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AmericanMineralogist,Volume70,pages 44-355,1985

Genesis f diamond:a mantlesagaHsNnv O. A. MeYEnDepartment of GeosciencesPurdue Uniuersity

West Lafayette, lndiana 47907Abstract

A model for the genesis f natural diamond is presented asedon the physical,chemicaland mineralogicalpropertiesand features f diamond.Optical studiessuggesthat individualdiamondshave had complex growth histories n which growth and dissolutionmay haveoccurred.Growth wasnot always continuousnor did diamondsgrow in necessarily imilarchemicalenvironments.Evidence or this is providedby variation in the nitrogen and traceelement ontents n diamondsas well as nformation from studiesof the minerals ncluded ndiamond. Isotopic data suggest hat diamondsformed from carbon whosesourcesvariedisotopically.The possibilityexists hat somediamondsmay be productsof recycled ubductedcarbon,whereasothers have formed from primordial material either through magmaticormetasomaticprocesses.t is also likely that most diamonds formed in the ArchaeanorProterozoic.The cognatehost rocks for diamond in the mantle were severalbut can bebroadly grouped into eclogitic and ultramafic (peridotitic); however, n mineralogic andchemical detail these rocks are quite diverse.Although diamond is commonly found inkimberlite and in lamproite at the earth'ssurface, hese wo rocks are not geneticallyelatedto diamondformation. nstead hey are the transportingvehiclesn which diamondascendedrapidlyfrom mantledepths o thecrust.

Introduction initial evidence or this latter idea was the discovery ofAlthough diamond has beena sourceof fascination, he diamond in an eclogitexenolith from kimberlite (Bonney,origin of this mineral has for centuriesperplexedman. 1899).Du Toit (1906),Wagner(1914)and Sutton (1928)Greek philosophers and medieval alchemists ziscribed modified his idea and suggestedhat theeclogiteand peri-many mystical propertiesto diamond. When taken as a dotite xenoliths were cognate with the kimberlite. Dia-powder,voluntarily or involuntarily, t could, amongother mond was thus genetically related to the early crys-things, cure diseases, oison ones enemiesor make the tallizationof kimberlitemagma.honest strong and agile. An unusual belief, especially heldin Greece and India was that diamond could procreateitself-a boon to the owner of a diamond mine.

In 1772 Lavoisier demonstrated that diamond, likecarbon, would burn in air. However, it was only later in1797 that Smithson Tennant proved that diamond consist-ed of carbon. This led several gentlemen scientists of thenineteenth century to suggest that diamond was formedthrough the action of heat and pressure on plant remains(Des Cloizeaux, 1855; Goppert, 1862).

The discovery of diamonds in a volcanic rock (kimber-lite) at Kimberley, South Africa in 1871 ed to more scien-tific, and less philosophical studies. This did not, however,deter various authors from presenting opposing view-points, as summarized by Williams (1932). For example,Lewis (1887)considered hat diamond formed in the crustas the kimberlite host rock solidifled-the carbon beingderived from coal and other carbonaceous material.In contrast others maintained that diamonds had orig-inally formed in ultrabasic rocks at depths, and were subse-quently released as the rocks fractured upon incorporationinto the kimberlite melt (Harger, 1905; Holmes, 1936).The0003-{04xl85/0304-{344$02.00

The above wo hypotheses ave asted until the presentand have developedwith some modifications into thephenocrystversusxenocrystschools Dawson,1980).Forexample,Gurneyet al.(1979)and Harte et al. (1980)main-tain that diamonds are genetically elated to early crys-tallization productsof kimberlite within the upper mantleand are thus phenocrysts. n contrast, Meyer and Tsai(1976a),Robinson (1978),and Meyer (1982 a,b) haveargued hat diamondsare accidentalnclusions n kimber-lite and thus are xenocrysts; he associationof diamondand kimberlite being one of passenger nd transportingvehicle.Most scientistsamiliar with diamond concedehat dia-mond hasgrown stablywithin the uppermantle(Kennedyand Nordlie, 1968;Meyer and Boyd, 1972;Orlov, L973;Sobolev,1974;Robinson,1978).Omittedfor purposes fthis discussionare the polycrystallineaggregates f dia-mond (carbonado, ramesite,boart) which have receivedlittle scientific tudy Trueband DeWys,1969;1971;Trueband Barrett, 1972; Gurney and Boyd, 1982) and whoseorigin is evenmore uncertainthan the singlecrystal dia-mond considered ere.

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Suggestionss to the sourceof carbon from which dia-mond forms have beendiverseand range from coal andplant remainsas favored n the 1800's,o carbon dioxideand methane oday.However,whetheror not the carbon sprimitive or from recycledcrustal material is a necessaryquestion.Currentstudieson carbon sotopes Deines,1980;1982;Milledgeet al., 1983), s well as on nitrogen (Becker,1982)and rare gasesOzimaand Zashu,1983)bear on thisquestion.An important factor in understandinghe formation ofnatural diamond is afforded by detailed examinationofminerals ncluded n diamond.Thesestudies,mostly crys-tallographicand mineralogical, avebeen eviewedby So-bolev (1974),Meyer and Tsai (1976a),Harris and Gurney(1979)and Meyer (1982a).sotopic studiesof these smallinclusions n diamond are now possibleand future workshouldprovidesignificant esultsconcerningdiamond andthe evolutionof the uppermantle.This papersuggests model for the genesis f diamond,and its subsequent assageo the earth'ssurface.Currentinterest n the evolution of the upper mantle and magmageneration onsiders iamond o be an unreactive hemicalprobe from the depths.One aim of the discussionandmodel presented erein s to place he genesis f diamondwithin the correct context of mantle processes.t is alsohoped that the discussionwill removevarious misunder-standings hat are prevalentwith respect o diamond andits relationship o kimberlite and other rocks.A subsidiaryaim of this paper is to bring to the attention of mineral-ogists he large amount of important information contrib-uted by physicists o diamond research,and equally toexposephysicistso geologicalprocessesttendenton dia-mond formationand thesubsequent istoryof diamond.Although the host rocks for diamond at the earth's sur-faceare kimberlite and lamproite, t is believed hat theserocks are not genetically elated o diamond.Accordingly,it is not the aim of this paper o dwell on the natureof thechemical and mineralogical differencsbetween variouskimberlites,and betweenkimberlitesand lamproites.Theinterested eader s referred o Dawson(1980) or kimber-lites, Mitchell (1984) or lamproites,and the proceedingsvolumesof the three nternationalKimberlite Conferences.

Physical features of diamondA considerable mountof detailedstudy nto the physicsof diamond has beenundertakenover the past 35 years(Berman,1965;Field, 1979).Much of this research assignificanceo mineralogyand bears on the formation ofdiamond.Figure la is a photographofa typicalclearand colorlessdiamond without any visible laws. This clarity, shownbymany diamonds,suggestso the observer rystallization na singleuninterruptedevent.This is not the case. n Figurelb is shown a polishedand etchedsurfaceof a diamonddisplayinga series f geometricalayers-referred to as thestratigraphy of diamond (Harrison and Tolansky, 1964;Seal, 1965).These patterns were interpreted by Frank(1966)as beingdue to periodicgrowth on octahedraland

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Fig. l. (a)A transparent,learand well shaped ctahedronfdiamond.Octahedral dge mm.(b)A polishedand etched ec-tion throughan octahedraliamond2.4mm on edge), howingthe nternal tratigraphyf diamond. ariousgrowth ayers reeitherType or Type I diamondFigure .1;Harrison ndTol-ansky, 964).

cuboid surfaces.More detailed descriptionsof this phe-nomenonare to be found in Suzuki and Lang (1976)andLang(1979).The stratigraphyof diamondcan alsobe llus-trated by cathodoluminescencen polishedsurfaces fdia-mond (Moore, 1979)and by X-ray topography (Lang,1979). he growth stratigraphy s observed ecause ariouslayers consist of either Type I or Type II diamond, andthese two types have different chemical and physicalproperties Table1).The presence f Type I and II diamondwas irst demon-stratedby Robertsonet al. (1934)basedon differencesnUV and IR absorption.Lonsdale 1942) howed hat TypeI diamond producesextra X-ray diflraction reflections,orspikes.Thesespikeswere nterpreted o be due to plateletswithin the diamond structure (Frank, 1956).Kaiser andBond (1959), nd ater Lightowlersand Dean(1964) roved

