at university of new mexico · l. leroy corbitt, department of geology, eastern new mexico...
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AT THE UNIVERSITY OF NEW MEXICO \
A ST1W OF S I L I C I C PLUTONIC ROCKS IN THE ZUNI AND FLORIDA MOUNTAIFfS TO EVALUATE THE POSSIBLE OCCURRENCE OF
GISSENINATED !!RANIUP? AND THORIUR DEPOSITS
URANIUM AND THORIUM ABUNDANCES AND WHOLE ROCK CHEMISTRY
PRELIMINARY STUDY OF THE FLORIDA MOUNTAINS, NEW MEXICO:
NMEI REPORT NO, 77-1104C
DECEMBER 1978
This research was conducted with the support of the New Xexico Energy and Minerals Department (EMD). and the New Kexico Energy I n s t i t u t e a t The University of New Mexico ( N M E I a t UNM) under Contract 77-1104. However, any opin- ions, f indings, conclusions, or recommendations expressed within this report are those of the authors and do not necessar i ly re f lec t the views of the EMD o r of the NMEI a t UNM.
NMEI Report No. 77-1104C
i
A STUDY OF SILICIC PLUTONIC ROCKS I N THE ZUNI AND FLORIDA
DISSEMINATED URANIUM AND THORIUM DEPOSITS MOUNTAINS TO EVALUTE THE POSSIBLE OCCURRENCE OF
Uranium and Thorium Abundances a n d ' 6 h e Rock Chemistry of the Florida Mountains, New Mexico:
Preliminary Study
Final Report
August. 15, 1977 - August 14, 1978
P r inc ipa l Inves t iga to r s
Douglas G. Brookins, Department of Geology, Universi ty of New Mexico
Chris topher E. Rautman, New Mexico Bureau of Mines and Mineral Resources
L. LeRoy Corbitt, Department of Geology, Eastern New Mexico Univers i ty
Authors
Douglas G. Brookins, Department of Geology, Universi ty of New Mexico
Chris topher E. Rautman, New Mexico Bureau of Mines and Mineral Resources
L. LeRoy Corbitt, Department of Geology,'Eastern New Mexico Universi ty
NMEI #77-1104C
December 1978
1
Uranium and Thorium Abundances and Whole Rock Chemistry of the Florida
Mountains, New Mexico: Preliminary Study
Douglas G. Brookins, Department of Geology, University of New Mexico
Christopher E. Rautman, N.M. Bur. Mi.nes.Min. Res.
L. LeRoy Corbitt, Department of Geology, Eastern New Mexico University
abstract
The uranium and thorium abundances in the Precambrian granitic and of
the syenitic rocks (age unknown) of the Florida Mountains have been .
analyzed by delayed neutron activation analysis. The average uranium
content of 90 surface and drill core samples is 3.12 ppm and thorium content
for 66 samples is 12.33; Th/U = 3.97, well within the normal range for
granitic rocks (3.7 - 4.2). Although the Th/U ratio is normal for granitic
and syenitic rocks, a negative correlation between uranium (and Th/U)
with A1203, K20, and (K 0 f Na20) is observed. This-may be due to (a) der-
ivation. of the syenitic rocks from parent, low uranium. gabbroic rocks o r
(b) uranium loss during weathering. For the latter, significant amounts
2
of uranium may have been removed and possibly not transported far from the
source area. The syenitic rocks do not possess high uranium contents
typical of other areas.
L
Introduction
The Florida Mountains, south-central New Mexico are of interest because
of the presence of syenitic rocks (Corbitt, 1971) and the assumed association
of uranium enrichment with uranium. This assumption prompted part of this
study, vi?.. to determine if the rocks of the Florida Mountains were indeed
uranium rich and, if so, whether they represented a possible, low grade
uranium resource. If uranium poor, then uranium loss may be postulated
which would indicate that uranium exploration in the surrounding sediments
may be justified.
The Florida Mountains are very complex geologically; syenites originally
mapped as Mesozoic by Corbitt (1971) have been indicated as much older
(i.e., from early Phanerozoic (?) to Precambrian; Brookins, 1974). Whole
rock chemical studies and petrographic studies have also been carried out
to help assess the relationship between the granitic rocks and those with
syenitic affinities. Some of this work is still in progress, and additional
age work is contemplated and essential to attempt any material balance
between the granites and syenites.
