内蒙古锡林浩特喇嘛音乌苏地区晚更新世玄武质火山作用特征

发布时间：2018-05-24 21:00

本文选题：内蒙古喇嘛音乌苏 + 晚更新世　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：内蒙古锡林郭勒盟地区分布有大面积北西-南东向分布的新生代火山岩区,与蒙古共和国东南部的达里干加新生代火山岩相连,为亚洲最大的新生代板内玄武岩,作者在前人研究的基础上对内蒙古锡林浩特喇嘛音乌苏地区新生代火山岩进行调查研究,查明了火山机构类型、火山岩相及火山喷发时代等,划分了火山喷发期次,研究了岩石地球化学特征及大地构造环境,取得了有意义的成果和认识。通过野外调查与综合研究,将晚更新世火山作用划分为四个喷发亚旋回,且每个喷发亚旋回可进一步划分2个以上数量不一的喷发韵律。划分出五种主要岩相类型包括喷溢相、火山爆发崩塌相、火山喷发沉积相、涌流相及火山通道相,包括锥状、盾状、玛珥式火山。火山作用产物分布特征是火山口附近主要有玄武质集块岩、浮岩、含火山弹火山角砾岩、玄武质凝灰角砾岩、致密块状橄榄玄武岩、气孔状橄榄玄武岩,形成火山机构主体,远离火山口主要是橄榄玄武岩浆溢流的熔岩流,构成熔岩台地,产状平缓,局部球形风化。玄武岩中常见有幔源橄榄石、辉石及下地壳斜长石捕掳晶,少量的花岗岩捕掳体。通过地球化学分析表明,玄武岩中Ti、Y等呈“V”形,亏损；Ba、Nb、La等呈峰状,富集,总体反映强不相容元素富集。稀土元素总量(ΣREE)均值为214.50×10-6,轻重稀土比(LREE/HREE)值在2.05-4.56之间,δ Eu在0.94-1.13之间,异常不明显,CeN/YbN的值在4.99-13.20之间,属于轻稀土富集型。新生代玄武岩形成于板块边缘拉张环境下,板内裂谷型玄武岩,并且与地幔柱活动有关。通过火山喷发沉积相中获得光释光(osl)年龄为116.4±5.6Ka和123.2±5.5Ka,进一步厘定了内蒙古锡林浩特喇嘛音乌苏地区新生代火山作用时代为晚更新世,为该地域该期火山作用的年代学研究提供了重要的依据。
[Abstract]:There is a large area of Cenozoic volcanic rocks in the Xilingulmeng area of Inner Mongolia, which is connected with the Dariganga Cenozoic volcanic rocks in the southeast of Mongolia, and is the largest Cenozoic intraplate basalt in Asia. On the basis of previous studies, the author investigates and studies the Cenozoic volcanic rocks in the Lama-yinwusu area, Xilinhaote, Inner Mongolia, and finds out the types of volcanic institutions, volcanic facies and volcanic eruption epoch, and divides the volcanic eruption periods. The characteristics of geochemistry and geotectonic environment are studied, and significant results and understanding are obtained. Through field investigation and comprehensive study, the late Pleistocene volcanism is divided into four eruptive subcycles, and each eruption subcycle can be further divided into more than two different eruptive rhythms. There are five main lithofacies types, including ejection facies, volcanic eruption collapse facies, volcanic eruption sedimentary facies, inrush facies and volcanic channel facies, including conical, shield and Maar volcanoes. The distribution characteristics of volcanic products are that there are mainly Black Tortoise mass rocks, pumice rocks, volcanic breccia, Black Tortoise tuff breccia, dense block olivine basalt and stomatal olivine basalt near the crater, which form the main body of volcanic mechanism. Far away from the crater is mainly the lava flow overflowing by olivary Black Tortoise magma, which forms a lava platform with a gentle occurrence and local spherical weathering. Mantle-derived olivine pyroxene and lower crust plagioclase are common in basalt and a small amount of granites. Through geochemical analysis, it is shown that Tiao Y is "V" shape in basalt, and Bajiu Nbni-La in depleted basalt is peak and enriched, which reflects the enrichment of strongly incompatible elements in general. The mean value of total rare earth element (危 REE) is 214.50 脳 10 ~ (-6), the LREE / HREE value is 2.05-4.56, 未 EU is 0.94-1.13, and the abnormal CeN- / YbN value is between 4.99-13.20, which belongs to the light rare earth enrichment type. The Cenozoic basalts were formed in the extensional environment of the plate margin, and the intraplate rift basalts are related to mantle plume activity. The age of photoluminescence in sedimentary facies of volcanic eruption is 116.4 卤5.6Ka and 123.2 卤5.5 Ka. it is further determined that the Cenozoic volcanic epoch in Xilinhaote, Inner Mongolia, is the late Pleistocene. It provides an important basis for the chronological study of volcanism in this region.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.14;P317

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