Mineral–fluid interactions in the late Archean Closepet granite batholith, Dharwar Craton, southern India

Abstract : The chemical composition of different rocks as well as volatile-bearing and volatile-free minerals has been used to assess the presence of fluids in the Closepet batholith and to estimate the intensity of the fluid−rock interactions. The data were processed using polytopic vector analysis (PVA). Additional data include measurements of water content in the structure of volatile-free minerals and an examination of growth textures. The composition of mineral domains indicated formation/transformation processes with common fluid−mineral interactions. In general, the results suggested that the processes occurred in a ternary system. Two end-members were likely magmas and the third was enriched in fluids. In contrast, analysis of the apatite domains indicated that they likely formed/transformed in a more complex, four-component system. This system was fluid-rich and included hybrid magma with a large mafic component. PVA implies that the fluids do not appear to come from one source, given their close affinity and partial association with mantle-derived fluids. A dynamic tectonic setting promoting heat influx and redistribution, and interaction of fluids suggests that the formation/ transformation processes of minerals and rocks occurred in a hot-spot like environment.