745

The Canadian M inc ralo g ist Vol. 33, pp. 745-752 (1995)

Cr-V OXIDESFROM THE RAMPURA AGUCHA Pb-Zn-(Ag) DEPoSll ,INDIA

WOLFRAM HOLLER ANDEUGEN F. STIIMPFL

Institute of Geological Sciences, University Leoben, Peter-Twmer-Strasse 5, 8700 Leobea Austria

Arsrrasr

Two new compositionalvarieties of rme oxide minerals have been studiedby microscopyand electron-microprobe analysis in samplesfrom the high-grademetamorphic, stratiform RampuraAgucha Pb--Zn{Ag) deposit, Rajasthan,India- We haveestablished the presenceof a Cr-V-Fe spineland a Cr-V rhombohedraloxide. The compositionsof the two minerals, Vs.s-1.15Cr9.6a_1.15Fej.6_n.67Mn6.12+.y.Mgo.A4zrzno.os-o.ozOaand V1.111.6Crs.36_4.sFe6.62_n.17O3, respectively, differ from known end-membersbecause of considerablesubstitution of Cr for V. Similar solid-solution seriesof spinels in the system FeCrrO. - FeVrOo- MnCrrOa- MnV2O4,such as manganochromite,worelainenite and coulsonite,as well as relatively pure karelianite and eskolaite, have been reported from several high-grademetamorphic deposis and areas.The rare V-oxide schreyerite,V2Ti3O9, also occursas exsolution lamellae in rutile at RampuraAgucha. These unusual compositions are arcributed to locally high concentrationsof V in the precursorsediments; they further underscorethe isochemicalnature of regional metamorphismof the orebody.

Keryord*: coulsonite, ma:rganochromite,vuorelainenite, rutile, eskolaite, karelianite, schreyerite,Cr-V spinel, Rampura Agucha,Rajasthan, India.

SoMraans

Deux groupesd'oxydes rares ont 6t6mis en 6videnceau coursde notre dtudep6trographique et nos analysespar microsonde 6lectroniqued'6chantillons de rochesfortement m6urnorphisdes du gisementstrattforme n Pb--Zn-(Ag) de RampuraAguch4 au Rajasthan,en Inde. tr s'agit d'un spinelle I Cr-V-Fe et d'un oxyde rhombo€driquede Cr-V. l,a composition des deux min6raux,Vo.s_r.rsCro.s4_r.r5Fq.6_a.67Mnp.12_a )Nll .Ma'/no.0il.07o4 et Vl.1!1.63cr03e_o.sFeo.o2_o.rzO:,respectivemen! dilfbre de celle des p6les d causede la substitutionconsid6rable du Cr pour le V. Des solutions solidesdans le systlme de spinelle FeCr2Oa- FeV2Oa- MnCrrO, - MnV2q, impliquant dslg manganochromite,worelainenite et coulsonite,ainsi que des exemplesrelativement purs de karelianiteet d'eskolaite,ont 6t6 signal6sdans plusiews gisementspartageant le memecontexte mdtamorphique.La schreyerite,V2TirOe, est prdsente sous forme de lamellesd'exsolution dans la rutile. Cescompositions assez inhabituellesresulteraient des teneursdlevdes en V des s6dimentspr6curseurs. Elles soulignentle caractlre essentiellement isochimiquedu m6tamorphismer6gional qui a affectdces roches. (Iraduit par la R6daction)

Mots-cl6s: coulsonite,manganochromite, worelainenite, rutile, eskolarte,kar6lianite, scbreyerite,spinelle i Cr-V, Rampura Agucha,Rajasthan, Inde.

