element distribution is presented as

follows ;

- 99 -

1. There is a gradual increase in the Cu traces from granites to

quartzites and from quartzites to schists and phyllites.

2 . The variation is distinct in the samples of the northern part of

the belt. The granites have low dispersion of copper. Felspathic quartzites

occurring in contact with granites are also poor in Cu, while amphibole

quartzites and phyllites occurring in contact of the schists show appreciable

increase of Cu-traces. Schists in turn give highly anomalous values, for

C u . Other rock types in exceptional cases have high content of Cu.

3. Pb has a low dispersion in granites and granitic rocks and poor in

quartzites. Schistose rocks and phyllites indicate appreciable abandance

of lead. The other rock types also show some enrichment in Pb contents.

There is no such area in the belt which can be said to have any sort of

preferential concentration of Pb.

4. Zn records a marginal fluctuation (as compared to the background

value) in all the samples. In most cases it shows an antipathic relation-

ship with Cu. In general Zn shows a controlled dispersion.

FERROMAGNESIAN GROUP FELSIC GROUP

ppm 400

300

200 100 30

23

M l ffin

400

300

200 100 SO

25

0 l a i HBciEian

NOT DETECTABLE

400

300

200 100 30

23

0

Sampk Nos

I Sample Nos

-HORNBLENDE

• ••Ji l l - . SimptcNos

-BIOTITE

NOT detectable

Sample Nos

I OUABTI k FELDSPARS

TEXT FIG. NO. 7

- 100 -

DISTRIBUTION OF SOME TRACE ELEMENTS IN THE SEPARATED MINERAL FRACTIONS OF GRANITES AND GRANITIC

ROCKS AND HOST ROCKS OF COPPER ORES

Granites and granitic rocks (see Text Fig.7 )

Ten samples were selected from the different outcrops of granites

and granitic rocks of the area. Their ferroraagnesian and felsic mineral

fractions were separated and analysed for traces of Cu, Pb, Zn, Ni, Co

and Cr and the results were plotted in histograms.

The ferromagnesian minerals viz., epidote, hornblende and biotite

were separated as more or less pure tnonomineralic fractions (about 95 per

cent pure). Only in two samples (No. 1 and 2) in which hornblende and

epidote coexist, they had to be separated from one another. The results

of analyses are plotted separately. Quartz and feldspars have been collected

together as a felsic group for analyses.

All plotting has been done on ppm values. The serial number of the

samples in the figure is with r e f e r e n c e to their location in the belt. For

example Sample No. 1 belongs to the extreme northern part while Sample No.10

to the extreme southern part of the belt where such rocks are exposed.

A quantitative assessment is made in two ways. Firstly, a general

trend of elements in the ferromagnesian and felsic group is considered and

their order and preference of concentration are discussed. Secondly, the

behaviour of these trace elements in each rock sample and their variation

in the belt is considered.

- 101 -

General assessment

Cu, Pb, Zn, Ni, Co and Cr are preferably concentrated in the ferromagnesian

phase.

Cu entered both hornblende (5B ppm) and biotite (62 ppm) with almost equal

ease. This was particularly observed in the samples of hornblende-granite

gneiss and biotite-granite gneiss from the southern part of the belt. In

general Cu has a greater concentration in hornblende than biotite and rela-

tively more In biotite than epidote (38 ppm).

Cu in alJ the samples of the felsic group reads insignificant values.

Pb, 2n, Ni and Cr are concentrated in hornblende, biotite and epidote in

order of decreasing abundance.

Zn is exceptionally high in hornblende (415 ppm) and biotite (295 ppm) in

the southern part of the belt.

Pb (10 to 29 ppm) and Zn ( 3 to 47 ppm) value are quite low in all samples

of the felsic group.

Ni and Cr to some extent show a consistency in being accumulated in the ferro-

magnesian fractions. They preferably concentrate more in hornblende than

in biotite and least in epidote.

Co behaves differently.. It has slightly greater concentration in biotite

(69 ppm) than hornblende (60 ppm) and least concentration in epidote (29ppra).

Ni has a very low accumulation (6 to 13 ppm) in the felsic group.

Co and Cr are characteristically absent in all samples of felsic group.

MrlhSIO-parl

1. Hornblende - Where Cu is high, the values of Pb, Zn and Ni are low and

where Cu is low,the values of Pb, Zn and Ni are high. Co and Cr remain

low in both the cases.

2 . Epidote - Where Cu is high, the values of Pb, Zn - and Cr are high, while

Ni and Co are low. Where Cu is low, the values of Pb and Cr are low while

S E P A R A T E D MINERAL F R A C T I O N S O F H O S T R O C K S OF C O P P E R O R E S

too

300

200

100

50

25

0

IJJ_L1JJ_JlJ_L-L1-a b o b a b c o b c a b c a b (

O U & R T Z A N D F E L D S P A R S

B I O T I T E

T E X T F I G . N 0 . 8

- 102 -

Zn, Ni and Co are high.

3. Biotite - Where Cu is high, the values of Pb, Zn, and Co are low, while

those of Ni and Cr are moderate. Where Cu is low the value of Pb, Zn and

Co are high while Ni and Cr continue to record intermediate values.

/

Sourthern part

Hornblende - Where Cu is high, the value of Pb is low. Zn shows an

exceptionally high value while Cr, Ni and Co are appreciably high.

2. Biotite - Where Cu is high, the value of Zn is intermediate. Pb and Cr

give low values while Ni and Co are relatively low. Where Cu is low, the

values of Pb, Ni and Co and Cr are high, while Zn continues to read inter-?

mediate values.

Felsic group

The felsic group does not show any specific pattern. The values of

Cu, Pb, Zn and Ni are almost insignificant and do not indicate any relation-

ship with one another.

Host Rocks (see Text Fig. 8)

Six samples were selected from the host rocks of copper ores. Three

samples were collected from Madhan-Kudhan copper mines and three samples

from Kolihan copper mine. The separated mineral fractions (95 per cent

purity) include garnet, amphibole, biotite and quartz plus feldspars

(felsic group). They were analysed for traces of Cu, Pb, Zn, Ni, Co and

C r . The analytical results were plotted in histogram.

- 103 -

General Assessment - The following assessment has been made considering the

points as stated in the case of granites and granitic rocks.

Cu, Pb, Zn and Co show preferable enrichment in amphibole. Ni and

Cr are relatively higher in biotite. Garnet have comparable concentration

of all the above trace elements. Felsic group has the least metallic

content.

Copper is predominently concentrated in amphibole (363 ppm) than

garnet (330 ppm) and biotite (313 ppm). The garnets of garnetiferous

biotite-schist (Kolihan copper mine) have low Cu content (85 ppm) whilfe

garnets of the garnetiferous quartz-chlorite schist of Madhan-Kudhan mine

give higher content of Cu (330 ppm). The amphibole from amphibole quartzite

of the Kolihan mine contain 295 ppm of Cu while that of Madhan-Kudhan mine

records 363 ppm of Cu.

