鄂尔多斯盆地纸坊组微量元素地球化学特征及沉积环境指示意义

发布时间：2018-10-13 10:28

【摘要】：沉积岩中的微量元素对沉积环境的水介质变化有着较高的敏感度,是研究沉积物沉积时的古气候、古环境的有效手段。鄂尔多斯盆地纸坊组是三叠系具有油气显示的新层系,其古气候及古水体环境对于恢复该时期盆地沉积格局、重建古地理及成藏研究具有重要意义。采用ICP-MS对鄂尔多斯盆地纸坊组剖面及岩芯21件泥岩及粉砂岩样品进行了微量元素测试,选择对沉积环境介质较为敏感的锶(Sr)、钡(Ba)、钍(Th)、铀(U)、钒(V)、镍(Ni)、钴(Co)等元素作为判别指标,并结合沉积学标志及孢粉分析,对鄂尔多斯盆地纸坊组沉积环境及古气候特征进行研究。结果表明:通过Li、Sr、Ni、Ga含量及Sr/Ba值判别研究区为淡水—微咸水沉积环境;U/Th值分布在0.09~0.38,δU值分布在0.43~1.07,V/(V+Ni)值分布在0.69~0.89,V/Cr值分布在0.87~5.57、Ni/Co值分布在1.21~2.93,指示水体分层不强的氧化—弱还原过渡环境;纸坊组水体深度平均深度小于30 m,大型"汇水"湖泊尚未形成;Sr/Cu比值在0.85~16.7之间,大部分小于10,仅个别值大于10,表明纸坊组古气候已由和尚沟组干热气候趋于温暖气候。
[Abstract]:Trace elements in sedimentary rocks are highly sensitive to the variation of water medium in sedimentary environment and are an effective means to study paleoclimate and paleoenvironment during sediment deposition. The Zhifang formation in Ordos Basin is a new layer with oil and gas in Triassic. Its paleoclimate and paleo-water environment are of great significance for the restoration of sedimentary pattern and the reconstruction of paleogeography and reservoir formation in this period. The trace elements of Zhifang formation section and 21 core mudstone and siltstone samples in Ordos Basin were measured by ICP-MS. Elements such as strontium, (Sr), (Ba), thorium, (U), vanadium, (V), nickel, (Ni), and cobalt (Co), which are sensitive to sedimentary medium, were selected as discriminant indexes. The sedimentary environment and paleoclimate characteristics of Zhifang formation in Ordos Basin were studied by means of sedimentological markers and sporopollen analysis. The results show that the Li,Sr,Ni,Ga content and Sr/Ba value of the study area are freshwater and brackish water sedimentary environment, the U/Th value is 0.09 ~ 0.38, the 未 U value is 0.43 ~ 1.07 V / (V Ni) value, the distribution is 0.69 ~ 0.89 V / Cr value and the value of 0.87 ~ 5.57% Ni ~ (+) Co is 1.212.93, indicating that the water layer is not strong in the oxidation-weak reduction transition environment. The average depth of water body in Zhifang formation is less than 30 m, the large "catchment" lake has not been formed, and the Sr/Cu ratio is between 0.85 and 16.7, most of which is less than 10, only a few values are greater than 10, indicating that the paleoclimate of Zhifang formation has become warm from dry and hot climate of the Xionggou formation.
【作者单位】：成都理工大学沉积地质研究院;中国石油长庆油田分公司勘探开发研究院;中国石油长庆油田分公司数字化与信息管理部;
【基金】：国家科技重大专项专题(2016ZX05046-005-001) 四川省教育厅重点项目(16ZA0103)~~
【分类号】：P618.13

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