Ilrrnotucttox arp of hydrothermalconvection, when metals were accu- GEoLocIcALSnrrnrc mulated in a trough with prolific biological activity Qeb 1992,Deb & Smkar1990), as confirmed by 613C The Proterozoic Aravalli-Delhi belt in central values from graphite of. -24 to -29%o. Pb isotope Rajasthan,India, hosts a large number of stratabound studiessuggest a model age of 1.8 t 0.04 Ga for the depositsofbase-metal sulfide that are of considerable RampuraAgucha deposit .(D,ebet al. L989). Around economic significance. The stratiform, sediment- 1.5 Ga ago, parts of the Banded Gneissic Complex hosted Rampura Agucha Pb--Zn-(Ag) deposit is were thrust over the westem margin of the Bhilwara located in volcano-sedimentaryrocks of the Bhilwara belt @eb et al. 1989,Sugden et al. l99O),which led to belt (Fig. 1) at the contactwith the Archeanbasement metamorphic conditions of the upper amphibolite ("Banded Gneissic Complex"). The Bhilwara belt, a facies@eb 1992). thick pile of metasedimentaryrocks, was formed by The deposit occursin a doubly plungng synformal intracratonicrifting of the Archean basementaround structure of elliptical shape, comprising sillimanite- 2.0 Ga ago.The depositwas formed as a consequence and graphile-bearing mica schists within garnet -

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ARAVALLI. DELHI BELT

ll ,l! tt

I t I I I I

W DeccanBasalts

ffi| ErinpuaGranite E Vindhyansupogroup

EIW DelhiSupergroup AravalliSupergrcup OREDEPOSITS ES f Khetri C-opperBelt (Cu) ffi BhilwaraBelt 2 SaladipurAiC,r-Ztl- 3l(hoDaiba(Cu) [:E] JhmlBelt 4 RampuraAgucha @b-.Zn) 5 Rajpura Dariba (Zn-Pb-C\) lFl BerachGranite 6 Tawar (Pb.Z.n) 7 Pipela (Crr-7-n) lli$l BandedGneissisComplex E Deri-Ambaji GUAFCU)

Frc. 1. Simplified geologicalmap of the Aravalli-Delhi belt (after Sugdener al. 1990), including the main ore deposits.Inset map showsthe location of the orogen.

biotite - sillimanite gneiss, with intercalations of The general sfike of the ore zone is roughly amphibolile,calc-silicate roctrs, and aplite. It is ideaUy NE-SW; the dip of the orebodyvaries from 75oto 50o suited for open-pit mining. The ore zone has sha4r to the SE. The lengft of the deposit is 1550 m, the contactswith the hangingwall and footwall. The minimum depth 350 m; the width rangesfrom 2 to were metamorphosedwith the host rocks under P-T 100 m. The proven reservesarc 39.2 Mt probable conditions of the upper amphibolite facies, and have ressrves13.8 Mt, andpossible reserves 10.7 Mt (total undergone polyphase deformation (Gandhi et aI. 63.7 Mt) of ore (IZL Statr 1992) grading L3.6Vo7n, 1984). L.9VoPb,9.58VoFeand 45 ppmAg.

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Frc. 2. (a) Euhedralcrystat ofCr-V spinel (Spl) containingexsolution-induced bodix of (Cr,Y)2O3enclosed in pyrrhotite (Po) near graphite (Gr), as well as (Cr,V)2O3(Kar) at the interfacebetween massive pyrrhotite and biotite (80. (b) hismatic crystalsof (Cr,V)rOuat the interfacebetween massive pyrrhotite and biotite. (c) Anhedralto subhedralgrains of (Cr,V)2O3 at the interfacabetween sulfides (pyrrhotite and )and plagioclase@l), as well as graphiteand sphalerite(Sp). (d) SubhedralCrains ofCr-V spineland (CI,V)2O3between sulfidas (sphalerite and pyrrhotite) andgraphite. (e) Exsolution- induced lamellae of schreyerite (Scbr) in rutile (Rt). (0 Euhedral to subhedral grains of Cr-V spinel' containing exsolution-inducedbodies of (Cr,V)2O' at the interface betweenpynhotite and graphite. The scale bar correspondsto 15 gm in eachcase.

