SHRIMP U-Pb zircon dating of Yueshan intrusion in the Yueshan ore field, Anhui, and its significance

The Yueshan intrusion is the most important intermediate-acid intrusive body in the, Yueshan ore field, which is in the Anqing-Guichi ore deposit concentrated area in the mineralization belt of the Middle and Lower Beaches of the Yangtze River area. In this paper we present a SHRIMP U-Pb zircon age of 138.7 +/- 0.5Ma for diorite from the Yueshan intrusion, which suggest an Early Cretaceous age for the formation of this intrusion. The result is coincident with the age of high-K calc-alkaline intermediate-acid intrusive rocks in the Tongling ore deposit concentrated area, but earlier than the formation age of granitic intrusion in the Yueshan ore field and the shoshonite series rocks in the Luzong and Ningwu volcanic basins. On the base of an integrated study of available petrological, geochemical and isotopic dating of magnitic rocks and deposits in the Yueshan ore field, we concluded that the magmatism and mineralization of the Yueshan ore field is a continuous process in the Yanshanian era, which took place in a transitional tectonic environment from compression to extension in Mesozoic.