Uranium and Thorium Investigation
The uranium abundance in the Florida Mountains is of interest for
several reasons. First, the rocks in which one might logically expect
uranium enrichment, viz. syenites and quartz syenites, are depleted in
uranium and thorium and Th/U is also low. Secondly, syenites typically
show a positive correlation between potassium (or potassium plus sodium)
and uranium. In Figures 2 to 5 are plotted U VS. K20, U VS. A1203, Th/U vs.
A1203, and U VS. (Na20 + K20). In all cases uranium shows a negative
correlation with increasing alkali and alumina content. Despite scatter,
3
this holds true for surface samples as well as drill core samples. These
data may be interpreted in several ways, the two most obvious explanations
are: (1) The syenites were derived from an alkali gabbro parent with low
Th and U; this model is possible as hornblende gabbro, presumably gradational
into syenite, is noted in the northern Floridas by Corbitt (1971). (2) Uranium
has systematically been'lost due to weathering or other processes. If (2)
is correct, then, assuming normal U in the range of 4-5 ppm for granitic
to syenitic rocks, some one million tons of uranium m y (hypothetically)
have been released from just 100 km of rock. This in turn indicates that 3
either high uranium in stream sediments near the Floridas might result
or that small (?) uranium deposits may be found in some of the sedimentsf
sedimentary rocks nearby. Critical to evaluating (1) versus (2) is the
exact age relationship between the granites and syenites; Brookins (1974)
has suggested that the syenites are not coeval with the granites, but how
much younger has not been resolved. This problem needs much more detailed
work.
The Th/U ratio for the Florida samples is shown as Figure 6 ; despite . the positive correlation, deviation from ThfU = 4 is apparent. The U and
Ti correlation is tested in Figure 7; a negative correlation between U
and Ti is indicated with Ti enriched in the U-depleted syenitic rocks.
Surface samples and dril1,core samples show the same trend. Collectively
these data hdicate, as mentioned earlier, that a systematic variation
between granitic and syenitic rocks exists. The problem of temporal
relationship between the two rocks remains unsolved.
Whole Rock Chemistry
The'whole rock chemistry for the Florida samples is presented in Table 2.
Although rocks mapped as syenites (FM-3, FM-4, F"7 (upper six samples), FM-8)
4
are justified based on petrography (See appendix), their Si0 contents
are slightly higher than normal syenites, a point made by Brookins (1974)
and Brookins and Corbitt (1974). High total alkalis and alumina support
classification as syenites. Those rocks identified as granites possess
Si02 contents from 71-77 percent and are characterized by lower alumina,
total alkalies, titania. Iron is not systematically distributed between
the various rocks although it is. fairly constant for any one drill hole
thus suggesting relatively little iron loss.
2
The.whole rock chemical data will be more carefully interpreted when
trace element data are available and additional Rb-Sr studies have been
completed.
Acknowledgments
Partial financial support was provided by the N.M. Energy Resources
Board (Grant #77-1104). The N.M. Bur. Mines and Min. Resources provided
assistance in the drilling and in the x-ray fluorescence spectrography.
R. T. Hicks, K. T. Emanuel and R. S. Della Valle of the University of
New Mexico assisted in the work. The facilities of P-2 and CNC-11 at
the Los Alamos Scientific Laboratory were used for the uranium and thorium
analyses by delayed neutron activation analysis; acknowledgment is due
M. Bunker and J. P. Balagna.
5
REFERENCES CITETI
Brookins, D. G., 1974, Radiometric Age Determinations from the Florida
Mountains, New Mexico: Geology, v..2, p. 555-557.
Brookins, D. G., and Corbitt, L. L., 1974, Preliminary Rb-Sr Study of
Igneous Rocks of the Florida Mountains, New Mexico: EOS Trans. Am. Geophys. Un., V. 55, p. 470-471.
Corbitt, L. L., 1971, Structure and Stratigraphy of the Florida Mountains,
New Mexico: Unpub. Ph. D. Thesis, Univ. Xew Mexico, 115 p.