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t46 MEYER: GENES/SOF DIAMOND: A MANTLE SAGAthe presence f nitrogen n Type I diamondsand showedacorrelationbetweennitrogen content and optical absorp-tion at 7.8pm (1282cm- r). In contrast Type II diamondcontainsvery ittle nitrogen and no platelets.The aboveevidence uggestshat the stratigraphyof dia-mond recordsperiodic growth in chemicallydifferent envi-ronments,at least with respect o the amount of nitrogenpresent.Alternatively, he rate of crystallization,or lengthof residenceime after partial growth may also contributeto differencesn nitrogencontent.At high pressuret is possible o causemigration of thesubstitutional nitrogen in diamond so that the nitrogenaggregatesincluding platelets) ound in natural diamondsare produced Evansand Qi, 1982).Basedon the resultsofthis study Evans and Qi suggest hat Type Ia diamondmust haveexisted or between200 million and 2000millionyears.This range n time is admittedly arge but is due toinsuffrcient nowledgeof the activationenergyof migrationof certain aggregatesn diamondat high pressure nd tem-perature.Nevertheless,he data indicate that some dia-monds have had gestationperiods n excess f the age ofthe kimberlite eruption that transported hem to the crust.In summary,although individual diamonds are grosslysimilar in physical propertiesdetailedexamination showssubtle differences esulting in four distinct types of dia-mond (Table 1). Growth of diamonds is crystallogra-phically discontinuous and reflectspossiblevariation inchemistryof the growth environment.Experimentalaggre-gation of nitrogen to form plateletsand other nitrogenaggegates n diamond suggests ery long residence imesfor diamond within the uppermantleprior to reaching heearth'ssurface.

Chemical features of diamondThe presence of nitrogen as a major impurity in dia-

mond has been noted, as also has the occurrence of boron( < 20 ppm) which accounts for the semi-conductingproperties of Type IIb diamond (Table 1). As a chemicalsink for various elements, diamond is fairly poor withregard to concentration levels, although 58 elements havebeen recognized at the trace impurity level (Sellschop,1979).Most of the results reported by Sellschop were ob-tained using instrumental neutron activation analysis, butearly studies used emission spectrographic techniques(Chesley, 1942;Raal, 1957).Elements occurring in amountsgreater than I ppm are listed in Table 2 (Sellschop, 1979),and most of these elements are typically present in silicateand sulfide magmas.

In a significant contribution, Fesq et al. (1975)suggestedthat in certain instances the trace elements in diamondwere contained in sub-microscopic inclusions that repre-sented quenched, or temperature re-equilibrated, melt fromwhich diamond had crystallized; composition of the meltwas thought to be picritic. At the time of the study (1972-73) Fesq and coworkers were able only to examine batchesof diamonds, and thus the data represent diamond of dif-ferent type and origin. Recent developments in analytical

Table 1. Somepropertiesof diamondC as s f i c a t i o n

T y p e l a - X o s r c o m n o n , a p p r o r . 9 8 1 o f n a t u r a l d i a n o n d s . C o n t a i n sn i t r o g e n u p t o 2 5 0 0 p p n b y u c . s s a g g r e g a r e s a n d p l a t e l e t s

T y p e l b - R a r e i n n a t u r c b u t m o s c sy n t h e c i c d i a m o n d E a r e o f l h i s L y p eN i t r o g e n < 2 0 p r b y p t i n d r s p e r s c d E u b s t i t u t i on a l f o m .

T y p e l l a - V e r y r a . e . N i t r o A e n . 2 0 p F b y u r , O f t e n t h e v e r yl a r g e g e n d i a m o n d s a r e r h i s r y p e .

T y p e 1 l b - E x t . e o e l y r a r e 3 nd g e n e r a l l y b l c i n c o l o r . S e m i _ c o n d u cr i n s( B .2 0 p r b y w t . ) u o s c p u r e E y p e o f d i a d o n d .

Space croup: Fd3tu - Oi lu n i t c e l l : 3 . 5 6 6 8 3 + o . o O 0 0 I t o 3 . 5 6 1 2 5 . O . o O O O r lD e n s r y :

T y p e I - 1 . 5 1 5 3 7 + 0 . 0 0 0 0 5 g o c n - 3 -T y p e 1 I - 3 , 5 1 5 0 6 + 0 , 0 0 0 0 5 g o c n - r

U l t r s v i o l e t a n d l n f r a r e dT y p e I - S r r o n S a b s o r p L i o n < 1 4 0 n n a n d b l t e e n 6 to l l x l o 3 nmT y p e I I - T r s n s p a r e . r to 22 5 n m a .d b e r u e e n 6 t o l l x l o 3 n m

T y p e r a - v a r i o u s ( e . e . c o l o r t e s s , p a l e y e r r o v , b r o m )r y p e l b - v a r i o u s ( e . s . y e r l o u , d a r k b r o m )t y p e l I a _ C o l o r l e s s , b r o e nT Y p e t I b - l l l u e

T h e r f t a l C o n d u c t r v i E yT y p e l a - 6 O O -1 O O O - I K - l ( a t 2 9 3 " K )T y p e l I - Z O O O -z t O O m -1 K - l ( a t 2 9 3 ' K )

R e s s t L v r yT v p e I - > 1 0 1 6 o h m nI y p e l l a - c a . l u ' " o h n nT y p I I b - t o l - t o 5 " n . '

techniques (e.g. nuclear activation and ultra sensitivegamma ray spectroscopy) have enabled trace elements tobe studied in a single diamond, and the results should pro-vide significant information regarding the chemical differ-encesbetween the various types ofdiamond.Various diamonds have diflerent trace element contents(Sellschop, 1979). This variation in trace element contentsuggests that different diamonds have not always formedunder identical chemical conditions even though the dia-monds may have been obtained from the same kimberlitepipe. If color is due to variation in trace element content,

Table 2. Elements resentn diamond maximumppm by weight)Element

HINo

NaMgA Is i

I r 00IO

5500r700

3437 0I0 0EO

EleEnt

N TCuAgBa

CeHg

28040305 8t4t 15

Elenent Anounts 9 0

c l cK 4 8

ca 19 5T i 8c r t000l n 5Fe t4 0

E l e n e n t 6 p r e s e n t i n d i a r c n d< l p F b y u t :

E l e n e n t s p r e s e n t i n d i a b o n dbu t n o a b s o l u t e v a l u e s a v a r l a b l e :

F , S c , V , A s , R b , S r , S b , C 3 , I h , E u ,Tb , D y , H o , Y b , L u , H f , T a , W, I r , A u

A r , z n , G a , G e , B r , Z r , S n ,N d , U , S n , G d E r , P t , P b ,

D a t a f rm s e l l s c h o p ( 1 9 7 9 , a nd p e r s . c o o m . )

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then the wide range of colors in different diamonds fromthe same pipe can also be used, in part, to support theabove arguement (Robinson, 1978).Isotopic studies

Geochemical information bearing on the genesis of dia-mond is available from studies on the isotopes of carbon,nitrogen and rare gases.Carbon

On the basis of a few measurements, the d13C value fordiamond was once considered to be generally in the range-4 to -9o/oo Craig, 1953;Wickman, 1956).More recentlyseveral authors (Galimov et al., 1978; Gurkina et al., 1979:Sobolev et al., 1979;Deines, 1980and Milledge et al., 19g3)have extended he range from *3 to -34%oo.Nevertheless,the majority of diamonds studied (e.g.,Deines, 19g0)have613Cvalues n the range -4 to -8oln.In a significant study, Milledge et al. (1983)have exam-ined the d13C content of 18 Type II diamonds and ob-tained a range of values between 0 and -32y@, althoughonly two values were below - l5y@. t was concluded thatType II diamond is isotopically lighter than Type Ia dia-mond which presumably comprises the majority of dia-monds. as noted above.The existenceof a range of dr3C values for diamond hasa bearing on the source of carbon and the chemical reac-tions that produce diamond. Recent models (Deines, 1980;Mitchell, 1975) as to the role of a vapor phase in diamondformation have proven ambiguous, although the presenceof a vapor could help explain the range of d13C. Deines(1980)concluded that this range was most likely inheritedfrom the source carbon, suggesting isotopic heterogeneityin the mantle. Mitchell (1975) n contrast has pointed outthat variation in the isotopic composition of diamond maybe the result of re-equilibration (isotopic) of the solid phasewith changing carbon-bearing gas compositions.Discussed later is the fact that minerals included in dia-mond can be assigned to either an ultramafic or eclogiticsuite. A careful study by Sobolev et al. (1979) involvedexamination of d13C valuesof diamonds in terms of wheth-er they contained ultramafic or eclogitic suite inclusions.For diamonds with ultramafic inclusions the majority hada 613C value of -5%ooand a restrict ed range between -2and -9'/oo. Conversely, diamonds with eclogitic suite in-clusions had 613C values ranging from 0 to -34%o. Aspointed out by Milledge et al. (1983), his latter range issimilar to that of Type II diamond, whereas the peak at-5Y* for the ultramafic suite diamonds corresponds tothat of Type I. A study of the type of diamond in whicheclogitic inclusions occur has yet to be undertaken.Nitrogen and rare gases

