本文選題：青海南山 + 西秦嶺北緣��； 參考：《大地構(gòu)造與成礦學(xué)》2017年05期

【摘要】：青海南山構(gòu)造帶是銜接宗務(wù)隆構(gòu)造帶、南祁連構(gòu)造帶和西秦嶺造山帶的重要結(jié)合帶。溝后巖漿雜巖體位于青海南山構(gòu)造帶東段,主要由輝長巖、輝長閃長巖、石英閃長巖、花崗閃長巖組成。本文對溝后巖漿雜巖體進(jìn)行了詳細(xì)的巖石學(xué)、巖石地球化學(xué)和LA-ICP-MS鋯石U-Pb同位素年代學(xué)研究。結(jié)果表明,輝長巖、輝長閃長巖、石英閃長巖、花崗閃長巖及暗色微粒包體的結(jié)晶年齡分別為248.8±2.6 Ma、243.2±2.1 Ma、243.1±0.9 Ma、244.0±2.1 Ma和249±3 Ma。輝長巖富鐵、鎂,貧堿;輝長閃長巖高鋁、富鈣和鈉,二者均為鈣堿性巖類。石英閃長巖和花崗閃長巖為準(zhǔn)鋁-弱過鋁質(zhì)高鉀鈣堿性巖,暗色微粒包體屬鈣堿性-堿性巖系列。不同巖石類型均表現(xiàn)為富集大離子親石元素(Cs、Rb、K)和Pb,虧損高場強(qiáng)元素(Nb、Ta、Ti)和P、Ba負(fù)異常;稀土元素配分曲線均具有輕重稀土分異的右傾特征,具弱-中等負(fù)Eu異常。巖相學(xué)和巖石地球化學(xué)特征表明溝后巖漿雜巖體具殼幔巖漿混合特征,暗示其可能形成于由俯沖流體交代地幔楔部分熔融的幔源巖漿底侵作用下的構(gòu)造環(huán)境。輝長巖為幔源巖漿經(jīng)分離結(jié)晶的產(chǎn)物,輝長閃長巖為幔源巖漿經(jīng)分異演化并混染少量殼源巖漿的產(chǎn)物;中基性巖漿與殼源中酸性巖漿發(fā)生混合并經(jīng)歷一定的分異演化過程形成了石英閃長巖和花崗閃長巖。結(jié)合區(qū)域地質(zhì)資料分析認(rèn)為,溝后巖漿雜巖體可能代表了研究區(qū)早三疊世晚期-中三疊世早期宗務(wù)隆洋向南消減作用相關(guān)的構(gòu)造巖漿事件。
[Abstract]:The Nanshan tectonic belt in Qinghai is an important conjunctive zone connecting Zongwu uplift tectonic belt, South Qilian tectonic belt and West Qinling orogenic belt. The Gouhou magmatic complex is located in the eastern segment of the Nanshan tectonic belt in Qinghai Province and is mainly composed of gabbro, pyroxenite, quartz diorite and granodiorite. In this paper, detailed petrology, geochemistry and U-Pb isotopic chronology of LA-ICP-MS zircon have been carried out for the Gouhou magmatic complex. The results show that the crystallization ages of gabbro, pyrodiorite, quartz diorite, granodiorite and dark particle inclusions are 248.8 鹵2.6 Ma-243.2 鹵2.1 Ma-243.1 鹵0.9 Ma-244.0 鹵2.1 Ma and 249 鹵3 Ma, respectively. Gabbro is rich in iron, magnesium and alkali, and pyroxenite is high in aluminum, calcium and sodium, both of which are calc-alkaline. Quartz diorite and granodiorite are quasi-aluminum-weakly peraluminous high-potassium calc-alkaline rocks, and the dark particle inclusions belong to the calc-alkaline rock series. The different rock types are characterized by enrichment of large ion lithophile elements (Cslr Rbtl K) and Pb, and depletion of high field strength elements (NbTX Tatii) and PnbBa negative anomalies, and the REE partition curves all have the characteristics of right deviation of REE differentiation and weak to medium negative EU anomalies. The petrographic and petrogeochemical characteristics indicate that the Gouhou magmatic complex is characterized by a mixture of crust-mantle magma, suggesting that it may have been formed in a tectonic environment in which mantle magma submersed by subducting fluid metasomatic mantle wedge partially melted. Gabbro is the product of the separation and crystallization of mantle-derived magma, while the amphiolite is the product of the differentiation and evolution of mantle-derived magma and mixed with a small amount of crust-derived magma. The intermediate-basic magma and crust intermediate-acid magma mix and undergo a process of differentiation and evolution to form quartz diorite and granodiorite. Based on the analysis of regional geological data, it is concluded that the Gouhou magmatic complex may represent the tectonic magmatic events related to the subduction of Zongwulong ocean in the late early Triassic to the early Middle Triassic in the study area.
【作者單位】： 西部礦產(chǎn)資源與地質(zhì)工程教育部重點(diǎn)實(shí)驗(yàn)室國土資源部巖漿作用成礦與找礦重點(diǎn)實(shí)驗(yàn)室長安大學(xué)地球科學(xué)與資源學(xué)院;山東理工大學(xué)資源與環(huán)境工程學(xué)院;中國地質(zhì)大學(xué)(北京)地球科學(xué)與資源學(xué)院;南陽理工學(xué)院土木工程學(xué)院;
【基金】：國家自然科學(xué)基金(41472191、41502191、41172186) 中國地質(zhì)調(diào)查局地質(zhì)調(diào)查項(xiàng)目(12120114041201、12120114018219) 中央高�；究蒲袠I(yè)務(wù)費(fèi)專項(xiàng)資金(CHD2011TD020、2013G1271091、2013G1271092)聯(lián)合資助
【分類號】：P581;P597.3

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