Emplacement sequences and geochronology of the Shaxi porphyry copper-gold deposit,Anhui Province,East China

Shaxi deposit is a typical porphyry Cu-Au deposit,which locates in the Tancheng-Lujiang fault and the northwest margin of the Luzong volcanic basin in the Middle and Lower Yangtze River metallogenic belt. The Shaxi porphyry deposit contains 1Mt Cu and 40t Au,which is dominated by vein-style mineralisation with chalcopyrite and gold hosted in a quartz stockwork vein that is intimately associated with potassic alteration in the core of the deposit. To determine the age of mineralization and the magmatic rocks of Shaxi deposit is very important for the study of deposit genesis and regional metallogenic regularities. On the basis of geological and petrographic studies,we collect the primary types of magmatic rocks( coarse grained diorite porphyry,biotite quartz diorite porphyry,medium quartz diorite porphyry,fine quartz diorite porphyry and diorite porphyry) and molybdenite with paragenetic chalcopyrite and get the age of the magmatic rocks( they are 130. 60 ± 0. 97Ma,129. 30 ± 1. 00Ma,127. 10 ± 1. 50Ma,129. 46 ± 0. 97Ma and 126. 7 ±2. 1Ma,respectively) by zircon Cameca,LA-ICP-MS U-Pb dating and mineralization( 130. 0 ± 1. 0Ma) by Re-Os dating of Shaxi deposit,and reclassify the emplacement sequences of magmatic rock. Our work also indicates that Shaix deposit is the second stage porphyry mineralization,which is different from the deposit and magmatic rocks of Luzong basin and the first stage porphyry deposits,imply that Shaxi deposit is the product of the geotectonical evolution of bith the Tancheng-Lujiang fault and the Changjiang fault.