Attempts to determine the origin of diamond and thegeochemical nature of the upper mantle have also involvedstudies of the isotopes of nitrogen as well as those of raregases,notably helium. Data on nitrogen isotopes are sparseand consequently any conclusions are speculative. Wand et

347al. (1980)obtained a mean value for 61sN of +L5h,whereasBecker 1982)eporteda meanvalueof *29oln torfivediamonds,with a rangeof 0 to * Sc/n. oth thesemeanvaluesat present esult n diamondbeing sotopically ight-er in nitrogen than mantle rocks (Beckerand Clayton,1977)whose anges +6 to +20o/',. tudies f raregasesndiamond (Ar, He, Ne) have been undertakenby Takaokaand Onma (1978),Oama and Zashu(1983), nd Ozima etal. (1983).The latter authors reported 3HelnHevalues orthree diamonds hat were n excess f the primordial valuefor meteorites1.42+ 2 x l0-a; Reynolds t al.,1978), ndclose to the solar value (-{ x 10-a; Black, 1972).Asecondgroup of diamonds have much lower 3He/aHeratios. Ozima and coworkersproposethat the diamondswith high 3He74Heratios trapped primitive helium soonafter the formation of the earth. whereas hosewith lowervaluesmay haveformed later and includedmore evolvedhelium rom the mantle.Most of the variations n isotopic contents of diamondcan be explainedby consideringhat the carbon haspassedthrough a subductioncycle Frank, 1966). n contrast,veryhigh 404r/36Ar ratios obtained by Takaoka and Ozima(1978)are interpretedas indicating that the carbon fromwhich diamond formedhas never reached he earth's sur-face;a similar comment s pertinentfor the high 3He/4Hevaluesof Ozima et al. (1983).Melton and Giardini (1980)obtaineda 4o{rf361ltratio of 190 or a diamond rom thePrairie Creek diatreme,Arkansas,well below that of theatmospherewhich is taken as 296. Interestingly, his dia-tremehas recentlybeen eclassified s a lamproitic kimber-lite (ScottSmith and Skinner, 1984),whereasMitchell andLewis(1983) egardpart of the diatreme o be a madupite.The data of Melton and Giardini (1980) epresenthe firstpublishedresultsof rare gas contents n diamond from anon-kimberlitic primary source seealso Roedder,1984,p.508-51 ).Geochemicaland isotopic studiesshow that diamondcontains many elements n trace amounts, but generallythoseoccurring n the largestconcentrations re similar tothosepresentn silicateand sulfidemagmas.This suggeststhat diamond grew in a similar environment to mostsilicate-bearing ocks. Isotopic data,particularly the d13Cvalues,show that the carbon from which diamond formedwas isotopically variable. Furthermore, the variation ind13CbetweenType I and Type II diamond can be inter-pretedas diamond having formed n more than one envi-ronment,and onepossibility s that somediamonds epre-sent recycledcrustal carbon. It is important that futureisotopic studiesbe carried out on well-documented peci-mens, ncludinggeographic ourceand type of diamond.

Mineral inclusionsVarious studiesof minerals ncluded n natural diamondare documented by Sobolev (1974), Meyer and Tsai(1976a),Harris and Gurney (1979)and more recentlyby

Meyer (1982a). he significance f mineral inclusionswithregard to diamond genesis and the upper mantlecharacterizationwas appreciatedearly (e.g.,Bauer, 1896),

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348 MEYER: GENESISOF DIAMOND: A MANTLE SAGAbut apart from Sutton (1921)and Williams (1932) ittlework was done until the 1950's G0belin, 1952; Mitchelland Giardini, 1953;Futergendler,956,1958, 960). hesewere mostly optical and X-ray diflraction studies,and itwasnot until 1967 hat the first electronmicroprobeanaly-ses were obtained (Meyer, 1968; Meyer and Boyd, 1969,1972).Since hen others have contributed significantly othe study of inclusions seeMeyer, I982a or references).A number of results rom thesestudiesbear on the gen-esisof diamond. For example,most inclusionscan be as-signed o one of two mineral suites-an ultramafic suiteand an eclogitic suite(Table3). Membersof the two suitesare mutually exclusive; hat is, mineralsof one suite do notcoexist n the samediamond with minerals of the othersuite.The discoveryof this phenomenon Meyerand Boyd,L972;Prinzet al., 1975)was he first proof that diamondsgrew n more than onegeochemicalnvironment.

It should be noted that inclusionscan also be subdividedinto protogenetic, yngenetic, nd epigenetic. or purposesofthis discussion nly proto- and syngeneticnclusionsareconsidered.Many syngenetic nclusions,particularly oli-vine, display a cubo-octahedralmorphology that is im-posedby the diamond host. In spite of diligent searchbyscientistshrough several ensofthousandsofdiamondsnomacroscopic or microscopic fluid or gaseous nclusionshavebeen ound(Roedder,1982;1984).The majority of mineral nclusionsare small (- 100pm)and monominerallic,although bi- and polyminerallic n-clusionsdo occur. Multiphase nclusionsare mportant be-cause he chemicaland physical nformation they provideenables stimationof thepressure nd temperature f equi-libration of the inclusions, nd by inferencehat of the hostduring diamond genesis.Estimated conditions of equili-bration for co-existingultramafic suite inclusions n dia-mond are between 900 and 1300'C and 45 to 65 kbar(Prinz et al., 1975; Meyer and Tsai, 1976b; Hervig et al.,1980;Boyd and Finnerty, 1980). hesevalues ie within theregion of diamond stability (Kennedyand Kennedy,1976)and are similar to those obtained or diamond-bearing nddiamond-free arnet herzolite xenoliths Shee t al., 1982).It is not possible o determineunequivocallypressures fequilibrationfor eclogitesuite nclusions, ut temperatureslie within the rangecalculated or the ultramaficsuite.A major unsolvedproblemat presents the direct deter-mination of the age of diamond from the diamond itself.Currently, it is necessaryo obtain the age of syngeneticmineral inclusions and to assume his approximates hediamond age. Kramers (1979) examined batches ofinclusion-bearing diamonds from kimberlites in SouthAfrica, and using lead isotopic techniquesdemonstratedthat in generalthe inclusions,and by inference he dia-monds, were much older than the kimberlite eruption. Inthe caseof the Finsch and Kimberleykimberlites, he ageof the diamonds s greater han 2 b.y.,whereas he kimber-lites erupted about 90 m.y. ago. More recent work byOzimaet al. (1983) uggestshat somediamondsmayhaveages omparable o the ageof the earth.Most ultramafic and ecloeitic suite inclusions have

Table 3. Mineralsoccurringas nclusionsn diamond

U l t r e n e f i c Su i t eO l v i n eE n E t a t i t eDiops id eCr -pyropePh ogopi teC -sp i n eMg-i 1reni teZ rco oSu l i d e sDianond

E c l o g i t i c s u i t eOmphaci ieP y o p e - a l n a n d i n eKyani tec o e s i t e ( Q u r t z )Ru t i IeRubyI l nen i teC h r o o i t es u 1 f i d e sD ianond

EP GENETICS e r p e n t i n c , c o e t h i t e , c r a p h i t e , K a o l i n i t e

H e n a t i t e , S e l l a i t e , X n o t i n e

IJNCERTAIN PAMGENESISH u s c o v i t e , B i o t i ! e , S e n i d i n e , U a g n e t i t e , A n p h i b o l e

chemistries hat differ in detail from similar minerals hatoccur n kimberlite.This is not to say that one cannot indin kimberlite rare examples f minerals hat are chemicallyequivalentto those occurring as inclusions(Gurney andSwitzer,1973)but thesemineralsare most probably xeno-crystsunrelated o kimberlite crystallization.Kimberlite and lamproite

