本文選題：藏北羌塘榮瑪鄉(xiāng)地區(qū) + 晚古生代�。� 參考：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：藏北羌塘榮瑪鄉(xiāng)地區(qū)的晚古生代基性巖位于龍木錯-雙湖縫合帶、羌塘中央隆起帶南緣,屬于羌塘中部基性巖墻群的一部分,其產(chǎn)出于石炭世-早二疊世裂谷型沉積為主的淺變質(zhì)巖系中,主要由輝綠玢巖、輝長巖、輝綠輝長巖和玄武巖組成;對其中的輝綠玢巖進行LA-ICP-MS鋯石U-Pb定年,獲得其加權(quán)平均年齡值為(334.7±3.6)Ma。基性侵入巖與玄武巖二者在空間上密切共生,地球化學(xué)特征較為相似,均顯示富Ca O、Mg O、Al2O3,貧堿,低P2O5、Ti O2的特征。大離子親石元素Rb、Th、U、Pb相對富集,高場強元素Nb、Ta、Ti、P相對虧損,玄武巖較基性侵入巖有更為明顯的Nb、Ta虧損,可能其巖漿在上升過程中受到地殼物質(zhì)的混染所致。輕、重稀土元素分餾明顯,輕稀土元素總量高于重稀土元素,微量元素構(gòu)造環(huán)境判別圖解均顯示其形成于大陸板內(nèi)陸內(nèi)裂谷環(huán)境。由二者野外的接觸關(guān)系及地球化學(xué)特征可知,其應(yīng)具有相同的源區(qū)。微量元素Nb/Zr圖和Y/Zr圖顯示基性巖漿來源于由榴子石+尖晶石二輝橄欖巖組成的富集地幔源區(qū),其熔融程度在10%~20%之間。研究區(qū)基性巖應(yīng)為岡瓦納北緣裂解的產(chǎn)物,其圍巖是一套至少從早石炭世大塘期就已經(jīng)開始接受裂谷型沉積的地層。
[Abstract]:The late Paleozoic basic rocks in Rongmaxiang area, Qiangtang, northern Tibet, are located in the Longmuco-Shuanghu suture zone, the southern margin of the central Qiangtang uplift belt, and belong to the central Qiangtang basic rock dike group. It occurred in the Carboniferous to early Permian rift type sedimentary shallow metamorphic series, mainly composed of pyroxene porphyrite, pyroxene, pyroxene and basalt, and carried out LA-ICP-MS zircon U-Pb dating of the pyroxene porphyrite. The weighted average age was (334.7 鹵3. 6) Ma. The basic intrusive rocks and basalts are closely symbiotic in space, and their geochemical characteristics are similar, indicating that they are rich in Ca, O, mg, O, Al 2O 3, poor in alkali and low in P _ 2O _ 5 and Ti _ 2O _ 2. The heavy ion lithophile element RbPe, the high field strength element NbtadaTiOP is relatively depleted, and the basalt has a more obvious Nb-Ta depletion than that of the basic intrusive rock, which may be caused by the mixing of crustal materials during the rising process of the magma. The fractionation of light and heavy rare earth elements is obvious and the total amount of light rare earth elements is higher than that of heavy rare earth elements. According to the contact relationship and geochemical characteristics of the two in the field, it should have the same source area. The trace element NB / Zr and Y / Zr diagrams show that the basic magma is derived from the enriched mantle source consisting of eclogite spinel and peridotite, and its melting degree is between 10% and 20%. The basic rock in the study area should be the product of pyrolysis in the northern margin of Gondwana, and its surrounding rock is a set of strata which have been receiving rift type sediments since at least the early Carboniferous Datang period.
【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】：P588.124

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