西准噶尔吾尔喀什尔地区泥盆纪火山岩锆石U-Pb年代学和地球化学研究  

U-Pb Zircon Dating and Geochimical Research of Devonian Volcanic Rocks in Ur kashgar of Western Junggar

作　　者：翁凯[1,2] 徐学义[1] 马中平[1] 孙吉明[1] 张涛[1,2] 

机构地区：[1]国土资源部岩浆作用成矿与找矿重点实验室,西安地质调查中心,西安710054 [2]长安大学地球科学与资源学院,西安710054

出　　处：《地质学报》2013年第4期515-524,共10页Acta Geologica Sinica

基　　金：阿尔泰-准噶尔北缘成矿带基础地质综合研究(编号1212011085009);天山成矿带基础地质综合研究(编号1212011085055);西北基础地质调查成果集成与综合研究(编号1212011220649)资助的成果

摘　　要：西准噶尔吾尔喀什尔地区萨吾尔山组上亚组的火山岩为一套浅海相中基性火山碎屑岩夹火山熔岩,对其内安山岩LA-ICP-MS锆石U-Pb测年结果显示其形成年龄为391±3Ma。本区火山熔岩都呈现出大离子亲石元素(K、Rb、Cs、Sr、Ba)富集、高场强元素(Nb、Ta、Zr、Hf)明显负异常等典型弧火山岩的地球化学特征,但玄武安山岩(SiO2=52.9%～55.3%)与安山岩(SiO2=62.01%～62.41%)之间具有明显不同的(La/Yb)N比值(分别为3.5～8.0、21.4～23.6),暗示它们具有不同的源区,偏基性的玄武安山岩的源区主要为被俯冲带流体不均一交代的地幔楔橄榄岩,而安山岩则具有类似于埃达克质岩浆的地球化学特征,为俯冲洋壳板片于榴辉岩相条件下发生部分熔融的产物。The igneous rocks in the upper Sawuershan Formation in the Ur kashgar area, West Junggar, are paralic mafic-intermediate pyroclastic rocks with volcano lava. LA-ICP-MS zircon U-Pb dating of the andesite yield an age of 391±3Ma. The igneous rocks are rich in LILE (K, Rb, Cs, Sr and Ba)and show negative anomalies in HFSE (Nb, Ta, Zr and Hf), reflecting typical geochemical characteristics of arc volcanic rocks. But basaltic andesite ( SiO2=52.9%~55.3% ) and andesite ( SiO2 62.01%~62.41% ) owns significantly different values of ( La/Yb )N (3.5~8.0,21.4~23.6 respectively), suggesting that they have different source areas. Basaltic andesite mainly sourced from mantle wedge peridotites metasomatized by fluid in subduction belt, while andesite has similar geochemical characteristics as adakitic magma, suggesting they were product of partially melting of subducted oceanic slab under eclogite facies conditions.

关 键 词：西准噶尔 泥盆纪 火山岩 地球化学 锆石U-PB测年 

分 类 号：P597.3[天文地球—地球化学]