内蒙古阿拉善北部杭乌拉地区早古生代硅质岩地球化学特征及其构造意义

发布时间：2019-03-04 09:49

【摘要】：内蒙古阿拉善北部杭乌拉地区位于中亚造山带的中段南缘,处于西伯利亚板块、塔里木板块和华北板块之间,是研究中亚造山带和古亚洲洋演化的重要区域。文中以杭乌拉地区硅质岩地球化学特征为主要研究内容,结合前人研究结果,对阿拉善北部地区早古生代构造背景进行分析。杭乌拉地区下古生界西双鹰山组和班定陶勒盖组硅质岩镜下可见黏土、陆源粉砂和放射虫等,表现为明显的沉积成因特征。硅质岩地球化学特征一致性较差,其中Fe、Mn、Al等主量元素、Sc/Th值、(La/Ce)_n值和δCe值反映出硅质岩为大陆边缘沉积,(La/Yb)_n值反映硅质岩接近于远洋沉积背景,δEu值表现为无热液作用影响,V、V/Y、Ti/V值多接近于洋中脊和大洋盆地硅质岩特征,U/Th、Ba/Sr值也属于热水成因硅质岩特征。硅质岩稀土元素配分曲线呈平坦状,无明显的右倾(大陆边缘轻稀土元素富集配分模式)和左倾(开放洋盆重稀土元素富集配分模式)特征。研究区早古生代地质记录相对较少,但是鉴于该地区晚古生代复杂的构造演化特征及其对早古生代古地理格局的继承,并结合上述硅质岩地球化学特征,认为研究区在早古生代为一个多岛洋环境。
[Abstract]:The north-east of Alashan, Inner Mongolia, is located in the southern margin of the middle section of the Central Asian orogenic belt. It is located between the Siberia plate, the Tarim plate and the North China plate, and is an important area for studying the evolution of the Central Asian orogenic belt and the ancient Asia. Based on the study of the geochemical characteristics of the silicalite in the area of the area of Hangzhou, this paper makes an analysis of the early Palaeozoic tectonic setting in the northern part of Alashan by combining the results of the previous studies. The clay, terrigenous silt, and radiation worm, etc., are observed under the siliceous rock mirror of the Lower Palaeozoic Xishuangshan Formation and the Ban Dingtao Lacquer Formation in the area of Hangula, and it is characterized by obvious sedimentary origin. The geochemical characteristics of the silicalite are poor, including the main elements such as Fe, Mn and Al, the Sc/ Th value, the (La/ Ce) _ n value and the value of the rare earth Ce reflect the deposit of the siliceous rock as the continental margin, and the (La/ Yb) _ n value reflects the proximity of the siliceous rock to the background of the pelagic deposit, and the Eu value is shown as the effect of no hydrothermal action, V, V/ Y, The value of Ti/ V is close to the characteristics of the siliceous rocks in the mid-ocean ridge and the ocean basin, and the value of U/ Th, Ba/ Sr is also the characteristic of the hot-water-origin silicalite. The distribution curve of the rare earth element in the siliceous rock is flat, and there is no obvious right inclination (the light rare earth element enrichment and distribution mode of the continental margin) and the left (open ocean basin heavy rare earth element enrichment and distribution mode). The early Palaeozoic geological record of the study area is relatively small, but in view of the complex structural evolution of the late Paleozoic in the region and the inheritance of the early Paleozoic palaeo-geographical pattern, and in combination with the geochemical characteristics of the above-mentioned silicalite, it is considered that the study area is a multi-island-ocean environment in the early Paleozoic.
【作者单位】：有色金属矿产地质调查中心;中国地质大学(北京)地球科学与资源学院;中国地震局第一监测中心;北京市地质研究所;河北省区域地质矿产调查研究所;
【分类号】：P534.4;P588.244

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