本文選題：溝里地區(qū)　切入點：變火山巖　出處：《長安大學》2015年碩士論文

【摘要】：東昆侖造山帶具有漫長的演化歷史,是一條復合的大陸造山帶,其中包括多條重要的構(gòu)造縫合帶。本論文以現(xiàn)代板塊構(gòu)造學理論為指導思想,從地質(zhì)客觀實際出發(fā),主要針對東昆侖造山帶東段溝里地區(qū)龍洼卡魯、智玉西側(cè)和山金礦業(yè)南側(cè)火山巖進行詳細的地質(zhì)特征、巖石地球化學特征及LA-ICP-MS鋯石U-Pb同位素年代學等方面的綜合研究,結(jié)合區(qū)域地質(zhì)背景對其形成時代、巖石成因、構(gòu)造環(huán)境歸屬和東昆侖造山帶東段早古生代構(gòu)造演化特征進行探討,為查明中央造山系和東特提斯構(gòu)造域早古生代以來的板塊構(gòu)造格局和恢復重建其演化進程提供依據(jù)。取得以下主要進展和認識:1、龍洼卡魯火山巖巖性主體為變基性火山巖(變玄武巖),夾少量變安山巖,變質(zhì)程度較低。地球化學特征顯示龍洼卡魯變基性火山巖為拉斑玄武巖,兼具島弧和大洋中脊特征,巖漿來源于富集地幔,變玄武巖主體上為地幔巖部分熔融的結(jié)果,形成于由俯沖作用引起弧后盆地構(gòu)造環(huán)境,并獲得變玄武巖中鋯石U-Pb年齡為442.0±5.4Ma,該年齡為變玄武巖的結(jié)晶年齡,表明龍洼卡魯變玄武巖的形成時代為早志留世初。該結(jié)晶年齡限制了變基性火山巖的時代歸屬,確定了與其相伴生的碳酸鹽巖是不同時代的產(chǎn)物。2、確定了智玉西側(cè)變火山巖巖性主要為變玄武巖,變質(zhì)程度低,達低綠片巖相,地球化學特征顯示出亞堿性拉斑玄武巖系列特征。稀土元素和微量元素都表現(xiàn)出與龍洼卡魯變玄武巖相似的特征,確定為弧后拉張環(huán)境的產(chǎn)物。通過巖石組合和構(gòu)造環(huán)境與區(qū)域上地層相對比,把該套火山巖歸屬于納赤臺巖群。3、確定了山金礦業(yè)南側(cè)變火山巖巖性為一套變中-中酸性火山巖(變安山巖與變英安巖),變質(zhì)程度相對較高,部分達高綠片巖相。地球化學特征上,變中-中酸性火山巖表現(xiàn)出LREE富集程度遠高于變玄武巖;在微量元素中表現(xiàn)出富集LILE,Nb、Ta等元素的相對虧損,表現(xiàn)出類似島弧的特征,變中-中酸性巖是屬于殼幔混合作用的產(chǎn)物。通過前人獲得同位素年齡,結(jié)合巖石組合與區(qū)域上地層相對比,確定了該套火山巖歸屬于納赤臺巖群。4、根據(jù)溝里地區(qū)龍洼卡魯、智玉西側(cè)及山金礦業(yè)南側(cè)火山巖的性質(zhì),并結(jié)合東昆侖東段區(qū)域地質(zhì)資料,探討東昆侖地區(qū)演化史。東昆侖地區(qū)在新元古代末處于裂解階段,產(chǎn)生大量火山巖;早寒武世早期,東昆侖地區(qū)存在著原特提斯洋殼,并在中寒武世,原特提斯洋向北發(fā)生俯沖,隨著俯沖強度的增大,導致東昆侖地區(qū)拉張成弧后小洋盆,出現(xiàn)以清水泉-可可沙-科科可特為代表的蛇綠巖組合,該階段形成了納赤臺巖群及龍洼卡魯變火山巖系;中-晚志留世東昆侖地區(qū)分別經(jīng)歷了原特提斯洋俯沖造山與碰撞造山;晚志留世-早泥盆世以和勒岡那仁巖體的形成為代表,表明了東昆侖地區(qū)開始向較為穩(wěn)定的陸內(nèi)構(gòu)造演化階段轉(zhuǎn)化。最終以牦牛山組的出現(xiàn),標志著早古生代原特提斯構(gòu)造域演化的徹底結(jié)束。
[Abstract]:With the evolution history of the East Kunlun orogenic belt, is a composite of the continental orogenic belt, including a number of important tectonic suture zone. This paper takes modern plate tectonics theory as the guiding ideology, from the geological objective reality, mainly to the east of Eastern Kunlun orogenic belt, ditch area south of the Jade Dragon wa Carew, Chi west the mountain and the volcano rock gold mining geological features detailed, comprehensive study of rock geochemistry and LA-ICP-MS zircon U-Pb isotopic chronology and other aspects, combined with the regional geological background of the formation age, petrogenesis, Eastern Early Paleozoic tectonic evolution characteristics of tectonic environment and the East Kunlun orogenic belt, in order to find out since the early Paleozoic Central Orogenic and the eastern Tethys tectonic framework and its evolution process provides the basis for restoration and reconstruction. The following major progress and understanding: 1, dragon wa Carew The main lithology volcano rock metabasic volcano (Xuan Wuyan), with a small amount of variable andesite, lower metamorphic grade. Geochemical characteristics show that the Dragon wa Karoo metabasic volcano tholeiitic Xuan Wuyan, with the characteristics of island arc and oceanic ridge, magma derived from the enriched mantle, the basalt body for partial melting of mantle rocks, formed by subduction caused by back arc basin tectonic