Gold mineralization of the Chencai-Suichang uplift and tectonic evolution of Zhejiang Province, southeast China

Abstract

A metallogenic model is proposed in which gold and base metal mineralization in SE China is related to plate interactions along the Pacific margin with Southeast Asia. From about 900 to 70 Ma, all depositional, orogenic, and metallogenic processes can be explained by subduction events along northeast-trending zones. With progressive accretion and cratonization along the continental margin, these subduction zones moved southeast for a distance of less than 150 km. As a result, the area is one of crustal reworking in which the rocks and mineral deposits of earlier events have been repeatedly modified. The Chencai-Suichang Uplift is an uplifted crustal block in central Zhejiang Province of mainland China, in which the Proterozoic basement is exposed as tectonic windows in overlying Mesozoic volcanics. Several gold and base metal deposits are located in these Proterozoic windows as well as in the younger volcanics. Most economic deposits were formed during the last major tectono-magmatic event affecting the area, the Yanshanian (160–170 Ma) event, although there is evidence for earlier mineralization that has been remobilized during the Yanshanian. It is suggested that crustal reworking was particularly important in remobilising and upgrading gold mineralization. The model presented is supported not only by local geology and isotopic data, but also by the regional distribution of gold deposits, which are arranged in a 50-km-wide belt parallel to the Yanshanian subduction zone. Three major episodes of mineralization occurred during: (1) a subduction-related period of metamorphism, partial melting, and mesothermal fluid generation and mineralization in the lower crust during the Caledonian; (2) subduction-related volcano-plutonic activity with epithermal mineralization during the early Yanshanian; and (3) hydrothermal mineralization during late Yanshanian tectono-magmatic event. In the third, two main categories of metallogenic control are recognized, namely: (1) hydrothermal fluid generation in the lower crust and (2) upper crust structural and lithological controls on mineralization.