石油与天然气地质 ›› 2008, Vol. 29 ›› Issue (2): 217-222.doi: 10.11743/ogg20080210

• 论文 • 上一篇    下一篇

塔中地区上奥陶统热液流体与热化学硫酸盐还原作用

李开开1,2, 蔡春芳1,2, 蔡镠璐1,2, 张春明3   

  1. 1. 中国科学院, 矿产资源研究重点实验室, 北京, 100029;
    2. 中国科学院, 地质与地球物理研究所, 北京, 100029;
    3. 长江大学, 地球化学系, 湖北, 荆州, 434023
  • 收稿日期:2008-02-13 出版日期:2008-04-24 发布日期:2012-01-16
  • 基金项目:

    国家重点基础研究发展规划(973)项目(2006CB202304);国家自然科学基金项目(40573034).

Hydrothermal fluid activity and thermochemical sulfate reduction in the Upper Ordovician,Tazhong area

Li Kaikai1,2, Cai Chunfang1,2, Cai Liulu1,2, Zhang Chunming3   

  1. 1. Key Laboratory of Mineral Resources, Chinese Academy of Sciences, Beijing 100029, China;
    2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;
    3. Geochemistry Department, Yangtze University, Jingzhou, Hubei 434023, China
  • Received:2008-02-13 Online:2008-04-24 Published:2012-01-16

摘要:

对塔中地区奥陶系裂缝充填矿物(方解石、萤石、重晶石等)进行稀土元素、87Sr/86Sr值以及流体包裹体测定.结果显示,所有裂缝充填矿物的87Sr/86Sr值(0.708 89~0.710 36)和地层水的87Sr/86Sr值都高于碳酸盐岩全岩及同期海水,裂缝充填物流体包裹体的均一化温度较上奥陶统所经历的最高温度高约20℃,反映该区存在热液流体,且具有富87Sr的特征.高87Sr/86Sr值的热液流体可能来源于寒武系或前寒武碎屑岩地层;而且该热液流体中Eu2+与Sr2+具有相似的成因,导致沉淀矿物具有正铕异常,且铕与锶呈良好的线性关系.该热液促使发生热化学硫酸盐还原作用(TSR),导致H2S气体和黄铁矿的产生.另一方面,富87Sr、相对低温低盐度裂缝充填萤石矿物的存在,反映了本区除受热液流体影响外还受到大气淡水或低温盆地流体的影响.

关键词: 稀土元素, 铕异常, 热液流体, 热化学硫酸盐还原作用, 塔中地区

Abstract:

Measurements of rare earth elements,value of 87Sr/86Sr,and fluid inclusion,had been carried out on facture-filling minerals(such as calcite,fluorite and barite) in Tazhong area.Results show that the 87Sr/86Sr va-lues of all the filling minerals(0.708 89-0.710 36) and formation water are higher than that of the whole-rock samples of fracture-carbonate rock and sea water in the same period,and the homogenization temperature of fluid inclusion is about 20℃ higher than that of the highest temperature ever experienced by the Upper Ordovician,signaling the presence of hydrothermal fluid and a high concentration of 87Sr.The hydrothermal fluid with high 87Sr/86Sr value is most likely derived from the Cambrian or pre-Cambrian clastic rocks.Its Eu2+ and Sr2+ are of similar origin,resulting in a positive Eu anomaly and a good linear relationship between Eu and Sr in the fracture fillings.It induced TSR and generated HSS and pyrite.Consequently,the process led to the replacement of barite by calcite.The presence of fracture-filling 87Sr-rich fluorite with relatively low temperature and low salinity as indicates that beside the influence of hydrothermal fluid,the area might also be affected by fresh water and basin fluid of low temperature.

Key words: rare earth element, Eu anomaly, hydrothermal fluid, thermochemical sulfate reduction, Tazhong area

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