Pb-isotope systematics at the Sopokomil shale-hosted massive sulfide deposit, North Sumatra, Indonesia

Abstract

Sopokomil is the best-explored shale-hosted massive sulfide Zn–Pb deposit on the Sumatra Island, Indonesia. At present, it is the most economically viable Zn–Pb deposit on the island. To understand the origin and metal sources of the deposit, Pb-isotope data were collected from galena in the Sopokomil stratiform ore. The data, which were acquired by laser ablation multi-collector inductively coupled mass spectrometry, showed highly radiogenic Pb-isotope ratios (206Pb/204Pb = 18.976 ± 0.010, n = 120; 207Pb/204Pb = 15.825 ± 0.009, n = 120; 208Pb/204Pb = 38.928 ± 0.016, n = 120) that are strongly correlated with one another (r = 0.58–0.99). Statistical analysis using analysis of variance and Welch’s t-test indicated that the Pb-isotope ratios are inhomogeneous, at both the inter-horizon and the intra-horizon levels. The results suggest that Pb in the Sopokomil ore deposit likely originated from the upper crust.