鄂尔多斯盆地西南缘中生代火成碳酸盐岩的发现及意义  

Discovery and significance of the Mesozoic igneous carbonate rock at the southwestern margin of Ordos Basin

作　　者：席胜利 李振宏[2] 刘新社 

机构地区：[1]中国石油长庆油田分公司勘探事业部,陕西西安710018 [2]中国地质科学院地质力学研究所,北京100081

出　　处：《石油与天然气地质》2016年第2期173-179,188,共8页Oil & Gas Geology

基　　金：国家自然科学基金项目(41372122);中国地质调查局地质调查项目(1212011121095)

摘　　要：鄂尔多斯盆地属于我国中西部地区稳定的克拉通盆地。盆地边缘构造活动强烈,逆冲推覆构造发育,岩浆活动频繁;盆地内部构造稳定,以前尚未有岩浆活动的报道。鄂尔多斯盆地西南缘庆深1井蓟县系白云岩中火成碳酸盐岩侵入岩脉的发现,为重新认识盆地内部的构造活动性提供了新的线索。该套侵入岩脉稀土元素球粒陨石标准化图解中没有明显的Eu异常,符合火成碳酸盐岩的基本特征。同时,在碳、氧同位素交汇图解中,分析点全部落入了火成碳酸盐岩的范围。通过锆石U-Pb同位素测年,该套火成碳酸盐岩的形成时代为176.2 Ma±3.3 Ma,属于早-中侏罗世构造活动的产物。火成碳酸盐岩的形成主要受控于北东-南西向基底大断裂带在早中侏罗世时期的隐性活动,为扬子板块向华北克拉通俯冲挤压之后区域伸展作用的产物。鄂尔多斯盆地西南缘早侏罗世末期火成碳酸盐岩侵入脉的发现,为认识华北克拉通早侏罗世区域拉张的构造背景提供了新的证据。Ordos basin is a stable cratonic basin in the central-west China. Along the margin of the basin,tectonic activity was intense,thrust-nappe structures were well developed and magmatic events were common. On the contrary,the inner part of the basin was very stable and no magmatic events have been recorded. Lately,we found some igneous carbonate rock dikes intruded into the dolomite of the Jixian System in Qingshen 1 well at the south-western margin of the Ordos basin. These intrusive dykes provide new clues for us to reconsider the tectonic activity inside the basin. In the REE distribution patterns,its characteristics are basically consistent with igneous carbonate rock without significant Eu anomaly. Besides,all data points fall within the range of igneous carbonate rock in the C-O isotope crossplot. According to the zircon U-Pb dating results,the age of the intrusive igneous carbonate rock is 176. 2 ± 3. 3 Ma. Therefore,the intrusive dykes formed during the regional extension after the subduction between Yangtze Craton and North China Craton,under the control of minor activities of the NE-SW trending basement faults in the Early-Middle Jurassic. These intrusive igneous dykes at the south-western margin of the Ordos basin provide new evidences for us to understand the regional extension background of North China Craton in the Early Jurassic.

关 键 词：碳、氧同位素 锆石U-PB年代学 火成碳酸盐岩 地球化学 中生代 鄂尔多斯盆地 

分 类 号：TE121.3[石油与天然气工程—油气勘探]