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Mineralization occurs predominantlyin graphite - Owing to the small grain-size of the rare odde sillimanite - mica schist,which is enrichedin V andNi minerals, it was not possible to confirm the crystal (Deb 1992).Coarse-grained sphalerite @gs. 2c, d), by structure of spinel and karelianite--eskolaitesolid- far the most widespreadsulfide mineral, is associated solution. with coarse-grainedgalen4 granular, locally idio- morphic pyrite, and pyrrhotite in various proportions. Mrr{FrAr-ocy The ore mineralscarry numerousinclusions ofrounded to subroundedgrains of feldspar,qu:gtz, sillimanite, Cr-V spinel muscovite,biotite and graphite.All mineralshave been thoroughlyrecrystallized and remobilizedduring or EuhedralgrainsofCr-Vspinel(averagesize15pm; after peak conditions of metamorphism.Galena is by maximum 30 pm) occur in close associationwith far the most mobile of the sulfides; it exhibits amnle graphite, pynhotite and minor sphalerite (Figs. 2a, evidence of plastic deformation and remobilization. d, f); they commonly show inclusions or exsolution- To a lesser extent, sphaleriteand pyrrhotite were relatedlamellaeof(C1V)2O3(Figs.2a,f).Thecolorof remobilized during and after high-grade metamor- the spinel in reflected light is dark grey, and very phism. Togetherwith Ag-sulfosalts,they filI fractures similar to that of sphalerite,with a brownish tinq the in quartz, feldspar and mica. Chalcopyrite and polishing hardnessis obviously higher than that of arsenopyriteare accessoryconstituents. CaV-bearing the coexisting sulfides. The mineral is distinctly oxides (e.9., karelianite--eskolaitesolid solution; see isotropic, without internal reflections. Reflectance below) are rare and have, so faro been found in five values in air, measuredagainst a calibratedchromite samples.Graphite is a commongangue mineral, and standard, arc:. 460 ntrn, l7.3Vo; 546 nm, L5.8Vo; representsup to 10 vol.Voof. the bulk of averageore. It 589 nm, L6.4Vo;660 nlr', 17.3Vo. These values are occurs as flakes in silicatesor as fracture fillings and slightly higher than those obtainedfor vuorelainenite on grain boundaries @igs. 2c, d, f). The size of from the Satra deposit, Sweden (Zafuewsk:. et al. the flakes, which me mostly aligned parallel to the 1982) and very similar to those of manganocbromite foliation, rangesfrom sometens of pm to 3 mm. from the Nairne pyrite deposit, South Australia The complex polymetamorphichistory of the (Graham1978). Bhilwaxa belt and its enclosedore deposits has not Electron-microprobe analyses, performed on been decipheredyet. Here, we presentthe first results 32 spinel grains, show considerablecompositional of suchinvestigations on the Cr-V oxide minerals;this variations. Substitution of trivalent Cr by V can be report forms paxt of a comprehensiveproject directed documented.VrO, contentsrange from 26.5 a 39Vo, at the mineralogy, geochernisty, and genesisof the and Cr2O3 contents, from 29.5 to 40.3Vo(Fig. 3, Rampura-Aguchadeposit.

