鄂尔多斯盆地东缘马家沟组元素地球化学特征及古沉积环境

Elemental geochemical characteristics and geological significance of Majiagou Formation, eastern Ordos Basin

王琳霖 浮昀 方诗杰

WANG Linlin FU Yun FANG Shijie

1. 中国地质科学院 矿产资源研究所, 国土资源部 盐湖资源与环境重点实验室, 北京 100037; 2. 长庆油田 第八采油厂采油工艺研究所, 西安 7100183; 3. 新疆油田公司 陆梁油田作业区, 新疆 克拉玛依 834000

1. Institute of Mineral Resources, Chinese Academy of Geological Sciences;MLR Key Laboratory of Saline Lake Resources and Environments, Beijing 100037, China; 2. Oil Production Technology Institute, Eighth Oil Production Plant, Changqing Oilfield Company, Xi'an, Shaanxi 710018, China; 3. Luliang Oilfield Operation District, Xinjiang Oilfield Company, Karamay, Xinjiang 834000, China

通过对鄂尔多斯盆地东缘奥陶系马家沟组的岩石类型和原生沉积物的主、微量元素的分布特征进行分析，探讨了马家沟组元素地球化学分布与沉积环境之间的关系。马家沟组主要岩石类型为碳酸盐岩和蒸发岩，主量元素中CaO和MgO含量较高且变化大，SiO2、Al2O3、Fe2O3、K2O和Ti2O等主要代表陆源组分氧化物的含量较低，反映马家沟组沉积受陆源物质影响较小，为正常的海相沉积。微量元素中Sr、U的平均含量相对上地壳略富集，Ba、Rb、Zn、Cr等平均含量相对上地壳亏损，指示奥陶纪时期研究区远离陆源碎屑。MgO/CaO、Rb/Sr、Sr/Cu和Sr/Ba等比值综合指示，马家沟组整体沉积时期研究区为咸水介质的沉积环境，主要为干热气候背景下的海相沉积且存在干湿交替的气候演化，在马二段、马四段和马五段沉积的中晚阶段，经历了短暂的干热气候向相对湿润气候转换。

Rock type and the distribution of major and trace elements of the Ordovician Majiagou Formation in the eastern Ordos Basin were used to elucidate the sedimentary environment and the origin of the sediments. The results showed that the main rock types in the Majiagou Formation are carbonate and evaporite rocks. The CaO and MgO contents are high and vary widely. SiO2, Al2O3, Fe2O3, K2O, Ti2O and other major representatives of a terrigenous component have low contents, indicating marine facies deposits. The average contents of Sr and U in the trace elements are slightly enriched compared with the upper crust, and the average contents of Ba, Rb, Zn, and Cr are lower than those in the upper crust, indicating a poor terrigenous supply. The distribution curves of Mgo/Cao, Rb/Sr, Sr/Cu and Sr/Ba ratios indicated that the Majiagou Formation was deposited in a marine environment under a dry and warm climate accompanying a dry-wet climate evolution. During the O2m2, O2m4 and O2m5 stages, there was a brief transition from dry-hot climate to relatively humid climate.

国家重大基础研究计划“973计划”项目“鄂尔多斯奥陶纪古陆表海盆成钾条件、机理和后期演化”（2011CB403001）资助。

https://doi.org/10.11781/sysydz201804519