environment, and change the zircon U-Pb age of Xuan Wuyan was 442 + 5.4Ma, the age variable crystallization age of Xuan Wuyan, that Xuan Wuyan Carew variable long depression were formed in the Early Silurian. The crystallization age restricted metabasic the age of volcano rock, carbonate rock and determine the associated are the products of different times.2, the Chi jade West variable volcano lithology is mainly Xuan Wuyan, low metamorphic degree, of low greenschist facies, geochemical characteristics show A tholeiitic series. The characteristics of REE and trace elements are shown with the Dragon wa Karoo alteration basalt similar characteristics, determine the product of back arc extensional environment. The rock assemblage and tectonic environment and regional upper layer compared to the volcano rock, red rock group from Taiwan belong to.3, determine on the south side of the mountain of gold industry becomes a volcano rock lithology change - acidic volcano rock (dacite and andesite variable variable), the degree of metamorphism is relatively high, some high greenschist facies. The geochemical characteristics, change in - acidic volcano rock show LREE enrichment degree is much higher than the variable performance of basalt; the enrichment of trace elements in LILE, in Nb, relatively depleted in Ta elements, showing similar characteristics of island arc, in - acid rock is a product which belongs to the crust mantle mixing. Isotope age by predecessors, combined with the rock combination and regional upper layer relative Is to determine the set of volcano rock belongs to Nachitai rock group.4, according to the ditch area dragon wa Carew, nature South and West Mountain volcano rock wisdom jade gold mining industry, and combined with the eastern section of East Kunlun regional geological data, explore the evolution history of the eastern regions of Kunlun. The East Kunlun area in the late Neoproterozoic in cleavage stage, resulting in a large number of volcano rock; Early Cambrian, Eastern Kunlun region exists Dhi Te Tis oceanic crust, and in the Middle Cambrian, proto Tethys northward subduction subduction, with increasing strength, leading to small ocean basin in eastern Kunlun to pull Zhang Chenghu, appeared in the Qingshuiquan - kekesha - Kekekete as the representative of the snake the stage of formation of the ophiolite combination, Nachitai rock group and long depression volcano rocks in the Karoo change; late Silurian in eastern Kunlun area experienced a proto Tethys subduction orogenic collision and orogeny; late Silurian Early Devonian to Gangnaren rock and le The formation indicates that the East Kunlun area began to transform to a relatively stable stage of intra continental tectonic evolution. Finally, the appearance of yyushan formation marks the complete end of the evolution of the early Paleozoic Tethyan tectonic domain.

【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P588.14

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