MErHoDsoF INvEsrrcATIoN

A detailedmicroscopic study of the ore on drill-core chip samples,representing the strike length and depth of the orebody,has been performed.After identifica- Chrodte Coulsontte tion of the main ore and gangueminerals, the most FeCr2Oa tr'eV2Oa important minof ptrages were analyzed with an ARL-SEMQ electron microprobe at the Institute of GeologicalSciences, Leoben, using the correctionsof qm Bence & Albee (1968). Accelerationvoltage used for RampuraAgucha analyseswas 15 kV at a beam currenl of 20 nA. n*2 Chromite (Cr, Fe, Mg, Al), willemite (Zn, Mn), ilmenite CIi) andand metallic Y wereused as staadards for analysesofthe oxides.The atomicproportions have been calculated on the basis of four oxygen atoms (spinel), three oxygen atoms (Cr-V oxide), nine oxygen atoms (schreyerite) and two oxygen atoms (rutile). All Fe, Mn, Zn and Mg was calculated as divalent whereasCr, V, and Al are calculatedas ftivalent ions. Microprobe analyseswere affectedby a q mind sysd6p of TiKp and CrKcl, as well as TiKF and MnCr2O4 m 60 80 Il[nVzO4 Vl(a peaks.Results of analysesof mineralswith high Manganochromtte Vuorelafoenlte Ti conlents, e.9., rutile schreyerite, and have been Fro. 3. Plot of compositionalvariations in spinelfrom Nairne, correctedaccordingly. Safta Outokumpu,Lovelock and RampuraAgucha-

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TABLE1. C}IEMICALCOMPCIIION OF SPINEI. I&RELhNM-ESKOLAM sollD SOLUnoN.SCHnEYERIIE Al'lD RUTIII 90 fBolrt ItlE BAMPUBAAGUCHA DEPoar 80 sFtuel (cr'V)tq scnieYcdb Rdre 70 SDIT Spl34 8p128 Kor2 ftrS Sc[r4 8.bt5 Rl I Bl2 e

Vrq ttu2 35f2 9M 6t&, 7sg 3gJ6 v,6 \61 2A 860 erq fi8 3,92 3q19 3&r a.5E 4gl 4rr 0,43 og7 o AI2G Ol0 0,10 0,10 LiL ni. 034 0,36 0,10 0,10 |r.50 Feo A$ 21g) \n 0,& oJ6 0,65 0'E0 n.d. 0,10 lltuo 4,49 430 411 0,10 0,10 !d !d dd. !d .9o 40 Mso 290 LX X93 0,10 0,10 !n 0,10 t.d. !.d" !) zao zJA ?-47 46 0,15 n77 !.d. lrt (L oi. Feo no, ,n lrl !d LiL nn 63J9 95JE 96,06

,xt% 9f2r g,Es r00r4 10rJ2 r00t90 9.9r v924 stJs W6 20

Y 091 L6 L14 18 1J1 136 1J6 Op 0,@ l0 cr LB o.9l 0.86 o:15 047 oP qlE l0 10 AI - 0,m 0,04 Fo 0,62 0,6t q63 0,@ op 0,(}0 q04 Mn 0,14 0,13 qB Pm€ Mc 0,16 0,14 O2r acrossa zonedgrain of karelianite-eskolaite 7a 006 0,or q06 FIc. 4. Traverse Tr ' 3 3'17 ogt o9t solid solution. o 4,m 4,m 4,00 3,@ 3,0 9,m 9,m 2,m 2.m

Table 1). Substitutionsinvolving the divalent cations 1,8to 41.EoClable 1, Fig. 5). The FeO contentnmges (Fe, Mn, Mg and Zn) are less extensivethan those from 0.5 to 5.67o,andZnO, from 0.1 to 0.87o,with involving the ftivalent cations,with FeO from 19.8 to MgO, MnO and Al2O3 netu or below the detection 2l.9Vo,NInOfrom 3.8to 4.8Vo,MgO from 2.4ro 3.9Vo, limit of the electronmicroprobe (table 1). There is no andZfiQ from 1.7 to 2.4VoCfable 1); Thesevariations correlation betweenthe Fe and Zn contents and the arenot relatedto substitutionsinvolving Cr and V. contentsof Cr and V.