The felsic group does not have any Cu content in all the samples.

Lead and zinc are generally concentrated more in amphibole than

biotite and least in garnet.

Nickel is high in biotite (6R to 80 ppm) than in amphibole (58 ppm,

amphibole and chlorite) and marginally low in garnet (48 to 55 ppm),.Amphibole

from amphibole quartzite show values varying from 28 to 36 ppm of Ni.

Cobalt has a higher concentration in amphibole (115 ppm, amphibole +

chlorite from garnetiferous quartz chlorite schist) than in garnet (72 to

94 ppm) and biotite (59 to 78 ppm). The garnet from garnetiferous quartz-

chlorite-schist have relatively more Co content (94 ppm) than in garnet from

the garnetiferous biotite-schist (45 ppm).

- 104 -

Chromium is markedly higher in biotite (165 to 250 ppm) than in

rest of the separated mineral fractions. Amphibole (amphibole + chlorite)

are more enriched in Cr content (132 ppm) than in garnet (68 to 121 ppm).

The garnet from garnetiferous biotite-schist gives higher values (121 ppm)

of Cr than the garnet of garnetiferous quartz-chlorite-schist (96 ppm).

Generally Pb, Zn, Cr, Co and Ni are present in low concentrations

in the felsic group and they occur in decreasing order of abundance.

Relationship of other trace elements with copper in individual

minerals

1- Amphibole - (sometimes with cholrite). Where Cu is high Pb, Ni, Co and

Cr are low.,while Zn is high. Where Cu is low Pb, Ni, Co and Cr are generally

high^while Zn is low.

2 . Garnet -

a) Garnet from oarnetiferous quartz-chlorite schist - Where Cu is high

Pb and Zn are low, while the values of Ni, Co and Cr are high. Where Cu

is low,the values of Pb and Zn are high, while Ni, Co and Cr generally

show low concentrations.

b) Garnet from garnetiferous biotite-schist - Where Cu is high generally

all the other trace elements are high and vice versa,

3. Biotite - Where Cu is high, generally all the othertrace elements are

high. Where Cu is low the other elements have marginally lower values.

VARIATION DIAGRAM SHOWING RELATIONSHIP B E T W E E N C u , P b . Z n , N i , C o & Cr CONTENT OF THE BULK ROCK

S. THEIR S E P A R A T E D M.INERAL FRACTIONS IN

GRANITE & GRANITIC ROCKS

TEXT FIG.NO. 9

- 105 -

REUTIONSHIP BETWEEN Cu, Pb, Zn, Nl, Co, AND Cr CONTENTS

OF THE BULK ROCKS AND IHEIR SEPARATED MINERAL

FRACTIONS IN GRANITES AND GRANITIC ROCKS

A comparative study of the distribution and relationship of some

trace elements in granites and granitic rocks and its ferromagnesian

fractions is done and the observations made are summarized below (see Text

Fig.9 ).

The concentration of Cu, Pb, Zn, Ni, Co and Cr are low in the bulk

rocks while the ferromagnesians in them show enrichment of these elements.

Investigations carried out by Putnam and Burnham (1963) show that

the Cu content of many bulk rock samples of granites are somewhat higher

than the amount contributed by the ferromagnesian phase. They attributed

this observation to the presence of small amounts of chalcopyrite in granites

The same authors also pointed out the p o s s i b i T i t ^ o f l ; h e ^ e s W c e ~ o f "small

amounts of Cu in feldspars. Earlier Newhouse (1936) and Ramdohr (1940) also

reported the presence of small amounts of chalcopyrite in granites.

In the present case the ferromagnesian minerals always give higher

values for Cu as compared to the bulk rock. This indicates that no copper

ore is associated with these granites and granitic rocks. Further the Cu

in these rocks appears to have preferably concentrated in the mafic minerals.

Putnam and Burnham (1963) also found that the Cu contents of biotlte

coexisting with chalcopyrite in the granites are higher as compared to the

coexisting hornblende. Shrivastava and Proctor (1962) found more Cu in the

augite-hornblende-chlorite group than in the biotites in quartz-monzonite

- 106 -

which was supposed to be source rock of copper ores. They also reported

small amounts of Cu in the feldspars.

Tn the rocks under study perhaps Cu entered into biotite and horn-

blende with almost equal ease. Biotltes show a marginal edge over hornblende.

This indicates that the ferromagnesian minerals of the granites may have

some primary copper in them and that they have not been affected by later

percolations or permeations. Further, Cu may have entered some of the'

ferromagnesian minerals by replacing Fe. Little occurrence of Cu in the

felsic group may be attributed to .the feldspars rather than quartz.

Similar to copper, Pb also shows enrichment in the ferromagnesian

minerals. It was also found in appreciable amounts in the felsic group..

It is generally believed that Pb enters into granites diadochally

with K^ and thereby potash-felspars may contain appreciable amounts of Pb

(SbTdschrnim, "Wedepohr,-1956t.i5hTivastava-and Pr0rct0T-(-1962> f^umJ-the^t

although Pb was preferably concentrated in the mafic minerals yet they

(mafic minerals) constituted a small fraction of the bulk rock. They further

considered feldspars as good hosts for Pb.

Lead in the present case reads higher values in the mafic minerals

than the bulk rock. Further, the felsic group, which forms the major part

of the bulk rock.ljas also appreciable amounts of Pb. Obviously Pb has also

a significant concentration in the felspars of the felSiic group. It was

also observed that the pink granite-gneisses rich in potash-felspars have

higher concentration of Pb than other rock samples.

- 107 -

Concentrations of zinc have been reported in basic igneous rocks

(Sandell and Goldish, 1943) as well as biotites (Lundegaordh, see WiJson

1953). Wedepohl (see Putnam and Burnham, 1963) found occasional presence

of Zn in feldspars.

The present analytical data show that the ferromagnesians are

enriched in Zn as compared to the bul'c rock. Further the felsic group also

shows significant amounts of Zn. This indicates that Zn is possibly present

in the silicate phase of the mafic minerals and feldspars of the felsic

group and not as a sulphide. It might have been accommodated by replacing

Fe and Mg of the mafic minerals(see Ahren, 1964).

Ni and Co are fellow travellers. Both these elements are found

preferably concentrated in the ferromagnesians as compared to the bulk rock.

The concentration of Ni is more than Co in general. The observations made

are as follows:

i) Co and Ni are solely present in the silicate structure (Goldschmidt,

1958).

ii) Co and Ni have antipathic relationship.

be iii) Co and Ni may/enriched in mafic minerals possibly substituting

2+ 2+ Fe (see Ringwood, 1955a) and Mg (see Carr and Turekian, 1961) respectfully

Cr is reported to be preferably incorporated in the silicate

structure and biotites are considered to be good hosts for Cr (see Carr

and Turekian, 1961).

