本文選題：韌性剪切帶 + 變形特征　； 參考：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：蘇魯造山帶作為印支期華北與揚(yáng)子板塊碰撞的產(chǎn)物,形成以來經(jīng)歷了多期構(gòu)造事件,其演化過程一直以來都是研究熱點。位于其西北緣的皇華-鐵镢山地區(qū)構(gòu)造變形較為強(qiáng)烈并發(fā)育韌性剪切帶,由于韌性剪切帶與造山過程有著非常密切的聯(lián)系,所以對韌性剪切帶變形特征及年代學(xué)的研究有利于加深對蘇魯造山帶構(gòu)造演化的認(rèn)識。本文通過詳細(xì)地野外調(diào)查和顯微構(gòu)造特征研究,對剪切帶幾何學(xué)和運(yùn)動學(xué)進(jìn)行了分析。結(jié)果顯示,研究區(qū)韌性剪切帶呈北東東向展布,幾何學(xué)形態(tài)表現(xiàn)為背形,并經(jīng)歷了兩期韌性變形作用:(1)早期韌性變形是在區(qū)域擠壓應(yīng)力下,由SEE向NWW近水平的滑脫作用造成;(2)晚期韌性變形是在區(qū)域伸展應(yīng)力下,由NNW-SSE的伸展滑覆作用造成。結(jié)合顯微鏡下礦物變形特點并依據(jù)定向樣品中石英c軸組構(gòu)EBSD圖像,對兩期韌性變形溫度進(jìn)行限定。結(jié)果顯示:(1)早期韌性變形發(fā)生在低角閃巖相-高綠片巖相環(huán)境中,變質(zhì)-變形溫度在500℃~600℃之間,局部達(dá)到高角閃巖相,溫度在600℃以上;(2)晚期韌性變形發(fā)生在低綠片巖相環(huán)境中,變質(zhì)-變形溫度在350℃~450℃之間。根據(jù)研究區(qū)巖漿作用及變形礦物的年齡,對兩期韌性變形的時代進(jìn)行限定。結(jié)果顯示:(1)研究區(qū)出露較多偉晶巖脈或淡色脈體,變形特征顯示其形成于早期剪切作用的晚期階段,且LA-ICP-MS鋯石U-Pb諧和年齡為150.1±1.1 Ma,表明早期韌性變形啟動時間不晚于150 Ma。(2)晚期形成的白云母40Ar-39Ar坪年齡為137.09±0.32 Ma,與反等時線年齡一致,且侵入剪切帶內(nèi)無變形的巖體(閃長玢巖)的LA-ICP-MS鋯石U-Pb諧和年齡分別為123.5±0.8 Ma和127.1±1.6 Ma,表明晚期韌性變形啟動時間不晚于137 Ma,并結(jié)束于127 Ma之前。綜合研究區(qū)內(nèi)已有的研究成果,本次研究認(rèn)為蘇魯造山帶西北緣早期韌性變形應(yīng)發(fā)生于陸內(nèi)造山的晚期階段,而晚期韌性變形發(fā)生于造山后的伸展階段,兩期構(gòu)造活動反映了蘇魯造山帶構(gòu)造體制轉(zhuǎn)換過程,該轉(zhuǎn)換過程受制于晚中生代中國東部巖石圈的伸展減薄及太平洋板塊的俯沖。
[Abstract]:The Sulu orogenic belt, as the product of the collision between North China and Yangtze plate in Indosinian period, has undergone many tectonic events since its formation, and its evolution process has always been a hot research topic. The tectonic deformation and ductile shear zone in the Huanghua-Tieshan area, located on the northwest margin of the region, are relatively strong. The ductile shear zone is closely related to the orogenic process, and the ductile shear zone is closely related to the orogenic process. Therefore, the study of deformation characteristics and geochronology of ductile shear zone is beneficial to further understanding the tectonic evolution of the Sulu orogenic belt. In this paper, the geometry and kinematics of shear zone are analyzed by detailed field investigation and microstructural study. The results show that the ductile shear zone in the study area is east-west distribution, geometry shape is back shape, and it has undergone two stages of ductile deformation: 1) the early ductile deformation is under regional compressive stress. The late ductile deformation caused by the near horizontal slippage of SEE to NWW is caused by the extension and slip of NNW-SSE under regional extensional stress. Combined with the characteristics of mineral deformation under microscope and according to the c-axis EBSD images of quartz in oriented samples, the two-stage ductile deformation temperature was limited. The results show that the early ductile deformation occurred in the environment of low amphibolite facies and high greenschist facies, and the metamorphic deformation temperature was between 500 鈩，

本文編號：1943248