The Genesis and Geological Significance of the DongquangobiRapakivi Granite in Heshuo of Xinjiang

Through 1∶50000 geological mapping of Malan,the authors discovered rapakivi granitein Dongquangobi area for the first time. Dongquangobi rapakivi granite is distributed in the middle section of South Tianshan collision belt,the rock is characterized by rich dark fine-grained dioritic inclusions and special rapakivi texture. This granite appears stock-like,its petrochemistry is characterized by higher Al₂O₃(14.47%～15.44%)、K₂O(3.93%～4.7%)和Na₂O(3.4%～3.7%), rich in LREE and LILE and with weak δEu (an average of 0.79) negative anomaly,showing that it has obviously different geochemical characteristics compared with typical wiborgite in the plate. Its formation age is the Late Carboniferous(305±1Ma),which exactly is the end stage ofSouth Tianshan ocean basin subducted northward collisional orogenesis,so it can be concluded that the Dongquangobi rapakivi granite may be a type of orogenic belt rapakivi granite,which is I-type granite formed in the uplifting environment after plate collision.