Sample
FM5-1 FM5-3 FM5-5 FM2-1 FM7-3 FM8-1 FM2-2
FM7-4 FM7-2 FM2-4 FMl- 6 FM7-1 FM7-6 FM-11 FM7-8 FM8-2 FM2-8 FM7-5 FMl-3 FM7-5 FM4-1 FM5-6 FMl-2 FMl-7 FM2-5 FMl-5 FM4-4 FM4-2 FM4-3 “2
FM2-3 “4
TABLE 1
Th and U Data: Florida Mountains
Th (ppd U (ppd
13.65 3.08 35.8 7.80 15.0 3.65 16.4 4.03
. 2.40 1.58
12.9 , 2.88 15.0 2.80 3.70 2.39 3.63 1.77 18.2 4.81 17.4 3.03 3.15 1.42 30.8 7.08 18.6 3.89 4.26 1.83 17.1 3.69 18.4 4.22 3.69 1.65
, 24.6 5.44 13.0 2.76 7.26 1.87
19.8 4.18 23.1 4.56 12.9. 2.33 11.5 2.57 16.3 4.17 2.67 1.50
5.08 1.25
3.29 1.47 18.9 2.77 14.5 3.15 16.2 3.35
6
Th/U
4.43 4.59 4.11 4.07 1.52 4.48 5.36 1.55 2.05 3.78 5.74 2.22 4.35 4.78 2.33 4.63 4.36 2.24 4.52 4.71 3.88 4.74 5.07 5.54 4.47 3.91 1.78 4.06 2.24 6.82 4.54 4.84
-
7
TABLE 1 (continued)
Sample
F1183 F1184 F1185 F1187 F1188 F1189 F1190 F1191 F1192 F1193 F1194 F1195 F1196 F1197 F1198 F1199 F1200 F1201 SP 9m0, CDSWSElO .
GPSWSW97 SPE4 SPSW3 GPNE31 SPSENE26 SPSESE15 CDSWNW18 CDNW34 GPNwNw18 sPswsw26 GPNENE24 SPSWSW22
”
”
”
”
”
”
12.8 19.0 3.14 7.23 11.4 11.1 16.4 24.6 2.48 2.01 28.3 22.3 12.66 4.74
2.98 3.05 8.04 3.63 1.38, 5.53 1.53 1.48 7.73 3.44. 4.80 3.56 5.61 2.62 6.43 1.55 1.16 2.60 4.10 4.40 1.55 1.76 2.55 3.65 3.80 5.95 1.64 0.86 7.50 4.73 3.45 2.15
8
TABLE 1 (continued)
Sample , Th (ppm)
GPCNW31 2.33. GP nTw6 2.05 SPNWNE23 2.54 SPC4 14.49 SPWC19 7.69 SPNwNw25 19.1 SPSW36 "
GPCNE31 10.6 GPNE13 6.22 CENENElO I
CDsw3 "
GPSESEM "
SP9 + s m o 4.22 GPSESE14 9.33 SPSWSW36 1.95 CDNElO 15.98 SP9 4.67 CDCNE3 3.34 GPNESWlZ 23.8 GPNWNW24 18.1 GPNESW14 8.75 SPSSW3 6.08
NOTES : (1) FM samples from drill core (see Fig. 1) (2) F1183-1202 surface samples; see Brookins
u bpm) 1.66 1.48 2.02 4.02 2.86 3.07 3.63 2.36 1.68 2.69 1.77 0.65 1.37 3.58 1.55 3.20 1.25 1.40 3.33 3.95 1.86 1.22
(1974) (3) CD = Capitol Dome Quadrangle (Corbitt, 1971) ( 4 ) GP = Gym Peak Quadrangle (Corbitt, 1971) (5) SP = South Peak Quadrangle (Corbitt, 1971)
9
FMl-1
71.42
13.03 .35
4.83 .19
4.28 .34
99.38 4.94
FM2-1
77.42
11.68 .32
2.32 .18 .02
5.06 2.38
99.38
m-2
63.36
17.36 .24
6.10 .56
4.00 .44
97.83 5.77
FM5-2
73.50
12.27 .31
4.17 .19
3.80 .35
4.79 99.38
TABLE 2
Whole Rock Analyses -- Florida Mountains
