本文選題：包頭-二連 + 花崗巖　； 參考：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：包頭-二連地區(qū)在大地構(gòu)造上橫跨了興蒙造山帶的西段和華北克拉通的北緣。通過對華北北緣小井溝花崗巖和興蒙造山帶額仁淖爾地區(qū)花崗巖開展年代學(xué)、地球化學(xué)和同位素研究,探討其巖石成因和形成的構(gòu)造背景,以期為確定古亞洲洋的最終閉合時(shí)限提供一些約束;結(jié)合最新的研究成果,建立起研究區(qū)顯生宙花崗巖的年代學(xué)格架,在此基礎(chǔ)上,總結(jié)分析研究區(qū)顯生宙花崗巖Hf同位素特征,以加深對包頭-二連地區(qū)深部新老地殼時(shí)空分布架構(gòu)的認(rèn)識。華北北緣小井溝巖體侵位于二疊紀(jì),侵位年齡為275±1Ma。屬于弱過鋁質(zhì)的高鉀鈣堿性系列,具有類似于I型花崗巖的特征,Hf同位素特征表明華北陸塊古元古代的地殼巖石應(yīng)該是其主要物源,可能有幔源物質(zhì)的參與。興蒙造山帶額仁淖爾地區(qū)衛(wèi)境巖體形成時(shí)代為279±1Ma,查干德勒巖體侵位時(shí)代為276±4Ma,均為二疊紀(jì)巖體。兩者均屬弱過鋁質(zhì)的高鉀鈣堿性系列,暗色礦物中出現(xiàn)角閃石,顯示出類似于I型花崗巖的巖石學(xué)和地球化學(xué)特征,Hf同位素特征表明衛(wèi)境巖體具有年輕的源區(qū)特征,查干德勒巖體應(yīng)是由古老地殼巖石發(fā)生部分熔融形成。高精度的年代學(xué)數(shù)據(jù)統(tǒng)計(jì)結(jié)果表明,研究區(qū)巖漿活動(dòng)大致可分為5個(gè)期次,具體包括奧陶紀(jì)-泥盆紀(jì)(485~359Ma),石炭紀(jì)(359~299Ma),二疊紀(jì)(299~252Ma),三疊紀(jì)(252~201Ma),侏羅紀(jì)-白堊紀(jì)(201~114Ma),其中二疊紀(jì)巖漿活動(dòng)最為強(qiáng)烈�；◢弾rHf同位素特征表明,研究區(qū)可以索倫-西拉木倫斷裂為界劃分為差異明顯的南北兩個(gè)帶,南帶花崗巖類具有負(fù)εHf值及老的模式年齡,北帶花崗巖總體上表現(xiàn)出正εHf值及年輕模式年齡的特征,局部出現(xiàn)具有負(fù)εHf值及老的模式年齡花崗巖,顯示可能有古老微陸塊存在的信息。從南蒙古到華北克拉通北緣地區(qū),二疊紀(jì)不是一個(gè)統(tǒng)一的構(gòu)造體制,具有同時(shí)異相的特征。二疊紀(jì)南帶應(yīng)該處于由俯沖向碰撞-后碰撞轉(zhuǎn)變的構(gòu)造背景,而北帶應(yīng)該處于后造山的構(gòu)造背景,古亞洲洋可能在晚二疊世以前就已閉合。
[Abstract]:The Baotou-Erlian area spans the western part of the Xingmeng orogenic belt and the northern margin of the North China Craton.Based on the geochronology, geochemistry and isotopic studies of the Xiaojinggou granites in the northern margin of North China and the granites in the Eren Nur area of the Xingmeng orogenic belt, the petrogenesis and tectonic setting of the granites are discussed.With a view to providing some constraints for determining the final closure time of the Paleo-Asian Ocean and combining the latest research results, the chronological framework of the Phanerozoic granites in the study area was established, on the basis of which,The HF isotopic characteristics of the Phanerozoic granites in the study area are summarized and analyzed in order to deepen the understanding of the space-time distribution framework of the deep new and old crust in Baotou-Erlian area.The Xiaojinggou intrusion in the northern margin of North China is located in the Permian with an emplacement age of 275 鹵1 Ma.It belongs to the weak peraluminous calc-alkaline series, which is similar to the I-type granite. The HF isotopic characteristics indicate that the ancient crustal rocks of the North China block Gu Yuan should be the main source of its material, and may involve the mantle material.The formation age of Weijing rock body and the emplacement age of Chagandler rock body are 279 鹵1Maand 276 鹵4Marespectively, all of which are Permian rocks.Both belong to a weak peraluminous calc-alkaline series with hornblende in dark minerals, showing petrological and geochemical characteristics similar to I-type granites. The HF isotopic characteristics indicate that the Weijing rock body has a young source area.Chagandler rock body should be formed by partial melting of ancient crustal rocks.The statistical results of high-precision geochronological data show that magmatic activity in the study area can be roughly divided into five periods.These include Ordovician Devonian (485U 359MaA), Carboniferous (359U 299Mag), Permian (299U 252MaA), Triassic (252Cretaceous) 201114MaU, Jurassic-Cretaceous (201114MaN), among which Permian magmatic activity is the strongest.The HF isotopic characteristics of granites indicate that the study area can be divided into two distinct north and south zones, and the southern belt has negative 蔚 HF value and old model age.The granites in the northern belt generally show positive 蔚 HF values and young model ages, and there are negative 蔚 HF values and old model age granites, indicating that there may be information of the existence of ancient microcontinental blocks.From southern Mongolia to the northern margin of North China Craton, Permian is not a unified tectonic system and has the characteristics of simultaneous heterogeneity.The southern belt of Permian should be in the tectonic setting of the transition from subduction to collision-post-collision, while the northern belt should be in the tectonic setting of post-orogeny, and the paleo-Asian ocean may have been closed before the late Permian.
【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】：P588.121;P597

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