Karelianite-esl

Members of the solid-solution series karelianite Schreyeriteforms fine (<5 pm) orientedexsolution (VzO:) - eskolaite(Cr2O) invariably occur at or near larnellae(Fig. 2e) in large grains of rutile. Its color is the interfacebetween massive pyrrhotite or sphalerite brownish, with pleochroism from yellow-brown to and silicale minerals (Figs. 2a b, c) or graphite grey-brown, and with stong anisotropism.Electron- (Fig. 2d). They occur preferably as anhedral to microprobeanalyses of scbreyeriteyield compositions subhedralgains (5 to 50 pm.in size), but a prismatic Clable 1) similar to thoseobtained for schreyeritefrom habit commonly is developed.The crystalsare mostly Kwale, Kenya (Medenbach& Schmetzer1978) and inclusion-free and partly intergrown with spinel from the Siitra deposit, Sweden (Zakzewski et aI. (Figs. 2a, 0. The color in reflected light is brownish 1982). ConsiderableCrp. contents (up to 574) and grey, and internal reflections were not seen.In some mino{ contents of Fe (<0.57oFeO) and Mg (<0.9Vo sections,a weak but distinct anisotropismcan be seen. MgO) havebeen measured. The polishing hardnessis obviouslyhigher than that of coexisting sulfides. Despite the large differences in Rutile compositionamong different grains,these do not vary significantly in reflectance.Reflectance values in air, Rutile forms roundedgrains enclosedin quartz and measuredagainst a calibratedcbromite standard,are: feldspar or at contactsbetween sulfides and silicates. 460 nm, 20.8Vo:546 nm, 2I.lVo; J$Q nltr., 22%ol The crystalsare mostly devoid of any inclusions,some 660 nm, 22.2Vo.T\esevalues are very simil6 to those contain oriented larnellae of scbreyerite (Fig. 2e). obt?ined for eskolaite (Kouvo & Vuorelainen 1958) Rutile contains up to 2.6VoY2O3 arlid 0.4Vo Ct2O3 and slightly higher than those reportedfor karelianite Clable 1), and all other elementsare near or below the from Outokumpu(Long et al. 1963). detectionlimit of the electronmicroprobe. Electon-microprobe analysesof 81 grains yield a wide specffum of compositions; few grains reveal Dlscusslox ANDCoNCT-usIoNs distinct zoning @g. 4). Thereis a significant extentof replacementof frivalent Cr by V. The V2O3 content (1) Cr-V oxides are commonly found in intensely rangesfrom 58 ta 8LVo,and the Cr2O3content from metamorphosedareas and ore deposits.The Rampura-

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Karellmltg Outokmpu Rampura Agucha

CrrO3 F4r E*olalte Hematite

Yzor

55

Cr2O3 Fe2O3

Itc. 5. Crp3-V2O3-Fe2O3 diagram showing the extent of Cr-for-V substitution in karelianite-+skolaitesolid solution, with additional information concerningthe kare- Iianite (Kouvo & Vuorelainen 1958) and eskolaite fron Outokumpu Q-onget al. 1963). Sulfide and silicate assemblagesof the three samplesanalyzed do not vary significantly. $amFle.A2 containsadditional Cr-V spinel, and sampleA6-1 contains scbreyerite.

Agucha Pb-Zn-(Ag) depositin Rajasthan,Indi4 was karelianite V2O3 @ong et al. L963), as well as a V, metamorphosedunder conditionsof upper amphibolite Mn-rich spinel (Long et al. 1963), occur in the facies and contains rare oxide minerals such as Outokumpu orebody, Finland, which has undergone schreyerite,@e,Mn)(V,Cr)2Oo (spinel group) and regional metamorphism with P-T conditions of (V,Cr)2O, ftarelianite--eskolaite solid solution). 600 t 50'C and3.5 * I kbar (freloar 1987).Eskolaite Eskolaite, CrrO3 (Kouvo & Vuorelainen 1958) and has also been found as minute grains in a meteorite

