Understanding the role of chalcophile-siderophile elements in the petrogenesis of metabasalts of Kudremukh greenstone belt, western Dharwar Craton, India: A Platinum group elements geochemical perspective

The Meso-Neoarchean Kudremukh greenstone belt (KGB) of Western Dharwar craton comprises predominant metabasalts associated with banded iron formations (BIFs). The metabasalts are characterized by moderate MgO (7.23–8.97 wt.%), Ni (48–374 ppm), Cr (33–188 ppm) with a wide variation in ∑ PGE (21.8–215.7 ppb) contents with 15.8–115.9 ppb Pd, 3.7–105.2 ppb Pt and 0.7–8.5 ppb Rh. Among IPGE group, Iridium, Osmium and Ruthenium range from 0.2–5.9, 1.4–7 and 1.8–7.8 ppb, respectively. These metabasalts are relatively enriched in ∑ PPGE (21.8–215.7 ppb) than ∑ IPGE contents (3.6–18.6 ppb). Their Pd/Ir (7.6–100.7) and Pd/Pt (0.8–5.5) ratios correspond to moderate to lower degree of melting. The abundance of PGEs in Kudremukh metabasalts is dominantly controlled by sulphide and chromite fractionation trend of the parent magma. Sulphur undersaturated nature of the parent magma is evidenced through the relationship of Pd vs . Cu. Further,̄ the Cu/Pd ratios of the studied volcanics (Cu/Pd = 1277–5747) is lower than primitive mantle (Cu/Pd = 7000), indicating early sulphide removal and S-undersaturation during magmatic differentiation. PGEs geochemistry of the studied rocks suggest early removal of sulphide melts followed by pronounced sulphide fractionation and the mantle melting episode is followed by metasomatism of the refractory mantle wedge by the fluids/melts derived from the subducting slab in a convergent margin setting. Research Highlights PGE systematics on the metabasalts from Kudremukh greenstone belt, western Dharwar Craton, India. The KGB metabasalts are characterised by low- moderate degrees of partial melting and high degrees of sulphide fractionation. PGE geochemistry of the KGB metabasalts infers the early sulphur undersaturated nature of magmas.