Abstract:

The Tianshan orogenic belt experienced a subduction and split plots during Late Paleozoic. Records of granite magma records provide important constraints on timing of subduction. The geochemical and chronological results show that Huamugou pluton is consistent with highly fractionated I-type granite of high silicon, rich alkali, poor iron. Ba, Sr, P, Ti are poorly concentrated and Cs, Rb, U, K are well concentrated. Pb isotope studies suggest crustal source with added mantle material. The LA-ICP-MS zircon U-Pb dating on zircons yields age of (330.2±5.7) Ma, belonging to the late Early Carboniferous. These geochemical characteristics indicate that the Huamugou pluton formed in a continental arc setting. Northern Tianshan oceanic crust still southward subducted in the late Early Carboniferous and Junggar plate is not collided with Yili plate, which shows that the Tianshan region is in the subduction stage.

Key words: Tianshan, Yili block, highly fractionated I-type granite, U-Pb zircon dating, Huamugou pluton, subduction