Kimberlitesare widely distributed hroughout the conti-nentalregionsof the world (Bardet,1974,1977;Wilson,1982).Most are not diamond-bearing, nd compared o thediamondiferousoneshave been ittle studied.Diamondi-ferouskimberlitesappear o be confinedmainly to the in-teriors of stable cratons.such as SouthernAfrica and Si-beria,althoughsomedo occurclose o continentalmarginsin LiberiaandSierraLeone Bardet,1974; aggerty, 982).Dawson (1980)has provided a review of kimberlites andtheir xenoliths,and recentlyClementet al. (1984)havepro-posed a redefinition and classificationof kimberlite (seealsoSkinner nd Clement, 979).Kimberlite occurs n diatremes, ikesand rarely as sills;multiple intrusions within a single diatremeare common.Neighboring diatremes,or pipes,may contain similar orverydifferentsuitesof xenoliths,or none at all. Somekim-berlites contain almost entirely xenoliths of eclogite, orexample the Roberts Victor kimberlite, whereasothers,suchas the Kimberley pipes,are rich in lherzolitic xeno-liths. Multiple intrusions n a singlepipeoften contain theirown suiteof xenoliths,or xenocrysts nd more mportantlydiamond.Type I and II diamondscan occur in the samepipe,and diamondswith ultramafic nclusionscoexistwithones that contain eclogiticsuite minerals. n spite of theeconomic mportance of diamond, t is a trace mineral inkimberlite and rangesonly up to I part in 2.5 million; aquoted igure s I in 20 million (e.g.,Kennedyand Nordlie,1968).Confusionhas arisen due to the discoveryof diamond-bearing ocks n north-westernAustralia hat unfortunatelywerereferred o initially askimberlite(Jacques t a1., 982;McCulloch et al., 1983). he so-called kimberlites" n that

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MEYER: GENES/SOF DIAMOND: A MANTLE SAGA 349region are tuffaceousamproites (i.e.,Ellendale,Argyle)----someof whichare rich in diamonds Jacques t al., 1984).Lamproitesare ultrapotassicocksthat may be plutonic,hypabyssal, r volcanic. n the latter instanceboth lavas,tuffs and vent brecciasmay be present.Generally thevarious ocksoccur n groups,or fields,but worldwide heyare relatively estricted e.g., euciteHills, Wyoming; WestKimberley,N.W. Australia).Mineralogically eucite or sa-nidine) and Ti-rich minerals are almost ubiquitous. Ti-amphibole,Ti-phlogopite,priderite,etc.are usuallypresentand dependingupon the abundanceand type of mineralsseveral ock namesare possible e.g.,orendite,wolgidite,wyomingite, itzroyite,etc.-Hughes, 197 ,p. 321 Mitchell,1984).The significanceof the diamond-bearing amproites isthat kimberlite s now not the only primary crustalsourceof diamond. t hasbeen eported hat somenon-kimberliticrocks in the Soviet Union contain diamonds (Kaminskyand Gevorkin,1976;Kaminsky,1980;Dawson,1980).nseveral nstances e-evaluationof what were once con-sidered odd" kimberliteshas shown hem to be amproitic.The diamond-bearingPrairie Creekdiatreme n Arkansasis one such example,and is now referred o as lamproite(ScottSmith and Skinner,1982,1984), nd most likely themetakimberlites Bardet,1974)of the Ivory Coast(Knopf,1970) nd Gabonare amproites.The question of whether or not diamonds from lam-proiteshavedifferent nclusions han those rom kimberlitehas been answeredn part from evidence t Prairie Creek,Arkansas.Diamonds from the Prairie Creek "lamproite"contain similar inclusions to those in diamonds fromkimberlite-namely, olivine,enstatite,diopside,Cr-pyrope,pyrope-almandine, hromite and sulfides(Newton et al.,1977;Pantaleoet al., 1979). t is anticipated hat similarmineral inclusionswill be present n diamondsfrom thelamproitesn N.W. Australia.

DiscussionRelation of diamonil to kimberlite and lamproite

The presence f diamonds n both kimberlite and lam-proite, the presence f similar inclusions n diamonds romkimberliteand lamproite, he chemicaldifferences etweenthese nclusionsand cognateminerals n the host kimber-lite and amproite,plus the largedisparity betweenhe agesof diamond and kimberlite intrusions lead to the con-clusion that diamond is not genetically elated to eitherkimberliteor lamproite.The relationshipof these wo rocktypes o diamond s that they are the transportingmediumby which diamond ascendso the earth'ssurface.Diamondis best describedas a xenocryst n kimberlite and lam-proite.Transport of iliamond

The processof kimberlite ascent hrough the mantle isunknown althoughseveralauthors have suggestedariousmodels which include zone refining (Harris and Middle-most, 1969),diapirism (Greenand Guegen, 1974;Wyllie,

1980;Anderson, 1982;Allegre, 1982)and conduit forma-tion (Mercier, 1979\.McGetchin and Ullrich (1973)calcu-lated a speedof ascent or kimberlite of approximately70km/hr on the basisof xenolith sizeand density.A similarvaluewascomputedby Mercier(1979)rom olivineanneal-ing data. Both these atesof ascentare consistentwith thecooling rates calculatedby McCallister et al. (1979) forexsolutionphenomenan pyroxenes rom kimberlite.Theevidenceat present thus favors a rapid ascent,possiblyhours, for kimberlite (and diamond) from depths in theupper mantle. Although geochemical rocessesn a diapirmay have contributed to the formation of kimberlite, theroute through the upper mantle was probably by crackpropagation D. H. Eggler,pers.comm.,1984).It can be argued hat the speedof ascenthas served opreserve iamonds hat would havebeenabsorbed nto thekimberlite magmawith slow ascent.Other factorsaflectingthe stability of diamondwould be temperature, articularlythe lengthof residenceime at high temperatures nd pres-sures outside the diamond stability field, and oxygen fu-gacity. Preliminary experiments Meyer, unpub.) on theeffect of temperatureandfo, on the oxidation rate of dia-mond at room pressure aveprovided nteresting ata.Atan fo, equivalent o 10-12 atm. and a temperature f1000'C, roughly between he FMQ and MW (fayalite-magnetite-quartz, magnetite-wustite) buflers, diamondwould disappear n about 2l days. n contrast under thesame1[o,but at 800"C diamond would remain for about110 years.At presentthe /or-temperature conditions forgenerationof kimberlitic, or lamproitic, magmasat depthare unknown. Arculus et al. (1982),Haggertyand Tomp-kins (1983)and Eggler (1983)suggest onditions n theregionof the FMQ-MW bufers.Mantle rocks and diamond

A large number of eclogite xenoliths that contain dia-mond are known (Hatton and Gurney,1979)but only asmall number of diamondiferous ltramafic xenolithshavebeen ound. In contrast, he majority of diamondsstudiedcontain ultramaflc suite inclusions (Boyd and Finnerty,1e80).Diamonds that contain eclogitic suite inclusions,anddiamonds that occur in eclogite are obviously easily as-signedto an eclogite source rock. Sobolev et al. (1972)documented his relationship by examining nclusions ndiamond that itself was contained n an eclogite.The in-clusionsand the constituentminerals of the eclogite clin-opyroxeneand garnet)werechemicallyequivalent, uggest-ing that the diamond is a constituentof the eclogiteandthus ormedcontemporaneously ith the eclogitehost.In contrast, t is lesseasy o determine he source ock inwhich diamonds with ultramafic suite inclusions ormed.One reason or this is that few rocks are known that havemineralphasesof comparablechemistry o the inclusions,Furthermore, he ultramaficxenoliths hat do contain dia-mond are chemicallyand mineralogically varied and in-cludedunites(garnet * olivine-Pokhilenko et al., 1977),harzburgites (garnet + olivine + orthopyroxene-

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350 MEYER: GENES/SOF DIAMOND: A MANTLE SAGASobolev, 1974; McCallum and Eggler, 1976), and lherzol-ites (garnet + olivine + clinopyroxene +orthopyroxene-Dawson and Smith, 1975; Shee et al.,1982). Diamond-bearing dunites consist of olivine andgarnet whose chemistries are somewhat simi lar to those ofthe ultramafic suite inclusions from Siberian diamonds(Pokhilenko et al., 1977). Thus some Siberian diamondsmay have been derived from the disaggregation of duniticrocks, but such dunites have not been recognized elsewherein the world. In contrast Shee et al. (1982), with specificreference to the Finsch kimberlite, South Africa, report nosimilarity in chemistry between the constituent minerals ofa diamond-bearing garnet lherzolite and inclusions in loosediamonds from the same kimberlite.Any model of diamond genesis for the ultramafic suitediamonds also must explain the chemical variation, on aworldwide basis, of some of the mineral inclusion types.For example, clinopyroxene inclusions show a range inCal(Ca * Mg) values rom sub-calcic

