巴音戈壁盆地下白垩统热水沉积岩地球化学特征及成因探讨  

Geochemical characteristics and genesis of Lower Cretaceous hydrothermal sedimentary rocks in Bayingebi Basin

作　　者：许亚鑫 戴朝成[1,2] 刘晓东[1,2] 卞从胜[3] 刘平辉[1,2] 吴兴星 鞠鹏 XU Yaxin;DAI Chaocheng;LIU Xiaodong;BIAN Congsheng;LIU Pinghui;WU Xingxing;JU Peng(School of Earth Sciences,East China University of Technology,Nanchang,330013;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang,330013;Petro China Research Institute of Petroleum Exploration and Development,Beijing,100083)

机构地区：[1]东华理工大学地球科学学院,南昌330013 [2]核资源与环境国家重点实验室,东华理工大学,南昌330013 [3]中国石油勘探开发研究院,北京100083

出　　处：《地质论评》2022年第1期122-137,共16页Geological Review

基　　金：国防科技工业局项目(编号:科工二司[2014]1587号)的成果。

摘　　要：巴音戈壁盆地因格井坳陷下白垩统巴音戈壁组热水沉积岩具有独特的沉积构造和矿物组成,本文通过岩石学、矿物学和地球化学的综合研究,详细描述巴音戈壁组湖相热水沉积泥岩特征。研究区泥岩可划分为以下5种类型:网脉状泥岩、斑点状泥岩、块状泥岩、纹层状泥岩和同生变形泥岩。矿物成分主要为白云石、铁白云石、方沸石、钠长石、伊利石和石英,并且在纵向上表现出明显的规律性,随着深度的增加白云石含量逐渐增加,对应的方沸石含量逐渐降低。泥岩中富集Ca、Mg、Mn等元素,具有LREE富集,HREE亏损,Eu负异常(δCe=0.96~1.06)的特征。碳、氧同位素呈现出δ^(13)C_(V-PDB)(2.35‰~5.51‰)偏正,δ^(18)O_(V-PDB)(-1.26‰~-10.16‰)偏负的特点,分析结果表明热水沉积岩形成于封闭的咸水湖泊环境,形成温度为36.23~79.9℃,平均值为51.21℃,属于低温“白烟囱”型热水沉积;硫同位素变化范围较大(-34.98‰~24.93‰),分析结果表明位于喷口附近的黄铁矿受热液影响较大,δ^(34)S值较高,但随着深度的减小,热液的作用降低,微生物作用加强,δ^(34)S值逐渐减小,呈现出热液与微生物共同影响的特征;锶同位素表明热液流体为壳源与幔源混合流体。Objectives:The hydrothermal sedimentary rocks of Lower Cretaceous Bayingebi Formation in Yingejing Depression of Bayingebi Basin has unique sedimentary structure and mineral composition.Methods:Based on the comprehensive study of petrology,mineralogy and geochemistry,this paper describes in detail the characteristics of lacustrine hydrothermal sedimentary mudstone of Bayingebi Formation.Results:The mudstones in the study area can be divided into five types:veined—network mudstones,spotted mudstones,massive mudstones,laminar mudstones and syngenetic deformed mudstones.The main mineral components are dolomite,ankerite,analcite,albite,illite and quartz,and show obvious regularity in the vertical direction.With the increase of depth,the content of dolomite gradually increases,while the content of analcite gradually decreases.The mudstone is rich in Ca,Mg,Mn and other elements,with LREE enrichment,HREE depletion and EU negative anomaly(δCe=0.96~1.06).Carbon and oxygen isotopes are characterized by positiveδ^(13)C_(V-PDB)(2.35‰~5.51‰)and negativeδ^(18)O_(V-PDB)(-1.26‰~-10.16‰).Conclusion:The results show that the hydrothermal sedimentary rocks were formed in a closed saline lake environment with a temperature of 36.23~79.9℃and an average value of 51.21℃.The hydrothermal sedimentary rocks belong to the low temperature"white chimney"type.The sulfur isotope has a large variation range(-34.98‰~24.93‰),which show that the pyrite near the vent has a great influence on the hydrothermal solution,and the content of δ^(34)S is relatively high.However,with the decrease of depth,the effect of hydrothermal solution decreased and the effect of microorganism strengthened.The value of δ^(34)S decreased gradually,showing the characteristics of the joint influence of hydrothermal solution and microorganism;Strontium isotopes indicate that the hydrothermal fluid is a mixture of crust source and mantle source.

关 键 词：巴音戈壁盆地 下白垩统 热水沉积岩 矿物学 同位素地球化学特征 

分 类 号：P534.53[天文地球—古生物学与地层学] P588.2[天文地球—地质学] P597.3