内蒙古苏尼特左旗北部恩格日音棚地区早石炭世火山岩的发现及其构造意义  

The Early Carboniferous volcanic rocks in Engeriyinpeng area of Sonid Left Banner, Inner Mongolia: Discovery and its tectonic significance

作　　者：吴煜 田强国 王振强 冯建之 康宏伟 肖中军 李新萍 WU Yu;TIAN Qiangguo;WANG Zhenqiang;FENG Jianzhi;KANG Hongwei;XIAO Zhongjun;LI Xinping(No.1 Institute of Geological and Mineral Resources Survey,Development of Geology and Mineral Resources of He'nan Province, Luoyang 471000, He'nan, China;Key Laboratory of Au-Ag-Polymetallic Deposit Series and Deep-seated Metallogenic Prognosis of He'nan Province,Luoyang 471000, He'nan, China)

机构地区：[1]河南省地质矿产勘查开发局第一地质矿产调查院,河南洛阳471000 [2]河南省金银多金属成矿系列与深部预测重点实验室,河南洛阳471000

出　　处：《地质通报》2019年第7期1170-1182,共13页Geological Bulletin of China

基　　金：中国地质调查局项目《内蒙古1∶5万浩宾塔拉幅(L49E020022)、吉尔戈郎图幅(L49E020023)、阿登锡勒大队幅(L49E021022)、塔拉布拉格幅(L49E021023)、朝勒更爱力幅(L49E022022)、阿尔善布拉格幅(L49E022023)区域地质矿产调查》(编号:1212011220452)

摘　　要：在内蒙古苏尼特左旗恩格日音棚地区新发现一套英安岩、流纹岩及对应的火山碎屑岩组合,测得英安岩LA-ICP-MS锆石U-Pb年龄为333.0±1.4Ma,为早石炭世中期,代表宝力高庙组火山岩的初始喷发年龄。其中多数样品具钙碱性系列特征,在TAS图解中,分别落入流纹岩区和粗面岩-英安岩区;所有样品具相似的微量、稀土元素特征,稀土元素总量中等(∑ REE=110.6×10^-6~273.3×10^-6),轻、重稀土元素分馏明显((La/Yb)N=2.39~5.31),具较弱的负Eu异常(δEu= 0.48~0.65)。微量元素以富集大离子亲石元素Rb、Th,亏损高场强元素P、Ti、Nb、Ta为特征,显示岩浆来源为地壳物质的部分熔融,形成于俯冲构造环境。通过区域对比,早石炭世火山岩与贺根山蛇绿岩带北侧二连东乌旗一带的早石炭世二长花岗岩、石英闪长岩、花岗闪长岩等共同构成了早石炭世与板块俯冲有关的岩浆弧。早石炭世贺根山洋盆开始向北俯冲进入消减阶段。This paper reports newly discovered Early Carboniferous volcanic rocks in Engeriyinpeng area of Sonid Left Banner, Inner Mongolia.LA- ICP- MS U- Pb zircon dating shows that the volcanic rocks has an age of 333.0 ± 1.4Ma, which suggests that Baoligaomiao Formation was erupted in Early Carboniferous. Geochemical analysis shows that most of the samples are characterized by calc-alkaline rock series. All the acidic volcanic rocks fall into rhyolite area, two of the neutral volcanic rocks fall into trachyte area, other samples fall into dacite area, and all samples are characterized by alkaline rock series in the TAS diagram. All samples have similar characteristics of REE patterns which are characterized by medium total REE content (ΣREE=110.6×10^- 6~273.3×10^-6), significant fractionation of HREE and LREE (La/Yb)N=2.39~5.31) and relatively strong negative Eu anomalies (δEu=0.48~0.65). The trace element geochemistry is characterized evidently by enrichment of LILE (Rb and Th), and strong depletion of HFSE (P, Ti,Nb and Ta). The ratios of Rb/Sr (0.50~6.64), Ti/Y (6.82~85.21) and Ti/Zr (2.27~19.71) all fall into the field of the earth's crust source. These characteristics indicate that the volcanic rocks might have originated from partial melting of the earth's crust,and they were formed in a subduction-related settings. Combined with the regional researching results and the previous research results, the authors hold that the Carboniferous volcanic rocks, together with other Early Carboniferous arc-related felsic magmatic rocks in the Erlianhot - Dongwu Banner region, constitute the magmatic arc caused by the northward subduction of Hegenshan Ocean.

关 键 词：内蒙古 苏尼特左旗 早石炭世 英安岩 LA-ICP-MS锆石U-PB年龄 贺根山洋盆 

分 类 号：P534.45[天文地球—古生物学与地层学] P597.3[天文地球—地质学]