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MEYER: GENESISOF DIAMOND: A MANTLE SAGA 351berlitemagma(e.g.,Wyllie, 1980).However, he formationof kimberlitewith or without CO, has ittle to do with themuchearlier genesis f diamond.Furthermore, f mostdia-mondsare Archaeanor Proterozoic,t could be questionedas to whetherpresent hermalmodelsof the mantle(Sleep,1979;Anderson,1980)are valid for discussions f the gen-esisof diamond.Carbon in a melt is unlikely to be in elemental orm(Olaffsonand Eggler,1983)but rather as somedissolvedspecies uch as CO, or CHo. Whether CO, or CHo ispresentn the melt depends n the redoxconditions.Stud-ies of ilmenite(Haggertyand Tompkins, 1983;Arculus etal., 1982)and megacrysts Eggler,1983)suggest., valuesin the mantle to range from fayalite-magnetite-quaftzomagnetite-wustite. heseconditionspossiblydo not reflectthoseof the early mantle which may have beenmore re-duced (Haggerty and Tompkins, 1982).Sobolev et al.(1981)havereportedmetallicFe inclusionsn Siberiandia-monds. In the event of a more reducedmantle, perhapsequivalent to iron-wustite bufer, the predominant dis-solvedspeciesn a magmawould be CHo (WoermanandRosenhauer,982;Egglerand Baker,1982;Eggleret al.,1980;Ryabchikov t al., 1981). he occurrencef CHn inthe mantleand its role in diamondformationhas been hesubjectof modellingby Deines 1980).It has beenhypothesized Gold, 1979;Gold and Soter,1979) hat the deepmantle s beingdegassed f methane.Melton and coworkers 1973,1974) eported he presenceof CO, and CHn among gases hat were evolved fromdiamonds hey crushedbetween teelanvils n a massspec-trometer.They found indications hat other organiccom-plexesof C and H were present,but their resultsrequireindependentsubstantiation.As noted earlier, no macro-scopic luid or gaseousnclusionshave beenobservedndiamond, although CO, has been recorded n fluid in-clusions n olivines rom xenoliths n kimberlite (Roedder,1963,1982, 984).In summary he evidence enerally avorsthe formationof diamond either directly from an igneousmelt or fromsome type of metasomatising luid that has pervadedvarious ypes of mantlerock, perhapsat differenttimes. tis not clearwhether he carbonwas derived rom CO, orCHn but the presence f CHn in diamond,metallic ron asinclusions,and Cr2+ in olivines ncluded n diamond ndi-cate educed onditionswhichwould favorCH..Source of mantle carbon

The source of the carbon that forms diamond is anenigma.Variations n d13Cvaluesor diamondsmay reflecteither an isotopically nhomogeneousmantle or the pres-enceof recycledcrustalmaterial,or both. A similar com-ment is valid for the 3He/4Heand 404r/364'rvalues,al-thoughmore data are obviouslyneededn order to removeambiguities. Meteorites, particularly the carbonaceousvariety,havea rangeof 613C alueshat is similar o thatfor diamond Robertand Epstein,1982).In addition to continualdegassing f the mantle n CHnand CO2 as suggested y Gold (1979), he intriguing and

speculativemodel of Dickey et al. (1983)providesa readysource of carbon. In this model elementalcarbon in thelower mantle s in the form of a metallic iquid. Subsequentperturbationscauseupward migration of the carbon re-sulting n the formation of mantleplumes.Oxidationof thecarbon producesCO, which causespartial melting andcarbonation of the mantle silicaterocks. Theoretically, felemental arbon ascendedrom the lower mantle t shouldpass through the hexagonaldiamond phase-lonsdaleite(Bundy and Kasper, 1967; Frondel and Marvin, 1967)before nverting to cubic diamond at lowerpressures. ow-ever, the absenceof lower mantle phasesas mineral in-clusionssuggestst is unlikely that the carbon of Dickey etal . 1983) irectly ormsdiamond.Recycled rustal carbon n the form of carbonate n themantle may be presentwithin regions of subduction. t isstable o appropriatedepths Wyllie,L978,1980)and underthe correct conditions diamond should be produced.Theinfluenceof such carbon is unknown, but generationofsome diamonds rom recycledcarbon(sayeclogitic ypes),and otherdiamond rom primitive carbon mostlyultrama-fic types)would account or variouschemicaland isotopicfeatures. f this is the caseand if eclogitic diamonds arealso very old (i.e.Proterozoicor older) then a corollary isthat subductionmust have beenoperativeduring the earlyhistoryof the earth.Summary

Various partial melting or metasomaticevents n whichdissolvedCHo or CO, were present, resulted in crys-tallization of diamond at depths of approximately180 kmin the upper mantle. Isotopic data, especially hat ofcarbon, are compatiblewith the possibility hat diamondsiormed from carbon whosesourceswere sotopicallydiffer-ent.Variation in isotopecontentcould havebeenproducedby inhomogeneityn primitivemantle material, he pres-ence of recycled crustal carbon, or both. The growth ofdiamond was not unique o a single ock but took place nany mantle material in which chemical nteractionspro-duced elementalcarbon. Consequentlyseveral types ofrock broadly groupedunder eclogiteand ultramafic(peri-dotite) are the original cognatehostsof diamond.Evidencesuggestshat this crystallization of diamond occurred nthe Archaeanor Proterozoic.Subsequentmobilization ofmantle diapirs and associated hysicaland thermalpertur-bation of the proximal mantle rocks resulted n the incor-poration of diamond and xenoliths. Dependingupon thelocationofthe diapirism elativeo the ithosphere,ariousmagmatic end productscould have beenproduced.Kim-berlite or lamproite magmas, ormedas a consequencefdiapiric processes,onveyeddiamond rapidly to the crust.Rapid ascentwas possiblythrough crack propagation nthe mantle, and through a thick cool lithosphere whosethermal regime esulted n little lossof diamond.

AcknowledgmentsI thankDrs.F. R. Boyd,D. Eggler, . Evans,. D. MacGregor,

R H. Mitchell, M. Moore, J. P. F. Sellschop and P. J. Wyllie for

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352 MEYER: GENESISOF DIAMOND: A MANTLE SAGAtheir constructive eviewsof the manuscript.Many of the ideasexpressed erein were ormulated during the award from NSF ofgrant EAR76-22698; owever, hasten o add that errors n inter-pretationare mine alone.Note aildeil n press:After the presentmanuscriptwas written and acceptedor pub-lication, Richardsonet al. (Science, 10,198-202,1984)havepre-sented sotopic evidence hat chrome-pyrop arnet nclusions ul-tramafic suite nclusions) n diamondshave model agesof 3.2 to3.5 b.y., whereas he host South Afr ica kimberlites were ntrudedroughly90 m.y.B.P.

ReferenceAllegre,C. J. (1982)Diapirism and magmagenesis: n instabilityanalysis.abstr.)Terra Cognita,2, 239.Anderson,D. L. (1982)The role of kimberli te n mantle evolution.(abstr.)Terra Cognita,2, 239.Anderson, O. L. (1980)The temperatureprofile of the uppermantle.Journal of GeophysicalResearch, 5,7003-7010.Arculus, R. J., Dawson, J. B., Mitchell, R. H. and Gust, D. A.(1982)The intrinsic oxygenfugacities /Or's) of megacryst l-menites rom southernAfrica kimberlites,TypesA and B spinelperidotites rom San Carlos, Arizona.(abstr.)Terra Cognita,2,228.Bailey,D. K. (1984)Kimberlite: "The Mantle Sample" ormedbyultra metasomatism.n Kornprobst, Ed., Kimberlites I: Kim-berlite and RelatedRocks,p. 323-334.Elsevier,New York.Bardet,M. G. (19'14)Geologiedu diamant. vol. II. Memoires duBureauRecherches eologieet Mineralogie.No.83,Paris.Bardet,M. G. (1977)Geologiedu diamant.vol. III. MemoiresduBureauRecherches eologieet Mineralogie.No.83,Paris.Bauer,M. (1896) recious tones.2 ols.ReprintoftranslationbyL. J. Spencer, 904.Dover Publications,New York, 1968.Becker,R. H. (1982)Nitrogen isotopic ratios of individual dia-mond samples. abstr.) Fifth International Conference Ge-ochronology, Cosmochronology, Isotope Geology. Nikko,Japan.Becker, R. H. and Clayton, R. H. (1977)Nitrogen isotopes nrocks. (abstr.) Transactions of the American GeophysicalUnion, 58,536.Berman, R. (1965)Physical Properties of Diamond. ClarendonPress,Oxford.Black,D. C. (1972)On the origins of trapped heliurn,neon, and

argon sotopic variations n meteorites-I. Gas-richmeteorites,lunar soil and breccia.Geochemica t CosmochimicaActa, 36,347,375.Boettcher,A. L., O'Neil, J. R., Windom, K. E., Stewart,D. C. andWilshire,H. G (1979)Metasomatism nd thegenesis f kimber-lites and alkali basalts.n F. R. Boyd and H. O. A. Meyer,Eds.,The Mantle Sample: nclusions n Kimberlites and Other Vol-canics,p. 173 182.American GeophysicalUnion, Washington,D C .Bonney,T. G. (1899)The parent rock of the diamond in SouthAfrica. Proceedings fthe Royal Society,65,223-236.Boyd, F. R. (1973)A pyroxenegeotherm.Geochimicaet Cosmo-chimica Acta. 37. 2533-2546.Boyd, F. R. and Finnerty, A. A. (1980)Conditions of origin ofnatural diamondsof peridotite affrnity.Journal of GeophysicalResearch.5.6911-6918.Bundy, F. P. and Kasper,J. S.(1967)Hexagonaldiamond-a newform of carbon.Journalof ChemicalPhysics, 6,3437-346.

