Origin of the Paishanlou monzogranite in Liaoning Province and its genetic connection with gold mineralization
辽宁省排山楼矿区二长花岗岩成因及其与金矿化的关系

The Paishanlou monzogranite stock is outcropped in the vicinity of the Paishanlou gold deposit hosted by a ductile shear zone occurred within Late Archean high-grade metamorphic sequences lying in the eastern segment of northern periphery of North China Craton. Mineralogy of the monzogranite consists principally of K-feldspars, oligoclase, quartz and biotite, with minor amphibole and trace zircon, sphene, apatite and ilmenite. The I-type monzogranite with high-K calc-alkaline attributes displays unique geochemical features including sodium enrichment relative to potassium, notably high Sr and Ba concentrations, strongly depleted heavy REE, as well as the presence of minor positive Eu anomalies on the REE patterns, suggesting that the magmas might be derived from the partial melting of amphibolitic protolithes under the P-T conditions of over-thickened continental lower crust. LA-ICP-MS zircon U-Pb dating yields absolute age of 128±1.3Ma indicating the stock was emplaced during Late Yanshanian, Cretaceous, during which a lithospheric extensional regime was prevailing in the region. As the monzogranite intrudes into the mylonite zone which are the ore-controlling structure and the granitoids develop gold mineralization. Also based on the close spatial and temporal relations between the monzogranite and ore-hosting ductile shear zones, with considering the intimate connections among regional thermal-tectonic events and mineralization, it is suggested that the emplacement of the monzogranite stock may probably genetically be related to the ore-hosting ductile shearing nearby to the south by the regional extensional tectonism during Late Yanshanian. But the possibility that the ore-control ductile fracture was active in a long period or there exists an earlier generation of gold mineralization can not be rejected.