The Jurassic volcanic–intrusive complex in the Dehua gold orefield, coastal region of SE China: Implications for the tectonic setting and epithermal mineralization

Abstract

The Dehua gold orefield is an important epithermal gold metallogenic district closely related to volcanic–subvolcanic rocks in the coastal region of the Cathaysia Block, southeastern China. This paper presents new LA-ICP-MS zircon U–Pb ages, elemental and Hf isotopic data for volcanic and intrusive rocks in the Dehua gold orefield. Our results show that the volcanic rocks were produced during the Middle Jurassic (ca. 169–164 Ma), whereas the intrusive rocks were formed in the Late Jurassic (ca. 163–157 Ma). Geochemically, these rocks are characterized by high-K calc-alkaline series and are commonly enriched in LILEs and LREE, depleted in HFSE with negative Nb, Ta, and Ti anomalies, and have lower Ta, Yb, Y and Rb contents, suggesting an arc magma geochemical affinities. Hence, this study firstly reports the Middle Jurassic high-K continental arc volcanic rocks in SE China, implying that the initial subduction of the paleo-Pacific plate began at least in the Middle Jurassic. Besides, in situ Hf isotopic analyses for dated zircon from the volcanic and intrusive rocks yield εHf(t) values range from −9.03 to +1.46 and the Paleo- to Mesoproterozoic two stage Hf model ages. The partial melting of the mixture of ancient continental crust materials and newly underplated potassic-rich mantle-derived mafic magmas likely explains the genesis of volcanic and intrusive rocks in the Dehua gold orefield. In addition, the exposed areas of the Jurassic volcanic rocks in the coastal region of SE China may have great potential to prospect the epithermal deposits.