The ferromagnesian are significantly enriched in Cr contents as

- 108 -

compared to the bulk rock. The higher concefltration of the metal in

hornblende and biotite sugqeststhat Cr is present in the silicate structure,

3+

It might have entered the lattice possibly substituting Fe (see Ring-

wood, 1955a).

- 109 -

Chapter - VI

GEOCHEMICAL DISPERSION OF TRACE ELEMENTS

Geochemical variation diagrams for Primary and Secondary

dispersion aureoles

Variation diagrams were used to represent graphically the geochemical

dispersion of Cu, Pb, Zn, Ni, Co, Cd, Cr, Li and Ag, in the various important

rock types of the Khetri Copper Belt. They precisely illustrate the dispersion

aureoles of these trace elements and their relative abundance in a particular

set of rock. An attempt has been made to use them to present the analytical

data of geochemical dispersion both for primary and secondary dispersion

aureoles.

Primary dispersion aureoles

All the rock types of the area were first classified into 3 major groups

based on their lithological and petrological characters. The primary dispersion

aureoles of the following major rock groups were prepared separately.

1. Granites and granitic rocks

2. Metamorphic rocks

(a) quartzites (b) Schists and phyllites

3. Khetri copper mine samples (including some ores).

For the quantitative determination of the above mentioned nine trace

elements, a total of 130 samples of rocks and ores were analysed by Atomic A

Absorption Spectrophotometer. Variation diagram was prepared separately for

each group of rocks. The details of the points of interest of the diagram

are as follows:

- 110 -

Indicator elements - Elements having different geochemical behaviour have

been used as indicator elements for different purposes, the reasons for

such use have been summarized in the previous chapter,

Li and Ag have been placed as the indicator elements for the stage

of mineralization. Cu, Pb and Zn have been used as indicator elements of

ore complexes. Co, Cd, Ni and Cr represent elements of the regional geo-

chemical background. Plotting was done on ppm range for all elements. The

range variation is 5 ppm and 10 ppm as the lower limits and 1,000 ppm as the

upper limit for all elements.

Each diagram has been divided into nine equal quadrants in the cases

of granites and granitic rocks and the samples from Madhan-Kudhan and Kolihan

mines, and into eight equal quadrants in the cases of quartzites, schists and

phyllites.

Concentration circles in ppm range on logrithraic scale were drawn for

values of 1,000 ppm, 500 ppm, 100 ppm, 50 ppm, 10 ppm and 5 ppm. Each

quadrant was further divided into per cent frequency having sectors of 25

per cent, 50 per cent, 75 per cent and 100 per cent.

Analytical data have been grouped into ranges with an interval of

10 ppm for values upto 100 ppm. Higher values have been plotted separately.

Values of -< 5 ppm and < 10 ppm have been plotted by drawing thin lines tapering

at the centre of the diagram. They indicate values above zero but less than

5 ppm (Cd) and less than 10 ppm (Ag).

Background values are taken from the values given by Carr and

Turekian (1961), Taylor, S.R. (1964) and Vinogradov (1962) for granites

- I l l -

and granitic rocks. For metamorphic rocks the average values of the

analysed samples of a particular rock group of the two parts of the belt

were calculated separately. Finally the average of the two values was

calculated and taken as the regional background values of the area. Values

for the samples from Madhan-Kudhan and Kolihan copper mines have been

calculated as average values from the obtained analytical data.

The residual soil samples of granites and granitic rocks, quartzites

and schists and phylHtes have also been analysed by Atomic Absorption

Spectrophotometer for traces of Cu, Pb and Zn. The analytical data were

presented with the help of single geochemical variation diagram. The

diagram is divided into three equal quadrants, each of which represents the

soil samples of a particular rock group. Each quadrant is again subdivided

into three equal divisions for Cu, Pb and Zn. The plotting of analytical

results was done similar to that of rock samples. The calculated background

values as well as the average values given by Hawkes (1962) have been

recorded and discussed.

The diagrams represent all the parameters clearly, with the scope

to accommodate any other relevant record. The dispersion patterns were

later discussed with a view to study the geochemical behaviour of trace

elements in a particular set of rocks or their residual soil samples and

the variation trend of these trace elements in that set.

The net of the diagram for the graphical representation of Geo-

chemical data has been used as proposed by Baimalibeili (1964).

GRAPHICAL REPRESENTATION OF GEOCHEMICAL DATA

oeOCHEHICAL VARIATION DIAGRAM fOR PRIMARY OlSPSRSION AUR£OL£S OF

VARIOUS TRACe eteMSNTS IN CRANire AND GRANITIC ROCKS

TEXT F I G . N O . I O

- 112 -

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GRANITE & GRANITIC ROCKS & THEIR RESIDUAL SOILS

JJL 3\4 5 € 7\e\9\to\n\f2\ 13|;s |rg|? 7|/fl \I9 \20\21 \22\23\2i^

VARIATION DIAGRAM FOR PRIMARY AND SECONDARY

DISPERSION PATTERN OF Cu , Pb & Zn.

T E X T FIG. N0.15

- 125 -

Comparative study of primary and secondary dispersion

patterns of Cu. Pb and Zn

Sixty-six rock samples of granites and granitic rocks, quartzites,

schists and phyllites and an equal number of their corresponding residual

soils were taken for a comparative study of the primary and secondary

dispersion patterns of Cu, Pb and Zn.

The analytical results were plotted on three diagrams. Each.diagram

represents a particular group of rock types and their residual soil, in

which the variation of Cu, Pb and Zn were shown individually.

Samples of a particular rock group and corresponding residual soil

were plotted separately for their contents of Cu, Pb and Zn. Concentration

curves are prepared by joining the respective points for rock samples and

residual soil sanqjles separately.

Dotted lines represent the variation trend of a metal in the rock

and the bold lines represent the variation trend of the same metal in the

residual soil. The values are plotted on ppm range and may be read with

the help of the graduations shown on the side of the diagrams.

Granites and granitic rocks (see Text Fig. 15 )

Copper - The rock samples clearly show low dispersion of Cu while the

corresponding residual soil samples show enrichment in the Cu contents.

It appears that during chemical weathering of the rock and sorting out of

various elements, Cu resisted considerably and as a result of which there

is a concentration of Cu in the residual soil. However, it is interesting

to note that the general pattern of dispersion of Cu both in the rocks and

OUARTZITIC ROCKS & THEIR RESIDUAL SOILS

ppm 1500 —I

1000 —

500 —

too

50

25

0

100

SOIL

ROCK

ROCK

VARIATION DIAGRAM FOR PRIMARY AND SECONDARY

DISPERSION PATTERN OF C u . P b 2n.