Chesley,F. G. (1942) nvestigationof the minor elementsn dia-mond.AmericanMineralogist,27,20-36.Clement,C. R., Skinner,E. M. W. and Scott-Smith,B. H. (1984)Kimberliteredefined. ournalof Geology,92,22T228.Craig, H. (1953)The geochemistry f stablecarbon sotopes.Ge-ochemica t CosmochimicaActa,3, 53-92.Dawson, J. B. (1980)Kimberlitesand Their Xenoliths.Springer-Verlag,New York.Dawson,J. B. and Smith, J. V. (1975)Occurrence f diamond n amica-garnet herzolitexenoliths from kimberlite. Nature, 254,580-581.Deines,P. (1980)The carbon isotopic compositionof diamond:relationship to diamond shape,color, occurrenceand vaporcomposition.Geochimica t Cosmochimica cta,44,943-961-Deines,P. (1982)The relationshipbetweennclusion compositionand carbon isotopic composition of host diamond. (abstr')Terra Cognita,2,2O2.DesCloizeaux,A. (1855)Note sur le diamant noir. Annalles desMinesMemoires,8, 30,t-306.

Dickey, J. S., Bassett,W. A., Bird, J. M. and Weathers,M' S.(1983) iquid carbon n the ower mantle.Geology,ll,2l9-22o.Du Toit, A. L. (1906)Geologicalsurveyof the easternportion ofGriqualand West. Eleventh Report Geological CommissionCapeColony,89-176.Eggler,D. H. (1977)The principleof the zoneof invariant vaporcomposition: An example in the systemCaO-MgO-SiO2lOz-H2O and implicationsfor the mantlesolidus.Yearbook of the Carnegie nstitution of Washington,'t6,428435.Eggler,D. H. (19?8)The effect of CO2 upon partial melting ofperidotite in the systemNarO{aO-Al2O3-MgO-SiO2{O2to 35 kb, with an analysisof melting n a peridotite-HzO{.O2

system. mericanJournalof Science,78,301343.Eggler,D. H. (1983)Upper mantleoxidation state:evidenceromolivine-orthopyroxene-ilmeniteassemblages. eophysicalRe'searchLetters,10,365-368.Eggler,D. H. and Baker, D. R. (1982)Reducedvolatiles n thesysternC-o-H: implications o mantlemelting, luid formation,and diamond genesis.n S. Akimoto and M. Monghnani,Eds.,High PressureResearchn Geophysics, .237-250. Center orAcademicPublications, okyo.Eggler,D. H. and Wendlandt,R. F. (1979)Experimentalstudieson the relationship betweenkimberlite magmas and partialmelting of peridotite. n F. R. Boyd and H. O. A. Meyer, Eds.,Kimberlites, Diatremes and Diamonds: Their Geology, Pet-rology and Geochemistry,p. 330-338.American GeophysicalUnion, Washington,D.C.Eggler,D. H., Baker,D. R. and Wendlandt,R. F. (1980)O, ofthe assemblage raphite-nstatite-forsterite-magnesite:xperi-ment and application to mantle O2 and diamond formation.(abstr.)GeologicalSocietyof AmericaProgram with Abstracts,12,420.Ellis,D. E. and Wyllie, P. J. (1980)Phase elations n the systemMgO-SiOr-HrO-CO2 at pressures p to 100 kbar and pet-rological mplications.AmericanMineralogist,65, 5'!0-556.Evans,T. and Qi, Z. (19E2\The kinetics of the aggregationofnitrogen atoms n diamond.Proceedings fthe Royal SocietyofLondon,A381,159-178.Fesq,H. W., Bibby, D. M., Erasrnus,C. S.,Kable, E. J. D. andSellschop, . P. F. (1975)A comparative race elementstudy ofdiamonds rom Premier,Finsch and Jagersfonteinmines,SouthAfrica.Physics nd Chemistry fthe Earth,9,817-836.Field, J. E. (1979\The Propertiesof Diamond. AcademicPress,New York.

8/3/2019 Am. Mineral. 70 (1985) 344

10/12

MEYER:GENESTSOF DIAMOND: A MANTLE SAGA 353Frank, F. C. (1956)On the X-ray diffraction spikesof diamond.Proceedings f theRoyalSocietyof London, A37,168-174.Frank, F. C. (1966)Defectsn diamond.ProceedingsnternationalIndustrial Diamond Conference,p. 119-135. ndustrial Dia-mond Information Bureau,London.Frondel, C. and Marvin, U. B. (1967)Lonsdaleite,a hexagonalpolymorphof diamond.Nature, 214,587-589.Futergendler,S. I. (1956)The study of inclusions n diamondsbythe method of x-ray structural analysis. in Russian)ZapiskiVsesoyznyiMineralogiaObshchestva,5,568-656.Futergendler,S. L (1958)X-ray study of solid inclusions n dia-mond (in Russian) ovietPhysics-{rysrallography, 3, 49U97.Futergendler,S. L (1960)X-ray study of solid inclusions n theUral and Yakutia diamonds.MaterialsVsesoiuznogo auchno-Issledovatel'skogo eologicheskogonstituta, no. zt0,3_82(inRussian).Galimov, E. M., Kaminsky, E. V. and Ivanovskaya, . N. (1928)Study of carbon isotopcompositionsof diamonds from theUrals, Timan, Sayany,Ukraine and other regions. in Russian)

Geokhimiy43,3fi-349.Gold, T. J. (1979)Terrestrial sourcesof carbon and earthquakeoutgassing. ournalof PetroleumGeology, , 1-19.Gold, T. J. and Soter, S. (1979)Brontides: Natural explosivenoises.Science, M, 37 -37 5.Goppert,H. R. (1862)Uber Einschlusen diamant.Breslau.Green,H. W. and GuegenY (1974)Origin of kimberlite pipesbydiapiric upwelling n the upper mantle. Nature physical Sci-enes,249,617-620.Giibelin, E. (1952) Inclusions in diamonds. Journal of Gem-mology,3, 174-187.Gurkina, G. A., Ivanovskaja, . N., Kaminski,F. V. and Galimov,E. M. (1979)Geokhimiy4 1897-1905.Gurney, J. J. and Boyd, F. R. (19E2)Mineral intergrowthswithpolycrystallinediamonds from the Orapa Mine, Botswana.Yearbook of the Carnegie nstitution of Washington,8l,267-273.Gurney, J. J. and Switzer,G. S. (1973)The discoveryof garnetscloselyrelated to diamonds n the Finsch pipe, South Africa.Contributions o Mineralogyand Petrology,39,103-116.Gurney,J. J.,Harris, J. W. and Pickard,R. S. (1979)Silicateandoxide inclusions n diamonds rom the Finschkimberlitepip.In F. R. Boydand H. O. A. Meyer,Eds.,Kimberlites,Diatremesand Diamonds: Their Geology,Petrologyand Geochemistry, .1-15.AmericanGeophysicalUnion, Washington,D.C.Haggerty,S. E. (1982)Kimberlites n WesternLiberia: An over-view of the geologicalsetting in a plate tectonic framework.Journal of GeophysicalResearch, 7, 08f f-10826.Haggerty,S.E. and Tompkins,L. A. (1983)Rdoxstateof Earth'suppermantle rorn kimberlitic lmenites.Nature, 3O3,295-ZW.Harger, H. S. (1905)The diamond pipes and fissuresof SouthAfrica.Transactionsof the GeologicalSocietyof South Africa,8. 110-134.Harris, J. W. and Gurney,l. J. (1979)nclusions n d iamonds. n J.E. Field, Ed., The Properties f Diamond,p. 555-594.AcademicPress,New York.Harris, P. G. and Middlemost,E. A. K. (1969)The evolution ofkimberlites.Lithos, 3, 77-88.Harrison,E. R. and Tolansky,S. (1964)Growh historyof a natu-ral octahedraldiamond. ProceedingsRoyal Societyof London,41279,490496.

Harte, 8., Gurney,J. J. and Harris, J. W. (1980)The formation ofperidotitesuite nclusionsn diamonds.Contributions o Miner-alogyand Petrology,72, 8l-190.