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(Kimura & Ikeda 1992). Vuorelainenite, MnV2O4, for providing drill-core samples for tiis study. from the Siitra pyrite mine in Bergslagen,Sweden Reflectance measurements were performed at the (Zakrzewski et al. L982), and mangtrnochrqmite, Institute of Mineralogy, University of Vienn4 with MnCr2Oa, from the Nairne pyrite deposit, South the kind permission of Prof. E. Tillmans. We also thank Australia (Graham 1978),were formed during amphi- Helmut Miihlhans for assistance with electron- bolite-facies metamorphism.Coulsonite, FeV2Oa, microprobe analysis, and Ren6 Dobbe, Free occurs within magnetite veins in metamorphosed University, Amsterdam, for discussions. The consffuc- igneousrock of the BuenaVista Hills, Nevada@adtke tive criticism offered by three referees and Johann L962) andat the Kalgoorlie deposigWestern Australia Raith, Mining University, Leoben, as well as financial (Spiridonov 1978),which has undergoneupper green- support of the Ausnian Research Council (FWF) schist metamorphism.Schreyerite, V2Ti3Oe, has been through glatrt no. 10322-:IEC to E.F. Stumpfl, are reported from a highly metamorphoseddeposit of gralefully acknowledged. komerupinein the Kwale district, Kenya (Medenbach & Schmetzer1978) and from the Siita deposit,Sweden Rrrmmqces (Zakrzewskiet aL 1982). (2) Cr and V are enrichedin black shale (Holland BnrcE, A.E. & Ar,nB, A.L. (1968): Empirical correction 1979).Investigations on twenty depositsof black shale factors for the electron microanalysis of silicates and (Vine & Tourtelot 1970)haveshown that Cr and V are oxides."L Geol. 76, 382403. preferablyassociated with the organic fraction. V also (1992):Lithogeochemistry of rocks aroundRampura clays et al. L990),chlorite Drs, M. may be enrichedin Gtpley Aguchamassive sulfide ore-body,NW India - impli- and montroseite (v,Fe)ooH (wano et al. $94). cationsfor the evolution of a hoterozoic "Aulakogen".In Clays and chlorite, presumablyprecursor minerals in Metallogeny Related to Tectonics of the Proterozoic the RampuraAgucha Zn-Pb-(Ag) deposit,as well as Mobile Belts (S.C. Sarkar, ed.). Balkhema Rotterdam, organic matter, were consumed during prograde The Netherlands(l-35). metamorphism to form graphite, mica and other silicateminerals. The releasedV and Cr may well have - & SARKA&S.C. (1990):Prot€rozoic tectonic evolu- been used to form oxide minerals.This would be an tion and metallogenesisin the Aravalli-Delhi Orogenic explanation for the occurrenceof Cr-V spinel and Complex,northwestem lrrdiu Precamb,Res. 46, ll5'137. karelianite-€skolaite solid solution near inlerfaces G.L. & Weoln, P.A. involving sulfide minerals, graphite and silicate Ttronrr, R.I., Cuvn'mic, (1989): Age, sourceand stratigraphicimplications of Pb The Cr-V oxides may also have formed minerals. isotopedata for conformable,sediment-hoste4 base metal directly from precursorminerals like montroseite. depositsin the ProterozoicAravalli-Delhi orogenicbelt (3) The considerableextent of replacementof Cr by northwesternIndia. Precamb.Res. 43, l'22. V in spinelfrom the RampuraAgucha deposit suggests a continuousseries between the end memberschromite GaNpr[ S.M., PAuwAL, H.V. & BuaryecaR, S.N. (1984): and coulsonile(Fig. 3). Karelianiteand eskolaite, noted Geology and ore reserveestimates of RampuraAgucha at Outokumpu and other occturences,are found as lead zinc deposit Bhilwara Districc J, Geol, Soc. Indi'a approximate end-membercompositions. Karelianite 25.689:705. from Outokumpu $.ong et al. L963) cottains 3.7Vo Crp3, whereaseskolaite from Outokumpu(Kouvo & Gnenau, J. (1978):Manganochromite, palladium antimonide, associationsat theNaimepyrite Vuorelainen 1958) contains458Vo Y2O3.Significant and someunusual mineral deposit,South Australia, Arn Mineral. 63, 1166-1174. mutual substitution of Cr and V in (Cr,Y)2O3from Agucha deposit suggests solid solution Rampura Hor,r-aro, H.D. (1979): Metals in black shales- a reassess- betweenkarelianite V2O3 and eskolaiteCrp3 €ig. 5). ment-Econ Geol, 74, 1676-1680. (4) Cr and V are commontrace elementsin rutile. High amounts of Cr (up to 8Vo,Tollo & Haggerty I{ZL Srerr (1992):Rampura Agucha mna Mining Mag. 167, 1987)and V (up to 1.27o;Shlyukova et aL.1985)are 372-375. reportedfrom the Orapakimberlite, Botswana andthe Khibiny pluton, Russia,respectively. The presentstudy I(nvruna,M. & IKEDA,Y. (1992):Mineralogy and petrology of genetic confirms that schreyeritefrom the Rampura Agucha an unusualBelg1cz-79M carbonaceous chondrite: the components. Proc. NIPR deposit has been exsolved from a previously more relationships among Synposiumon Antarctic Meteorites5,7+119. V-rich homogeneoustitanium oxide owing to decreas- conditions, as discussedby Medenbach& ing P-T Kowo. O. & Vuons-eNm{, Y. (1958): Eskolaite, a new Schmetzer(1978). cbromiummineral. Am- Minzral'.6, 1098-1106.

