Metallogeny in response to lithospheric thinning and craton destruction: Geochemistry and U–Pb zircon chronology of the Yixingzhai gold deposit, central North China Craton

Abstract

Magmatism and associated metallogeny provide important constraints on geodynamic processes. The Hengshan terrain of northern Taihang Mountains located within the central North China Craton is well-known for several Mesozoic gold deposits. Here we investigate the Yixingzhai quartz vein-hosted gold deposit associated with the Sunzhuang quartz monzodiorite intrusive complex. We present U–Pb data on zircon grains from the monzodiorite which constrain the timing of emplacement of the pluton as ca.134Ma, coeval with the formation of Yixingzhai quartz vein gold deposit (at ca. 131Ma). The magmatism and metallogenesis during early Cretaceous in the Hengshan terrain are part of a major regional magmatic and metallogenic event in the Taihang Mountains and elsewhere in the North China Craton at ca. 130Ma ago. We characterize the zircon grains from the Sunzhuang quartz monzodiorite through morphology, internal structures and chemistry, and also present data from analyses of the chemistry (Co and Ni), and S–Pb–D–O isotopes of the minerals from the Yixingzhai gold deposit and Sunzhuang quartz monzodiorite. Our results reveal a lower crustal signature with mantle input for the source magma of the Sunzhuang Pluton. The magma was enriched in water and alkalis and shows a wide range of crystallization temperature (850–550°C, and mainly 650 to 700°C) under high oxygen fugacity. The ore minerals and the mineralizing fluids in the Yixingzhai gold deposit were derived from magma generated in the lower crust with additional input of mantle components. Our study links the gold metallogenesis with magmatism in the Hengshan terrain. Based on the new results reported in this study, and in conjunction with our interpretation of the ultra-broadband high-precision magnetotelluric sounding profile from the region, we suggest that the lithosphere beneath the Hengshan terrain was strongly thinned and decoupled between the crust and mantle in the early Cretaceous, and that the partly destructed lithosphere was largely preserved through the Cenozoic to present. The metallogenesis in the Hengshan terrain was closely related to the lithosphere thinning and crust–mantle decoupling in the North China Craton.