Isotopic (Sr, Nd, and Os) compositions of Zhaxikang diabases, southern Tibet: Records of mantle‐plume activity and implications for Zhaxikang Sb–Pb–Zn–Ag mineralization

Diabases from the Zhaxikang Sb–Pb–Zn–Ag deposit in southeastern Tibet provide an opportunity to reveal the tempo‐spatial distribution of the recently identified Comei large igneous province and understand the association with Zhaxikang mineralization. Here we present whole‐rock geochemical and Sr–Nd–Re–Os isotopic data on the Zhaxikang diabases. The Zhaxikang diabases have a Re–Os isochron age of 136.1 ± 3.1 Ma. These rocks are characterized by high TiO2 content (3.0–4.2 wt%) and have alkaline ocean island basalt‐like trace element patterns with initial 87Sr/86Sr ratios of 0.7060–0.7069, εNd(t) values of 1.3–3.3, and 187Os/188Os(t) ratios of 0.12–0.13. The Zhaxikang diabases are part of the Comei large igneous province and were derived from partial melting of enriched garnet‐bearing mantle source and related to interaction of plume melts with subcontinental lithospheric mantle. Our new data provided additional evidence that Zhaxikang Pb–Zn(Ag)‐bearing Mn–Fe carbonate veins were not produced by a sedimentary exhalative event in Triassic–Jurassic rift environment.