Cr-V OXIDES from the RAMPURA AGUCHA Pb-Zn
745 The Canadian M inc ralo g ist Vol. 33, pp. 745-752 (1995) Cr-V OXIDESFROM THE RAMPURA AGUCHA Pb-Zn-(Ag) DEPoSll RAJASTHAN,INDIA WOLFRAM HOLLER ANDEUGEN F. STIIMPFL Institute of Geological Sciences, Mining University Leoben, Peter-Twmer-Strasse 5, 8700 Leobea Austria Arsrrasr Two new compositionalvarieties of rme oxide minerals have been studiedby ore 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.
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