Discovery of Jinning Cycle Magmatism in Eastern Part of Eastern Kunlun Orogenic Belt and Its Significance

摘要

From the isotopic dating study of gneissic granodiorite, the authors discovered magmatism of the Jinning cyclc. Intrusive rocks were formed in the Neoproterozoic, whose Pb-Pb ages range from (913± 4) Ma to (1 011±4) Ma and U-Pb concordia age is (703±15) Ma. The tectonic set- tings of the rocks are volcanic arc or syn-collision. After the formation of the intrusive rocks, these rocks also experienced reconstruction of Caledonian metamorpbism. Based on the Ar-Ar dating of metamorphic mineral of muscovite, the metamorphic time is determined to range from (386.8±0.8) Ma to (389.44±3.70) Ma.