GOLD MINERALIZATION OF THE CHENCAI-SUICHANG UPLIFT AND TECTONIC EVOLUTION OF ZHEJIANG PROVINCE, SOUTHEAST CHINA

A metallogenic model is proposed in which gold and base metal minerali zation 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 e vents along northeast-trending zones. With progressive accretion and c ratonization along the continental margin, these subduction zones move d 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 Up lift is an uplifted crustal block in central Zhejiang Province of main land China, in which the Proterozoic basement is exposed as tectonic w indows in overlying Mesozoic volcanics. Several gold and base metal de posits are located in these Proterozoic windows as well as in the youn ger volcanics. Most economic deposits were formed during the last majo r tectono-magmatic event affecting the area, the Yanshanian (160-170 M a) event, although there is evidence for earlier mineralization that h as been remobilized during the Yanshanian. It is suggested that crusta l reworking was particularly important in remobilising and upgrading g old mineralization. The model presented is supported not only by local geology and isotopic data, but also by the regional distribution of g old deposits, which are arranged in a 50-km-wide belt parallel to the Yanshanian subduction zone. Three major episodes of mineralization occ urred during: (1) a subduction-related period of metamorphism, partial melting, and mesothermal fluid generation and mineralization in the l ower crust during the Caledonian; (2) subduction-related volcano-pluto nic activity with epithermal mineralization during the early Yanshania n; and (3) hydrothermal mineralization during late Yanshanian tectono- magmatic event. In the third, two main categories of metallogenic cont rol are recognized, namely: (1) hydrothermal fluid generation in the l ower crust and (2) upper crust structural and lithological controls on mineralization.