Genesis of the Hengling magmatic belt in the North China Craton:Implications for Paieoproterozoic tectonics
作者单位：State Key Laboratory of Lithospheric EvolutionInstitute of Geology and GeophysicsChinese Academy of Sciences Department of GeologyUniversity of Leicester
会议名称：《中国科学院地质与地球物理研究所2012年度（第12届）学术年会》
会议日期：2013年
学科分类：070902[理学-地球化学] 0709[理学-地质学] 07[理学]
基 金：supported by the National Basic Research Program of China(973 Program grant number 2012CB416601) the National Natural Science Foundation of China(NSFC grant numbers 41072146 and 41030316)
关 键 词：North China Craton Paleoproterozoic Mafic dyke swarm Hengling magmatic belt Intra-continental rift Tectonics
摘 要：The 2200-1880 Ma igneous rocks in the central and eastern parts of the North China Craton(NCC) constitute a new Hengling magmatic belt(HMB),which includes the -2147 Ma Hengling mafic sill/dyke swarm,the -2060 Ma Yixingzhai mafic dyke swarm,and the -1973 Ma Xiwangshan mafic dyke *** three swarms are contiguous and have experienced variable degrees of metamorphism from greenschist to low amphibolite facies(Hengling),medium granulite facies(Yixingzhai),and medium/high-pressure granulite fades(Xiwangshan).They are all tholeiitic in composition typically with 47-52 wt.%SiO and 4-10 wt.% MgO,and all show light rare earth element enrichments and Nb- and *** Nd T ages are in the range of 2.5-3.0 ***,the Hengling and Yixingzhai dykes/sills are depleted in Th,U,Zr,Hf and Ti,whereas the Xiwangshan dykes are enriched in U and weakly depleted in other *** Sr-anomalies indicate significant feldspar accumulation(positive anomalies) or ***εNd(t)) values of the three swarms are:-3.2-+3.0(Hengling),-1.7-+1.8(Yixingzhai) and -1.4-+1.0 (Xiwangshan). These mafic representatives of the HMB originated from the2.5 Ga sub-continental lithospheric mantle of the NCC,and with A-type granites and other igneous associations in this belt they likely evolved in an intracontinental *** progressive changing compositions of the three swarms are interpreted in terms of their source regions at different depths,i.e.,shallower and shallower through *** the decrease in scale and size of the intrusions and their magma volumes indicate the progressive weakening of magmatism in this rift. The rocks in this belt are different chronologically,petrologically and chemically from those in the Xuwujia magmatic belt(XMB).We propose that the two magmatic belts represent two different magmatic systems in different blocks of the NCC,i.e.,an eastern block(with the HMB) and a western block(with the XMB). Terminal collision was possibly a result of r