Metamorphic fluids and multiple lithologies as sources for the gold-quartz vein deposits: Evidence from REE and isotope studies (Experience from the Kolar Gold Field, India)

Abstract

The auriferous Kolar Schist Belt in the Dharwar craton of southern India is considered to be a late Archean suture between two gneissic terranes. Therefore the famous Kolar gold deposits offers an excellent opportunity to understand the relation between tectonic processes, fluid evolution and gold metallogeny. In Kolar gold occurs as steeply dipping sheeted quartz veins within the sheared komatiitic amphibolite only on the eastern part of the greenstone belt. The gold quartz veins have structural, mineralogical and textural features characteristic of mesothermal, low sulfide and high gold deposits present elsewhere in the world. We discuss here the nature of the fluid, fluid-path, and the processes involved in the formation of gold quartz vein deposits using lanthanide geochemistry, radiogenic and stable isotope data on various representative samples including gold quartz veins, altered and unaltered wall-rock, mineral separates (quartz, pyrite and calcite) and mafic inclusions from the gold quartz veins, and the intrusive pegmatites. The gold quartz vein samples have LREE - enriched HREE - depleted chondrite-normalised patterns without Eu anomaly.