新疆西天山阔库确科铁铜矿区成矿岩体地球化学、年代学特征及其地质意义

发布时间：2018-04-14 07:24

  本文选题：元素地球化学 + 矿物化学　； 参考：《矿物学报》2017年Z1期

【摘要】：位于新疆西天山北缘的博罗科努晚古生代岛弧带出露有大量的中酸性侵入体分布有一系列与斑岩-夕卡岩型铁铜多金属矿床,本文对该岛弧带中部阔库确科夕卡岩型铁铜矿区与成岩相关的花岗岩和闪长岩进行了元素地球化学、矿物化学和锆石U-Pb同位素年代学研究。岩体富Si和K,A/CNK1.1,属于准铝质-弱过铝质I型花岗岩。岩石富集轻稀土和大离子亲石元素,亏损重稀土和高场强元素,具有明显的Eu负异常,表现出俯冲带岩浆作用特征。岩石Nb/Ta比值(9.8~13.3)、黑云母Mg O质量分数(9.45%~10.99%)和角闪石M值(0.73~0.85)均介于壳源型和幔源型之间,表明其形成具有壳幔源物质参与。锆石LA-ICP-MS U-Pb同位素定年结果显示,花岗岩和闪长岩形成时代相近,二者加权平均年龄分别为(362.3±2.8)Ma和(363.4±3.7)Ma,Rb-(Yb+Nb)和Rb-(Yb+Ta)图解显示岩石几乎都为火山弧花岗岩,(Sr/Y)-Y和(La/Yb)N-YbN图解显示它们均属经典岛弧岩石,说明岩体形成于晚泥盆世板块俯冲的大地构造背景下。锆石饱和温度(705~760℃)和黑云母形成温度(710~750℃)显示岩体为下地壳部分熔融的产物,Th/Ce-Sr/Th和Th/Yb-Sr/Yb的关系反映成岩流体来自于沉积物脱水,Harker图解以及Ba、Sr、P、Ti和Eu等元素的显著亏损,暗示结晶分异作用的发生。我们认为,晚泥盆世时期,在北天山洋向伊犁板块俯冲的构造背景下,俯冲带沉积物脱水产生的流体引发下地壳发生部分熔融,伴随着地幔物质的加入以及一定程度的结晶分异作用,形成了阔库确科矿区岩体。
[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 卤2.8)Ma and 363.4 卤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，

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