本文選題：元素地球化學(xué) + 礦物化學(xué)　； 參考：《礦物學(xué)報(bào)》2017年Z1期

【摘要】：位于新疆西天山北緣的博羅科努晚古生代島弧帶出露有大量的中酸性侵入體分布有一系列與斑巖-夕卡巖型鐵銅多金屬礦床,本文對該島弧帶中部闊庫確科夕卡巖型鐵銅礦區(qū)與成巖相關(guān)的花崗巖和閃長巖進(jìn)行了元素地球化學(xué)、礦物化學(xué)和鋯石U-Pb同位素年代學(xué)研究。巖體富Si和K,A/CNK1.1,屬于準(zhǔn)鋁質(zhì)-弱過鋁質(zhì)I型花崗巖。巖石富集輕稀土和大離子親石元素,虧損重稀土和高場強(qiáng)元素,具有明顯的Eu負(fù)異常,表現(xiàn)出俯沖帶巖漿作用特征。巖石Nb/Ta比值(9.8~13.3)、黑云母Mg O質(zhì)量分?jǐn)?shù)(9.45%~10.99%)和角閃石M值(0.73~0.85)均介于殼源型和幔源型之間,表明其形成具有殼幔源物質(zhì)參與。鋯石LA-ICP-MS U-Pb同位素定年結(jié)果顯示,花崗巖和閃長巖形成時(shí)代相近,二者加權(quán)平均年齡分別為(362.3±2.8)Ma和(363.4±3.7)Ma,Rb-(Yb+Nb)和Rb-(Yb+Ta)圖解顯示巖石幾乎都為火山弧花崗巖,(Sr/Y)-Y和(La/Yb)N-YbN圖解顯示它們均屬經(jīng)典島弧巖石,說明巖體形成于晚泥盆世板塊俯沖的大地構(gòu)造背景下。鋯石飽和溫度(705~760℃)和黑云母形成溫度(710~750℃)顯示巖體為下地殼部分熔融的產(chǎn)物,Th/Ce-Sr/Th和Th/Yb-Sr/Yb的關(guān)系反映成巖流體來自于沉積物脫水,Harker圖解以及Ba、Sr、P、Ti和Eu等元素的顯著虧損,暗示結(jié)晶分異作用的發(fā)生。我們認(rèn)為,晚泥盆世時(shí)期,在北天山洋向伊犁板塊俯沖的構(gòu)造背景下,俯沖帶沉積物脫水產(chǎn)生的流體引發(fā)下地殼發(fā)生部分熔融,伴隨著地幔物質(zhì)的加入以及一定程度的結(jié)晶分異作用,形成了闊庫確科礦區(qū)巖體。
[Abstract]:The late Paleozoic island arc belt of Bolokonu in the northern margin of the western Tianshan Mountains of Xinjiang has a large number of intermediate-acid intrusive bodies distributed in a series of iron and copper polymetallic deposits related to porphyry skarn type.Element geochemistry, mineral chemistry and zircon U-Pb isotopic chronology of diagenetic granite and diorite in the Kuankuchoko skarn type iron-copper deposit in the middle of the island arc belt have been studied in this paper.The rock mass is rich in Si and K _ (1) A / CNK _ (1.1), and belongs to quasi-aluminum-weakly peraluminous I-type granite.The rocks are enriched with light rare earth elements and large ion lithophile elements, and are depleted of heavy rare earth elements and high field strength elements, with obvious EU negative anomalies, showing the characteristics of magmatism in subduction zones.The Nb/Ta ratio of rocks and the mass fraction of biotite mg O are 9.450.99 and 0.730.85, respectively, which are between the crust-source and mantle-derived types, indicating that the formation of the rocks is characterized by the involvement of crust-mantle material.The isotopic dating of zircon LA-ICP-MS U-Pb shows that the age of formation of granite and diorite is similar.The weighted mean ages are 362.3 鹵2.8)Ma and 363.4 鹵3.7 MaRb-Yb Nb and Rb-(Yb Tab, respectively. The graphical analysis shows that the rocks are almost all volcanic arc granites, Sr-P / Y ~ (-Y) -Y ~ (-Y) and La / R _ (Yb) N-YbN, which indicate that the rocks were formed in the tectonic setting of the subduction of the late Devonian plate.The relationship between the saturation temperature of zircon (705 ~ 760 鈩，

本文編號：1748275