Abstract:

The Wurinitu granitoid pluton, located in the northwestern of the Wurinitu Village, Chaganaobao town, Sunidzuoqi County, Inner Mongolia, is a concealed rock mass and mainly composed of fine to middle-fine grained granite and adamellite. Petrography and geochemical characteristics indicate that it belongs to high-K calc-alkaline series. Its SiO₂ contents range from 74.85% to 78.10%, while K₂O/Na₂O ratios and A/CNK values vary from 1.45 to 3.08 and 1.00 to 1.21, supposed to a suite of peraluminous rock. Rb, Th and U elements are enriched in the intrusion while Ba, Nb, Sr, P and Ti depleted. REEs show characteristics of obvious negative Eu anomalies(δEu= 0.22-0.39)and right-dipping“V”patterns with LREE enrichment. On the basis of LA-ICP-MS U-Pb chronological study of zircons, the U-Pb dating results from the granites are 139 Ma implying that they formed in Early Cretaceous, Late Yanshanian stage. Chemically, the granitoids belong to A-type, implying that they formed under an extensional tectonic setting. The source compositions of the granites are different, and they are mainly derived from clay-rich pelite with a spot of arenite, resulted from metamorphism.

Key words: W-Mo deposit, granite, geochronology, geochemistry, Wurinitu, Inner Mongolia