本文選題：秦嶺南緣　切入點(diǎn)：勉略構(gòu)造帶　出處：《長(zhǎng)安大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：秦嶺南緣勉略構(gòu)造帶是中國(guó)南北陸塊完成拼合的主要結(jié)合帶,其物質(zhì)組成、構(gòu)造屬性及構(gòu)造演化研究對(duì)于秦嶺造山帶的形成演化以及揚(yáng)子板塊和華北板塊的碰撞造山過程研究具有重要意義。針對(duì)學(xué)術(shù)界存在的主要爭(zhēng)議,本文對(duì)勉略構(gòu)造帶經(jīng)典區(qū)段康向—略陽(yáng)一帶進(jìn)行了系統(tǒng)的野外地質(zhì)調(diào)查和室內(nèi)巖石學(xué)、地球化學(xué)及同位素年代學(xué)研究,并取得了以下主要研究成果和認(rèn)識(shí):1、對(duì)勉略構(gòu)造帶內(nèi)變火山巖巖石組成進(jìn)行了巖石學(xué)、地球化學(xué)及年代學(xué)研究。通過系統(tǒng)的地球化學(xué)分析,將勉略帶內(nèi)火山巖分為洋殼型、O型埃達(dá)克質(zhì)巖型、陸緣弧型及裂谷型四大類,其中洋殼型火山巖在康縣地區(qū)和略陽(yáng)地區(qū)略有差異,康縣地區(qū)由N-MORB、E-MORB、OIB型等玄武巖組成,略陽(yáng)地區(qū)主體為N-MORB;厘定略陽(yáng)地區(qū)張兒溝O型埃達(dá)克質(zhì)巖,并獲得其成巖年齡為840Ma左右,為洋盆俯沖階段洋殼部分熔融產(chǎn)物;獲得研究區(qū)不同位置弧火山巖成巖年齡為837~797Ma,巖石組合為安山巖夾少量玄武巖、流紋巖及英安巖,地球化學(xué)特征及巖石組合具有陸緣弧特征;裂谷型火山巖年齡為783~728Ma。結(jié)合前人成果,認(rèn)為勉略構(gòu)造帶及鄰區(qū)火山巖主體形成于新元古代,少量為早古生代。2、將勉略構(gòu)造帶內(nèi)(變質(zhì))沉積巖進(jìn)行了系統(tǒng)梳理,并劃分為南華紀(jì)—震旦紀(jì)裂解—穩(wěn)定型沉積巖系、寒武紀(jì)—志留紀(jì)伸展裂陷型沉積巖系、泥盆紀(jì)—石炭紀(jì)穩(wěn)定臺(tái)盆—臺(tái)地型沉積巖系等三個(gè)不同時(shí)代、不同沉積環(huán)境的沉積體系。獲得上南華統(tǒng)關(guān)家溝組底部砂巖碎屑鋯石年齡為877~718Ma和861~678Ma,物源主要為相鄰新元古代巖漿巖。解體原臨江組(Z2~?1)為相公山白云巖(Z2?1x)和臨江組(?1l),并確定臨江組硅質(zhì)巖具有大陸邊緣較深水環(huán)境地球化學(xué)特征,表征早古生代研究區(qū)可能無(wú)洋盆存在。3、綜合本文及前人研究成果,對(duì)勉略構(gòu)造帶及其鄰區(qū)區(qū)域構(gòu)造演化進(jìn)行了探討。認(rèn)為勉略洋盆存在時(shí)限主要為新元古代早中期,其在新元古代早中期(~800Ma)雙向俯沖于秦嶺微板塊和揚(yáng)子板塊之下,并于800Ma左右兩大板塊完成拼合,形成了勉略構(gòu)造帶及揚(yáng)子板塊西北緣大面積分布的洋殼型火山巖及弧火山巖,新元古代中晚期(800Ma~)進(jìn)入裂解進(jìn)程,區(qū)域上發(fā)育呈點(diǎn)(面)狀分布的裂谷型火山巖,這一過程很可能與全球性Rodinia超大陸的裂解事件相對(duì)應(yīng);新元古代中晚期裂解作用在震旦紀(jì)稍作停歇,于寒武紀(jì)進(jìn)入新一輪陸緣裂解過程,并于志留紀(jì)形成勉略裂陷海槽,后經(jīng)歷晚古生代穩(wěn)定臺(tái)盆—臺(tái)地型沉積,至早中三疊世海槽閉合并進(jìn)入新一輪陸內(nèi)演化階段。
[Abstract]:The Mianliao tectonic belt on the southern margin of Qinling Mountains is the main conjunctive zone of the northern and southern continental blocks of China. The study of tectonic attributes and tectonic evolution is of great significance to the formation and evolution of the Qinling orogenic belt and the collision orogenic process between the Yangtze plate and the North China plate. In this paper, a systematic field geological survey and laboratory petrology, geochemistry and isotopic chronology have been carried out on the classical section of Mianliu structural belt, Kangxiang-Lueyang area. The petrology, geochemistry and geochronology of volcanic rocks in Mianliao tectonic belt are studied by systematic geochemical analysis. The volcanic rocks in the Mianliao belt are divided into four types: the oceanic crust type, the continental margin arc type and the rift type. The oceanic crustal volcanic rocks are slightly different in Kangxian area and Lueyang area, which are composed of N-MORBE-MORBOIB type basalt, etc. The main body of Lueyang area is N-MORB.The Zhangergou O-type adakitic rocks in Lueyang area were determined, and their diagenetic age was about 840Ma, which was the partial melting product of