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Serpentinised Dunites of the Neoarchean Shimoga Greenstone Belt, Western Dharwar Craton, India: Insights on Ni-PGE Mineralisation and Genesis.

Our study reveals the geochemical evidence of Ni-PGE mineralisation in serpentinised dunites from the Shimoga greenstone belt, Western Dharwar Craton, India and discusses its genesis. The presence of disseminated sulphides and pronounced serpentinization in the studied rocks suggest a combination of Type II (disseminated sulphides) and Type IV (post-magmatic alterations) komatiite-related Ni-PGE deposits. Geochemical signatures indicate the parental melts were generated from plume-sourced Al-depleted komatiites with significant crustal contamination during emplacement. The high Ni (~6511 ppm avg.) and PGE (∑PGE=3078 ppb avg.) concentrations confirm the fertile/mineralised nature of the komatiitic source and the potential for Ni-PGE mineralisation in the study area.

The genesis of Ni-PGE mineralisation in the Shimoga ultramafic (SUM) rocks is depicted through (a) plume-sourced komatiitic melt interacting with the continental lithospheric mantle (CLM) en route to the Archean crust followed by (b) thermo-mechanical erosion through the interaction of the parent hot komatiitic (Al-depleted) magma with the Archean crustal components and (c) progressive cotectic accumulation of olivine and sulphide liquid to form Ni-PGE-bearing disseminated sulphides.

Schematic genetic model for Ni-PGE mineralisation in serpentinised dunites of the Shimoga Greenstone Belt.

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