地质学报2017，Vol.91Issue(7)：1467-1482,16.
内蒙古京格斯台晚石炭世碱性花岗岩年代学及地球化学特征——岩石成因及对构造演化的约束
Geochronology and Geochemistry of Late Carboniferous Jinggesitai Alkaline Granites, Inner Mongolia: Petrogenesis and Implications for Tectonic Evolution
摘要
Abstract
In this paper,we present zircon U-Pb dating,in-situ Hf isotopic analysis,whole rock Nd isotopic and geochemical data of the late Carboniferous alkaline granites from Jinggesitai region,central part of the Xingmeng Orogenic Belt.Zircon U-Pb dating give weighted average age of 301.3±1.5Ma (n=21,MSWD =1.3),indicating that this intrusion was formed in late carboniferous.These rocks show the characterics of high silica (75.16～76.96％),alkali(K2O=4.61～5.04％,Na2O=3.98～4.24％) contents,low CaO (0.08～0.25％),MgO (0.07～0.1％),FeOt(1.05～2.05％) contents,respectively,but with high FeOt/ MgO ratios (12.85～29.66),which are similar with typical A-type granite.Trace elemental data of these rocks show enrichment of Rb,Th,U,K,Zr,Hf,but strong depletion of Sr,Ba,P,Ti.Total REE contents are moderate (∑REE=70.19～193.93 × 10 6) with obvious fractionation between LREE and HREE((La/Yb)N range from 3.85 to 11.55) and strong negative Eu abnormity (δEu range from 0.03～ 0.07).Furthermore,these rocks have positive zircon εHf(t) and whole rock εNd(t) values,with two stage Hf and Nd model ages of Neoproterozoic,indicating the source of Jinggesitai alkaline granites of juvenile crust from mantle in Neoproterozoic.These geochemical and Nd-Hf isotopic signatures argue for derivation from partial melting of juvenile crust by depression and heating of upwelling asthenosphere in a extensional setting,demonstrating late Post-Orogenic tectonic regime of Erlian-Dongwuqi region in 301Ma.关键词
碱性花岗岩/京格斯台/晚石炭世/兴蒙造山带/后造山Key words
Alkaline granite/Late Carboniferous/XingMeng orogeny/Post-orogeny引用本文复制引用
王树庆,胡晓佳,赵华雷,辛后田,杨泽黎,刘文刚,何丽..内蒙古京格斯台晚石炭世碱性花岗岩年代学及地球化学特征——岩石成因及对构造演化的约束[J].地质学报,2017,91(7):1467-1482,16.基金项目
本文为中国地质调查项目(编号:1212014121079,1212011121079)资助的成果. （编号:1212014121079,1212011121079）
