地学前缘 ›› 2016, Vol. 23 ›› Issue (5): 45-55.DOI: 10.13745/j.esf.2016.05.005

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柴达木盆地东北部晚古生代盆地构造环境:来自碎屑岩地球化学的证据

 孙娇鹏, 陈世悦, 刘成林, 马寅生, 尹成明   

  1. 1. 西北大学 大陆动力学国家重点实验室, 陕西 西安 710069
    2. 中国石油大学(华东) 地球科学与技术学院, 山东 青岛 266580
    3. 中国地质科学院 地质力学所, 北京 100081
    4. 中国地质调查局 资源评价部, 北京 100037
  • 收稿日期:2015-10-10 修回日期:2016-01-11 出版日期:2016-09-15 发布日期:2016-09-15
  • 作者简介:孙娇鹏(1988—),男,博士,主要从事沉积学研究。
  • 基金资助:

    中国地质调查局项目“柴达木盆地油气资源潜力评价”(1212010818054);中国地质调查局项目“柴达木盆地古生代油气资源调查评价”(1212011120964)

Tectonic setting of Northeastern Qaidam Basin and its evolution during the Late Paleozoic: Evidence from geochemical characteristics of detrital rock.

 SUN  Jiao-Feng, CHEN  Shi-Yue, LIU  Cheng-Lin, MA  Yin-Sheng, YIN  Cheng-Meng   

  1. 1. State Key Laboratory of Continental Dynamics, Northwest University, Xi an 710069, China
    2. School of Geosciences, China University of Petroleum(East China), Qingdao 266580, China
    3. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
    4. Department of Mineral Resources Assessment, China Geological Survey, Beijing 100037,China
  • Received:2015-10-10 Revised:2016-01-11 Online:2016-09-15 Published:2016-09-15

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16898

摘要：

在对采集到的27件碎屑岩主微量元素系统测试与分析的基础上,结合前人已有研究成果,对柴达木东北部晚古生代盆地构造环境及原型盆地类型进行讨论。研究表明:较大陆上地壳,柴达木东北部地区上古生界碎屑岩整体呈现SiO2含量富集、其余主量氧化物亏损的特点,稀土元素含量整体偏低,但与大陆上地壳具有极为类似的分配型式,微量元素中相容元素整体强烈亏损,大离子亲石元素中等亏损,高场强元素无亏损—弱亏损。主量元素、微量元素含量及特征比值显示,测试样品与被动大陆边缘砂岩具有极为接近的地球化学特点,并且显示出与其他构造环境沉积物地球化学特征差别极为明显的特点。相关构造环境及物源岩石组合判别图解同样表明：柴达木东北部地区晚古生代持续发育被动大陆边缘盆地,物源区岩石几乎不存在中基性物质的加入且以大陆上地壳中酸性岩类为主。在地球化学分析的基础上,结合前人对岩石学特征、沉积相类型与沉积对比、古流向以及锆石年代学的工作,综合认为,柴达木东北部地区晚古生代为一个向北倾斜的被动大陆边缘海盆,其物源区为加里东造山运动形成的柴北缘加里东期造山带,海侵来自宗务隆裂陷海槽且自北向南进行。

关键词: 柴达木东北部地区, 上古生界, 砂砾岩, 地球化学, 盆山格局

Abstract:

On the basis of the systematic geochemical testing and analysis on 27 collected glutenite samples from northeastern Qaidam margin, combined with the existing research results, the tectonic environment and prototype basin of northeastern Qaidam area during the Late Paleozoic Era are discussed in this paper. Interrelated analyses conclude that, in contrast to the upper continental crust, the Upper Paleozoic detrital rocks from the northeastern Qaidam margin have the characteristics of the enrichment of SiO2 and the loss of the rest main oxides. All the rare earth elements contents are low, but have very similar distribution pattern to the UCCnormalized. The conglomerates contain variable contents of trace elements, but generally have a similar variation trend such as systematic severe depletion of incompatible trace elements, mediumdepletion of LILE, and weak depletion of HFSE. The geochemical characteristics of tested samples are very close to the passive continental margin sandstone. Interrelated tectonic environment and source rock combination discrimination diagrams also manifest that the passive continental margin basin was developed in northeastern Qaidam margin in the Late Paleozoic Era, that rock assemblage in the provenance is mainly composed of acidic rocks from the upper continental crust, scarcely any basicintermediate acidic rocks. Based on the previous statement geochemical analysis, combining existing research conclusions of petrologic feature, sedimentary facies types and sedimentary contrast, paleocurrent direction and geochronology of zircons, it is concluded that during the Late Paleozoic Era, the northeastern Qaidam area was a passive continental margin basin with northdipping slope, that its detrital material came from the north Qaidam caledonian orogenic belt, and that the transgression came from Zongwulong aulacogen.

Key words: northeastern Qaidam margin, Upper Paleozoic, sandy conglomerate, geochemistry, basinmountain framework

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