青海甘德三疊紀巴顏喀拉山群巖石學特征及物源分析
發(fā)布時間：2019-05-18 13:58
【摘要】：研究區(qū)位于青藏高原北東部三疊紀松潘甘孜造山帶青海巴顏喀拉造山亞帶,與西秦嶺造山帶的西南邊相鄰近,研究目的在于探究青海甘德巴顏喀拉山群的巖石學特征及其物源。研究有助于了解青海省內巴顏喀拉山群的構造發(fā)展史并且對其周邊地塊的巖漿活動、構造演化等有著很好的指示意義。松潘甘孜造山帶是一個從消耗古特提斯洋被動陸緣發(fā)展而來的造山帶,是在古特提斯洋最后關閉以及羌塘、昆侖、華北以及揚子的陸陸碰撞過程中形成。青海甘德區(qū),三疊紀巴顏喀拉山群廣泛發(fā)育,它是晚印支期參與造山的主要地層組分和造山帶的主體組分。其中三疊系巴顏喀拉山群地層分布廣泛,為一套砂泥質復理石-類復理石沉積,巖性簡單,以巖屑砂巖和長石砂巖為主,顏色單調,巖石淺變質,具活動型沉積特點,多為淺海-深海相濁流沉積環(huán)境。巴顏喀拉三疊紀沉積盆地自東至西、自下而上具有由被動大陸邊緣向活動大陸邊緣、大陸或大洋島弧演化的趨勢。研究區(qū)巖石主要為巖屑砂巖和長石砂巖,通過對研究區(qū)所采樣品進行的主微量元素測定,Si O2含量變化范圍為57.09%~73.76%,研究區(qū)在三疊紀時期所處構造環(huán)境以活動大陸邊緣為主,被動大陸邊緣與大陸島弧次之,沒有大洋島弧。研究區(qū)樣品總體還具有明顯的Eu負異常,(La/Sm)N平均值:4.03;(La/Yb)N平均值:10.63,輕稀土元素含量大于重稀土元素含量,稀土元素分布形態(tài)與上地殼基本一致。說明研究區(qū)三疊紀源區(qū)巖石總體上與大陸地殼組成基本一致。研究區(qū)砂巖碎屑鋯石的LA-ICP-MS U-Pb年齡集中分布于190-558Ma、787-1144Ma、1488-2590Ma,與揚子地塊和南秦嶺造山帶比較一致。而碎屑鋯石的Hf同位素特征也更偏向與揚子地塊和秦嶺造山帶,且明顯與華北地塊和羌塘地塊的特征不同,故青海甘德地區(qū)的物源區(qū)主要以揚子地塊和南秦嶺造山帶為主。
[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 鹵558 Ma, 787 鹵1144 Ma and 1488 鹵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.
【學位授予單位】：中國地質大學(北京)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P587
本文編號：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 鹵558 Ma, 787 鹵1144 Ma and 1488 鹵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.
【學位授予單位】：中國地質大學(北京)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P587
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，本文編號：2480064
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