Sulfur isotopes of lamprophyres and implications for the control of metasomatized lithospheric mantle on the giant Jiaodong gold deposits, eastern China

Abstract

The giant Jiaodong gold deposits represent one of the largest gold provinces (>5000 tons of Au) in the North China Craton of eastern China. They formed ∼1.7 b.y. after high-grade metamorphism of the crust. The metasomatized subcontinental lithospheric mantle (SCLM) has been increasingly proposed as the main source of such gold mineralization, but the direct geochemical links remain scarce. Here, we present a comprehensive δ34S dataset of sulfides from fresh lamprophyres (130−121 Ma) that formed from the metasomatized SCLM that is spatially and temporally associated with the Jiaodong gold deposits (ca. 120 Ma). Due to the negligible effects of crustal contamination and magmatic degassing, the consistently high δ34S (4‰−6‰, n = 73) of lamprophyres from variable localities reveals δ34S-enriched mantle sources relative to the asthenospheric mantle (−1.3‰ ± 0.3‰). Combined with the radiogenic Sr-Nd-Pb isotope signatures of these lamprophyres, we determined that such high δ34S signatures could have resulted from a period of mantle metasomatism related to subducted continental materials. The lamprophyres share δ34S (4.4‰ ± 0.8‰) and Sr-Nd-Pb isotopes with coeval gold-mineralized diorites (ca. 120 Ma) beneath the ore field (δ34S: 5.4‰ ± 2.5‰), which were interpreted to have sampled the magma chamber underlying the auriferous fluid systems. The lamprophyres and diorites consistently indicate the key control of metasomatized SCLM, although these mantle-derived magmas followed different pathways from source to crust. These relatively primitive and evolved magmas all show S and Pb isotopes similar to ore-related sulfides from the Jiaodong gold deposits, particularly those formed in the deep parts and at the early stage of the Jiaodong auriferous fluid system (δ34S: 5‰−7‰). Such results suggest that the primary auriferous fluids are genetically linked to the magmas derived from the metasomatized SCLM. Combined with radiogenic isotopes, our study on the sulfur isotopes of mantle-derived magmas identifies the metasomatized mantle source of the gold and provides new evidence for establishing a geochemical link between metasomatized SCLM, derivative magmas, and the giant gold deposits, supporting the model that subduction-related metasomatism plays a key role in the enrichment of volatiles and gold in the SCLM for large-scale gold mineralization.