Mantle-rooted fluid pathways and world-class gold mineralization in the giant Jiaodong gold province: Insights from integrated deep seismic reflection and tectonics

Abstract

The Jiaodong Peninsula in the eastern North China Craton is well-known for world-class deposits and as the only known late Mesozoic giant gold province located within a Precambrian metamorphic terrane. Here we synthesize deep seismic reflection data from the Jiaodong Peninsula, and on conjunction with existing interpretations of magnetotelluric data. We provide a new interpretation that offers insights into the possible crust-mantle interaction and deep ore-forming processes in this supergiant gold province. Six high-yield NNE-trending gold mineralized fault zones that span approximately 420 km across strike are identified: Sanshandao, Jiaojia, Zhaoping, Qixia, Guoji, and Muru. We identify distinct features in the coupled crust and lithospheric mantle beneath the Jiaodong gold province including a metamorphic core complex (MCC) and detachment fault systems at shallow crustal levels, a mid-crustal detachment belt (MCDB), a low-angle reverse fault in the lower crust, a reflection-transparent region and crust-mantle transition zone (CMT), as well as a deeper Moho discontinuity. Our study also reveals clear detachment or absence of the Moho and CMT beneath the Tan-Lu and Wulian-Yantai fault zones, the presence of weak wave impedance, or reflection-transparent regions in the deep parts of the high-angle faults, such as the Tan-Lu and Wulian-Yantai faults, and that in the core of the Linglong MCC. These are interpreted as zones formed through the homogenization of crustal materials as a result of the upward migration of heat, magmas, and fluids from the lithospheric mantle to the middle and upper crust. Important auriferous fluid pathways from the Moho include reverse faults at lower crustal levels, the MCDB, and detachment fault systems at upper crustal levels. The fluid pathway systems played a crucial controlling role in the intensity of formation of gold deposits. The CMT and MCDB are thicker, and the mineralization intensity and known gold resources are greater, where they are closer to the mantle-derived melt and fluid pathway.

We propose a new two-stage model to explain the origin of the giant Jiaodong gold deposits which is based on the crust-mantle interaction as indicated by seismic reflection and magnetotelluric profiles, combined with existing experimental petrology and thermodynamic simulations, as well as information on mineralization and tectonothermal events based on isotope data. We envisage that the subduction-collision at ∼250–220 Ma between the Yangtze and North China cratons resulted in the formation of enriched lithospheric mantle that served as one of the important sources of auriferous fluids. At ∼120 Ma, asthenosphere upwelling, which induced metasomatism and partial melting in the overlying enriched lithospheric mantle, resulted in the activation, migration and concentration of gold, generating one of the world's giant gold fields.