m - 2
71.92
12.54 .29
5.02 .29
4.04 .42
99.22 4.70
FM2-2
76.85
11.19 .32
4.14 .14 nd
4.67 2.31
99.62
FM3-3
62.86
16.29 .35
7.61 .41 .45
4.32
97.95 5.66
FM5-3
70.10
12.38 .65
7.36 .32
3.74 .16
4.56 99.27
FM1-3
70.90
12.36 .26
6.66 .63
3.32 .37
4.62 99.12
m - 3
74.28
11.63 .40
5.30 .21 nd
2.47
99.39 5.10
FM4-1
61.85 1.08
16.52 5.18 1.15
6.80 2.11
100.48 5.79
FM5-4
73.54
12.61 .33
4.14 .16 .20
4.33
99.60 4.29
FMl-4
72.46
12.49 .28
5.02 .32
3.57 .35
4.77 99.26
FM2-4
76.76
11.05 .33
4.45 .13
2.26 nd
99.65 4.67
FM4-2
60.47 1.24
16.35 6.32 1.84 2.52
5.43 6.74
100.91
FM5-5
73.90
12.48 .27
3.71 .20 .24
4.11
99.44 4.53
FMl-5 71.42
12.56 .30
5.42 .61
3.61 .49
4.88 99.29
FM2-5
73.48
12.55 .48
4.54 .23
3.03 nd
5.21 99.52
FM4-3
59.78 1.39 16.67 6.57 1.81 2.40 7.20
101.33 5.51
FM5-6
75.20
11.80 .28
4.02 .13
3.86 .12
4.36 99.77
FMl-6 72.14
13.10 .30
3.98 .24
4.38 .40
99.42 4.88
m - 7
74 * 98 .40
12.26 4.69 .15
2.95 nd
100.59 5.16
FM4-4
61.15 1.14 17.12 5.54 1.66 1.90
,5.77 6.82
101.10
FM7-1
65.56 .69
18.96 1.03 .43 .48
6.65
100.38 6.58
FMl-7 71.10
12.63 .33
4.96 .47
4.10 .38
99.02 5.05
FM2-8
74.56
12.49 .52
3.83 .10
2.85 nd
99.76 5.41
FM4-5
60.88 1.30
16.99 6.06 1.79 1.69 6.89
101.44 5.84
FM7-2
64.56 .74
18.12 3.08
. .41 .32
6.66
100.18 6.29
"8
70.79
13.07 .30
4.42
.53
.49
5.15 4.12
98.87
FM3-1
64.58
15.80 .28
5.85 .56 .48
4.00
97.99 6.44
FM5-1
72.41 .31
13.20 3.98 .20
2.85 .30
5.04 98.29
FM7-3 65.14
18.58 1.47 .36
6.69 .53
6.74 100.31
.80 "
10
FM7-4
Si02 65.09 Ti02 A1203 18.06
.63
Fe203 2.44
CaO .49
Na20 .49
6.58
total 100.08
MgO
K20 6.30
FM7-5
64.66
18.24 .58
2.44
.41
.40
6.61
99.92 6.52
FM7-6
70.45
15.20 .26
2.59 .30 .17
5.14
99.55 5.44
m7-7
70.41
16.02 .30
1.32 .26
5.75 .21
5.53 99.80
FM7-8
63.77
17.42 .68
.43
6.45 .41
6.19 99.83
4.48
FM8-1 FM8-2
68.23 .32
67.94 .29
14.31 14.56 4.40 .24
4.00 .19
.58 .68 5.74 6.44 5.45 99.27 99.52
5.42
FLORIDA MOUNTAINS "c
8.
7-
6- 0 Y (u
.5-
4i
FLORIDA MOUNTAINS 12
KzO VS. U A A
A SURFACE SAMPLE -SYENITE
A SURFACE SAMPLE - GRANITE
DRILL HOLE CORE SYENITE
x DRILL H&E CORE GRANITE ”+
X A X
FIGURE: 2
19
18
17
I:
1
FLORIDA MOUNTAINS A1203 VS. U
'c. Y o 0 '
o e
1 I
\ 0
8
13
2 3 4
FIGURE 3
e
14
19 -
18-
I 7-
16-
i 3-
12.
I I.
