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内蒙古狼山地区早志留世石英闪长岩体的厘定及其地质意义
引用本文:滕学建,田健,刘洋,张永,滕飞,段霄龙.内蒙古狼山地区早志留世石英闪长岩体的厘定及其地质意义[J].地球科学,2019,44(4):1236-1247.
作者姓名:滕学建  田健  刘洋  张永  滕飞  段霄龙
作者单位:中国地质调查局天津地质调查中心, 天津 300170
基金项目:阴山成矿带小狐狸山和雅布赖地区地质矿产调查项目DD20160039
摘    要:内蒙古狼山山脉西侧分布有零星的早古生代岩浆岩,早志留世侵入体主要出露于哈日音熬瑞-迈罕陶勒盖一带.该岩体岩性为石英闪长岩,LA-ICP-MS锆石U-Pb年龄显示,其206Pb/238U加权平均年龄为440±1 Ma.岩石富集大离子亲石元素Rb、K、Pb,不同程度地亏损高场强元素Nb、Ta、P、Ti;轻稀土富集,重稀土亏损,具有弱的负Eu异常,显示了岩浆弧的地球化学特征.εHf(t)值为-12.1~-8.8及TDM2在1 973~2 182 Ma之间,反映了源区以古元古代古老地壳为主,闪长质包体中的斜长石斑晶及矿物成因判别图解显示了岩体在形成过程中受到了岩浆混合作用.构造判别图解及Hf同位素特征表明该岩体可能形成于大陆边缘弧的构造背景.对比达茂旗、白乃庙地区新近发表的有关数据,早志留世石英闪长岩的岩石地球化学特征与之十分相似,由此可见,华北地块北缘早古生代俯冲带从白乃庙地区可以延伸到狼山地区. 

关 键 词:内蒙古    狼山地区    早志留世    石英闪长岩    大陆边缘弧    岩石学
收稿时间:2018-04-22

Definition and Geological Significance of Early Silurian Quartz Diorite Pluton in Langshan Area,Inner Mongolia
Abstract:The Early Paleozoic magmatites are sporadically distributed along the western side of the Langshan Mountains, Inner Mongolia.The Early Silurian rocks are mainly exposed in the zone of Hariyinaorui-Maihantaolegai.LA-ICP-MS zircon U-Pb dating shows that the 206Pb/238U weighted average age of quartz diorite is 440±1 Ma.The rocks show similar chondrite-normalized REE patterns, and display relatively high concentration of light rare earth elements (LREEs) but low contents of heavy rare earth elements (HREEs) with minor negative Eu anomalies. The overall chemical similarities of these rocks on the primitive mantle-normalized variation diagrams display affinity to arc signature; considering both tectonic discriminated diagrams and the Hf isotopic signature, it is proposed that the Langshan area was under the tectonic setting of continental margin arc during Early Silurian. It is concluded that the subduction zone of Early Paleozoic had been extended from the area of Damaoqi to Langshan, since these rocks show similar geochemical characteristics with the recently published data of Early Silurian quartz diorite in the area of Damaoqi and Bainaimiao. 
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