印度東部巴斯塔地塊晚太古代-早元古代索諾克漢綠色岩帶起源及成礦之岩石學調查

The Sonakhan greenstone belt (SGB), located in the north-eastern Bastar craton of the Indian shield, and comprises mafic-ultramafic and volcanic-intrusive sequences in the lower stratigraphic units. We investigate the Platinum-group element (PGE) relations of Boradih intrusion of the SGB to evaluate its tectono-magmatic evolution. The chondrite-normalized PGE patterns of boninitic cumulate rocks exhibit higher abundance of Palladium group PGEs (ΣPPGE = 292–496 ppb) relative to the Iridium group PGEs (ΣIPGE = 32– 52 ppb) along with variable Au concentrations (51.34–718.05 ppb). The PGE concentrations are attributed to a boninitic parental melt, where the IPGEs in the source possibly partitioned into a monosulphide solid solution. The Cu (22–80 ppm), elevated Pt (22–238 ppb), and Pd (31–377 ppb) concentrations indicate Pt and Pd have partitioned into a semi-metal rich melt during the later stages of crystallization. The geochemical characteristics of the basalts and ultramafic cumulates of the SGB indicate a suprasubduction zone tectonic setting for its formation. Similar geochemical and litho-tectonic correlations are also noticed between the SGB of Bastar craton and greenstone belts of the Eastern Dharwar craton of south India. The SGB (V/Yb =146 ± 25) and greenstone belts of Eastern Dharwar craton (V/Yb = 134 ± 52) record similar oxidation conditions of Phanerozoic subduction zones. Accordingly, we propose magmatic as well as tectonic correlations are possible for the Archean-Palaeoproterozoic Bastar and Eastern Dharwar cratons.