The discovery of the Early and Late Paleozoic magmatic activities in northwest Zhejiang Province, southeast China

It is generally considered that the Early Paleozoic geology of northwest Zhejiang and even the adjacent areas of Zhejiang such as Anhui, and Jiangxi Provinces(ZWG) is characterized by a series of folds, faults and the regional unconformity between the Late Paleozoic as well as the underlying Presinian epimetamorphic rocks and the lower part of the Early Paleozoic strata. These features resulted from the long-distance effect of the Caledonian tectonic event that occurred in South China. In contrast, Paleozoic magmatic activities in ZWG are generally to have been poorly developed. The authors obtained LA-ICP-MS zircon U-Pb weighted average ages of 445Ma±19Ma, 452.1Ma±2.7Ma, and 334.1Ma±2.4Ma for the magmatic rocks from the border area of Zhejiang and Anhui Provinces and the northern side of the Jiangshan-Shaoxing fault zone respectively, implying that only an intense tectonic activity once occurred in ZWG region during the Early Paleozoic, and there also existed a tectonomagmatic event along the fault zone during the Late Paleozoic. These data are valuable for the better understanding of tectonic evolution of Jiangshan-Shaoxing fault.