TEXT F(G. NO. 16

- 126 -

soils is more or less is matching.

Lead - The rock samples distinctly show higher dispersion of Pb as

compared to the residual soil samples. The effects of chemical weather-

ing on Pb appear to be unlike that of Cu. It indicates that in general

Pb was leached out considerably during the chemical weathering leaving

the residual soil depleted in its Pb contents.

Zinc - The rock samples in the northern part of the area which mostly

include granites show low values of dispersion of 2n as compared to the

samples of the residual soils. However, the case is somewhat different

with the granite gneisses of the southern part of the area where Zn is

generaly higher in the rock samples. Therefore, it is evident that Zn

in granites behaved differently from that in igrahite gneisses during

their chemical weathering.

Zn in the granites appears to be less mobile during chemical

weathering and thus the residual soils are enriched in Zn contents. In

the case of low lying granite gneisses, Zn was comparatively mobile and

thus there is a depletion in Zn contents in the soil samples.

In general, Pb was found to have a greater mobility than Zn, which

in turn, was more mobile than Cu.

Ouartzites (see Text Fig.i6 )

Copper - In general,Cu has a slightly higher dispersion in the rock

samples as compared to the samples of the corresponding residual soils.

Some of the soil samples of the southern part of the belt show enrichment

SCHISTS & PHYLLITES & THEIR RESIDUAL SOILS | 2 | j | < | 5 | g | 7 | < | 9 |/0|;; \I2\I3\I4 \15\I6\17\I8\I9\20\21\22\23\24\25

ROCK

too H

ROCK

VARIATION DIAGRAM FOR PRIMARY AND SECONDARY

DISPERSION PATTERN OF C u , P b & Zn.

TEXT FIG.N0.17

- 127 -

in the Cu-contents. It appears that during chemical weathering Cu was

slightly leached out from the soil samples which resulted in lowering the

Cu-contents marginally in the samples of the northern part.

It was observed that the dispersion patterns of Cu in the rocks

and soils have striking resemblances.

Lead -• There is an overall depletion in the Pb-contents of the residual

samples. The decrease is more pronounced in the samples of the

northern part. This indicates that removal of Pb was fairly affective

during chemical weathering.

Zinc - Zn shows higher values in the residual soil samples as compared to

the rock samples. This enrichment of Zn is more pronounced in the soil

samples of the northern part of the belt. It clearly indicates that Zn,

was not affected much during the chemical weathering.

Finally it was observed that Pb was more mobile than Cu, which

in turn has a greater mobility than Zn in the quartzites.

Schists and phvllites (see Text Fig. 17 )

Copper - In general the samples show a slightly higher concentration of

Cu in the residual soil samples than in the rock samples. It is more

distinct in the samples of the southern part of the belt where the overall

dispersion of Cu is comparatively low.

It is, therefore, inferred that the Cu was appreciably resistant

to chemical weathering and was not removed in appreciable quantity.

- 128 -

Generally Cu in the rocks as well as in soil samples indicate

more or less similar dispersion patterns.

Lead - Pb shows comparable dispersion in the rocks as well as in the

residual soil samples except in a few cases of soil samples in which Pb

shows marginal enrichment. It is, therefore, obvious that there was a

little effect on the dispersion of Pb during the conversion of the rocks

into residual soils due to weathering.

Zinc - 2n shows a general enrichnient in the residual soil samples as

compared to the rock samples. The enrichment is quite distinct in the

samples of the northern part of the area. However, some of the residual

soil samples from the southern part of the area show depletion in Zn

contents. It appears that Zn did not suffer much leaching during chemical

weathering and a greater part of it remained with the residual soil.

In this case the mobility of Pb was greater than Zn which in turn

was mobile than Cu.

General-remarks

All the three figures, therefore, clearly show that the dispersion

patterns of Cu in the rocks as well as residual soil samples of granites

and granitic rocks, quartzites,schists and phyllites have striking

resemblances.

The observations and the general quantitative assessment made

in the previous description led the author to suggest the following

schemes of relative mobilities of Cu, Pb and Zn during the process of

- J29 -

chemical weathering.

Rock groups and its residual Scheme of relative soil samples mobility

Granites and granitic rocks = Pb > Zn > Cu

Quartzites = Pb > Cu > Zn

Schists and phyllites = Pb > Zn > Cu

- 130 -

TRACE ELEMENT ISOCONCENTBATION MAPS

The spatia] abundance and distribution of traces of Cu, Pb, Zn, Ni

and Cr in the igneous and metamorphic rocks have been shown individually

on base geological map of the Khetri Copper Belt. The quantitative

analytical data of t.hese trace metals from the various rock types of the

belt have been plotted at the intersection points of the grids which

correspond to the location of the samples collected. Then the isoconcen-

tration contours are interpolated at known intervalss on ppm range.

The isoconcentration pattern of Cu shows that its concentration in

the rocks of the northern part of the belt is usually higher than in those

of the southern part. Zinc shows sufficient enrichment in the rocks

southwest of Saladipura. Further details regarding these two and other

elements have been given in the accompanying tables. The maps also show

that in certain cases concentration of an element in a particular rock type

has been preferential.

- 131 -

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Chapter - VII

SIGNIFICANCE OF TRACE ELEMENTS

Concentration trend of some trace elements

The concentration trend and geochemical behaviour of some trace

elements in granites and host rocks with copper ores fs studied.

The presentation is made on the lines proposed by Lionel C.Kilburn

(1960). Elements have been grouped for representation on triangular and

rectangular diagrams. The trace element data obtained for granites and

granitic rocks and host rocks with sulphide ores are plotted to study their

relative abundance and their significance with respect to copper minerali-

zation .

1. ^elatiQnships^mSJLg coppgr, apd lead

All the four elements are chalcophile in nature. Their traces

have manifold significance. Their geochemical behaviour in the granites

and host rock with sulphide ores has been used to understand whether there

is any genetic relation between the two.

a) Copper-zinc-lead (see Text Fig. 18)

The data were recalculated to hundred on weight percentage basis

and plotted on the coordinates of a triangular diagram both for granites

and host rocks with sulphide ores.

Granites and granitic rocks - The diagram shows that granites form a conti-

nuous series from Cu-Zn, through Zn-rich to Zn-Pb type. The end segments of

- 137 -

- 138 -

copper and lead concentration are almost blank both for Cu-Zn and Zn-Pb

series. The points are concentrated on the boundaries of Zn-Pb series and

fairly more towards the zinc end. In the Cu-Zn series concentration of

points is more towards zinc end.

Host rocks with sulphide ores - The diagram shows that there is a continuous

series from the Cu-Zn to the Zn-Pb series in the ores although the concen-

tration on Pb side is not distinct. Lead values are relatively low. The

points are concentrated nearer the boundary of Cu-Zn series and distinctly

towards the copper end. The consistency in low values for Pb indicate that

lead ores are not associated with the copper ores of the area.

