新疆西准噶尔萨吾尔地区早石炭世埃达克岩地球化学特征、岩石成因及其意义  

Geochemistry,petrogenesis and geological significance of Early Carboniferous adakite in Sawuer region,West Junggar,Xinjiang

作　　者：李海 李永军[1,2] 徐学义 杨高学[1,2] 王祚鹏 徐倩[1] 宁文涛 LI Hai;LI YongJun;XU XueYi;YANG GaoXue;WANG ZuoPeng;XU Qian;NING WenTao(School of Earth Science and Resources,Chang'an University,Xi'an 710054,China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,MNR,Xi'an 710054,China;China Aero Geophysical Survey&Remote Sensing Center for Land and Resources,Beijing 100083,China)

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]自然资源部岩浆作用成矿与找矿重点实验室,西安710054 [3]中国自然资源航空物探遥感中心,北京100083

出　　处：《岩石学报》2020年第7期2017-2034,共18页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41273033);国家重点研发计划项目(2018YFC0604001);中央高校专项基金(300102279209)联合资助。

摘　　要：新疆西准噶尔萨吾尔地区阿克塔木组(新建)为一套中性火山熔岩、火山碎屑岩夹少量酸性火山熔岩建造。流纹岩LA-ICP-MS锆石U-Pb年龄为337.9±0.77Ma,属早石炭世。安山岩地球化学特征表现为高SiO2(53.42%~64.74%)、Al2O3(16.05%~19.23%),富Na2O(4.05%~8.13%)贫K2O(0.36%~3.65%),富Sr(448.1×10^-6~1507×10^-6),低Yb(0.94×10^-6~1.79×10^-6)、Y(8.48×10^-6~16.92×10^-6),高Sr/Y比值(36.6~89.0),富集LREE,亏损HREE,弱Eu正异常,明显的Nb、Ta、Ti负异常,具有典型的埃达克岩特征,为玄武质洋壳在石榴角闪岩相高度部分熔融的产物。阿克塔木组火山岩形成于与洋内俯冲有关的岛弧环境,为早石炭世额尔齐斯-斋桑洋南向俯冲的岩浆记录。俯冲板片边缘受到来自板片窗的高温软流圈物质加热,部分熔融形成的埃达克质熔体与地幔橄榄岩发生熔体-岩石反应,从而形成埃达克岩+富Nb玄武岩组合,同时发生与之相关的Cu-Au成矿作用。阿克塔木组早石炭世埃达克岩的发现,为西准噶尔地区晚古生代岩浆活动、构造演化和金属成矿等研究提供了可靠的依据。The Aketamu Formation,as a new defined lithostratigraphic unit in Sawuer region,West Junggar,is composed of intermediate volcanic lavas and pyroclastic rocks,with minor of acidic volcanic lavas.The LA-ICP-MS zircon U-Pb age of rhyolite from the Aketamu Formation is 337.9±0.77Ma.Therefore,the rhyolite is formed in Early Carboniferous.Geochemically,the andesites in the Aketamu Formation are characterized by high SiO2(53.42%~64.74%),Al2O3(16.05%~19.23%)and Na2O(4.05%~8.13%),and low K2O(0.36%~3.65%).They have high Sr(448.1×10^-6~1507×10^-6)contents,high Sr/Y(36.6~89.0)ratios,and slightly positive Eu anomalies.Moreover,the andesites are enriched in large-ion-lithophile elements(such as K,Rb,Ba,Th and U)and light rare earth elements,and are depleted in high-field-strength elements(such as Nb,Ta and Ti)and heavy rare earth element,especially Y and Yb,showing the characters of a typical adakite.The studied results show that the andesites from Aketamu Formation were the products resulting from slab melting,with the residual minerals(eg.amphibole+garnet)in the source of garnet amphibolite.In combination with the regional geological background,the authors hold that the subducted oceanic slab edges were heated by the asthenospheric mantle rise through slab window,which is the result of the southward subduction of the Irtysh-Zaysan Ocean between Kazakhstan in the south and Altai in the north.The reaction of upward migrating adakitic magmas with mantle peridotite gave rise to the adakite and Nb-enriched arc basalt suites,and led to the Cu-Au mineralization at the same time.The discovery of Early Carboniferous adakite in Aketamu Formation provides evidence for further understanding of the Late Paleozoic tectonic evolution,magmatism and metallogenic of ore deposits in West Junggar.

关 键 词：埃达克岩 早石炭世 阿克塔木组 萨吾尔地区 西准噶尔 

分 类 号：P588.14[天文地球—岩石学] P597.3[天文地球—地质学]