Cr-V OXIDES FROM THE RAMPURA AGUCHA Pb-Zn-(Ag) DEPOSIT, RAJASTHAN, INDIA

WOLFRAM HÖLLER and EUGEN F. STUMPFL
Institute of Geological Sciences, Mining University Leoben, Peter-Tunner-Strasse 5, 8700 Leoben, Austria

Abstract

Two new compositional varieties of rare oxide minerals have been studied by ore microscopy and electron-microprobe analysis in samples from the high-grade metamorphic, stratiform Rampura Agucha Pb-Zn-(Ag) deposit, Rajasthan, India. We have established the presence of a Cr-V-Fe spinel and a Cr-V rhombohedral oxide. The compositions of the two minerals, V0.8-1.15Cr0.84-1.15Fe0.6-0.67Mn0.12-0.19Mg0.14-0.21Zn0.05-0.07O4 and V1.15-1.63Cr0.36-0.8Fe0.02-0.17O3, respectively, differ from known end-members because of considerable substitution of Cr for V. Similar solid-solution series of spinels in the system FeCr2O4 -FeV2O4 - MnCr2O4 - MnV2O4, such as manganochromite, vuorelainenite and coulsonite, as well as relatively pure end- members of karelianite and eskolaite, have been reported from several high-grade metamorphic deposits and areas. The rare V-oxide schreyerite, V2Ti3O9, also occurs as exsolution lamellae in rutile at Rampura Agucha. These unusual compositions are attributed to locally high concentrations of V in the precursor sediments; they further underline the isochemical nature of regional metamorphism of the orebody.

Keywords: coulsonite, manganochromite, vuorelainenite, rutile, eskolaite, karelianite, schreyerite, Cr-V spinel, Rampura Agucha, Rajasthan, India.