The concentration trend of the points in case of granites and

granitic rocks and host rocks with sulphide ores is not distinctly similar.

Pb shows some regularity in its distribution in both the cases.

b) Nickel-copper-zinc (see Text Fig. 19 )

When plotted on a triangular diagram the grouping is as follows:

Granites an(j granitic rocks - The presence of Ni is of some interest in

spite of its low concentration. The points are grouped on the boundary

lines of Cu-Zn and Ni-Zn series. The concentration is more towards Ni-Zn

series and particularly towards the Zn end. The Cu-Ni series does not

show any grouping of points. The copper rich end has a few concentration.

Ni-rich end does not show any concentration .

Host rocks with sulphide ores - They show prominent grouping of points near

the Cu-rich end. The boundaries of Cu-Zn series also show grouping. Ni

contents are not high. The Cu-Ni series does not show any concentration on

its boundary. The concentration of points is relatively nearer to Zn than Ni

Ni/Cu + Zn+ Pb Ni/Cu + Zn+ Pb

m X

I O CO H

73 O n

to

H I

c f— T> I

o m in

- 139 -

The Zn-rxch end and Ni-rich ends are equally blank.

General assessment - There is a similarity in the zinc and nickel behaviour

in granites and host rocks with copper ores.

Similar to the Cu-Pb-Zn series, the copper-rich end shows concentra-

tion of points in the sulphide ores, while in the granites the frequency of

concentration of points is nearer to the zinc end. The Cu-Zn series in

granites as well as In host rocks with sulphide ores show almost a similar

trend. The Cu-Ni series particularly towards the Ni-rich end are equally

blank in both the cases. The overall behaviour of Ni-Cu-Zn in the granites

is in some respects similar to those in the host rocks with sulphide ores.

Nickel in Ni-Cu series behaves like lead in Cu-Pb series in granites

as well as in the sulphide ores.

c) Nickel-copper-zinc-lead (see Text Fig.20 ).

The values of the elements are recalculated to one hundred per cent

and plotted on a tetrahedral coordinate system.

Granites and granitic rocks - The tetrahedral representation clearly shows

the behaviour of Ni/Cu+ Zn + Pb against Cu-Zn and Zn-Pb series. It forms a

continuous series from Cu-Zn rich through Zn-rich to Zn-Pb series.

In the Cu-Zn series the points are concentrated towards Zn-rich

end rather than the Cu-rich end. The pattern shows a gradual increase in

the Ni/Cu + Zn + Pb ratio from copper rich end towards the Zn-rich end

forming a smooth curve. There is a prominent grouping of points on the

boundary of zinc-rich end.

In the Zn-Pb series, like the Cu-Zn series, the concentration of

- 140 -

points is towards the Zn-rich end rather than the Pb-rich end. The points

show a pattern having a regular increase in the Nl/Cu + Zn + Pb ratio from

Zn-rich end towards Pb-rich end. It is represented by a straight line.

Host rocks with sulphide ores - When the sulphide ores are plotted on a

tetrahedral coordinate system like granites and granitic rocks, they show

striking resemblance with the latter in many respects. They also form a

continuous series from Cu-Zn series through Zn-rich to Zn-Pb series.

In the Cu-Zn series they show a gradual increase in the Ni/Cu +

Zn+Pb ratio from Cu-rich end towards Zn-rich end. The pattern is represented

by a curve which shows a significant similarity with that of granites and

granitic rocks.

The concentration of points is towards the Cu-rich end and not the

Zn-rich end but there is no grouping on the boundary of zinc as it is in

granites.

In the Zn-Pb series the similarity in the distribution of points

of Ni/Cu+Zn+Pb is more pronounced. There is also a regularity in increase

in Ni/Cu + Zn + Pb ratio from Zn-rich end to Pb-rich end. The pattern is

represented by a straight line which is very similar to that of granites

and granitic rocks. The overall point distribution is almost the same in

both the cases.

It has been observed that the concentration trend of points in the

triangular diagram for Cu-Zn-Pb in case of granites and granitic rocks and

host rocks with sulphide ores does not show much similarity. But when

plotted for Ni-Cu-Zn on a triangular diagram and for Ni-Cu-Zn-Pb on rectan-

gular diagram, the general trend of the distribution of points shows

- 141 -

distinct similarity] As pointed out by Kilburn (I960) such a criterion

may be used to establish a genetic relationship between the intrusive and

the adjacent ore deposit. It is, therefore, possible that, in the area

under study,the granitic rocks have a genetic relationship with the copper

deposits.

Geoch^mi^t^ry as applied to the Khotri copper ores

The application of geochemistry to the genesis of ore deposits in

the last two decades has opened new horizons and rethinking of the whole

issue. It has now been fairly established that the studies of trace elements

have an important bearing on the genesis of certain ores. The criterion

of isotopic composition of elements is a further step advanced in this

field. Much evidence has been collected either to discard or accept the

idea of genetic connection between granites and the ores.

Even after a colosal work has been done on the genesis of ores in

different countries of the world, it is not certain whether the related

intrusives should show depletion or enrichment in their metallic contents.

It is generally believed that "either enrichment or depletion of an intrusive

in ore metal could be taken as evidence for considering the intrusive as

the source of the ore" (see Krauskopf, 1967). 1

The present investigation shows that the granites and granitic

rocks of the area are generally depleted in the copper content although

in certain exceptional cases Cu as high as 38 ppm was recorded.

Investigations by Shrivastava and Proctor (1962) on the quartz-

monzonite intrusive. Searchlight, Nevada, have indicated that the depletion

- 142 -

in the copper content in the quartz monzonite may account for its genetic

connection with the associated cooper deposit. Belt (1960), on the basis

of his work on Cu and Zn deposits of New Mexico, pointed out that the

enrichment of a metal in an intrusive particularly, in an altered one, may

mean that ore-bearing solutions from elsewhere concentrated as deposits

and permeated the adjacent intrusive rocks. Stringham (1958) pointed out

the preferential association of copper with the quartz monzonite rock.

Warren and Devault (1959) extracted copper with aqua regia and found that

Cu content in the intrusives associated with the ore deposits are several

\

times higher than in the barren intrusives. He attributed this enrichment

to later permeations by ore forming fluids rather than to consanguinity.

Such an attemot was not considered necessary in the present investigation

because the granites of the area are not enriched but depleted in copper.

Recently, however, Kilburn (1960), Putnam and Burnham (1963) reported

enrichment of cooper in some acid igneous rocks associated with the copper

deposits ,

T'he granitic rocks of the area under study, show a general depletion

in Cu content. In the light of the investigations carried out by earlier

workers elsewhere as referred to above, this general depletion may be

attributed to a possible genetic connection between the Cu-ore and the

granites.

