Magmatism and ore-forming background of the main deposits in Taoxi circular structure along the Wuyishan ore belt

Abstract：Taoxi circular structure is one of the circular structures and also a part of Wuyishan uplift and appears as metamorphic core complexes. There are abundant medium-large sized copper and polymetallic ore deposits distributed within the circular structure, such as Zijinshan Cu-Au deposit, Yanbei Sn deposit and Hongshan Cu deposit. The Zijinshan Cu-Au deposit has the biggest gold ore reserves in China and the Yanbei deposit is a superlarge deposit with more than 300,000 t Sn. The area represents a rich segment of the Wuyi metallogenic belt. The main geochronologic dating of mineralization yielded ages in the range of 130-90Ma, suggesting the Late Yanshanian period. The ore deposits as well as most copper-gold ore deposits located in Taoxi circular structure are of porphyry-magmatic hydrothermal type. The Zijinshan Cu-Au deposit, the Yanbei Sn deposit and the Hongshan Cu deposit all how that the ore-forming porphyries are I-type granites and their ages are from 94 to 133Ma, close to the age of mineralization (125-90Ma). Both magmatism and mineralization occurred in the circular structure, which are called “Mesozoic magmatic and metallogenic explosion”. Geochronologic dating of ore-bearing porphyry stocks yielded ages of 90-133Ma, implying the middle to late period derivatives of Yanshanian magmatic complex that resulted from the interaction of the crust with the mantle and the lithosphere delamination in the Late Mesozoic period. The swelling of Taoxi circular structure and the development of the rift together with the intrusion and eruption of the magma accelerated metallogenic process in the study area. Taoxi circular structure is characterized by lithosphere thickening and delamination, intrusion of the asthenosphere-derived mafic rocks, and accompanied mineralization.