The Weak Neoproterozoic Thermal Records in North China and Its Significances for the Lithospheric Thickness
详细信息
- 责任者：Zheng Jianping (State Key Laboratory of Geological Processes and Mineral Resources ; Faculty of Earth Sciences ; China University of Geosciences ; Wuhan 430074 ; China) ; Ping Xianquan
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(7)
- 关键词：岩石圈 ; lithosphere ; 岩浆作用 ; igneous processes ; 华北地区 ; North China
- 页码：p.2456-2464
- 图表：6 illus., 3 tables, 57 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
It is generally accepted that the North China Block ( NCB) different from the South China Block ( SCB) are mainly characterized by the lack of widespread Neoproterozoic magmatic activity. However,what is the reason is unclear. We summarize the isotopic ages of the deep-seated xenoliths from four localities in the NCB. The possible position of the NCB in Rodinia supercontinent and its thickness of the lithosphere are also discussed. The deep-seated xenoliths include mafic granulites from the Fuxian Paleozoic kimberlites,garnet pyroxenites from the carbonatite kimberlite in Shexian,Hebei Provience,peridotites from the Xinyang Mesozoic volcanic rocks and Hannuoba Cenozoic basalt. The recorded ages include: the zircon lower intercepted age of 0. 61Ga from the Fuxian mafic granulites,the Sm-Nd internal isochron age of 0. 76Ga from the whole-rock and minerals of Shexian garnet pyroxenites,the zircon Neoproterozoic ages ( > 0. 64Ga) from the Xinyang peridotite and the Re-Os ages of 0. 9 ～ 0. 6Ga from the sulfides in Hannuoba peridotites. Different from the extensively developed Neoproterozoic magmatic activity in SCB,the limited Neoproterozoic records ( including the surface) in NCB might reflect their distinct location in the Rodinia supercontinent. That means the SCB is closer to the center of the supercontinent,while the NCB is far away from the center ( might at the edge ) . The difference of the situation demonstrates that the SCB has a thin lithosphere; however the NCB shows a thickness one. We thus speculate that the weakly thermal events and thickness lithosphere may result in the inconspicuous Neoproterozoic thermal records in NCB.