本文選題：拉脊山 + 中酸性侵入巖��； 參考：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：祁連微大陸是祁連造山帶內(nèi)的古隆起區(qū)之一,其南以宗務(wù)隆山-青海南山造山帶與歐龍布魯克微大陸相鄰,北以北祁連造山帶與阿拉善微大陸相隔,基底巖系由早元古代高級變質(zhì)巖系和具有蓋層屬性的中新元古代陸棚沉積巖系構(gòu)成,為具有典型二元結(jié)構(gòu)特征的新元古代古陸塊,其上覆蓋古生代沉積地層。受后期構(gòu)造肢解,現(xiàn)今呈北西至近東西走向的疏勒南山-拉脊山縫合帶將祁連微大陸分割為中祁連和南祁連微陸塊。拉脊山縫合帶南、北兩側(cè)分別與前寒武紀結(jié)晶基底呈斷層接觸,是一條具有多期活動屬性的縫合帶,古生代-中新生代經(jīng)歷了多期強烈的構(gòu)造變動。其內(nèi)部主體為早古生代(主要為寒武紀)的火山巖,并存在一條包含純橄巖、輝橄巖、輝石巖、輝長輝綠巖、硅質(zhì)巖的拉脊山蛇綠混雜巖帶,也見有大量斜長花崗巖、石英閃長巖、花崗閃長巖、閃長巖等中酸性侵入體。本文著重討論出露于拉脊山蛇綠混雜巖帶南側(cè)的三個小型中酸性侵入巖體的巖石學(xué)、地球化學(xué)特征和成巖時代,及其構(gòu)造意義。三個中酸性小巖體分別位于拉脊山西北峰、山隘和主峰東側(cè),呈帶狀分布,整體走向為北西-南東,與拉脊山蛇綠巖帶走向相近。三個小巖體均以閃長巖為主要巖石類型,其次為花崗閃長巖、石英閃長巖,巖石中常見有輝石閃長巖、角閃輝長巖等暗色巖包體,巖體內(nèi)部還常見有二長花崗巖等酸性巖透鏡體或巖脈。三個閃長巖巖體中巖石的主量元素成分表明其屬準(zhǔn)鋁質(zhì)鈣堿性巖系列;微量元素蛛網(wǎng)圖顯示其多具有Nb、Ta、Ti明顯虧損,Zr、Hf相對虧損的島弧玄武巖漿結(jié)晶巖石的成分特征;Sr、Nd同位素組成揭示它們的成巖母巖漿具有源于殼幔過渡帶,顯示以巖石圈地幔部分熔融為主,伴有地殼物質(zhì)疊加的特征。綜合研究認為,拉脊山蛇綠混雜巖帶南側(cè)三個閃長巖體的成因類型屬于I型花崗巖類,為鈣堿性巖系列,結(jié)合稀土和微量元素含量特征認為它們可能是島弧玄武質(zhì)熔漿上侵,形成島弧輝長巖堆晶后,殘余熔漿(伴有巖漿房周邊地殼物質(zhì)的加入)結(jié)晶產(chǎn)物。LA-ICP-MS鋯石U-Pb年齡測定結(jié)果揭示巖體的成巖年齡約為460-465Ma,即形成于中奧陶世。拉脊山蛇綠巖混雜巖帶南側(cè)三個中酸性侵入體成因和成巖年齡的最新研究認識揭示拉脊山縫合帶中奧陶世存在島弧俯沖、洋殼消減、島弧巖漿上侵的構(gòu)造體制。
[Abstract]:The Qilian microcontinent is one of the paleouplift areas in the Qilian orogenic belt. The southern Qilian orogenic belt is adjacent to the Euronbrook microcontinent, and the northern Qilian orogenic belt is separated from the Alashan microcontinent to the south. The basement rock series is composed of the early Proterozoic high grade metamorphic rock series and the MesoNeoproterozoic shelf sedimentary series with the property of caprock. It is a Neoproterozoic paleo-block with typical dualistic structure and covers the Paleozoic sedimentary strata. By later structural dismemberment, the Suture Zone of Sunan Mountain and Lachin Mountains, which is from north to west to near east to west, divides the Qilian microcontinent into middle Qilian and South Qilian microcontinental blocks. The southern and northern sides of the Lachinshan suture zone are in contact with the Precambrian crystalline basement respectively. It is a multi-stage active suture zone, and the Paleozoic to Mesozoic Cenozoic has undergone many strong tectonic changes. The main body is the volcanic rocks of early Paleozoic (mainly Cambrian), and there is a Lajieshan ophiolite melange belt containing pure olivine, pyroxenite, pyroxenite and siliceous rocks. Quartz diorite, granodiorite, diorite and other intermediate-acid intrusions. In this paper, the petrology, geochemistry, diagenetic age and tectonic significance of three small intermediate-acid intrusive rocks exposed to the southern side of the Lachinshan ophiolite melange belt are discussed. The three small intermediate-acid rock bodies are located in the northwest peak of Laki Mountain, the east side of the pass and the main peak, with a zonal distribution, and the whole strike is north-west to the south east, which is close to the strike of the Lachinshan ophiolite belt. The main rock types are diorite, followed by granodiorite and quartz diorite. There are usually gabbro diorite, hornblende gabbro, etc. There are also two-feldspar granite and other acid rock lenses or veins in the rock mass. The principal element compositions of the three diorite rocks indicate that they belong to the quasi-aluminous calc-alkaline rock series. The trace element cobwebs show that most of them are characterized by the composition characteristics of island arc Black Tortoise magmatic crystallization rocks, which are obviously depleted in NbTa-Ta-Ti and their igneous parent magma originates from the crust-mantle transition zone, and their isotopic compositions reveal that the diagenetic parent magma originates from the crust-mantle transition zone. It is shown that the lithospheric mantle is mainly partially melted with the characteristics of crustal material superposition. It is considered that the three diorite bodies on the southern side of the Lachinshan ophiolite melange belt belong to type I granites and belong to the calc-alkaline rock series. Combining with the characteristics of rare earth elements and trace elements, it is considered that they may be the island arc Black Tortoise magma uplift. After the island arc gabbro is formed, the residual magma (with the addition of crustal material around the magma chamber) crystallizes. LA-ICP-MS zircon U-Pb dating results show that the diagenetic age of the rock mass is about 460-465Ma. that is, it was formed in the Middle Ordovician. The recent study on the genesis and diagenetic age of three intermediate-acid intrusions in the southern side of the Lachinshan ophiolite melange reveals the tectonic system of island arc subduction, oceanic crust subduction and island arc magma intrusion in the middle Ordovician in the Laji Mountain suture zone.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.12

