青海甘德三叠纪巴颜喀拉山群岩石学特征及物源分析
发布时间：2019-05-18 13:58
【摘要】：研究区位于青藏高原北东部三叠纪松潘甘孜造山带青海巴颜喀拉造山亚带,与西秦岭造山带的西南边相邻近,研究目的在于探究青海甘德巴颜喀拉山群的岩石学特征及其物源。研究有助于了解青海省内巴颜喀拉山群的构造发展史并且对其周边地块的岩浆活动、构造演化等有着很好的指示意义。松潘甘孜造山带是一个从消耗古特提斯洋被动陆缘发展而来的造山带,是在古特提斯洋最后关闭以及羌塘、昆仑、华北以及扬子的陆陆碰撞过程中形成。青海甘德区,三叠纪巴颜喀拉山群广泛发育,它是晚印支期参与造山的主要地层组分和造山带的主体组分。其中三叠系巴颜喀拉山群地层分布广泛,为一套砂泥质复理石-类复理石沉积,岩性简单,以岩屑砂岩和长石砂岩为主,颜色单调,岩石浅变质,具活动型沉积特点,多为浅海-深海相浊流沉积环境。巴颜喀拉三叠纪沉积盆地自东至西、自下而上具有由被动大陆边缘向活动大陆边缘、大陆或大洋岛弧演化的趋势。研究区岩石主要为岩屑砂岩和长石砂岩,通过对研究区所采样品进行的主微量元素测定,Si O2含量变化范围为57.09%~73.76%,研究区在三叠纪时期所处构造环境以活动大陆边缘为主,被动大陆边缘与大陆岛弧次之,没有大洋岛弧。研究区样品总体还具有明显的Eu负异常,(La/Sm)N平均值:4.03;(La/Yb)N平均值:10.63,轻稀土元素含量大于重稀土元素含量,稀土元素分布形态与上地壳基本一致。说明研究区三叠纪源区岩石总体上与大陆地壳组成基本一致。研究区砂岩碎屑锆石的LA-ICP-MS U-Pb年龄集中分布于190-558Ma、787-1144Ma、1488-2590Ma,与扬子地块和南秦岭造山带比较一致。而碎屑锆石的Hf同位素特征也更偏向与扬子地块和秦岭造山带,且明显与华北地块和羌塘地块的特征不同,故青海甘德地区的物源区主要以扬子地块和南秦岭造山带为主。
[Abstract]:The study area is located in the Triassic Panganzi orogenic subbelt of the northern Qinghai-Xizang Plateau and is close to the southwest edge of the West Qinling orogenic belt. The purpose of the study is to explore the petrological characteristics and provenance of the Gan de Bayan Kara Mountains Group in Qinghai Province. The study is helpful to understand the tectonic development history of Bayan Kara Mountain Group in Qinghai Province and has a good indication significance for magmatic activity and tectonic evolution of the surrounding blocks. Songpan Ganzi orogenic belt is an orogenic belt developed from the passive continental margin of consuming the ancient Tethys Ocean, which was formed during the final closure of the ancient Tethys Ocean and the land-land collision of Qiangtang, Kunlun, North China and Yangtze. The Triassic Bayan Kara Mountain Group is widely developed in Gande District, Qinghai Province. it is the main stratigraphic component and the main component of the orogenic belt in the late Indochina period. Among them, the strata of Bayan Karashan Group of Triassic are widely distributed, which are a set of sand argillaceous feldspar-like feldspar deposits with simple lithology, mainly lithic sandstone and feldspar sandstone, monotonous in color, shallow metamorphism and active sedimentary characteristics. Most of them are shallow sea-deep sea turbid current sedimentary environment. The Bayan Kara Triassic sedimentary basin evolved from the passive continental margin to the active continental margin and the continental or oceanic island arc from east to west. The rocks in the study area are mainly lithic sandstone and feldspar sandstone. Through the determination of the main trace elements in the samples collected in the study area, the variation range of Si O _ 2 content is 57.09% to 73.76%. The tectonic environment of the study area during the Triassic period was dominated by the active continental margin, followed by the passive continental margin and the continental island arc, and there was no oceanic island arc. The samples in the study area also have obvious negative Eu anomalies, and the average value of (La/Sm) N is 4.03; The average value of (La/Yb) N is 10.63. the content of light rare earth elements is higher than that of heavy rare earth elements, and the distribution of rare earth elements is basically the same as that of the upper crust. It is shown that the rock composition of the Triassic source area in the study area is basically consistent with that of the continental crust. The LA-ICP-MS U-Pb age of sandstone clastic zircon in the study area is concentrated in 190 卤558 Ma, 787 卤1144 Ma and 1488 卤2590 Ma, which is consistent with the Yangtze block and the South Qinling orogenic belt. The Hf isotopic characteristics of clastic zircon are also more inclined to be different from those of Yangtze block and Qinling orogenic belt, and obviously different from those of North China block and Qiangtang block. Therefore, the provenance area of Gande area in Qinghai Province is mainly Yangtze block and southern Qinling orogenic belt.
