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现代地质 ›› 2016, Vol. 30 ›› Issue (3): 541-554.

• 岩石学与矿床学 • 上一篇    下一篇

云南思茅盆地白垩纪—古新世碎屑岩地球化学特征及地质意义

石海岩1，苗卫良2，马海州2，李永寿2，张西营2，严玲琴1，马维明1，王振东1   

  1. (1. 青海省地质调查局，青海 西宁 810001；2. 中国科学院 青海盐湖研究所盐湖资源与化学重点实验室，青海 西宁 810008)
  • 出版日期:2016-06-14 发布日期:2016-06-15
  • 作者简介:石海岩，女，硕士研究生，1987年出生，地球化学专业，主要从事钾盐沉积地球化学方面的研究。 Email:shy0407@sina.cn。
  • 基金资助:

    国家重点基础研究发展计划项目“中国陆块海相成钾规律及预测研究”子课题“兰坪-思茅新生代残留盆地成钾条件、机理和后期演化”(2011CB403004)；中国科学院知识创新工程重要方向项目“云南兰坪-思茅成盐盆地古钾盐成矿规律研究”(KZCX2-YW-344)。

Geochemistry of Cretaceous-Palaeocene Detrital Rocks in Simao Basin,  Yunnan Province and Its Geological Significances 

SHI Haiyan1，MIAO Weiliang2，MA Haizhou2，LI Yongshou2，ZHANG Xiying2，YAN Lingqin1，MA Weiming1，WANG Zhendong1   

  1. (1. Qinghai Geological Survey, Xining, Qinghai 810001, China; 2. Key Laboratory of Salt Lake Resources and Chemistry, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinhai 810008, China)
  • Online:2016-06-14 Published:2016-06-15

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摘要：

云南思茅盆地白垩纪—古新世地层包括曼岗组(K1m)、扒沙河组(K1p)、勐野井组(K2me)、等黑组(E1d)，主要由砂岩及砂泥岩组成。对盆地江城二官寨—和平寨—扒沙河道班剖面19件碎屑岩样品及江城勐野井矿区SHK4孔17件细碎屑岩样品的主量元素、稀土元素和微量元素进行了分析。结果显示：碎屑岩样品中δCe和δEu、δCe与∑REE、化学蚀变指数(CIA)与Th/U、CIA与Th/Sc不具有相关性，说明研究区白垩纪—古新世沉积物碎屑成分主要受控于源岩特征，不受化学风化作用及氧化－还原条件的影响；稀土元素配分模式基本相同，LREE/HREE值较高且负Eu异常明显，表明白垩纪—古新世沉积物具有相同的物源，岩石以亲花岗岩、长英质岩为主。Hf-La/Th、La/Sc-Co/Th、REE-La/Yb、Hf-Co-Th判别图解也反映了相似的物源特征。勐野井组至等黑组地层沉积期间，CaO含量、Gd含量、ICV值和(Gd/Yb)N值突然增加，表明源区自晚白垩世勐野井组沉积开始，构造活动性突然加强，整体上处于快速隆升、剥蚀阶段。研究为云南思茅盆地白垩纪—古新世沉积物物源属性的判别提供了一定的地球化学依据。

关键词: 思茅盆地, 白垩纪—古新世, 碎屑岩, 地球化学, 物源属性

Abstract:

The Cretaceous-Palaeocene strata in the Simao Basin consists of the Mangang Formation (K1m), the Pashahe Formation (K1p), the Mengyejing Formation (K2me) and the Denghei Formation (E1d), which are primarily composed of sandstone and mudstone. Based on the geochemical research into detrital rocks of 19 pieces of samples from ErguanzhaiHepingzhai-Bashahedaoban section and 17 pieces of samples from drilling hole SHK4 in Mengyejing deposit of Jiangcheng, three conclusions have been drawn which are presented as follows. Firstly, in theses samples, δCe vs. δEu, δCe vs. ∑REE, CIA vs. Th/U, CIA vs. Th/Sc show no correlation, which imply that the Cretaceous-Palaeocene clastic rocks are mainly controlled by source region rather than chemical weathering and oxidationreduction conditions. Secondly, the distribution patterns of rare earth elements are basically the same; LREE/HREE ratios are high; Eu negative anomalies are evident, indicating the same source region of the Cretaceous-Palaeocene sediments with little mantle material adding. The rocks are mainly pro-granite felsic, and the parent rock debris comes predominately from the upper crust which is in accordance with the features displayed by the Hf-La/Th,La/Sc-Co/Th,REE-La/Yb,Hf-Co-Th discrimination diagrams. Thirdly, during the deposition of Mengyejing and Denghei Formations, a sudden rise of CaO content, Gd content, ICV, (Gd/Yb)N  ratio demonstrates that the provenance area is in an rapid uplift and erosion stage. The research provides a geochemical basis for the provenance of Cretaceous-Palaeocene strata in the Simao Basin.

Key words: Simao Basin, Cretaceous-Palaeocene, detrital rock, geochemistry, provenance property

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