文章摘要
吴涛涛.大兴安岭北段根河地区早白垩世玄武岩年代学、地球化学及其地质意义[J].地质与勘探,2018,54(6):1270-1281
大兴安岭北段根河地区早白垩世玄武岩年代学、地球化学及其地质意义
Geochronology and geochemistry of the Early Cretaceous basalt in the Genhe area, northern Great Xing’an Range and geological implications
投稿时间:2018-07-28  修订日期:2018-10-12
DOI:10.12134/j.dzykt.2018.06.019
中文关键词: 板内碱性玄武岩 岩石圈伸展 玛尼吐组 根河地区 大兴安岭北段
英文关键词: within plate alkali basalts, lithosphere extension, Manitu Formation, Genhe area, north part of the Great Xing’an Range
基金项目:中国地质调查局项目(编号:DD20160104和DD20160047)资助
作者单位E-mail
吴涛涛 中国地质调查局沈阳地质调查中心辽宁沈阳 zhouyongheng@mail.cgs.gov.cn 
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中文摘要:
      大兴安岭北段根河地区出露一套玄武岩。为明确该套玄武岩的岩石成因、地层时代归属及形成的构造背景,本文对该玄武岩进行了锆石LA-ICP-MS U-Pb年代学和岩石地球化学研究。锆石U-Pb测定结果表明,根河地区玄武岩形成于早白垩世(142.0±2.1 Ma),将其暂归置于玛尼吐组,并非前人认为的下石炭统莫尔根河组。岩石地球化学特征表明,该玄武岩富钠低钾,属碱性系列,稀土元素总量(ΣREE)较低(91.50×10-6~108.57×10-6),轻重稀土分馏较明显((La/Yb)N=10.82~13.49),轻稀土元素和K、Rb、Ba、Sr等大离子亲石元素相对富集,亏损Th、U、Hf、Ti、Nb、Ta等高场强元素和重稀土元素。综合本次研究和区域构造演化,认为根河地区早白垩世玄武岩为来源于富集的岩石圈地幔的板内碱性玄武岩,形成于蒙古-鄂霍茨克洋闭合后的岩石圈伸展背景。
英文摘要:
      A set of basalt is exposed in the Genhe area, northern Great Xing’an Range. The objective of this work is to clarify its petrogenesis, stratigraphic age and tectonic setting by virtue of zircon LA-ICP-MS U-Pb geochronology and petrochemistry. The results of zircon U-Pb measurement indicate that this basalt formed in the Early Cretaceous (142.0±2.1 Ma), temporarily placed in the Manitu Group, rather than Lower Carboniferous Mo'ergenhe Group suggested in previous research. The geochemical characteristics of the rock indicate that the basalt is rich in sodium and low potassium, which belongs to the alkaline series. The total amount of rare earth elements (ΣREE) is low (91.50×10-6~108.57×10-6), and the light and heavy rare earth fractionation is obvious (La/ Yb)N=10.82~13.49), light rare earth elements and K, Rb, Ba, Sr and other large ion lithophile elements are relatively enriched, depleted in Th, U, Hf, Ti, Nb, Ta and other high field strength elements and heavy rare earth elements. Combining this study and regional tectonic evolution, it is suggested that the Early Cretaceous basalt in the Genhe area is an intraplate alkaline basalt derived from the enriched lithospheric mantle, which formed in a setting of lithospheric extension after the closure of the Mongolia-Okhotsk ocean.
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