FLORIDA MOUNTAINS
0 \ @
0 4
vs. Th/U
\: e
0
I3 i .t
0 nl 2 O 9 Y i II ,
A
7
FLORIDA MOUNTAINS' 15
(No20 + K201 vs. U
A SURFACE SAMPLE -SYENITE
A SURFACE SAMPLE-GRANITE
SYENITE
e GRANITE @ DRILL HOLE CORE
X DRILL HOLE CORE
A e
A
A A X X
A X
X ' x X x X X
X . x A xx
X A
X A X
A
X ' A
X X
.A
A
n
30
n
n E 20 n
IO
0
FLORIDA MOUNTAINS Th vs. U
e e
7' OI c
a e-' 8 e
17
I .4
I .... a
I .2
1‘ :d n
Y 0.9
c!? 0.8 0.7 0.6
0.5 0.4
0.3,
0.2,
0.
FLORIDA MOUNTAINS Ti02 vs.. U
A
0
a
x X P%xpx X xx X
A M A A
A
x
X A
A
18
r
Spec. No.
"1 -2 -3 -4 -5 -6 -7
FM2-1 -2
' -3 -4 -5 -6 -7 -a
FM3-1 -2
' -3 F M4-1
-2 -3 -4 -5
FM5-1 -2 -3 -4 -5 -6
FM7-1 -2 -3 -4 -5 -6 -7
-a
-a FM8-1
-2
FLORIDA MOUNTAINS
Sample Descriptions and SpecGen Status
Location . Depth
0- 5 5-10 10-15 15-20 .
' 20-25 25-30 30-40. 40-50
SE/NE/Se/13/26S/8W 0- 5
10-15. 5-10
15-20
25-30 30-35 35-40 '
20-25
0- 5 5-10 10-15 - ~.
0- 5 5-10 10-15 15-20 20-21 0- 5
10-15 5-10
15-20 20-25 25-30 0-10 10-20 20-30 30-35 35-40 40-45 45-50 50-55 0- 5 5-13
Map Unit
FLORIDA MOUNTAINS
Description and Location of Rocks
1. Orthoclase,Granite Sections 10, ll', 14 T. 25 S., R. 8 W. Capital Dome area.
i
2. Hornblende Perthite Syenite to Quartz Syenite Sections 25, 35, 36 T. 25 S., R. 8 W. NW Portions Sections 6, 18 T. .26 S., R. 7 W. Mostly nortii of major fault.
3. Per th i te Bio t i te Syeni te Section 25 T. 25 S., R. 8 W. Sections 30, 31 T. 25 S., R. 7 W. North of major fault.
4. Perthite Quartz Syenite Section 36 T. 25 S.; R. 8 W. Section 31 T. 25 S., R. 7 W. North of major f au l t .
5. Hornblende Pe r th i t e Granite Sections 25, 36 T. 25 S., R. 8 W. Section 31 'I. 25 S., R. 7 W. Sections 9, 10, 14 T. 26.S., R. 8 W. Section 18 T. 26 S., R. 7 W. Iden t i ca l to hornblende perthite syenite and per thi te syeni te except more quartz.
6 . Orthoclase Plagioclase Microcline Perthite Granite Sections 2 , 9, 10, 12, $3, 14, 15, 16, 23, 24 T. 26 S., R. 8 W. Sections 18, 1 9 T. 26 S., R. 7 W. South of major f au l t .
LOCATION
m4-3-
FM4-5- SPNW-25- SPNW-25"-
GPNWNW-6- SPNENE-35-
GPNWNWL8B GPCNW-6B-
GPSWNE-30- SPNENE-25-
GPCNE-3lA-
SPNWNE-23- SPSESE-23- SPCNE31B-
CDCNE31- SPSWSE31-
FM7-4-
FX7-6-
SPSW-36-
SPSWSE36-
FM8-2
SPNWNW25- SPSENE-26A- SP-SW-36(?)- GPNW-31A- SPSENE-14- GPSENE14
SP9+SW-lOA SP9i-SW-lOB s999w-10-
SPSENE26B- SPWNE-26-
SPNENE-35- SPSESE-26-
SPSW-36A- SPSESE-2- SPNE-2- SPNESE-4-
Brecciated
Hornblende It
11
It
I t
I1
I t
Biotite 11
It
Perthite I ,
11
I 1
11
Perthite
Perthite
Brecciated
Brecciated
Hornblende
I,
I,
I,
I,
11
11 .
1,
I,
I t
Perthite 11
1,
I,
I ,
I ,
I,
I t
Hornblende
Perthite I,
1,
11
11
11
I.
