Low-Al tourmalines of 'oxy-dravite'-povondraite series from Cu-Au deposit of Ghagri area, Salumber-Ghatol belt, Aravalli Supergroup, Rajasthan

摘要

Petrology and mineral chemistry of tourmalines from Cu-Au deposit in the Ghagri area, southeast Rajasthan are presented. The Cu-Au deposit is formed during the initial phase of Palaeoproterozoic Aravalli basin evolution with dominant deposition of shelf facies pelite-carbonate sequence of the Debari Group. This study suggests that the tourmalines possess a major povondraite component and follow an 'oxy-dravite'-povondraite crystallization trend. Extensive ultra-alkaline alterations, reported presence of scapolite- bearing assemblages, development of povondratic tourmalines and high Mg-bearing dravitic tourmalines with affinity to ultra-saline environments suggest that the tourmaline-bearing alteration zones in Cu-Au deposits of the Salumber-Ghatol belt have developed in an evaporitic environment.