Multiple magmatism and origin of the sulfide mineralization of the Getashankou mafic–ultramafic intrusion in Eastern Tianshan, Central Asian Orogenic Belt

Hosting a significant magmatic Ni–Cu sulfide cluster, the Eastern Tianshan region lies on the southern margin of the Central Asian Orogenic Belt. The recently discovered Getashankou intrusion marks the easternmost extent of this cluster. However, the magmatism and the origin of sulfide mineralization in this intrusion are still unclear. The Getashankou intrusion comprises five units (No. I–V), with lens-shaped and vein-like morphologies. Sulfide mineralization occurs in the No. II and No. III sequences, which consist of lherzolite, websterite, and gabbro. The mineralization includes sparsely disseminated and moderately disseminated types. Olivine within the Getashankou intrusion exhibits Fo values from 83.7 to 86.4 mol.% and Ni contents varying between 856.5 and 2490.9 ppm. The Getashankou intrusion displays light rare earth element (LREE) enrichment relative to heavy rare earth element (HREE), along with high-field-strength element (HFSE) depletion (e.g., Nb, Ta), large-ion lithophile element (LILE) enrichment (e.g., Ba, Pb), and moderately positive εHf_(t) values (+9.99 to +14.03). Collectively, these characteristics indicate a subduction-modified mantle source. The parental magma of this intrusion is characterized as high-Mg basaltic melt. Mass-balance simulations for Pd and Ni contents illustrated that the parental magmas of lherzolite and websterite + gabbro have experienced 0.013 % and 0.022 % early sulfide removal, respectively. Rayleigh simulations for Fo and Ni contents in olivine illustrated that the Getashankou intrusion underwent ∼2 % crystallization to achieve sulfide saturation. The mass-balance modeling indicates that the sulfide mineralization hosted in lherzolite and websterite + gabbro has been generated from multiple pulses of parental magma, containing 0.01 ppb of Os and 0.3 ppb of Pd with R-factors ranging from 2000 to 50000, and 0.012 ppb of Os and 0.1 ppb of Pd with R-factors from 5000 to 30000, respectively. Low Se/S ratios indicate that the addition of crustal sulfur is instrumental for promoting the saturation of sulfur in the Getashankou deposit. The subduction-modified mantle sources, multiple pulses of magma replenishment, and significant crustal sulfur addition in the Getashankou intrusion meet the requirement to generate large deposits, making it a promising target for further exploration.