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兴安地块东北部晚侏罗世C型埃达克质花岗岩年代学、地球化学特征及构造环境意义

Late Jurassic adakitic granites in northeastern Xing'an block: geochronology and geochemical characteristics and tectonic significance
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摘要 大兴安岭地区发育强烈的中生代岩浆作用,一直以来是本地区地质构造研究的热点,但关于晚侏罗世花岗岩的研究报道较少。文中根据三件花岗岩样品的锆石U-Pb LA-ICP-MS测年结果获得的(158.5±1.6) Ma、(156.1±0.59) Ma和(154.1±1.1) Ma年龄结果将兴安地块东北部原定为早中生代的花岗岩形成时间厘定为晚侏罗世。该晚侏罗世花岗岩以中粗粒花岗闪长岩—二长花岗岩为岩石组合,岩石具富硅碱、高钾、过铝、低铁钛镁等特点,属于过铝质高钾钙碱性系列,富集LREE,亏损HREE、Y和HFSE,高Sr,低Yb,高La/Yb、Sr/Y比值,具有“C型”埃达克质岩的特点。该花岗岩的形成与蒙古鄂霍茨克洋闭合引起的陆陆碰撞造山作用密切相关,岩浆源于造山带加厚的下地壳底部基性岩的部分熔融,岩浆形成演化中有富铝地壳物质的加入。该系列花岗岩与紧邻的早、中侏罗世TTG花岗岩反映侏罗纪蒙古鄂霍茨克洋经历了由洋壳俯冲到陆陆碰撞的构造演化。 Although intense Mesozoic magmatism widely occurred in the Great Hinggan Range and is a hot topic in tectonic research,reports on the Late Jurassic granites is scarce.In this paper,we present three new LA-ICP-MS zircon U-Pb ages 158.5±1.6 Ma,156.1±0.59 Ma and 154.1±1.1 Ma for granite outcrop in northeastern Xing’an block to confirm that the granite emplacement occurred in the late Jurassic,not the early Mesozoic.These Late Jurassic granites are composed of medium coarse-grained granodiorite and monzonitic granite.Petrochemically they belong to peraluminous and high-K calc-alkaline series with high Si,K,Na and Al contents and low Fe,Mg and Ti contents.They are enriched in light rare earth elements(LREE)and large ion lithophile elements(LILE,e.g.Rb,Ba,Th,U,Sr),depleted in heavy rare earth elements(HREE),Y and high field strength elements(HFSE,e.g.Nb,Ta,Zr,Hf),with high La/Yb,Sr/Y ratios and possibly belong to "C-type"adakites.Genetics of the granite is closely related to the continental collision orogeny caused by the closure of the Mongol-Okhotsk ocean.The magma originated from the partial melting of basic rocks of the thickened lower crust under the orogenic belt with the addition of rich Al crustal material during magmatic evolution.The difference between the Late Jurrasic adakitic and adjacent Early-Middle Jurassic TTG granites reflects the tectonic evolution of the Mongol-Okhotsk ocean from subduction to continental collision during the Jurassic.
作者 赵院冬 车继英 许逢明 朱群 王奎良 ZHAO Yuandong;CHE Jiying;XU Fengming;ZHU Qun;WANG Kuiliang(Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China)
出处 《地学前缘》 CSCD 北大核心 2018年第6期240-253,共14页 Earth Science Frontiers
基金 国家自然科学基金项目(41502063) 国家重点研发计划项目“深地资源勘查开采”专项(2017YFC0601305) 中国地质调查局地质调查项目(12120114055701).
关键词 兴安地块 埃达克质 花岗岩 蒙古-鄂霍茨克洋 碰撞造山 Xing'an block adakitic granite Mongol-Okhotsk ocean continental collision
作者简介 赵院冬(1981-),男,博士,高级工程师,主要从事岩浆过程与深部作用方面研究。E-mail:zhaoyd1981@qq.com
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