DOI: 10.57760/sciencedb.32693
title: Two-stage Ni-Cu sulfide mineralization of high-Mg basaltic magma: the Lubei example in the western segment of Eastern Tianshan orogenic belt, NW China
title: Two-stage Ni-Cu sulfide mineralization of high-Mg basaltic magma: the Lubei example in the western segment of Eastern Tianshan orogenic belt, NW China

description: Accurately determining the genetic relationships between mafic-ultramafic complexes within the same exploration block is critical for efficient exploration and offers key insights into the ore-forming processes of magmatic nickel-copper sulfide deposits. The Lubei magmatic Ni-Cu sulfide deposit in the Eastern Tianshan orogenic belt comprises two distinct mine fields: Lubei and Yunhai. Geochemical evidence indicates that rocks from the two mine fields have a common high-Mg tholeiitic basaltic parental magma. The Cu/Pd ratios and model calculations suggest that the magma experienced approximately 0.001 wt.% prior-sulfide segregation at depth. The variations observed in the magmas suggest a two-stage Ni-Cu sulfide mineralization. The first stage occurred at greater depths with lower oxygen fugacity (from FMQ – 1.03 to FMQ + 1.57), resulting in sulfides with higher PGE concentrations in the Lubei mine field. The second stage took place at shallower depths with higher oxygen fugacity (from FMQ + 1.94 to FMQ + 2.30), formed sulfides characterized by lower PGE concentrations in the Yunhai mine field. The negative correlation between initial 87Sr/86Sr ratios and Ni contents in sulfide ores indicates that crustal contamination might have played a role in hindering sulfide saturation. In contrast, olivine crystallization appears to trigger the sulfide saturation, as the modeling of olivines reveals a causal relationship between the olivine crystallization and sulfide segregation processes. The increase in oxygen fugacity may potentially account for the termination of sulfide saturation. At last, this study summarizes the indicators that help determine the evolutionary relationships and relative mineralization potential of different complexes.
description: Accurately determining the genetic relationships between mafic-ultramafic complexes within the same exploration block is critical for efficient exploration and offers key insights into the ore-forming processes of magmatic nickel-copper sulfide deposits. The Lubei magmatic Ni-Cu sulfide deposit in the Eastern Tianshan orogenic belt comprises two distinct mine fields: Lubei and Yunhai. Geochemical evidence indicates that rocks from the two mine fields have a common high-Mg tholeiitic basaltic parental magma. The Cu/Pd ratios and model calculations suggest that the magma experienced approximately 0.001 wt.% prior-sulfide segregation at depth. The variations observed in the magmas suggest a two-stage Ni-Cu sulfide mineralization. The first stage occurred at greater depths with lower oxygen fugacity (from FMQ – 1.03 to FMQ + 1.57), resulting in sulfides with higher PGE concentrations in the Lubei mine field. The second stage took place at shallower depths with higher oxygen fugacity (from FMQ + 1.94 to FMQ + 2.30), formed sulfides characterized by lower PGE concentrations in the Yunhai mine field. The negative correlation between initial 87Sr/86Sr ratios and Ni contents in sulfide ores indicates that crustal contamination might have played a role in hindering sulfide saturation. In contrast, olivine crystallization appears to trigger the sulfide saturation, as the modeling of olivines reveals a causal relationship between the olivine crystallization and sulfide segregation processes. The increase in oxygen fugacity may potentially account for the termination of sulfide saturation. At last, this study summarizes the indicators that help determine the evolutionary relationships and relative mineralization potential of different complexes.