【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】：P587
本文编号：2480064
[Abstract]:The study area is located in the Triassic Panganzi orogenic subbelt of the northern Qinghai-Xizang Plateau and is close to the southwest edge of the West Qinling orogenic belt. The purpose of the study is to explore the petrological characteristics and provenance of the Gan de Bayan Kara Mountains Group in Qinghai Province. The study is helpful to understand the tectonic development history of Bayan Kara Mountain Group in Qinghai Province and has a good indication significance for magmatic activity and tectonic evolution of the surrounding blocks. Songpan Ganzi orogenic belt is an orogenic belt developed from the passive continental margin of consuming the ancient Tethys Ocean, which was formed during the final closure of the ancient Tethys Ocean and the land-land collision of Qiangtang, Kunlun, North China and Yangtze. The Triassic Bayan Kara Mountain Group is widely developed in Gande District, Qinghai Province. it is the main stratigraphic component and the main component of the orogenic belt in the late Indochina period. Among them, the strata of Bayan Karashan Group of Triassic are widely distributed, which are a set of sand argillaceous feldspar-like feldspar deposits with simple lithology, mainly lithic sandstone and feldspar sandstone, monotonous in color, shallow metamorphism and active sedimentary characteristics. Most of them are shallow sea-deep sea turbid current sedimentary environment. The Bayan Kara Triassic sedimentary basin evolved from the passive continental margin to the active continental margin and the continental or oceanic island arc from east to west. The rocks in the study area are mainly lithic sandstone and feldspar sandstone. Through the determination of the main trace elements in the samples collected in the study area, the variation range of Si O _ 2 content is 57.09% to 73.76%. The tectonic environment of the study area during the Triassic period was dominated by the active continental margin, followed by the passive continental margin and the continental island arc, and there was no oceanic island arc. The samples in the study area also have obvious negative Eu anomalies, and the average value of (La/Sm) N is 4.03; The average value of (La/Yb) N is 10.63. the content of light rare earth elements is higher than that of heavy rare earth elements, and the distribution of rare earth elements is basically the same as that of the upper crust. It is shown that the rock composition of the Triassic source area in the study area is basically consistent with that of the continental crust. The LA-ICP-MS U-Pb age of sandstone clastic zircon in the study area is concentrated in 190 卤558 Ma, 787 卤1144 Ma and 1488 卤2590 Ma, which is consistent with the Yangtze block and the South Qinling orogenic belt. The Hf isotopic characteristics of clastic zircon are also more inclined to be different from those of Yangtze block and Qinling orogenic belt, and obviously different from those of North China block and Qiangtang block. Therefore, the provenance area of Gande area in Qinghai Province is mainly Yangtze block and southern Qinling orogenic belt.
【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】：P587
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