内蒙古苏尼特左旗红格尔地区中生代火山岩岩石学特征

发布时间：2018-05-07 22:28

本文选题：苏尼特左旗 + 中生代火山岩　；参考：《石家庄经济学院》2015年硕士论文

【摘要】：本文以“内蒙古1:5万准和热木音苏木等六福区域地质矿产调查”项目为依托,对内蒙古苏尼特左旗红格尔地区中生代火山岩进行研究。研究区大地构造位置处于西伯利亚板块东南大陆边缘晚古生代陆缘增生带,位于二连—贺根山板块对接带的西北侧。该造山带古生代属古亚洲洋构造域,中生代则处于滨太平洋构造域。研究区构造单元划分属于兴蒙造山带北方造山带,位于内蒙古北西部边境地区。区内岩浆岩活动频繁,晚古生代及中生代有强烈的火山喷发及岩浆侵入活动。区域上中生代火山岩仅分布在1:5万区域地质调查图准和热木音苏木幅,呈条带状分布,在图幅东北角延伸至测区邻幅,与下伏石炭纪碱长花岗岩体呈火山喷发不整合接触。红格尔地区白音高老组火山岩处于NNE向断裂带,被白垩系大磨拐河组碎屑岩地层角度不整合覆盖,火山岩发育近于直立劈理和褶皱构造。岩性以流纹岩为主,夹凝灰岩、熔结凝灰岩、英安岩和黑曜岩薄层,南北两端被石炭纪黑云母二长花岗岩侵入。本文中生代火山岩LA-ICA-MS锆石测年所挑选的锆石颗粒很少且为继承性锆石,其年龄结果代表了石炭纪碱长花岗岩的形成年龄,通过与邻区已发表的白音高老组火山岩对比,发现具有一致的地球化学特征,显示相同岩浆性质进而推断二者为同期岩浆产物,因此参考邻区准和热木音苏木白音高老组火山岩的两个LA-ICP-MS锆石U-Pb同位素测年的加权平均年龄分别为135.1±5.6Ma和135.2±3.8Ma,说明本文研究区火山岩应形成于早白垩世。在内蒙古1:5万准和热木音苏木等六福区域地质矿产调查报告中,前人将其厘定为宝力高庙组二段火山岩(Cb2),本文将其重新厘定为白音高老组火山岩(K1b).苏尼特左旗红格尔地区中生代火山岩Si O2含量介于69.52wt%-71.44wt%之间,富钾且富铝,含量分别为K2O=3.92wt%-4.72wt%和Al2O3=14.17wt%-14.7wt%。全碱(Na2O+K2O)含量为7.6wt%-8.78wt%,里特曼指数(δ)介于2.15-2.71之间,属钙碱性系列;A/CNK=0.99-1.10,A/NK=1.25-1.39,出现微量刚玉标准矿物,属于准铝质-弱过铝质岩石。稀土配分图解显示轻稀土富集,重稀土亏损,(La/Yb)N较高为23.31-39.98,说明其轻重稀土的分馏程度强,意味着岩浆源区出现残余石榴石,表明造山后加厚岩石圈构造背景。微量元素蛛网图中,岩石显示富集大离子亲石元素(LILF)Rb、Ba、K,亏损高场强元素(HSFE)Nb、Ta和Ti,个别元素如Sr、P表现出明显负异常,是岩浆由基性向酸性演化的结果,反映了本文研究区岩浆来自于造山后岩石圈地幔的演化岩浆,并非原生岩浆,是蒙古-鄂霍茨克大洋板块向南俯冲远程效应的产物。
[Abstract]:Based on the project of "investigation of regional geology and mineral resources in Liufu area of Inner Mongolia with 1: 50 000 Zhonghian and Thermoyengyumu", the Mesozoic volcanic rocks in Honggu area, Sunita, Inner Mongolia, are studied in this paper. The tectonic position of the study area is located in the late Paleozoic continental margin accretive zone of the southeastern continental margin of the Siberian plate, and is located in the northwestern side of the Erlian-Hegenshan plate docking zone. This orogenic belt belongs to the Paleozoic Asian oceanic tectonic domain and Mesozoic to the riparian Pacific tectonic domain. The tectonic units in the study area belong to the northern orogenic belt of Xingmeng orogenic belt and are located in the northern and western border areas of Inner Mongolia. Magmatic activities in the area are frequent, and there are strong volcanic eruptions and magmatic intrusions in late Paleozoic and Mesozoic. The Mesozoic volcanic rocks are only distributed in the 1: 50 000 regional geological survey map, which are banded and unconformable with the volcanic eruption of the lower Carboniferous alkali feldspar granite body in the northeast corner of the map, extending to the adjacent area of the survey area. The volcanic rocks of the BaiyinggaoLao formation in Honggu area are located in the NNE fault zone, covered by unconformity of clastic rocks of the Damoguahe formation, Cretaceous, and the volcanic rocks are developed near vertical cleavage and fold structure. The lithology is dominated by rhyolite, intercalated tuff, fused tuff, dolomite and obsidian thin layer, and the north and south ends are intruded by Carboniferous biotite monzogranite. The LA-ICA-MS zircon dating of the Mesozoic volcanic rocks selected in this paper has very few zircon grains and is inherited zircon. Its age represents the age of formation of Carboniferous alkali feldspathic granites, and is compared with the volcanic rocks of the Baiyingao formation published in the adjacent area. It is found that there are consistent geochemical characteristics, indicating the same magmatic properties and inferring that they are contemporaneous magmatic products. Therefore, with reference to the weighted mean ages of two LA-ICP-MS zircon U-Pb isotopic dating for the volcanic rocks of the Quasi-and Thermo-Sappa Baiyingao formation in the adjacent area, respectively, the weighted mean ages are 135.1 卤5.6Ma and 135.2 卤3.8 Ma, respectively, indicating that the volcanic rocks in this study area should have been formed in the early Cretaceous. In the investigation report of the regional geology and mineral resources of Liufu region, such as 1: 50, 000 in Inner Mongolia, and thermosone, the former people determined it as the volcanic rock of the second stage of the Baoligaomiao formation, and the volcanic rock of the Baiyingao formation was reclassified as the volcanic rock of Baiyingao formation in this paper. The Sio _ 2 content of Mesozoic volcanic rocks in Hongger area, Sunita Zuo Qi is between 69.52 wt- 71.44 wt%, K _ 2O -3.92 wt-4.72 wt% and Al _ 2O _ 3 14.17 wt-14.7 wtbatt. The content of Na2O K _ 2O is 7.6 wt- 8.78 wt. the Ritman index (未) is between 2.15-2.71, belonging to the calc-alkaline series A / CNK _ (0.99-1.10) A / N ~ (K) 1.25-1.39. There are trace corundum standard minerals, which belong to quasi-aluminite-weakly peraluminous rocks. The REE partition diagram shows that LREE is enriched and the heavy REE depleted La- / Ybnn is higher than 23.31-39.98, indicating that the fractionation degree of REE is strong, which means the residual garnet appears in the magmatic source area, indicating the tectonic setting of the thickening lithosphere after orogeny. In the trace element cobweb diagram, the rocks show the enrichment of the large ion lithophile elements LILFFN RbPBA K, and the depletion of the high field strength elements HSFEN, NB, Ta and Ti. Some elements, such as Srnp, show obvious negative anomalies, which are the result of the evolution of magma from the basic to the acidic. It is shown that the magma in this study area is derived from the evolution magma of the lithospheric mantle after orogeny and is not primary magma but the product of the remote subduction effect of the Mongolia-Okhotsk oceanic plate towards the south.
【学位授予单位】：石家庄经济学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.14

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