【參考文獻】

相關(guān)期刊論文 前10條

1 楊鐘堂,肖思云,肖朝陽,李寶強,段永民,蘇亮紅;祁連成礦帶鎢礦成礦特征及其區(qū)域找礦標(biāo)志[J];中國地質(zhì);2004年03期

2 張旺生,馮光勝,高山,孫林華;拉脊山-化隆變質(zhì)核雜巖構(gòu)造及其隆升機制探討[J];地球科學(xué);2003年04期

3 邱家驤,張珠福;北秦嶺早古生代海相火山巖的實驗、成分與構(gòu)造開合[J];地球科學(xué);1997年03期

4 葛肖虹,劉俊來;北祁連造山帶的形成與背景[J];地學(xué)前緣;1999年04期

5 肖序常;陳國銘;朱志直;;祁連山古蛇綠巖帶的地質(zhì)構(gòu)造意義[J];地質(zhì)學(xué)報;1978年04期

6 吳漢泉;;東秦嶺和北祁連山的藍閃片巖[J];地質(zhì)學(xué)報;1980年03期

7 徐克勤;胡受奚;孫明志;張景榮;葉俊;;論花崗巖的成因系列——以華南中生代花崗巖為例[J];地質(zhì)學(xué)報;1983年02期

8 侯青葉,趙志丹,張宏飛,張本仁,陳岳龍;北祁連玉石溝蛇綠巖印度洋MORB型同位素組成特征及其地質(zhì)意義[J];中國科學(xué)(D輯:地球科學(xué));2005年08期

9 董國安;楊懷仁;楊宏儀;劉敦一;張建新;萬渝生;曾建元;;祁連地塊前寒武紀基底鋯石SHRIMP U-Pb年代學(xué)及其地質(zhì)意義[J];科學(xué)通報;2007年13期

10 李春昱;劉仰文;朱寶清;馮益民;吳漢泉;;秦嶺及祁連山構(gòu)造發(fā)展史[J];西北地質(zhì);1978年04期

，

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