本文選題：滿洲里東部　切入點(diǎn)：白云母花崗巖　出處：《吉林大學(xué)》2017年碩士論文

【摘要】：眾多研究顯示,白云母花崗巖有其特殊的巖石成因及構(gòu)造意義,與白云母花崗巖分布非常較廣、研究程度較高的我國華南地區(qū)相比,在被譽(yù)為“花崗巖�！钡拇�、小興安嶺地區(qū)卻鮮有白云母花崗巖出露,因而相關(guān)研究也很少。幸運(yùn)的是,我們在大興安嶺中部的滿洲里東部發(fā)現(xiàn)了石榴石白云母花崗巖,本文對其進(jìn)行詳細(xì)的巖相學(xué)、鋯石U-Pb年代學(xué)、地球化學(xué)以及鋯石Hf同位素的研究,討論了其巖石成因和形成的構(gòu)造背景。所研究的石榴石白云母花崗巖出露于滿洲里東部的嵯崗鎮(zhèn)北部,包括中粒石榴石二云母花崗巖和細(xì)粒石榴石白云母花崗巖兩類,后者呈脈狀侵入到前者中。鋯石U-Pb測年結(jié)果顯示中粒二云母花崗巖形成于236±3Ma的中三疊世,細(xì)粒白云母花崗巖形成于130±2Ma的早白堊世。中粒二云母花崗巖和細(xì)粒白云母花崗巖都具有高硅(SiO2=74.65%-78.12%)富堿(Na2O+K2O=7.74%-8.35%)、貧鎂(Mg#=0.14-0.35)低鐵(TFe2O3=0.34%-1.03%)的地球化學(xué)特征,均屬于過鋁質(zhì)的高鉀鈣堿性系列。它們的稀土元素總含量都非常低(∑REE=17.73×10-6-73.52×10-6),相對富集輕稀土元素虧損重稀土元素,具有明顯負(fù)Eu異常(δEu=0.19-0.51);相對富集Rb、Th、K等大離子親石元素,而虧損Sr和Ba,虧損Nb、Zr、P、Ti等高場強(qiáng)元素,相對富集Ta。這兩類花崗巖的鋯石初始Hf同位素成分εHf(t)值分別為10.34-16.63和12.07-16.17,兩階段模式年齡(TDM2)分別為606-203Ma和413-138Ma。中粒二云母花崗巖和細(xì)粒白云母花崗巖的Zr含量(15.5×10-6-99.7×10-6)和(Zr+Nb+Ce+Y)含量(78.4×10-6-166.9×10-6)明顯低于典型的A型花崗巖的最小值250×10-6和350×10-6,且A/NK比值(1.17-1.24)大于A型花崗巖的平均值(1.05),結(jié)合分異指數(shù)(DI=92.60-95.75)及相關(guān)微量元素判別圖解,表明它們均是高分異的I型花崗巖。中粒二云母花崗巖顯示出低Sr高Yb的地球化學(xué)特征,屬于南嶺型花崗巖;細(xì)粒白云母花崗巖具有低Sr低Yb的地球化學(xué)特征,屬于喜馬拉雅型花崗巖。本文認(rèn)為這兩類花崗巖均起源于新增生的基性下地殼的部分熔融,但相比之下,細(xì)粒白云母花崗巖的巖漿源區(qū)更深。中三疊世中粒二云母花崗巖形成于與蒙古-鄂霍茨克構(gòu)造域有關(guān)的活動大陸邊緣環(huán)境,而早白堊世細(xì)粒白云母花崗巖形成于加厚巖石圈的伸展環(huán)境。
[Abstract]:Many studies have shown that Muscovite granite has its special petrogenetic and tectonic significance. Compared with Muscovite granite, which is widely distributed in South China, it is called "Granite Sea". However, there are few Muscovite granite exposed in Xiaoxinganling area, so there are few related studies. Fortunately, we found garnet Muscovite granite in the eastern part of Manzhouli in the central part of Daxing'an Mountains. Zircon U-Pb chronology, geochemistry and zircon HF isotopes are studied in this paper. The petrogenesis and tectonic setting of the zircon are discussed. The garnet Muscovite granites are exposed to the northern part of Sagangzhen, east of Manzhouli. There are two types of medium-grained garnet dimica granites and fine-grained garnet Muscovite granites, the latter being veined into the former. The zircon U-Pb dating results show that the medium-grained dimica granites were formed in the Middle Triassic of 236 鹵3Ma. The fine-grained Muscovite granites were formed in the early Cretaceous of 130 鹵2Ma. Both the medium-grained dimica granites and the fine-grained Muscovite granites have geochemical characteristics of high SiO2O2-74.65-78.12) alkali-rich Na2OK2O-7.74-8.35m, Mg#0.14-0.35) low Fe _ 2O _ 3- 0.34-1.03T). They all belong to peraluminous calc-alkaline series. The total contents of rare earth elements in them are very low (鈭，

本文編號：1692145