本文選題：青海省 + 賽多浦崗日　； 參考：《吉林大學(xué)》2015年碩士論文

【摘要】：賽多浦崗日二長(zhǎng)花崗巖體位于青海雁石坪西南約50km處，大地構(gòu)造上位于拉竹龍－金沙江縫合帶和班公錯(cuò)－怒江縫合帶之間的羌塘地塊北部，唐古拉邊緣前陸盆地的雁石坪坳陷中。本文通過(guò)對(duì)賽多浦崗日二長(zhǎng)花崗巖巖石學(xué)、巖石地球化學(xué)及礦物地球化學(xué)特征的研究，探討了其形成的源區(qū)性質(zhì)及大地構(gòu)造背景。同時(shí)為建立該類花崗巖礦物學(xué)標(biāo)型特征積累了數(shù)據(jù)資料。 二長(zhǎng)花崗巖巖石學(xué)研究表明，花崗巖中SiO2所占的比重大(70.89%~71.39%)，K2O含量高，略高于Na2O，顯示準(zhǔn)鋁質(zhì)-過(guò)鋁質(zhì)性質(zhì)，常量元素的地化特征表明，該花崗巖為I型花崗巖。樣品中輕重稀土分異明顯。稀土配分為不對(duì)稱向右陡傾的曲線，δEu值在0.56～0.68之間，為銪弱負(fù)異常，說(shuō)明其源區(qū)有少量斜長(zhǎng)石的殘留或存在分離結(jié)晶作用。富集LREEs，虧損HREEs和HFSEs，Sr/Y比值介于72.47～83.48之間，大于40%，LaN/YbN比值介于53.06～107.36之間，大于20%等這些特點(diǎn)顯示出埃達(dá)克巖的地球化學(xué)特征，說(shuō)明該花崗巖為埃達(dá)克質(zhì)巖石。通過(guò)討論得出花崗巖形成于加厚的鎂鐵質(zhì)下地殼部分熔融過(guò)程。鋯石U-Pb法測(cè)年得出賽多浦崗日地區(qū)二長(zhǎng)花崗巖的時(shí)代為古近紀(jì)中的古新世。 斜長(zhǎng)石成分測(cè)試表明，斜長(zhǎng)石牌號(hào)較高，An介于24.83到31.66之間，屬于更長(zhǎng)石與中長(zhǎng)石。斜長(zhǎng)石環(huán)帶從核部到外部An牌號(hào)依次為An31.66-An31.12-An24.84-An26.37-An25.23，顯示為韻律環(huán)帶，從核部-中間環(huán)帶An牌號(hào)反而升高，出現(xiàn)斜長(zhǎng)石的反環(huán)帶可認(rèn)為發(fā)生過(guò)巖漿混合作用，，也說(shuō)明該花崗巖為新生代花崗巖。堿性長(zhǎng)石礦物中，Or含量為67.78%-92.58%，Ab次之,為7.32%-31.44%， An分子含量很少都小于1，屬于正長(zhǎng)石。黑云母電子探針?lè)治霰砻�，黑云母為高鐵鎂云母。 巖石地球化學(xué)測(cè)試數(shù)據(jù)反映在造山帶演化的Y-Nb圖上，樣品投入到島弧花崗巖區(qū)域，同時(shí)也投入到了同碰撞區(qū)域，在R1-R2圖上，樣品投入到了同碰撞區(qū)域，因此該區(qū)的地殼加厚過(guò)程可能是由板塊碰撞導(dǎo)致的，說(shuō)明本時(shí)代花崗巖可能是由于板塊之間的碰撞導(dǎo)致了地殼變厚形成的。黑云母富鎂、相對(duì)富鋁以及缺少鈦等特性表明，二長(zhǎng)花崗巖形成于造山構(gòu)造環(huán)境。 上述研究表明，二長(zhǎng)花崗巖巖石地球化學(xué)特征與礦物地球化學(xué)特征可以相互佐證，為利用礦物地球化學(xué)特征判斷花崗巖巖石成因、物質(zhì)來(lái)源及構(gòu)造背景提供理論依據(jù)。
[Abstract]:The Xidopugang Erzhang granite body is located about 50km southwest of Yanshiping, Qinghai, and is located in the north of the Qiangtang block between the LazhulongJinshajiang suture belt and the Bangongcao-Nujiang suture belt. The Yanshiping depression in the Foreland basin of Tanggula margin. In this paper, the petrology, geochemistry and mineral geochemistry characteristics of the Xidopugang Erzhang granite are studied, and the origin properties and tectonic setting of the source region are discussed. At the same time, it accumulates data for the establishment of mineralogical typomorphic characteristics of this kind of granite. The petrological study shows that the content of K _ 2O is high (70.89%) and slightly higher than that of Na _ 2O, indicating that the granite is quasi-aluminum-peraluminous and characterized by geochemistry of the major elements, which indicates that the granite is I-type granite. The difference of light and light rare earth elements in the sample is obvious. The rare earth distribution can be divided into asymmetrical and steep right dip curves. The 未 EU value is between 0.56 and 0.68, which is a weak negative anomaly of europium, indicating that there is a small amount of plagioclase residue or separation and crystallization in its source region. LREEs-enriched, depleted HREEs and HFSEsN Sr-r-Y ratios between 72.47 and 83.48, larger than 40% LaN- / YbN ratios between 53.06 and 107.36, and more than 20% show the geochemical characteristics of the adakites, indicating that the granites are adakitic rocks. Through discussion, it is concluded that granite formed in the partial melting process of thickened magnesia-iron lower crust. Zircon U-Pb dating indicates that the age of the two feldspar granites in the Sedopu Gangri area is Paleogene in the Middle Paleogene. The composition test of plagioclase shows that the plagioclase grade is between 24.83 and 31.66, which belongs to the more feldspar and the meso-feldspar. The number of an of plagioclase is An31.66-An31.12-An24.84-An26.37-An25.23, which is a rhythmic ring, and the number of an from nuclear to middle annulus increases, and the anticlinal zone of plagioclase can be considered to have magmatic mixing. It also shows that the granite is a Cenozoic granite. In alkaline feldspar minerals, the content of Or is 67.78 -92.58% and the second is 7.32- 31.444.The content of an molecule is rarely less than 1, and belongs to orthoclase. The electron probe analysis of biotite shows that biotite is high-iron magnesium mica. The geochemistry data are reflected on Y-Nb diagram of orogenic belt evolution. Samples are input to island arc granite area, and also to the same collision area. In R1-R2 diagram, the sample is input into the same collision area. Therefore, the crustal thickening process in this area may be caused by plate collision, which suggests that the granite in the present age may have been thickened due to the collision between plates. The characteristics of biotite rich in magnesium, relatively rich in aluminum and lack of titanium indicate that the monzogranite was formed in the orogenic tectonic environment. The above results show that the geochemical characteristics of the rock and mineral geochemistry of the monzogranite can be mutually corroborated, which provides a theoretical basis for judging the genesis, material source and tectonic background of the granite by using the geochemical characteristics of the minerals.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P588.121

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