Formation Time and Sources of the Huaiguang "Migmatitic Granodiorite" in Bengbu,Anhui Province:Evidence from SHRIMP Zircon U-Pb Geochronology
JIN Ke XU Wenliang WANG Qinghai GAO Shan LIU Xiaochun ( 1) College of Earth Sciences, Jilin University, Changchun, Jilin , 130061;2) Key Laboratory of Continental Dynamics , Northwestern University, Xi'an , Shaanxi ,710069;3) Institute of Geomechanics, CAGS,Beijing, 100081)
Petrography of the Huaiguang "migmatitic granodiorite" and existence of magmatic zircons indicate that the granodiorite was formed by the crystallization of magma and was subjected to late stress. The granodiorite was formed at 130 ± 2.0 Ma based on the ages of magmatic zircons. Most inherited zircons were formed at 1 800-1900 Ma,2 300 - 2 517 Ma and 3 443 Ma,suggesting that the Huaiguang granodioritic magma might have been derived from the partial melting of the basement of the North China Block. The early Cretaceous (130 Ma ± ) magmatism probably resulted in a major Pb loss in some inherited and detrital zircons and might have been an important period of the lithospheric thinning in the eastern part of the North China Block. The 130 Ma magmatism and lithospheric thinning could be attributed to the subduction of the Pacific plate.