Perthite
11
Quartz 11
11
I,
11
Quartz
Plagioclase
Perthite
Perthite
Perthite
I1
I,
I1
11
11
1,
ROCK - Perthite
Quartz 1,
I,
I t
11
I1
I ,
Quartz 11
11
Syenite
11
I t
11
I t
Syenite
Quartz
Quartz
Orthoclase
Granite
71
I1
11
11
It
It
11
I.
11
(Cont.)
Quartz
Syenite II
11
11
11
11
1,
Syenite (calcito) I,
11
Syenite
Syenite
Quartz
(cent. )
LOCATION
SPE-4- SPCN-4 SPSW-3A- SPSW-3B- SPSSW-3- GPNwNw-18C- GPSESE-14C- GPNWSE-14- GPNENE-23-
GPESE 14 SPSWNW-16
FM 1-8
SPNESE 26- SP-SW?NW?-2- SPSW-3- - SPSN-3E- SPSW-3c-
SPSWSW9-
FM-3-
SP-SW-3D- SPSW-3-
SP9i-W-lOB-
SPSW16
FM5-2 FM5-6 CDNE-10
CDSWSE-10
GPNESW-12 GPSWSW-13
GPSESE-14B
GPCSE14 SPNWNW-14?
GPSWNE14 GPSWNW14 GPNESW14
Perthite. I,
11
11
(1
11
I,
11
11
1.
II
I.
Brecciated I f
11
11
I1
I,
Perthite
11
Orthoclase
Orthoclase
Orthoclase
Orthoclase It
11
.Granophyric
Perthite 11
Perthite
Perthite 11
I I
I ,
I ,
SPSESE-14-15 or R "
SPSE16D SPSE16B SPSE-45?
11
I ,
I ,
21
' ROCK -
11
Perthite 11
II
I t
I t
I1
Orthoclase
I,
Granite
Plagioclase
Perthfte
Granite ,I
I,
Granite
I!
11
11
11
11
Granite
11
Granite
Granite
(Calcite)
Orthoclase Granite
Plagioclase Granite I, ,I
Granite
Orthoclase Plagioclase 11 I,
11 I t
I1
11 I ,
rr 11 I1
11 I t
I , I,
It I,
LOCATION
SPSWSE15
GPNESE13
GPSW31B
FM2-8
SP99SWlOA
GPSESE14A
cDswsWl4 SPSESE14
SPSESE-15
SPSE16E
GPSwNw18
GPNWNW24
GPNENE24
GPSWSElOA
SP9SWlOA
GPNWNWl8A
SPSE45?
CDNWNE14
CDSWSWll CDSWll
GPSWSWl7?
GP-SWNE36
GP-SW3lA
SPSENW16 SPSWNE12 SPE17 SPSWSW22?
SPCNW6A
SPCNE34C?
Granophyric
Perthite
Granophyric
Granophyric
Perthite
Perthite
Orthoclase
Orthoclase
Granophyric
Microcline
Hornblende
Orthoclase
Orthoclase
Granophyric
Plagioclase
Orthoclase
Granophyric
Perthite
Orthoclase I1
Perthite
Orthoclase
Biotite
Perthite It
I,
I ,
Perthite
Biotite
Perthite
Orthoclase
Perthite
Perthite
Orthoclase
Orthoclase
Perthite
Perthite
Perthite
Perthite
Orthoclase
Plagioclase
Perthite
orthoclase
Orthoclase
Plagioclase
Perthite
Plagioclase
Granite
. .
II
Granite
Quartz
Orthoclase
Orthoclase I,
I1
I,
Orthoclase
Perthite
ROCK - Orthoclase Plagioc :lase
Microcline Plagioclase
Orthoclase Granite
Orthoclase Plagioclase
Quartz Granite
Grkite
Plagioclase Granite
Granite
Orthoclase Plagioclase
Granite
Plagioclase Granite
Granite
Granite
Granite
Granite'(Ca1cite)
Granite
Orthoclase Plagioclase
Granite
. ..
Syenite (Calcite)
Syenite
Quartz Syenite I, I,
I 1 I,
I1 ,I
Plagioclase Quartz
Orthoclase Syenite (Calcite)
22
Granite
Granite
Granite
Granite
Granite
Syenite