本文關(guān)鍵詞：西藏納木錯西蛇綠巖成巖成礦作用　出處：《成都理工大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 蛇綠巖 巖石學(xué) 巖石地球化學(xué) 構(gòu)造意義

【摘要】：蛇綠巖對古板塊運(yùn)動具有指示作用,同時其賦存的鉻鐵礦等礦產(chǎn)是我國所短缺的礦產(chǎn)類型,所以蛇綠巖的研究具有重大的意義。納木錯西地處拉薩板塊中部,班公湖-怒江縫合帶與雅魯藏布江縫合帶之間的拉果錯—嘉黎蛇綠混雜巖帶東段;蛇綠巖分布錯亂,巖塊支離破碎,但巖石類型齊全,地幔橄欖巖類、堆晶雜巖類、鎂鐵質(zhì)席狀巖墻雜巖類、火山雜巖類及放射蟲硅質(zhì)巖等在研究區(qū)均有出露。研究區(qū)位置的蛇綠巖研究程度不高,且該區(qū)域蛇綠巖的形成環(huán)境及構(gòu)造單元?dú)w屬存在較大的爭議;此外區(qū)內(nèi)礦產(chǎn)多為新發(fā)現(xiàn)的礦床,研究其成礦作用對找礦前景具有重大意義。本文根據(jù)野外作業(yè)所得的資料與室內(nèi)研究相結(jié)合,分析巖石組合、巖石地球化學(xué)等特征,從而對納木錯西蛇綠巖各組成單元及其形成的構(gòu)造環(huán)境以及巖漿巖源區(qū)等進(jìn)行深入討論。結(jié)合在區(qū)域上構(gòu)造演化的特征,對納木錯西地區(qū)的構(gòu)造演化的研究提出新的地質(zhì)依據(jù)及地質(zhì)認(rèn)識。此外,對研究區(qū)內(nèi)與蛇綠巖建造有關(guān)的金屬礦產(chǎn),如鉻鐵礦、鎳礦等,研究其礦產(chǎn)特征并對比他區(qū)蛇綠巖成礦作用,分析研究區(qū)蛇綠巖中礦產(chǎn)成因等。主要成果如下:(1)納木錯西蛇綠巖帶巖石組合齊全,包括地幔橄欖巖、堆晶雜巖、席狀巖墻群、枕狀玄武巖四個單元,發(fā)現(xiàn)的伴生產(chǎn)物有條帶狀放射蟲硅質(zhì)巖及沉凝灰?guī)r等。(2)研究區(qū)內(nèi)蛇綠巖自底部到頂部其元素含量具有一個逐漸變化的過程;很好的解釋了各單元的產(chǎn)生順序。(3)綜合前人研究數(shù)據(jù)和本次研究的玄武巖測年數(shù)據(jù)以及放射蟲硅質(zhì)巖中采獲化石得出納木錯西蛇綠巖形成年代大致在晚侏羅世晚期的結(jié)論。(4)通過一系列巖石化學(xué)圖解處理玄武巖的地學(xué)數(shù)據(jù),了解到納木錯西蛇綠巖類似于消減帶上的弧后盆地,通過洋中脊擴(kuò)張作用產(chǎn)生。結(jié)合區(qū)域上發(fā)生的地質(zhì)構(gòu)造事件發(fā)現(xiàn)中生代時,中北岡底斯巖漿弧并不是一個統(tǒng)一的陸塊,侏羅紀(jì)時,在其中北部一個伸展體制下形成了一個弧后盆地,并在早白堊世前消減閉合。(5)研究區(qū)中鉻鐵礦是當(dāng)俯沖板塊俯沖熔融的同時其中的水和CO_2逸散,形成熱流進(jìn)入地幔,導(dǎo)致地幔物質(zhì)熔點(diǎn)降低,進(jìn)而促進(jìn)地幔橄欖巖的熔融,而一次或者數(shù)次熔融過程之后,導(dǎo)致鉻富集,最終形成鉻鐵礦。(6)通過對比研究發(fā)現(xiàn),研究區(qū)內(nèi)玉古拉鎳礦床的巖石學(xué)特征及巖石化學(xué)特征均與國內(nèi)先前發(fā)現(xiàn)的幾種鎳礦床類型有較大的區(qū)別,可能為一種新的鎳礦床成礦模式。
[Abstract]:The ophiolite could indicate the paleo plate movement, and the occurrence of chromite mineral resources in China are the shortage of mineral types, so the study of ophiolite is of great significance. The Nam Co is located in the Central West Lhasa plate, the Bangong Lake Nu River suture zone and the Yarlung Zangbo Suture Zone between Lagkor co - Jiali OPHIOLITIC MELANGE zone; ophiolite rock distribution disorder, but the rock types, reduced to fragments, mantle peridotite, cumulate complex rocks, mafic sheeted dyke complex, volcano complex rocks and radiolarian siliceous rocks in the study area were exposed. The location of the study area of ophiolite research degree high, and the area of the ophiolite controversial environment and tectonic units belong; in addition in mineral for new deposits, the mineralization is of great significance to prospecting. Based on the field work of the The data and laboratory research combined with analysis of rock composition, geochemical characteristics, and in-depth discussion on tectonic environment of each unit of ophiolite and the formation of the West Nam Co and magmatite source area. Combining the characteristics of the tectonic evolution in the region, put forward the understanding of geological basis and new geological structure of West Nam Co the evolution of the area. In addition, the study area and the ophiolite formation about metal mineral, such as chromite, nickel ore, study its mineral characteristics and contrast the ophiolite metallogenic analysis, mineral genesis of ophiolite. The main results are as follows: (1) west of Nam Co ophiolite rock combination complete, including the mantle peridotite cumulate complex, sheeted dike swarm, Pillow Basalt four units, found a byproduct of banded radiolarian siliceous rock and tuff. (2) in the study area from ophiolite The bottom to the top of the element content is a process of gradual change; a good explanation of the order of each unit. (3) the previous research data and the study of the Xuan Wuyan dating data and radiolarian siliceous rocks has been collected in the fossil that Nam Co West ophiolite formed in Late Jurassic generation roughly conclusion. (4) data through a series of rock chemical graphic processing Xuan Wuyan, learned that Nam Co West ophiolite is similar to the subduction zone of the back arc basin, produced by the effect of ocean ridge spreading. Combining with the geological structure that happened on the part that regional Mesozoic, North Gangdise magmatic arc is not a unified Jurassic continental block, in which a northern extension system formed a back arc basin, and cut closed in the early Cretaceous. (5) chromite in the study area is when the subducting plate subduction and its melting The water and the emission of CO_2, the formation of heat flow into the mantle, the mantle material leads to low melting point, and then promote the partial melting of mantle peridotite and one or several times after the melting process, resulting in chromium enrichment, and ultimately the formation of chromite. (6) it is found that both the petrological characteristics and chemical characteristics of rocks in the research area of jade goulas there is great difference between the nickel deposit and several nickel deposit types previously found at home, may be a new nickel deposit metallogenic model.

【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：P611;P588

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