Hatton, C. J. and Gurney,J. I. (1979)A diamond-graphite clogitefrom the RobertsVictor mine. In F. R. Boyd and H. O. A.Meyer, Eds.,The Mantle Sample Inclusions n KimberlitesandOther Volcanics, p. 29-36. American Geophysical Union,Washington,D.C.Hervig R. L., Smith, J. V., Steele, . M., Gurney, J. J., Meyer, H.O. A. and Harris, J. W. (1980)Diamonds: Minor elements nsilicate nclusions: Pressure-ternperaturemplications.Journalof Geophysical Research,85, 69194929.Holmes, A. (1936)A contribution to the petrology of kimberliteand its inclusions.Transactionsof the Geological Society ofSouth Africa, 39,379427.Hughes,C, J. (1982)greous Petrology.Elsevier,New York.Jacques, . L., Gregory,G. P., Lewis,J. D. and Ferguson, . (1982)The ultrapotassic ocks of the West Kimberley region, WesternAustralia, and a new class of diamondiferouskimberlitc. (Ex-tendedabstr.)Terra Cognit4 2,251152.Jacques, . L ., Lewis, J. D., Smith, C. B., Gregory, G. P., Fergus-on, I., Chappell, B. W. and McCulloch, M. T. (1984) The

diamond-bearing ultrapotassic (lamproitiQ rocks of the WestKimberley region,WesternAustralia. n Kornprobst,Ed., Kim-berlite : Kimberlites and related rocks,223-254.Elsevier,NewYork.Kaiser, W. and Bond, W. L. (1959)Nitrogen, a major impurity incornmon ype diamond.PhysicsReview, 15,857-863.Kaminsky, F. V. (1980)Authenticand valid diamond occurrencesin alkali-basaltoids nd ultramafic (non-kimberlitic)bodies. inRussian)Zapiski VsesoyrrmyiMineralogia Obshchestva,109,488-493.Kaminsky, F. V. and Gevorkin, P. G. (1976)Non-kimberlitic primary diamonds. (in Russian) zvestia An. Armenia SSR, 2,32-q.Kennedy, C. S. and Kennedy, G. C. (1976) The equilibriumboundary betweengraphiteand diamond. Journal GeophysicalResearch, 1,24'l -247 4.Kennedy,G. C. and Nordlie, B. E. (1968)The genesis f diamonddeposits.EconomicGeology,63,495-503.Knopf, D. (1970)Les kimberliteset les rochesapparenteese Coted'Ivoire. SODEMI, Abidjan.Kramers, J. D. (1979)Pb, U, Sr, K, and Rb in inclusion-bearingdiamonds and mantle-derived enoliths from southern Africa.Earth and PlanetarySciences etters,42,58-70.Lang, A. R. (1979) nternal structure. n J. E. Field, Ed., ThePropertiesof Diamond,p.425469. AcademicPress,New York.Lewis, C. (1887)On a diamondiferous eriodotiteand thc genesisof the diamond.GeologicalMagazine, ,22-24.Lightowlers,E. C. and Dean,P. J. (1964)Measurement f nitrogenconcentrations n diamond by photon activation analysisandoptical absorption. Diamond Research1964,p. 21-25. Sup-plement o Industr ial Diamond Review,London.Lindsley, D. and Dixon, S. H. (1975)Coexisting diopside andenstatiteat 20 kbar and 900-1200"C.AmericanJournal of Sci-ence,276, 285-1301.Lonsdale,K. (1942)Extra reflexions rom the two types of dia-mond. Proceedings fthe Royal Society,4179,315-320.MacGregor, l. D. (1974)The system MgO-A.lrOr-SiOr: Solu-bility of AlrO, in enstati te or spineland garnetperidotitecorn-positions.AmericanMineralogist,59, 10-l 19.McCallister,R. H., Meyer, H. O. A. and Aragon,R. (1979)Partial

thermalhistory of two exsolved linopyroxenesrom the ThabaPutsoakimberlite pipe, Lesotho. n F. R. Boyd and H. O. A.Meyer, Eds.,The Mantle Sample:nclusions n Kimberlitesand

8/3/2019 Am. Mineral. 70 (1985) 344

11/12

354 MEYER: GENESISOF DIAMOND: A MANTLE SAGAOther Vofcanics,p. 244-248. American Geophysical Union,Washington,D.C.McCallum, M. E. and Eggler,D. H. (1976)Diamonds n an uppermantleperiodotitenodule from k imberlite n SouthernWyom-ing. Science,192,253-256.

McCulloch, M. T., Jacques, . L, Nelson,D. R. and Lewis, J. D.(1983)Nd and Sr isotopes n kimberlitesand lamproites romWesternAustralia: an enrichedmantleorigin. Nature,3O2,4W-403.McGetchin, T. R. and Ullrich, G. W. (1973)Xenoliths n maarsand diatremeswith inferencesor the Moon. Mars and Venus.Journalof Geophysical esearch,8,1833-1853.Mercier, J.-C. C. (1979)Peridotite xenoliths and the dynamicsofkimberlite intrusion. In F. R. Boyd and H. O. A. Meyer, Eds.,The Mantle Sample: nclusions n Kimberlites and Other Vol-canics,p. 197-212.American GeophysicalUnion, Washington,D.C.Melton, C. E. and Giardini, A. A. (1974)The composition andsignificance f gas released rom natural diamonds rom Africaand Brazil. AmericanMineralogist,59,775-782.Melton, C. E. and Giardini, A. A. (1980)The isotopecompositionof argon ncluded n an Arkansasdiamond and its significance.GeophysicalResearch etters,7, 461464.Melton, C. E., Salotti, C. A. and Giardini, A. A. (1974)The obser-vation of nitrogen,water,carbondioxide,methaneand argonasimpurities in natural diamond. American Mineralogist, 57,1518-1523.Meyer, H. O. A. (1968) nclusions n diamond. Yearbook of theCarnegie nstitution of Washington,66, 44450.Meyer,H. O. A. (1982a)Mineral nclusionsn natural diamond.InternationalGemologicalSymposiumProceedings, . 441465.Gemological nstitute of America,Los Angeles.Meyer, H. O. A. (1982b)The genesis f diamond. (abstr.)TerraCognita,2,199.Meyer, H. O. A. and Boyd, F. R. (1969) nclusions n Diamond.Yearbook of the Carnegie nstitution of Washington,68, 315-324.Meyer,H. O. A. and Boyd, F. R. (1972)Compositionand origin ofcrystalline nclusions n natural diamonds.Geochimicaet Cos-mochimicaActa. 36. 1255-1273.Meyer,H. O- A. and Giibelin,E. (1981)Ruby n diamond.Gemsand Gemology, 7, 153-156.Meyer, H. O. A. and Tsai, H.-M. (1976a)Mineral inclusions nnatural diamond: their nature and significance.Mineral Scienceand Engineerin ,8, 242-261.Meyer, H. O. A. and Tsai, H.-M. (1976b)Mineral inclusions ndiamond: Temperatureand pressureof equilibration, Science,191, 49-851.Milledge,H. J. (1961) oesite s an inclusionn C. E. C. syntheticdiamonds. ature,190, 181.Milledge, H. J., Mendelssohn,M. J., Seal,M. Rouse, . E., Swart,P. K. and Pillinger, C. T. (1983)Carbon isotopic variations nspectral ype I diamonds.Nature, 303,791-792.Mitchell, R. H. (1975)Theoreticalaspects f gaseous nd isotopicequilibria n the systemC-H-O-S with application to kimber-lite. Physics nd Chemistryof the Earth, 9, 903-915.Mitchell, R. H. (1985)A review of the mineralogyof lamproites.TransactionsGeologicalSocietyofSouth Africa, n press.Mitchell, R. H. and Lewis,R. D. (1983)Priderite-bearing enolithsfrom the Prairie Creek mica peridotite, Arkansas.CanadianMineralogist,21, 59-64.Mitchell, R. S. and Giardini, A. A. (1953)Oriented olivine in-clusions n diamond.AmericanMineralogist,38, 136-138.

