Geochronology and Significance of Granites Associated with Gold Deposits in the Jidong Area, China

The Jidong area is located on the north margin of the North China craton. It is a nucleus composed of the oldest rocks in China. Precambrian metarnorphic rocks with various Phanerozoic granitoids invaded are widespread. Gold deposits here have close spatial relations to granitoids. Some deposits occur within them and others in the outer zone of the contact belt of the intrusion, extending thousands of metres. There have been controversial views in regard to the relations of the deposits to the intrusions although traditional techniques have been used to date the intrusions. In order to solve such a problem, the SHRIMP technique was adopted to date the U‐Pb ages of zircon collected from the Yuerya intrusion which hosts the large‐sized Yuerya Au deposit and Qingshankou intrusion 2 km away from the Jinchangyu (larger‐sized) Au deposit. Analysis shows that the ages of 175±1 Ma and 174±3 Ma for Yuerya intrusion and the age of 199±2 Ma for Qingshankou granite indicate the Early Yanshanian stage of the Mesozoic. The Yuerya intrusion also contains inherited zircon aged at about 2500 Ma, indicating that part of its source materials are Archaean metamorphic rocks. In addition to the SHRIMP data of this study, a great deal of data related to the alteration of Au deposits indicate the formation of the deposits at the Yanshanian stage of the Mesozoic, so the ore formation of Au deposits is inferred to relate to granitic intrusion.