古地理学报 ›› 2019, Vol. 21 ›› Issue (3): 490-504. doi: 10.7605/gdlxb.2019.03.031

• 地球化学与沉积环境 • 上一篇    下一篇

龙江盆地西缘中侏罗统万宝组物源分析:来自碎屑锆石年代学和岩石地球化学的制约*

张渝金, 张超, 吴新伟, 谭红艳, 马永非, 李伟, 汪岩   

  1. 中国地质调查局沈阳地质调查中心,辽宁沈阳 110034
  • 收稿日期:2018-05-02 修回日期:2018-07-03 出版日期:2019-06-01 发布日期:2019-05-23
  • 作者简介:张渝金,男,1984年生,高级工程师,从事地层学及沉积环境等研究。E-mail: syzhangyujin@163.com。
  • 基金资助:
    *国家自然科学青年基金项目(编号: 41702032)和中国地质调查局项目(编号: DD20160048-04,DD20190039,DD20190042,DD20190360)联合资助

Provenance analysis of the Middle Jurassic Wanbao Formation on western edge of Longjiang Basin: Constraints from detrital Zircon ages and geochemistry characteristics

Zhang Yu-Jin, Zhang Chao, Wu Xin-Wei, Tan Hong-Yan, Ma Yong-Fei, Li Wei, Wang Yan   

  1. Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China
  • Received:2018-05-02 Revised:2018-07-03 Online:2019-06-01 Published:2019-05-23
  • About author:Zhang Yu-Jin,born in 1984,is a senior engineer in Shenyang Center of Geological Survey. He is mainly engaged in stratigraphy and sedimentary environment. E-mail: syzhangyujin@163.com.
  • Supported by:
    [Co-funded by the Young Scientists Foundation of National Natural Science Foundation of China(No.41702032) and the projects of China Geological Survey(Nos. DD20160048-04,DD20190039,DD20190042,DD20190360)]

摘要: 龙江盆地是新厘定的松辽盆地外围中新生代盆地之一。有关该盆地中的沉积物特征及物源区大地构造背景是亟待解决的问题之一。通过对龙江盆地中侏罗统万宝组碎屑岩的砂岩碎屑组分、重矿物组合、岩石地球化学及锆石U-Pb年代学等进行研究,可以推测出物源的相关特征: (1)砂岩碎屑组分和重矿物组合反映了万宝组母岩以中酸性岩浆岩和中—低级变质岩为主、含有少量中基性岩浆岩的特点;(2)地球化学特征显示,龙江盆地万宝组沉积物轻稀土元素富集、重稀土元素亏损,配分曲线表现出平缓的右倾模式,微量元素呈规律性变化,富集高场强元素(HFSE)CsThU,亏损NbPTi,具有与上地壳相似的地球化学特征;(3)碎屑锆石显示4组年龄峰值,主要峰值为167.5 Ma,次要峰值为236.4 Ma309.1 Ma363.2 Ma,反映了万宝组沉积物具有多物源的特点,母岩主要来自于中侏罗世火山岩,其次来自于晚泥盆世—三叠纪的岩浆活动产物。综合分析认为,龙江盆地万宝组的物源具有长英质和中性火山岩特征,大部分来自于上地壳,原岩形成于活动大陆边缘背景下的大陆岛弧环境,中侏罗世沉积演化可能受到与古太平洋板块俯冲作用和蒙古—鄂霍茨克缝合带演化双重作用的影响。该研究成果可为龙江盆地沉积演化分析和古地理环境恢复提供重要依据。

关键词: 龙江盆地, 中侏罗统, 万宝组, 岩石地球化学, 重矿物, 碎屑锆石, 物源分析

Abstract: Longjiang Basin is one of the newly established Meso-Cenozoic basins in the periphery area of the Songliao Basin. Analysis on clastic components of sandstones,heavy mineral combination,rock geochemistry and zircon U-Pb ages,and related comprehensive research of clastic rocks from the Middle Jurassic Wanbao Formation in Longjiang Basin,were carried out in this paper. The combination of sandstone clastic components and heavy minerals reflects that the mother rocks of the Wanbao Formation are mainly middle acid magmatic rocks and low grade metamorphic rocks,followed by a small number of medium basic magmatic rocks. Geochemical characteristics of sediment materials from the Wanbao Formation show that they are enriched in LREEs and depletion in HREEs,with a right-dipping signature. Meanwhile,they are enriched with(HFSE)Cs,Th,U,depletion of Nb,P,and Ti,which have similar geochemical characteristics of the Upper Crust. Detrital zircon shows four age peaks,the main peak is 167.5 Ma,the secondary peak ages are 236.4 Ma,309.1 Ma and 309.1 Ma,which reflect the multi-source characteristics of sediments in the Wanbao Formation. These sediments are mainly from the Middle Jurassic volcanic rocks,followed by products from the Late Devonian-Triassic magmatic activities. The comprehensive analysis shows that the sediments of the Wanbao Formation in the Longjiang basin have the characteristics of acid and neutral volcanic sources,most of which come from the upper crust. The primary rocks of the Wanbao Formation are formed in continental island arc environment under the background of active continental margin background. The Middle Jurassic of the Longjiang Basin may be affected by the dual effects of the subduction of the paleo-Pacific plate and the evolution of the Mongolian-Okhotsk suture zone.

Key words: Longjiang Basin, Middle Jurassic, Wanbao Formation, petrogeochemistry, heavy minerals, detrital zircons, provenance analysis

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