SHRIMP zircon U-Pb dating and geochemistry of metallogenic dioritoids in the Xinliaodong copper-polymetallic ore district, eastern Guangdong Province, and their geological significance

The Xinliaodong copper-polymetallic ore district, located in the southwestern volcanic-intrusive belt of coastal southeast China, is a newly discovered deposit in eastern Guangdong Province. The diorite-porphyry and quartz diorite closely related to copper mineralization were studied using mineral mineralogy, SHRIMP zircon U-Pb dating and lithogeochemical methods. This study yielded a SHRIMP zircon U-Pb age of 160.2±1.4 Ma and 161.9±1.1 Ma for diorite-porphyry and quartz diorite, respectively, suggesting that they formed in late Jurassic. This is consistent with tin-copper mineralization period(late Jurassic, 161～145 Ma)in eastern Guangdong Province. All the rocks in the mining area are found to commonly contain amphibole, sphene and magnetite. Diorite-porphyry belongs to metaluminous, high-K calc-alkaline series. Diorite-porphyry and quartz diorite are enriched in Rb,U,Ce,Zr,Hf,Y and Nd, delepted in K,Sr,Nb,Ta,P and Ti. Right-dipping REE distribution pattern, distinct fractionation between LREE and HREE, and mean negative Eu anomalies are characteristic of I-type granitoid. Some quartz diorite and mineralized quartz diorite were altered chemically by mineralization.