Another interesting feature observed in the area was that the

granite gneisses of the southern part of the belt gave relatively higher

values of copper (no enrichment in general) than the granites of the northern

part. This difference in the copper content may be attributed to the

difference in the proportion of mafic and felsic conten+s of the rocks of

- 143 -

the two parts .

Mafic minerals, being relatively better hosts, may accommodate

more copper. It may, therefore, be reasonably assumed that the granites

of the northern part of the belt being poor in the ferromagnesian content

could retain very little copper with them. This resulted in depletion of

copper in the granites. It is, therefore, more likely that the bulk of

copper moved away from the granites and concentrated in the adjacent rocks.

On the other hand,the granite gneisses of the southern part of the

belt, being rich in the ferromagnesian content, could retain relatively

more copper with them. This resulted in relatively enriching the granite

gneisses with copper ores. The above observations made in the two parts

of the area suggest to predict a larger copper deposit in the northern part

of the area as compared to the southern part provided that the genetic

relation between the intrusive and the ore is established. Such an assump-

tion may not at first appear sound. But it has been estimated that a

3

depletion of about 3 ppm of the metal in 100 km granite is sufficient to

concentrate a million ton of Cu, Pb, or Zn ore (see Krauskopf, 1967). Thus,

a slight depletion or enrichment in the copper content in granites and

granite gneisses of the area may account for the magnitude of the copper

ore deposit.

It is true that the granites of the northern part of the belt

particularly, those near Gotro village do not occur over a large area and the

further no granite has so far been encountered in/underground sections of

the Madhan-Kudhan and Kolihan mine sections. Therefore, an attempt to

associate such a small exposure of granite as the possible source of a large

- 144 -

copper deposit in the adjoining area will be doubted. But it has been

universally accepted that granite batholiths are huqe masses and their

major portion usually lie concealed at deeper levels. Possibly, the outcrop

of granite near Gotro village comprises an insignificant part of a deeply

buried batholith. Its extent at still deeper mine levels cannot be entirely

ruled out at present.

Further attempts to tackle the problem of ore genesis on the basis

of geochemical studies have been made by studying the behaviour of trace

elements in the separated mineral fractions. Several workers have carried

out investigations on these lines and the results obtained are worth

exploring.

Recently Putnam and Burnham (1963) investigated that the mafic

minerals in certain intrusive rocks of Arizona have a higher content of

copper in the areas of copper mineralization. Parry and Nackowski (1963)

recorded that the Basin and Range quartz-monzonites have biotites with

higher content of copper near the copper deposits while zinc shows depletion

and Pb gives normal values.

In the case under study, the separated ferromagnesian mineral

fractions of the granites and granitic rocks which include hornblende,

epidote and biotite, show a general enrichment in copper. Both hornblende

and biotite are good hosts for copper. The values for zinc are fluctuating

while that of lead are almost consistent in all cases. Such an observation

as made by Parry, and Nackowski (1963) may be tried here to correlate the

intrusive rocks and the ore.

- 145 -

The views as stated above were further strengthened when the

weight percentages of certain trace elements were plotted on triangular

and rectangular diagrams in the course of discussing the subject. The

chemical trend of these trace elements in granites and granitic rocks and

the host rocks with copper ores were found to have distinct similarities

in cases of (a) Cu-Zn-Pb, (b) Ni-Cu-Zn, (c) Ni-Cu-Zn-Pb as it has been

discussed earlier in this chapter.

Kilburn (1960) is of the opinion that the similarities in the

trends and the general geochemical relationship of trace elements in rock

and ore may be considered as a possible means to establish a genetic

connection in between the two.

As has been discussed earlier, these elements have distinct similari-

ties in their distribution trends and there is a close interrelationship

of elements in the rocks as well as copper ores. It is, therefore,

reasonable to believe that the granites were the source rocks of the ore

fluids.

Chapter - VIII

SlM^^ARY AND CONCLUSIONS

In the present investigation, which the author started in November

1968, an attempt has been made to emphasize the importance and precise use

of geochemical data in the distribution of certain metals and their probable

relation to the productive copper deposits in the Khetri Copper Belt,

Bajasthan. The study revealed certain interesting geochemical behaviour

I

of the major and some trace elements in different rock groups, residual

soil samples and separated mineral fractions of granites and granitic

rocks, the sulphide ores and their host rocks in this area. Rock and soil

samples were collected largely from the surface, divided into grids and

picking up the samples at an interval of one km on a 4" to a mile map.

Some samples from the underground copper workings were also collected.

Additionally, a considerable attention was given to study in sufficient

detail the lithology and petro-mineralogy of various types of rocks

encountered. A brief summary of the investigation and the conclusions

arrived at are recorded as follows:-

1. The Khetri copper ore deposits are mainly confined to the a(g^lla-

ceous group of metasediments belonging to Ajabgarh series,which is a part

of the Delhi System of Precambrian age. Copper mineralization has taken

place largely along a major strike fault at the contact of Ajabgarh and

Alwar'series. A large part of the area has been intruded by a number of

1 /lA

- 147 -

igneous intrusives. There is a series of faults of several types and

the rocks have a number of doubly plungtnci folds. The general trend of

strike of the rocks series is NE-SW and dip varies from 30°to 70® towards

west and north-west.

The major host rock of copper is the garnetiferous quartz-chlorite

schist. Pyrite, pyrrhotite and chalcopyrite are the dominant sulphide

minerals, whose paragenetic sequence has the same order of arrangement

as recorded above. The degree of metamorphism of the rocks, is generally

higher in the north and gradually becomes low towards south.

The copper ores do not show any significant evidence of strati-

graphic or lithological control. Structural features appear to have some

control on the localization of ores. The shape of the ore bodies are

generally lensoid.

2. Pink and grey granites, granite gneisses and aplites of varying

mineralogica1 compositions occur in the area. Their litholigical and

structural characters are also variable. Dolerite dykes occur frequently.

Among the metamorphic rocks, various types of schists,qu&rtzites and

phyllites are common. The carbonate rocks have limited occurrence and

amphibole is commonly associated with them.

The petromineralogical and petrochemical studies also indicate

that the granites in the vicinity of Gotro village are intrusive. Some

of the metamorphic rocks are comparable to the amphibolite facies of

s

Eskola in their grade of metamorphism. Three kinds of garnets have been

identified in the garnetiferous quartz-chlorite schist. Some of these

garnets show evidence of rotation. Anthophyllite/cummingtonite usually

- 148 -

occur as coexisting amphiboles.

Petrochemical evidence from the ACF diagram points out that the

parent material of the metaraorphic rocks were grey-wackes, clay and shales

and that of basic intrusive were andesitic and basaltic rocks.

