| 内蒙古正镶白旗贡淖尔地区中二叠统额里图组下段 细碎屑岩地球化学特征及意义 |
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| 引用本文：汪彪,施立志,阮壮,黄静宜,罗立艳.2022.内蒙古正镶白旗贡淖尔地区中二叠统额里图组下段 细碎屑岩地球化学特征及意义[J].地球学报,43(4):569-583. |
| DOI：10.3975/cagsb.2021.113001 |
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| 基金项目:中国地质调查局项目“二连盆地及外围石炭-二叠系油气地质调查”(编号: 202016000000180202);中央级公益性科研院所基本科研业务费专项(编号: KK2005);国家自然科学基金项目“兴蒙地区晚二叠世海相沉积的古环境重建”(编号: 41572098) |
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| 中文摘要:广泛发育于内蒙古正镶白旗及邻区的额里图组的沉积建造近些年来被认为是我国北方晚古生代重要的潜在含油气地层, 因其地处兴蒙构造带与华北板块拼合的交界区, 并于中二叠世形成的一套一段下部以碎屑岩、上部以凝灰质胶结的苔藓虫生物格架礁灰岩、二段以浅海相喷出岩为特点的海相沉积-火山岩沉积建造。本文通过在前人研究的基础上, 对正镶白旗贡淖尔地区额里图组剖面进行了修测、采样。重点对剖面下段的粗碎屑岩开展了详细的镜下岩相学研究, 以及广泛发育的细碎屑岩进行了全岩主量元素、微量元素和稀土元素特征分析。结果表明: (1)砂岩的颗粒分选性差, 主要呈棱角状-次棱角状, 颗粒主要由火山岩岩屑、石英颗粒、长石、燧石组成, 填隙物为凝灰物质和泥质杂基, 整体上为近源快速堆积的低成熟度的岩屑长石硬砂岩; (2)细碎屑岩源区的古气候条件呈现出略微寒冷干燥→温暖湿润→略微寒冷干燥→温暖湿润→略微寒冷干燥的演变趋势, 整体上属于温暖潮湿的气候环境; (3)细碎屑岩大多属于构造活跃地区的第一次旋回的沉积物, 源区成分主要以上地壳的长英质火成岩和石英质沉积岩为特征; (4)源区大地构造背景为活动大陆边缘和大陆岛弧环境, 沉积盆地为弧后盆地。 |
| 中文关键词:额里图组 细碎屑岩 地球化学 大地构造背景 内蒙古 |
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| Geochemistry and Significance of Siliciclastic Rocks from the Lowest Elitu Formation of Middle Permian in the Gongnaoer Area, Zhengxiangbaiqi, Inner Mongolia |
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| Abstract:The Elitu Formation of Middle Permian is widely developed in Zhengxiangbaiqi and its adjacent areas in Inner Mongolia and in the junction area of Xingmeng orogenic belt and North China plate. In recent years, it has been considered as a potential oil and gas bearing Upper Paleozoic strata in the northern China. This formation is characterized by marine siliciclastic rocks in the lowest member, tuff-cemented bryozoan reef limestone in the upper part, and shallow marine eruptive rocks in the second member. We measured the Gongnaoer profile of the Elitu formation in Zhengxiangbaiqi and conducted detailed microscopic petrographic studies on the lower section of the profile. Whole rock geochemistry, including the major elements, trace elements, and rare earth elements (REEs), of the fine-grained siliciclastic rocks widely developed in the lower section was analyzed. The results show that (1) the sorting of sandstone is poor, with angular sand grains. The particles are mainly composed of volcanic rock debris, quartz particles, feldspar, and chert. The cement is tuffaceous material and argillaceous matrix. Overall, it is a low-maturity lithic feldspar greywacke with near-source rapid accumulation. (2) The paleoclimatic conditions of the source area of fine clastic rocks has an evolving trend of slightly cold and dry→warm and humid→slightly cold and dry→warm and humid→slightly cold and dry, which is a generally warm and humid climate environment. (3) Most of the fine clastic rocks belong to the sediments of the first cycle in the active tectonic area, and the source area is mainly composed of felsic igneous rocks and quartziferous sedimentary rocks from the upper crust. (4) The tectonic background of the source region is the active continental margin and continental island arc environment, and the sedimentary basin is the back-arc basin. |
| keywords:Elitu Formation fine clastic rocks geochemistry tectonic background Inner Mongolia |
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