地质通报2017，Vol.36Issue(8)：1369-1384,16.
内蒙古吉尔嘎郎图早古生代岩体成因——年代学、地球化学及Nd-Hf同位素制约
Petrogenesis of the Early Paleozoic Jiergalangtu pluton in Inner Mongolia: Constraints from geochronology, geochemistry and Nd-Hf isotopes
摘要
Abstract
Early Paleozoic granites are distributed on the northern margin of Xingmeng orogenic belt discretely,and the genesis of these granites has important implications for the reconstruction of regional Paleozoic tectonic setting and orogenic evolution.Jiergalangtu pluton outcropped in northern Abag Banner and located in the middle of the early Paleozoic granite belt is the biggest composite pluton in the granite belt.Zircon LA-ICP-MS U-Pb dating shows that the early stage of the pluton was emplaced during 455.0～495.6Ma.Geochemically,the Jiergalangtu granites show moderate SiO2 values (59.49％～68.22％) and depletion of magnesium and iron,with K2O/Na2O ratios less than 1 (0.64～0.85) and A/CNK values being 0.96～1.09;in addition,most of the samples present subalkaline and weak per-aluminous signature.The trace element data of these rocks display enrichment of Cs,Rb,Th,U,Pb and depletion of Ba,Sr,P and HFSE such as Nb,Ta,the pluton exhibits indistinct negative europium anomalies (δ Eu=0.04～0.25)with moderate total REE content.Jiergalangtu pluton shows depleted isotopic compositions,(87Sr/86Sr)i=0.7053～0.7034,e Nd(t) =0.39～4.29,and both samples for Hf isotopic analysis have positive ε Hf(t) values,being 7.6～10.8 and 3.7～7.9 respectively.Integrated geochemical,geochronology and Sr-Nd-Hf isotopic data suggest that the Jiergalangtu granites were generated in early Paleozoic and resulted from the subduction of Paleo-Asian Ocean along Sunid-Xilinhot.The granites were formed by partial melting of juvenile crust which was modified by subduction slab fluids.The back-arc extension and opening of Hegenshan Ocean possibly resulted in the separation ofJiergalagntu pluton from predominant Sunid-Xilinhot island arc.Along with the closure of Paleo-Asian Ocean,the pluton ultimately occurred on the northern margin of Xingrmeng orogenic belt and was separated from the subduction zone by Hegenshan ophiolite complex.关键词
早古生代/锆石U-Pb定年/Nd-Hf同位素/岛弧岩浆岩/兴蒙造山带/新生地壳Key words
Early Paleozoic/zircon U-Pb dating/Nd-Hf isotopic compositions/arc magmatic rocks/Xingmeng orogeny/juvenile crust分类
天文与地球科学引用本文复制引用
杨泽黎,王树庆,胡晓佳,赵华雷,李承东,辛后田,孙立新..内蒙古吉尔嘎郎图早古生代岩体成因——年代学、地球化学及Nd-Hf同位素制约[J].地质通报,2017,36(8):1369-1384,16.基金项目
中国地质调查局项目《二连-东乌旗成矿带西乌旗和白乃庙地区地质矿产调查》(编号:DD20160041)、《华北重大岩浆事件及其成矿作用和构造背景综合研究》(编号:1212014121079)、《兴蒙造山带中段古生代花岗岩的组成、性质、时代和成矿作用研究》(编号:1212011121079) （编号:DD20160041）
