本文選題：混合巖 + 巖石類型�。� 參考：《合肥工業(yè)大學》2017年碩士論文

【摘要】：在大陸深俯沖和碰撞形成造山帶過程中,地殼普遍存在的深熔作用可影響造山帶內地殼的熱力學和流變學性質,進而可能會導致造山帶最終垮塌。造山帶中的混合巖主要由深熔作用形成,所以混合巖研究對于理解部分熔融、變質演化和造山過程的相互關系具有重要意義。大別造山帶的北大別構造單元廣泛發(fā)育混合巖。前人對北大別混合巖的命名和分類比較混亂,缺乏系統(tǒng)的觀察和分類;對于北大別混合巖的成因機制各個學者觀點不一,且對于混合巖形成的確切時代依然存有爭議。選擇羅田和岳西穹隆中混合巖開展了野外觀察、巖相學、礦物化學、巖石化學和鋯石LA-ICP-MS U-Pb定年等系統(tǒng)工作,發(fā)現北大別混合巖主要分為疊層狀和膨脹結構中等深熔混合巖以及眼球狀和析離體狀高度深熔混合巖兩種類型。疊層狀淺色體、淺色脈體和花崗巖顯著虧損Fe_2O_3、MgO、MnO、TiO_2和CaO,高度深熔淺色體則稍微富集這些元素。疊層狀淺色體的全巖主量元素組成分為花崗質和英云閃長質,淺色脈體為花崗質。高度深熔淺色體的全巖主量元素組成與片麻巖相似,為花崗閃長質。淺色體和花崗巖表現為LREE以及不相容元素Ba、Th和U的富集,而Nb和Ti顯著虧損。疊層狀淺色體具有強烈的Eu正異常,花崗質淺色脈體和花崗巖則表現為Eu負異常,高度深熔淺色體無明顯Eu異常。這些都指示高度深熔淺色體、疊層狀淺色體和花崗質淺色脈體具有成因聯系,分別結晶于不同演化程度的熔體。鋯石U-Pb同位素定年結果表明,北大別混合巖的原巖主要為來自新元古代的巖石、另有少量的古元古代地殼。混合巖化作用從145 Ma持續(xù)到124 Ma。斜長石-角閃石溫壓計估算結果顯示,混合巖形成的溫壓條件為723-768°C和3.7-5.2 kbar,對應于中上地殼環(huán)境�；旌蠋r的成因機制以長英質片麻巖水飽和條件下的富水熔融為主。其反應為:黑云母+石英+斜長石+水=角閃石+斜長石(殘留)+花崗質熔體。少數混合巖的成因機制為角閃片麻巖中角閃石的脫水熔融。其反應為:角閃石+斜長石+石英=單斜輝石+富水熔體。
[Abstract]:During the process of continental deep subduction and collision forming orogenic belt, the deep melting in the crust can affect the thermodynamic and rheological properties of the crust of the orogenic belt, which may lead to the eventual collapse of the orogenic belt.The migmatite in the orogenic belt is mainly formed by deep melting, so the study of migmatite is of great significance in understanding the relationship between partial melting, metamorphic evolution and orogenic process.Migmatite is widely developed in the Beidabie tectonic unit of the Dabie orogenic belt.Previous scholars have confused the naming and classification of Peking University migmatite, lack of systematic observation and classification, different scholars have different views on the genetic mechanism of Peking University migmatite, and there are still disputes about the exact age of the formation of migmatite.Luotian and Yuexi dome migmatists were selected to carry out systematic work such as field observation, petrography, mineral chemistry, petrochemistry and zircon LA-ICP-MS U-Pb dating.It is found that the Beidabie migmatite is mainly divided into two types: laminated migmatite and expandable structure medium deep melt migmatite and eyeball and exfoliated high deep melt migmatite.Laminated light-colored bodies, light-colored veins and granites are significantly depleted of Fes _ 2O _ 3MgO _ 2O _ (mn) O _ (2) TiO _ 2 and CaO _ 2, and are slightly enriched in these elements by the highly deep-melt light-colored bodies.The main element compositions of the laminated light-colored bodies are granitic and diorite, while the light-colored veins are granitic.The main element composition of the whole rock is similar to that of gneiss and is granodiorite.The light-colored bodies and granites are characterized by enrichment of LREE and incompatible elements Ba-Th and U, while NB and Ti are significantly depleted.There are strong positive EU anomalies in laminated light-colored bodies, negative EU anomalies in granitic light-colored veins and granites, and no obvious EU anomalies in highly submersible light-colored bodies.All of these indicate that there is a genetic relationship between the laminated light-colored bodies and granitic light-colored veins, and they are crystallized in melts with different degrees of evolution.The results of zircon U-Pb isotopic dating show that the primary rocks of the Beidabie migmatite are mainly from Neoproterozoic rocks and a small amount of Paleoproterozoic crust.The migmatization lasted from 145 Ma to 124 Ma.The temperature and pressure conditions of the mixed rocks are 723-768 擄C and 3.7-5.2 kbar. which correspond to the middle and upper crustal environment.The genetic mechanism of migmatite is water-rich melting of felsic gneiss under water saturation.The reaction was: biotite quartz plagioclase water = amphibole plagioclase (residual) granitic melt.The genetic mechanism of a few mixed rocks is dehydration and melting of amphibole in hornblende gneiss.The reaction is: amphibole plagioclase quartz = clinopyroxene rich water melt.
【學位授予單位】：合肥工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P588.36

【參考文獻】

相關期刊論文 前10條

1 劉曉強;閆峻;王愛國;李全忠;張媛媛;;大別造山帶岳西地區(qū)中生代巖漿巖年代學研究[J];地質論評;2016年04期

2 曾令森;梁鳳華;Paul Asimow;陳方遠;陳晶;;深俯沖陸殼巖石部分熔融與蘇魯超高壓榴輝巖中長英質多晶包裹體的形成[J];科學通報;2009年13期

3 ;A perspective view on ultrahigh-pressure metamorphism and continental collision in the Dabie-Sulu orogenic belt[J];Chinese Science Bulletin;2008年20期

4 李全忠;謝智;徐夕生;陳江峰;高天山;;大別造山帶早白堊世基性巖的同位素特征及下地殼物質對巖漿源區(qū)的貢獻[J];巖石學報;2008年08期

5 ;SHRIMP zircon U-Pb dating for two episodes of migmatization in the Dabie orogen[J];Chinese Science Bulletin;2007年13期

6 ;Architecture and Kinematics of the Dabie Orogen,Central Eastern China[J];Acta Geologica Sinica(English Edition);2005年03期

7 吳元保;鄭永飛;龔冰;唐俊;趙子福;查向平;;北淮陽廬鎮(zhèn)關巖漿巖鋯石U-Pb年齡和氧同位素組成[J];巖石學報;2004年05期

8 謝智,陳江峰,張巽,周泰禧,楊剛,李惠民;北淮陽新元古代基性侵入巖年代學初步研究[J];地球學報;2002年06期

9 ;Discovery of the eclogite and its petrography in the Northern Dabie Mountain[J];Chinese Science Bulletin;2000年03期

10 鄧尚賢,王江海,孫敏,常向陽;湖北省羅田鳳凰關混合巖淺色體的類型及其鋯石U-Pb年齡[J];地球化學;1997年02期

，

本文編號：1772983