3 . The complete analyses of four granites and granite rocks, ,

four metamorphic rocks and one metadolerite were done in order to determine

all the fourteen major constituents of those rocks. Further, the mineral

fractions of ten granites and granitic rocks and six host rocks of copper

ores are separated by Frantz Isodynamic Magnetic Separator. About 250

samples, including almost all the rock types of the area, separated

mineral fraction of some rocks and ores, and residual soil samples were

analysed for determining quantitatively some of the important trace metals

by Atomic Absorption Spectrophotometer.

The significance and distribution of these trace elements in the

parent rock/mineral was studied with a view to probe their inter-relationship

The granite gneisses of the southern part of the belt show a higher concen-

tration of Cu, Zn and Ni as compared to the granites of the northern part.

The granite gneisses have abundant ferromagnesians as compared to the

granites. This indicates that Cu, Zn and Ni are usually concentrated in

the ferromegnesian phase and their abundance is controlled by the ratio of

mafic and felsic minerals in case of such rocks.

Copper is concentrated both in the quartzites and schists but it

has a higher concentration in schists than in quartzites. The samples of

Khetri copper ores as well as their host rocks show distinctly higher values

- 14^9 -

for Cu, Zn, Ni and Co. Nickel was found to be concentrating more in

pyrrohdtite than in the coexisting chalcopyrite. Dolerites also give

good indications of the presence of Cu, Zn, Ni and Cr. Generally Pb has

a limited dispersion in all the rock types of the area.

The concentration trend of Cu, Pb and Zn in the residua] soil

samples of almost all the rock types of the area was studied. The trend

is somewhat similar to that of the respective parent rocks.

Tlie studies of trace elements in the separated mineral fractions in

granites and granite rocks show that they are preferably concentrated in

the ferromagnesian phase. Cu, Pb, Zn, Ni and Cr show distinctly higher

concentration in hornblende than in biotite and least in epidote. The

felsic group (quartz-feldspar) does not show any significant trace of these

elements except Pb. Similarly, the separated mineral fractions of host

rocks show that Cu is more concentrated in amphiboles than in garnet or

in biotite. The felsic group, in this case, shows traces of Pb, Zn and Cr.

Further, the relationship between some trace elements in granites

and granitic rocks and their separated mineral fractions is studied and the

nature of the occurrence in silicate and sulphide phase is indicated.

4 . The geochemical dispersion of certain trace elements has been studied

with the help of geochemical variation diagram. The pattern of dispersion

aureoles (primary and secondary) of each trace element in a particular rock

group and corresponding residual soil has been studied and the observations

have been recorded in a tabular form.

- 150 -

Cu, Pb and Zn have been taken as indicator elements of ore com-

plexes on the basis of their geochemical behaviour diiring the fractional

crystallization of magma as has been worked out by many previous workers.

Ni, Cd and Cr have been grouped as indicator elements of the regional

geochemical background on account of their controlled dispersion and close

association with the sulphide ores in the area. In accordance with the

views expressed by some earlier workers, Li and Ag have been taken as the

elements indicating the stage of mineralization.

5. A comparative study of the primary and secondary dispersion patterns

for Cu, Pb and Zn in various rock groups and their residual soil samples

has been made. It led the author to work out a scheme of relative mobilities

of these trace elements during the chemical weathering of rocks and their

conversion into soils which is presented below.

p Relative mobilities Bock Group . ,

^ of elements

Granites and Granitic rocks Pb Zn <. Cu

Quartzites Pb < C u < Zn

Schists and Phyllites Pb < Zn < Cu

6. The isoconcentration maps have been prepared in order to show clearly

the distribution of Cu, Pb, Zn, Ni and Cr in all the rock groups of the area.

Copper shows anomalously high values in the northern part of the belt around

the Madhan-Kudhan, Kolihan and Akwali mine sections which are now being

developed for the exploitation of copper. Satkui also shows indications of

copper mineralization. There is an unusual dispersion of zinc in some of

the rock samples north-west of Saladipura. The dispersion of other trace

elements, however, is as usual.

- 151 -

7, An attempt has also been made to investigate a probable connection

between the intrusive granites and the copper ores of Khetri. Following

Kilburn (I960) the weight percentages of Cu, Zn, Pb and Ni have been plotted

on triangular and rectangular diagrams in which the trends of concentration

of these elements are very significant. The concentration trend and

geochemical behaviour of Cu-Zn-Pb and Ni-Cu-Zn in the triangular diagrams

and Cu-Zn-Pb plotted against Ni/Cu+Zn+Pb in the rectangular diagrams show

distinct similarities in cases of granites and granitic rocks as well as

host rocks of copper ores. This similarity has been used as a criterion

to establish a possible genetic relationship of granites with the copper ores

Again, according to similar investigations made elsewhere by some

previous workers,which are now widely accepted, the general depletion of

copper content in the granites and granitic rocks of the belt provides some

useful evidence to establish a genetic connection between the copper ore and

the intrusive. This view is further supported by the observation that copper

shows higher conc6ntration in hornblende and biotite separated from the

samples of the intrusive granite.

The above observations led the author to believe that the copper

ores of Khetri are of epigenetic origin and the adjacent granite of Gotro

is the probable source rock for the ore fluids.

R E F E R E N C E S

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Arogyaswamy.R.N.P. 1949

Asvgathanarayan, 1964

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Auden, J.B.

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1937 Atomic structure of minerals. Cornell Univ.Press, Ithaca, N.Y.

1950 Ore genesis, Thomas Murby & Co., London, 204p.

- 152 -

- 153 -

Buddington, A.F. 1927

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- 154 -

Das Gupta, S.P.

Deb. S.

DuBietz

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Goldschmidt, V.M,

Hacket, C.A.

Hawkes, H.E. & J.S. Webb

Hegmann, F.

Heron, A.M.

1964 Genesis of sulphide mineralization in the Khetri Copper Belt, Rajasthan, India (Abstract). Bep. Inter. Geol. Cong. 22nd Session, India.

1970 Sulphide deposits of Saladipura, Khetri Copper belt, Rajasthan, Econ. Geol., Vol. 65, pp.331-339,

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1955 The content of chromium and nickel in the C a l e d o -

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1947 See Goldschmidt, V.M., 1954.

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p p . 279-303.

1958 Geochemistry in mineral exploration. Harper & Row publisher, N.Y., 415p.

1943 See Goldschmidt, V.M., 1954. Rec.

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- 155 -

Heresy, G.R., 1931 Hobble and Arthur Holmes

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- 156 -

Parry, W.T. & 1963 M.P. Nackoi'jski

Pascoe, E.H.

Pauling, L.