oceanic crust during the subduction stage of the ocean basin. The diagenetic age of arc volcanic rocks in different locations is 837797 Ma.The rock assemblage is composed of a small amount of basalt, rhyolite and dolomite. The geochemical characteristics and rock assemblages are characterized by continental margin arc. The age of rift volcanic rocks is 783 / 728 Ma.According to the previous results, it is considered that the main body of volcanic rocks in Mianliao structural belt and its adjacent areas were formed in Neoproterozoic, and a few in early Paleozoic. The sedimentary rocks in Mianliao tectonic belt were systematically sorted out. It is divided into three different periods: the South China Sinian pyrolysis stable sedimentary rock series, the Cambrian Silurian extensional rift sedimentary rock series, the Devonian Carboniferous stable platform basin platform platform sedimentary rock series. The zircon ages of sandstones at the bottom of Guanjiagou formation of Upper Nanhua formation are 877 718 Ma and 861 0 678 Ma, mainly derived from adjacent Neoproterozoic magmatic rocks, which are derived from adjacent Neoproterozoic magmatic rocks. 1) for the Xianggongshan dolomite Z2? 1x) and Linjiang formation? It is determined that the siliceous rocks of the Linjiang formation have the geochemical characteristics of the deep water environment on the continental margin, indicating that there may be no oceanic basin in the early Paleozoic study area. The tectonic evolution of the Mianliao tectonic belt and its adjacent area is discussed. It is considered that the time limit for the existence of the Mianliao oceanic basin is mainly in the early and middle Neoproterozoic, and it subducted under the Qinling microplate and the Yangtze plate in both directions at the middle and early Neoproterozoic times. The assemblage of the two plates was completed at about 800Ma, forming a large area of oceanic crustal volcanic rocks and arc volcanic rocks distributed in the Mianluo tectonic belt and the northwest margin of the Yangtze plate. In the region, there are rift-valley volcanic rocks distributed in the area, which may correspond to the global Rodinia supercontinent pyrolysis events, and the late Neoproterozoic pyrolysis stopped slightly during the Sinian period, and the pyrolysis occurred in the late Neoproterozoic period, and in the late Neoproterozoic period, the pyrolysis occurred during the Sinian period. During the Cambrian period, it entered a new process of continental margin pyrolysis, and formed a slightly rift trough in Silurian, and then experienced the late Paleozoic stable platform basin-platform deposits, and closed the trough in the early Middle Triassic and entered a new stage of intra-continental evolution.
【學(xué)位授予單位】：長(zhǎng)安大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P542

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本文編號(hào)：1561528