The Yanshanian (Mesozoic) metallogenesis in China linked to crust-mantle interaction in the western Pacific margin: An overview from the Zhejiang Province

Abstract

The connection between multi-plate convergence and Mesozoic metallogenic explosion in the western Pacific continental margin is a frontier theme of research. A key to understanding of the Mesozoic tectonics in South China involves the spatio-temporal distribution and tectonic control of Mesozoic deposits in this region. The Zhejiang Province in South China is located in the middle segment of the western Pacific metallogenic belt, where tectono-magmatic and metallogenic activities during the Yanshanian Period (Jurassic-Cretaceous) were frequent and intense. This region is an ideal window for investigating oceanic slab subduction and recycling, continental marginal magmatism, deep geological processes, and mineralization in the western Pacific continental margin. Here we present a comprehensive synthesis of information from petrology, isotope geochronology, geochemistry, igneous geology, and tectonics of the Zhejiang metallogenic deposits to evaluate the spatio-temporal distribution and formation mechanism of the Yanshanian mineral deposits. The early Yanshanian deposit types are mainly Fe or Pb–Zn ores, which are distributed in the northwestern Zhejiang region. The ore-bearing magmatic rocks in this period are highly fractionated I-type granites, which originated from continental crust together with depleted mantle materials. In the mid-Yanshanian, Mo deposits are the main type and are distributed throughout the region. Magma types in this period are relatively diverse, most are S-type granites, which were derived from the remelting of old continental crust and mixed with juvenile mantle-derived and crust-derived magmas. The late Yanshanian deposit types are mainly W–Sn, which are distributed in the southeastern part of the Zhejiang Province. The ore-bearing magma has the characteristics of A-type granite with mantle origin. Combined with numerical simulation, we discuss the deep processes of Mesozoic metallogenic explosion in South China. We correlate the early Yanshanian mineralization with flat subduction of the Paleo-Pacific Plate and the foundering of the oceanic slab; the mid-Yanshanian mineralization is associated with the destruction and thinning of lithospheric mantle caused by mantle melting related to the sharp subduction; and the late Yanshanian mineralization witnessed a decrease in the volume of mantle materials and the eastward retreat of the trenches.