PbSL dating of garnet and staurolite:Constraints on the Paleoproterozoic crustal evolution of the Eastern Block,North China Craton
作者单位：Department of Applied GeologyCurtin University of Technology
会议名称：《中国科学院地质与地球物理研究所第11届（2011年度）学术年会》
会议日期：2012年
学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学]
基 金：supported by the National Science Foundation of China (Grants Nos.40873009 and 40925007) the State Key Laboratory of Lithospheric Evolution(Grant No,Zhuan 0809)
关 键 词：Eastern Block North China Craton Liaohe Group Jiao-Liao-Ji belt Pb step-leaching dating Garnet Staurolite
摘 要：It is well accepted that the North China Craton formed by assembly of the Eastern and Western blocks along the Trans-North China Orogen,with cratonization in the Paleoproterozoic(～1.85 Ma).However, there is controversy about the formation of the Eastern and Western blocks themselves,especially the timing of cratonization of the Eastern *** Jiao-Liao-Ji orogenic belt is the most important Paleoproterozoic Orogenic belt in the Eastern Block and consists mainly of the North and South Liaohe Groups and the Liaoji *** timing of metamorphism of the Liaohe Group is the key to understanding the evolution of the Eastern Block of the North China *** the isotope systematics of metamorphic minerals can be used to date parts of the prograde thermal histories of metamorphic belts,dating of minerals, such as garnet and staurolite has the distinct advantage that time information can be related directly to the pressure-temperature-deformation history recorded by the same *** this paper we present results of precise Pb/Pb stepwise-leaching(PbSL) dating of garnet and staurolite from the metasedimentary rocks of the south Liaohe *** primitive Pb and radiogenic Pb are selectively extracted from garnet and straurolite by leach steps and determined by multiple collector(MC-) 1CP-MS. The garnet and staurolite record two groups of Pb/Pb ages,at 1.93-1.91 Ga and～1.86 Ga,respectively. These constrain the time of peak metamorphism of the Liaohe Group during collision between the Longgang Block in the north and the Liaonan(Nangrim) Block in the south and a subsequent post-col-lisional event,*** data for the South Liaohe Group and previously published data for the Liaoji Granite,combined with key lithological,structural and metamorphic information,indicate that the cratonization of the Eastern Block of the North China Craton occurred at 1.93-1.91 Ga.