摘要
鄂尔多斯盆地马六段在盆地大部分地区被剥蚀,仅在盆地周缘地区分布,因此,有关该盆地马六段白云岩成因研究较少。本文通过对马六段白云岩岩石学特征、阴极发光特征、微量元素特征以及碳氧同位素地球化学特征进行分析,对鄂尔多斯盆地南部马六段白云岩特征及形成机制进行了研究。研究结果表明,盆地南部马六段白云岩主要由细-中晶白云岩组成,白云石具"雾心亮边"结构,阴极发光呈暗红色光。微量元素总体上具有较低的Fe、Mn值,平均值分别为447×10-6和62×10-6,较高的K、Na值,平均值分别为517×10-6和252×10-6,以及中等含量的Sr元素值,平均值为155×10-6。δ13C值平均为-0.617‰,δ18O值平均为-7.6‰,以上特征均反映出海源流体特征。白云石的"雾心"和"亮边"结构中微量元素含量相差不大,认为是在相同成岩环境的不同成岩阶段形成,其中"雾心"形成于浅埋藏环境的渗透回流白云石化作用,而"亮边"是在深埋藏环境下对早期白云石的调整和加强。
Member 6 of Majiagou Formation in south Ordos basin has been eroded in most part of the south Ordos basin,and is hence only distributed in the periphery of the basin.Therefore,less studies have been done on the origin of dolomite in member 6 of Majiagou Formation of the basin.Based on petrologic analysis,cathodoluminescence images,trace elements and carbon and oxygen isotope characteristics,the authors studied the characteristics and formation mechanism of dolomite in member 6 of Majiagou Formation in south Ordos basin.The results reveal that the dolomite of member 6 in south Ordos basin is mainly composed of finemedium crystal dolomite with cloudy cores and clear rims as well as dark red luminescence.The dolomite has relatively low Fe and Mn content(average of 447×10-6 and 62×10-6),relatively high K and Na content(average of 517×10-6 and 252×10-6)and moderate content of Sr(average of 155×10-6).Average value ofδ13C andδ18O is-0.617‰and-7.6‰respectively,moderate indicating its marine origin.The trace element content of cloudy cores is close to that of clear rims,which indicates that they were formed in similar diagenesis environments.The cloudy cores were formed in a shallow buried environment by seepage reflux dolomitization model,while the clear rims were recrystallized and adjusted in a deep buried environment.
作者
刘丽红
王春连
李丽霞
杜治利
唐跃
韩淼
LIU Lihong;WANG Chunlian;LI Lixia;DU Zhili;TANG Yue;HAN Miao(Oil&Gas Survey,China Geological Survey,Beijing 100083,China;Oil and Gas Research Center,School of Earth and Space Sciences,Peking University,Beijing 100871,China;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;CNOOC Research Institute,Beijing 100028,China)
出处
《中国地质》
CAS
CSCD
北大核心
2020年第3期810-820,共11页
Geology in China
基金
国家自然科学基金项目(41802173)
中国地质调查局地质调查项目(DD20160175,DD20190106,DD20190708,DD20190090)联合资助。
关键词
马六段
白云岩特征
白云岩化机制
油气勘查工程
鄂尔多斯盆地南部
6th member of Majiagou Formation
characteristics of dolomite
dolomitization mechanism
oil and gas exploration engineering
south Ordos basin