Acroqowr*eDcm/BlTs LoNc, J.V.P., VuonruenwN, Y. & Kuovo, O. (1963): Karelianite, a new vanadium mineral. Am- Mineral. 4E, 1ys tlank Dr. S.M. Gandhiand HindustanZtncLtd. 334L.

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MEDENBAcH,O. & SctnmrzeR, K. (1978): Schreyerite, Tou.o, R.P. & Haccmrv, S.E. (1987): Nb{r-rutile in tne VzT:Os, a new mineral.Anr" Mineral. 63, I 182-1 I 86. Orapakimberlite, Botswana.Can Minzral. 25, 251-26/..

RADrrc, A.S. (1962): Coulsonite, FeV2Oa, a spinel-type TRB,oA&P.J. (1987): The Cr-mineralsof Outokumpu- their mineral from Lovelock, Nevada. Am. Mineral. 47" chernistryand significance.J. Petrol. 2E,867-886. 128/F1291,. Vtr{e, J.D. & Tounruror, E.B. (1970): Geochemisty of black Rpr-Ey, E.M., Ssarrm., N.R. & Gnsrnep, M.S. (1990): shaledeposits - a summrry rcWrt, EcorL Geol. 65,253- Distribution ald geochemical characteristicsof metal 272. enrichment in the New Albany shale @evonian- Missisippian),lndiana. Econ. Geol. 85, 1790-1807. WANry,R.8., Gomuerm, M.B. & Nonrrnop, H.R. (1990): Geochemistryof vanadium in an epigenetic,sandstone- SHLyuKovA,2.V.,TspN, A.I., Bonrsova,yo.A., Vr-lsova, hosted vanadium-uraniumdeposil Henry Basin, Utah. Yr.V. & DMffRryEvA,M,T. (1985): New vanadium - Econ GeoI.85.n0-284. zirconium - niobium rutile variety. Dokl. Al

Suooml,T.J., Ds, M. & Wnor.ev,B.F. (1990):The rectonic settingof mineralizationin the hoterozoic Aravalli-Delhi orogenic belt, N.W. lndrz. In hecarnbrian Continental Crust and its Economic Resources(S.M. Naqui, ed.). Received November 8, 1994, revised manuscript accepted Elsevier,Amsterdam, The Netherlands(367 -390). February 16, 1995.

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