新疆阿舍勒铜锌矿区潜玄武安山岩的岩石地球化学特征及其地质意义  

Geochemical characteristics of basaltic andesite subvolcanic rocks in the Ashele Cu_Zn deposit and their geological significance

作　　者：吴玉峰[1] 杨富全[1] 刘锋[1] 

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037

出　　处：《岩石矿物学杂志》2016年第1期65-80,共16页Acta Petrologica et Mineralogica

基　　金："十二五"国家科技支撑计划项目(2011BAB06B03_02);国家自然科学基金项目(41272103)~~

摘　　要：对新疆阿舍勒铜锌矿区潜玄武安山岩进行了岩石学、岩石地球化学和同位素地球化学研究,结果表明:岩石具有中等的SiO_2(51.90%~52.85%)、MgO(4.44%~5.08%)、Al_2O_3(14.94%~16.11%)、TiO_2(0.99%~1.03%)含量,较低的K_2O(0.01%~0.27%)含量,属于低钾拉斑玄武岩系列;岩石具有较低的稀土元素总量,ΣREE=38.07×10^(-6)~41.70×10^(-6),亏损轻稀土元素,LREE/HREE=0.57~0.61,(La/Yb)N=0.84~0.91,具有明显Eu正异常(δEu=1.13~1.23);富集Sr、Ba、Th等大离子亲石元素,亏损Nb、Ta、Zr、Hf等高场强元素,具有洋中脊玄武岩(MORB)和岛弧拉斑玄武岩(IAB)的特征,形成于岛弧(或弧前)环境;具有相对高的εNd(t)值(+6.9^+7.6),表明其原始岩浆来源于俯冲流体交代地幔楔的部分熔融,没有明显深海沉积物加入。结合阿尔泰造山带南缘的区域地质资料及潜玄武安山岩的地球化学特征,认为阿尔泰南缘在晚古生代处于活动大陆边缘,阿舍勒盆地处于岛弧(或弧前)背景。Geology, geochemistry and isotopic geochemistry are reported for the subvolcanic rocks from the Ashele Cu-Zn deposit. The rocks are basaltic andesites belonging to low-K tholeiite series, and are characterized by intermediate SiO2 （51 .90% - 52,85% ）, MgO （4.44% - 5.08% ）, Al2O3 （ 14.94% - 16.11% ）, TiO2 （0.99% - 1.03% ） values and low K20 （0.01%- 0.27% ） content. They have low REE values （EREE = 38.07 × 10 6-41.70 × 10^ 6） and exhibit LREE depletion with LREE/HREE ratio of 0.57-0.61 and （La/Yb）N ratio of 0.84-0.91, and positive Eu anomaly. The trace elements are characterized by enrichment of Sr, Ba, and Th and depletion of Nb, Ta, Zr and Hr. They show both compositional characteristics of the mid-ocean ridge basalt （MORB） and the island arc basalt （IAB）. Relatively high εNd （t） values （＋ 6.9± 7.6） suggest that their primitive magma was possibly generated by partial melting of a metasomatic mantle source modified by the subducted slab-derived fluid rather than by the slab-derived melt. Combined with the tectonic evolution of the southern margin of the Altay, the authors hold that the southern margin of the Altay was in an active continental margin setting during the late Paleozoic, and the Ashele Basin was in an island arc or forearc setting.

关 键 词：潜玄武安山岩 地球化学 SR-ND同位素 岛弧背景 阿舍勒 

分 类 号：P588.13[天文地球—岩石学] P59[天文地球—地质学]