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古地理学报 ›› 2012, Vol. 14 ›› Issue (6): 757-766. doi: 10.7605/gdlxb.2012.06.007

• “白云岩成因与油气储集层”专题 • 上一篇    下一篇

塔里木盆地柯坪地区中寒武统准同生白云岩孔洞充填物期次、地化特征及形成条件*

刘 玲1，2 朱井泉2 由雪莲1，2 何 凯1，2   

  1. 1 中国科学院研究生院，北京 100049;
    2 中国科学院地质与地球物理研究所，北京 100029
  • 收稿日期:2011-11-10 修回日期:2012-05-24 出版日期:2012-12-01 发布日期:2012-12-01
  • 通讯作者: 朱井泉，男，1956年生，中国科学院地质与地球物理研究所研究员，主要从事沉积学、储集层沉积学和沉积地质学研究工作。 E-mail:liuling522@sohu.com
  • 作者简介:刘玲，女，1986年生，中国科学院地质与地球物理研究所博士研究生，石油地质学专业。联系电话：010-82998497；E-mail:liuling522@sohu.com。
  • 基金资助:

    国家重点基础研究发展计划“973”项目“中国海相碳酸盐岩层系多种储集层形成机理与分布模式”(编号：2005CB422103)和国家科技重大专项专题“海相碳酸盐岩层系大中型油气田分布规律及勘探评价”（编号：2011ZX05005）共同资助

Generations，geochemistry characteristics and their precipitation conditions of cave fillings of the Middle Cambrian penecontemporaneous dolostone in Keping area，Tarim Basin

Liu Ling1，2 Zhu Jingquan2 You Xuelian1，2 He Kai1   

  1. 1 Graduate University of Chinese Academy of Sciences，Beijing 100049;
    2 Institute of Geology and Geophysics，Chinese Academy of Sciences, Beijing 100029
  • Received:2011-11-10 Revised:2012-05-24 Online:2012-12-01 Published:2012-12-01
  • About author:Liu Ling，born in 1986， is a candidate for Ph.D.degree in Institute of Geology and Geophysics,Chinese Academy of Sciences. She majors in petroleum geology.E-mail:liuling522@sohu.com.
    About the corresponding author Zhu Jingquan，born in 1956，is a research professor in Institute of Geology and Geophysics，Chinese Academy of Sciences.He is mainly engaged in sedimentology，reservoir sedimentology and sedimentary geology.

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摘要：

对塔里木盆地柯坪地区蓬莱坝剖面中寒武统沙依里克组萨布哈白云岩及其溶孔中的多期次充填物进行了岩石学和地球化学分析，以对其沉淀时的流体环境进行恢复。孔洞中的环带状充填物可分为4期，由白云岩向内依次为：（1）乳白色粒状方解石；（2）铁质浸染的杂色柱状方解石；（3）无色透明的石英；（4）紫色粒状萤石。碳氧同位素、微量元素及稀土元素分析结果表明：白云岩具有高的Sr/Ba值5.47，低的U/Th值0.2954（明显小于0.7），高的Zr/Hf值36.86，相对高的稀土总量，相对高的 δ18O值-7.444‰，盐度指数Z值为120.56，表明它形成于相对低温、富氧和盐度相对较高的流体环境，进一步证实其是形成于蒸发环境的准同生白云岩。第1期方解石具有低的Sr/Ba值2.33，相对高的U/Th值1.3，低的Zr/Hf值20.857，相对居中的稀土总量，相对低的δ18O值-13.758‰，盐度指数Z值为105.35（小于120），表明它形成于温度相对较高、缺氧、盐度较低的流体条件下。第2期方解石具有具有相对低的Sr/Ba值2.77，相对高的U/Th值1，相对低的Zr/Hf值32.08，相对居中的稀土总量，相对低的 δ18O值-11.344‰，盐度指数Z值为116.51，表明其形成于温度相对较高、贫氧、盐度较低的流体条件下。萤石具有居中的Sr/Ba值3.15，相对高的U/Th值0.8666，相对低的Zr/Hf值31.875，相对低的稀土总量，其配分模式与岩浆成因萤石较为接近，表明其形成于温度相对较高、缺氧、低盐度的流体条件下。这些特征反映该套地层经历了准同生期白云岩化后的埋藏—抬升—再埋藏—最终抬升至地表的过程。

关键词: 孔洞充填物, 碳氧同位素, 微量稀土, 流体条件, 塔里木盆地

Abstract:

In order to rationally analyze and evaluate the developing and preserving condition of penecontemporaneous dolostone caves related with evaporation in burial diagenetic environment，the petrology and geochemistry of the Middle Cambrian dolomites and their cave fillings in the Keping area，Tarim Basin have been studied in details，and the precipitation conditions of the cave fillings have been recovered.It has been discovered that the cave fillings show obvious generational features.There are at least four generations of fillings from the bedrock to the center of the cave：(1) ivory granular calcite;(2)iron dipped variegated columnar calcite;(3)achromatic transparent quartz;(4)purple fluorite.The analytical data of carbon and oxygen stable isotope，trace elements and REE compositions show that the host dolomite has these characteristics such as high Sr/Ba ratio 5.47，low U/Th ratio -0.2954<0.7，high Zr/Hf ratio 36.86，relatively high total REE，relatively high δ18O -7.444‰，salinity index Z was 120.56，which show a relatively lower temperature，oxygen rich and relatively high saline environment. The calcite fillings of the first generation has these characteristics such as low Sr/Ba 2.33，high U/Th 1.3>1.25，low Zr/Hf ratio 20.857，moderate total REE，relatively low δ18O -13.758‰，salinity index Z was 105.35<120，which shows a relatively higher temperature，hypoxia and relatively lower saline environment. The second generation has these characteristics such as relatively low Sr/Ba 2.77，high U/Th 1，in the range 0.75～1.25，relatively lower Zr/H ratio 32.08，moderate total REE，relatively low δ18O -11.344‰，salinity index Z was 116.51<120，which also shows a relatively high temperature，Oxygen-poor and low saline condition. The fluorite fillings of the fourth generation has these characteristics such as relatively low Sr/Ba 3.15，relatively high U/Th 0.8666，in the range 0.75～1.25，relatively low Zr/Hf ratio 31.875，low total REE，and the REE pattern is similar to that of the magmatic origin fluorite，which also shows a relatively high temperature，oxygen-poor and low saline precipitation condition.The precipitation conditions of cave fillings reflect that this set of strata experienced a process of burial-uplift-and then buried-and ultimately uplifting to the surface after the penecontemporaneous dolomitization.

Key words: cave fillings, carbon and oxygen isotope, trace and REE elements, precipitation condition, Tarim Basin

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