Zircon U-Pb and molybdenite Re-Os geochronology of copper-molybdenum deposits in southeast Liaoning Province, China

摘要

Liaoning Province in China is an area known for the occurrence of numerous copper and/or molybdenum deposits of variable size. However, the age of mineralization and tectonic setting in this region are still a subject of debate. In this study we describe the geology of these deposits and apply zircon U-Pb and molybdenite Re-Os isotopic dating to constrain their ages and define the metallogenic epochs of this province. The Huatong Cu-Mo deposit yields molybdenite Re-Os model ages of 127.6-126.3 Ma and an isochron age of 127.4 +/- 0.7 Ma. The Dongbeigou Mo deposit yields molybdenite Re-Os model ages of 132.6-127.1 Ma, an isochron age of 128.1 +/- 5.1 Ma, and a zircon U-Pb age of 129.4 +/- 0.3 Ma for the associated monzogranite. The granodiorite associated with the Wanbaoyuan Cu-Mo deposit yields a zircon U-Pb age of 128.4 +/- 1.1 Ma; the plagiogranite associated with the Yaojiagou Mo deposit yields an age of 167.5 +/- 0.9 Ma; and the biotite-plagioclase gneiss from the Shujigou Cu deposit yields an age of 2549.4 +/- 5.6 Ma. These results, together with previous geochronology data, show that intense Cu-Mo porphyry and skarn mineralization were coeval with Early-Middle Jurassic and Early Cretaceous granitic magmatism. The former was associated with the orogeny that followed the collision of the Siberian and North China plates and the resulting closure of the palaeo-Asian Ocean, and the latter with rifting that followed the subduction of the palaeo-Pacific Plate and associated lithospheric thinning. Volcanogenic massive sulfide Cu deposit. mineralization took place much earlier, in the late Archaean, and was related to continent-continent collision, palaeo-ocean closure, the formation of a united continental landmass, bimodal volcanism, magma emplacement, and subsequent metamorphism and deformation of syn-collisional granites.