1950

1960

Putnam, G.W. and 1963 C.W.Burnham

Rankama, K. and 1950 Th.G. Sahama

Rao, N.K. and 1968 G.V.U. Rao

Roy, B.C. 1958

Roy Chowdhury. M.K. 1962 G.H.S.V.Prasad Rao,

V.Venkatesh, A.S. Rarniengar, S.P. Das Gupta and W.K.Natarajan

Roy Chowdhury. M.K, & 1965 S.P.Das Gupta

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Shand, S.J.

Shaw, D.M.

1947

1953

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- 157 -

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1965

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1963

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- 158 -

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1923

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- 159 -

EXPLANATION OF PLATES

Field Photographs

PLATE I

Fig. 1 Bird's eye view of Khetrinagar and Gotro village showing low lying outcrops of pink granite,

vein Fig. 2 A view of quartz/cuttinq across the outcrop of pink granite.

Locality Gotro village.

Fig. 3 Prominent shear jointings in felspathic quartzite , northwest of Madhan-Kudhan mine section.

PLAT£ II

Fig. 1 An outcrop of magnetite-quartzite near Madhan-Kudhan mine.

Fig. 2 An outcrop of garnetiferous quartz-chlorite schist in the vicinity of Madhan-Kudhan mime.

Fig. 3 An outcrop of amphibole marble showing bands of dark coloured amphiboles . Locality near Kolihan miire.

PLATS III

Fig. 1 A contact between faulted magnetite-quartzite and quartz vein.

Fig. 2 A panormic view of the northern part of the Khetri copoer belt.

Fig. 3 An old surface working in the vicinity of Madhan-Kudhan mine.

Photographs of hand specimens

PLATE IV

Fig. 1 A contact breccia collected from the contact of granite and felspathic quartzite.

Fig. 2 A pink granite showing bands of amphibole (dark) along joint planes

-160 -

Fig. 3 A grey granite gneiss with a thick lighter ban(j of felspathic material.

PLATE V

Fig. 1 A pink granite gneiss with angens of potash feldspars.

Fig. 2 A pegmatite specimen showing radially arranged crystals of tourmaline.

Fig. 3 Pegmatite showing three big crystals of tourmaline (black)

arranged in a somewhat radiating fashion.

I

PLATE VI

Fig. 1 Folded pegmatite showing occurrence of tourmaline and felspathic material in alternate hands.

Fig. 2 Meta-dolerite showing big porphyries of nlaqioclase felspars.

Fig. 3 Garnetiferous quartz-chlorite schist showing garnets arranged along the planes of schistosity.

PLATS VII

Fig. 1 Garnetiferous quartz-chlorite schist showing irregular bands of garnets (dark grey).

Fig. 2 Biotite-andalusite schist showing a crystal of andalusite (greyish-white) with a carbonaceous streak in the centre.

Fig. 3 A hand specimen of puckered phyllite.

Photo micrographs

All magnifications 35 i ,

PLATE VIII I

Fig. 1 Microcline megacrysts in pink granite showing veins of ground mass material.

Fig. 2 A big crystal of twinned plagioclase in pink granite.

Fig. 3 Deformation and dislocation of the twin compositional planes of a crystal of plagioclase in pink granite.

- 1 6 1 -

PLATE IX

Fig. 1 Micrographic intergrowth texture in pink granite.

Fig. 2 Cordierite crystals with abundant inclusions of flaky minerals in a pink granite gneiss.

Fig. 3 Hornblende crystals arranged parallel to the foliation planes of grey granite gneiss.

P W T E X

Fig. 1 Tourmaline crystals in pegmatite showing zoning.

Fig. 2 Relict of porphyritic and ophitic texture in epidlorite, and zoning in plaqioclase crystals.

Fig. 3 Mosaic texture in the massive quartzite.

PLATE XI

Fig. 1 A xenoblast of rotated garnet with "S"-shaped arrangement of inclusions in the garnetiferous quartz-chlorite schist.

Fig. 2 An idioblastic garnet crystal with rounded and oriented quartz inclus ions.

Fig. 3 Prismatic crystals of anthophyllite/cumningtonite in garneti-ferous quartz-chlorite schist.

PLATE XII

Fig. A section of phyllite showing the early stage of development of schistosity.

PERSONAL VITAE

I was born in a Sunnl Muslim family in Bhopal, Madhya Pradesh,

India, where we are settled for over a hundred years. My father and grand-

father were in the service of the Nawab of Bhopal. My father expired in

1947 and my mother remained solely responsible for my upbringing and

education.

I had all my education in Bhopal. X obtained Master's degree in

Chemistry in i960 from Vikram University (Ujjain) and started ray career

as a Lecturer in Chemistry In Saifia Degree College, Bhopal, While on job

I did M.Sc. in Geology in 1962 from Vikram University. My desire to engage

myself in laboratory work prompted me to seek appointment in a non-gazetted

capacity in the Chemical Laboratory, Geological Survey of India, Hyderabad,

in December, 1962. I was promoted to Assistant Chemist (Gazetted II) in

the G.S.I, in January, 1964.

During ray stay at Hyderabad with ray maternal uncle, Mr. Syed Sajid

All, B.A., B.T. (Alig.), retired Deputy Director of Public Instructions,

Hyderabad, I received immense encouragement from him in pursuing my profe-

ssional as well as educational ambitions.

I was inspired to take up research in 1964, after attending the

International Geological Congress held in New Delhi, along with my friends

M r . Noman Ghani, Lecturer in Geology, Aligarh Muslim University, Aligarh,

and Mr. H.H. Khan, Assistant Geologist, Geological Survey of India, Bhopal.

Since I had the background of Chemistry as well as of Geology, I w«s keen

to work on some problem in Geochemistry closely connected with ray

laboratory assignments.

After ray marriage (February, 1965), I was transferred (1966) from

Hyderabad to Bhopal, my home town. I visited Aligarh in July 1968 where

Professor F. Ahmad, Hea<?, Department of Geology, Aligarh Muslim University,

Aligarh, was kind enough to allow me to join research leading to the degree

of Ph.D. and Dr. S.H. Rasul kindly consented to supervise my work. After

three years of research work I have been able to complete my thesis in

the present form.

During the course of this study Mr. Noman Ghani extended invaluable

help to me by way of giving fresh ideas and inspiration.

On this occasion I wish to dedicate this thesis to my revered

mother but for whom my long patient work would not have been possible. I

owe ray gratitude to my wife and love to my two little daughters, Faiza and

Farah, who played a vital role in the completion of this work.

PLATE I

- - • _ \

PLATE II

• •''it*'

PLATE I I I

PLATE IV

PLATE V

r .

-'V

• i ^ %

' 1-

PLATE VI

> f

PLATE V U

PLATE VIII

PLATE IX

r v 'vTiwwF V ^ , i ' t ' F > - V • - ^

PLATE X

M . ^ -A

PLATE XI

PLATE XII

A P P E N D I X