Moore, M. (1979)Optical studiesof diamond and their surfaces:reviewof the late Professor olansky'swork. In J. E. Field, Ed.,The Propertiesof Diamond, p.243-277. AcademicPress,NewYork.Newton, M. G., Melton, C. E. and Giardini, A. A. (1977)Mineralinclusions n an Arkansasdiamond.American Mineralogist,62,583-586.Olaffson,M. and Eggler,D. H. (1983)Phase elationsof amphibo-le, amphibole-carbonate, nd phlogopite-carbonate eridotite:petrologicconstraintson the asthenosphere.arth and Plane-tary Science etters,64, 305-315.O'Neil, H.St.C. and Wood, B. J. (1979)An experimental tudy ofFe-Mg partitioning betweengarnetand olivine and its calibra-tion as a geothermometer. ontributions to Mineralogy andPetrology,70, 9-70.Orlov, Yu. L. (1973)The mineralogyof the diamond. zdatel'stvaNauka.(Transl., .Wiley and Sons,New York, 1977).Ozima, M. and Zashu, S. (1983)Primitive helium in diamonds.Science, 19,1067-1068.Ozima, M., Zashu, S. and Nitoh, o. (1983) HeloHe ratio, noblegasabundanceand K-Ar dating of diamonds-An attempt tosearch or the recordsof early terrestrialhisrory.GeochimicaetCosmochimicaActa,47, 22172224.Pantaleo,N. S.,Newton, M. G., Gogineni, S. V., Melton, C. E.and Giardini, A. A. (1979)Mineral inclusions n four Arkansasdiamonds: their nature and significance. American Mineral-ogist,64, 059-1062.Pokhilenko,N. P., Sobolev,N. V. and Lavrentyev,Yu. G. (1977)Xenoliths of diamantiferousultrarnafic rocks from Yakutiankirnberlies. abstr.)Second nternationalKimberlite Conference.AmericanGeophysicalUnion, Washington,D.C.Prinz, M., Manson, D. V., Hlava, P. F. and Keil, K. (1975) n-clusions n diamonds. Garnet lherzolite and eclogite assem-blages. hysics nd Chemistry fthe Earth,9,79'l-815.Raal, F. A. (1957)A spectrographic tudy of the minor elementcontentof diamond.AmericanMineralogist,42,35+361.Reynolds, . H., Frick, U., Neil, J. M. and Phinney,D. L. (1978)Rare gas-rich separates rom carbonaceous hondrites. Ge-ochimicaet CosmochimicaActa,42, 177 -1797.Robert, F. and Epstein,S. (1982)The concentrationand isotopiccompositionof hydrogen, arbonand nitrogen n carbonaceousmeteorites.Geochimica t Cosmochimica cta,46, 81-95.Robertson,R., Fox, J. J. and Martin, A. E. (1934)Two typesofdiamond. Philosophical Transactions of the Royal Society,A232,463-538.Robinson,D. N. (1978)The characteristics f natural diamondand their interpretation.Minerals Science nd Engineering, 0,55-'t2.Roedder,E. (1963)Studiesof fluid inclusions I: freezingdata andtheir nterpretation.EconomicGeology,58,167211.Roedder,E. (1982)Fluid inclusions n gemstones:Valuable de-fects. International Gemological Symposium Proceedings, .479-502.Gemological nstitute of Americ4 Los Angeles.Roedder,E. (1984)Fluid Inclusions.Reviews n Mineralogy, Vol.12.MineralogicalSocietyof America.Ryabchikov,. E., Green,D. H., Wall, V. J. and Brey,G. P. (1981)The oxidation state of carbon in the reduced-velocity one.Geochemistrynternational,18,221-232.Seal, M. (1965)Structure in diamonds as revealedby etching.AmericanMineralogist,50,105-123.

Sellschop, . P. F. (1979)Nuclear probes in physical and geo-chemicalstudiesof natural diamonds. n J. E. Field, Ed., ThePropertiesof Diamond,p. 107-163. cademicPress,New York.

8/3/2019 Am. Mineral. 70 (1985) 344

12/12

MEYER: GENESISOF DIAMOND: A MANTLE SAGA 355Scott Smith, B. H. and Skinner,E. M. W. (1984)A new look atPrairie Creek, Arkansas. n Kornprobst, Ed., Kimberlites I:Kimberlitesand related ocks,p. 255154. Elsevier,New York.Shee, S. R., Gurney, J. J. and Robinson, D. N. (1982) Twodiamond-bearingperidotie xenoliths from the Finsch kimber-

lite, South Africa. Contributions to Mineralogy and Petrology,81,79-87.Skinner,E. M. W. and Clement,C. R. (1979)Mineralogicalclassi-ficationof southern African kimberlites. n F. R. Boyd and H.O. A. Meyer, Eds., Kimberlites, Diatremes and Diamonds:Their Geology, Petrology and Geochemistry, p. 129-139.AmericanGeophysicalUnion, Washington,D.C.Sleep,N. H. (1979)Thermal history and degassing f the earth:Somesimplecalculations. ournal of Geology,87,671-686.Smyth,J. R. and Hatton, C. J. (19'17) coesite-sanidinerospyditefrom the Roberts Victor kimberlite.Earth and PlanetarySci-ences etters,34,28+290.Sobolev,N. V. (1974)Deep-seatednclusions n kimberlitesandthe problem of the compositionof the upper mantle.(Trans-lation by American Geophysical Union, Washington, D.C.,r977).Sobolev,N. V., Ellimova, E. S. andPospelova, . N. (1981)Nativeiron in Yakutian diamonds, ts paragenesis.in Russian)Ge-ology and Geophysics, oklady Akademii Nauk SSR,SiberianDivision. 12.25-29.Sobolev,N. V., Efimova, E. S., Koptil, V. I., Lavrent'yev,Yu. G.,and Sobolev,V. S. (1976) nclusionsof coesite, arnetand om-phacite in Yakutian diamond: the first discovery of coesiteparagenesis.in Russian)Doklady Akademii Nauk SSSR,230,1442-1446.Sobolev,N. V., Galimov, E. M., Ivanovskaya, . N. and Yefimova,E. S.(1979)The carbon sotopecompositionsof diamondscon-taining crystallographic nclusions. in Russian)Doklady Aka-demiiNauk SSSR,249, 217-1220.Sobolev,V. S., Sobolev,N. V. and Lavrent'yev, u. G. (1972)Inclusions n diamond extracted rom a diamondiferouseclo-gite. in Russian)Doklady AkademiaNauk SSSR, O7,&-167.Sobolev,V. S., Sobolev,N. V. and Laurent'yev, u. G. (1975)Chrome-rich clinopyroxenesrom the kimberlites of Yakutia.Neues ahrbuch iir Mineralogie,Abhandlungen, 23,213-218.Sutton, J. R. (1921) nclusions n diamonds from South Africa.MineralogicalMagazine, , 2O8-21O.Sutton, J. R. (1928)Diamond: A descriptive reatise.T. Murby,London.

Suzuki, S. and Lang, A. R. (1976) nternal structuresof naturaldiamonds revealing mixed growth habit. Diamond Research1976,p. 39 47. Supplement o Industrial Diamond Review,London.Takaoka, N. and Ozima, M. (1978)Rare gas isotopic compo-sitions n diamond.Nature,271,4546.Trueb, L. F. and Barrett, C. S. (1972)Microstructural investi-gation of ballas diamond. American Mineralogist, 57, 1664-1680-Trueb,L. F . and De Wys,E. C. (1969)Carbonado:Natural oly-crystallinediamond.Science, 65,799-802.Trueb, L. F. and De Wys, E. C. (1971)Carbon from Ubangi-amicrostructuralstudy.AmericanMineralogist,56, 1252-1268.Wagner, P. A. (1914)The Diamond Fields of Southern Africa.Reprinted 97l,C. Struik (fty) Ltd, CapeTown.Walker, D. (1983)New developrnentsn magmaticprocesses. e-viewsof Geophysics nd SpacePhysics, 1,1372-1384.Wand, U., Nitzsche,H.-M., Muhle, K. and Wetzel,K. (1980)Ni-trogen isotope composition n natural diarnond-First results.Chemieder Erde,39,85-87.Wells, P. R. A. (1977)Pyroxene hermometry n simple and com-plex systems.Contributions in Mineralogy and Petrology,62,129-139.Wickman, F. E. (1956)The cycle of carbon and stable carbonisotopes.Geochimica t Cosmochimica cta,9, 13G153.Williams, A. F. (1932)The Genesis f Diamond, 2 vols.London:E. Benn.Wilson,A. N. (1982)Diamonds rom birth to eterni ty. Gemologi-cal Institute of America,Los Angeles.Woerman,E. and Rosenhauer,M. (1982)Oxygen ugacityand thefluid C-H-O phasen the earth'smantle. abstr.)Terra Cognita,2,227.Wyflie, P. J. (1977)Peridotite-Co2-HrO and carbonatitic iquidsin the upper asthenosphere.ature, 266,4547.Wyllie, P. J. (1978) Mantle fluid compositions buffered inperidotite-CO2-HrO by carbonates,amphibole, and phlogo-pite.Journal of Geology,86,687-713.Wyllie,P. J. (1980)The origin of kimberlite.Journalof Geophysi-cal Research, 5,6902-6910.

Manuscript receioed,February 9, 1984acceptedfor publication, Nouember 15, 1984.