摘要
通过对西准噶尔北部博什库尔-成吉斯岩浆弧内谢米斯台山泥盆纪的火山岩进行地球化学及同位素年代学研究,结果显示:该火山岩岩石组合以钙碱性的玄武岩和玄武安山岩为主,岩石w(SiO2)为50.44%~56.35%,w(TiO2)为0.79%~1.53%;w(P2O5)为0.05%~0.27%,具有较高的w(Al2O3)(15.92%~18.07%)和w(MgO)(2.66%~5.55%),Mg#范围在47~57之间;稀土总含量(ΣREE)为41.73×10^-6~116.72×10^-6,平均77.34×10^-6,轻稀土(LREE)与重稀土(HREE)分异明显,其中LREE/HREE比值为6.45~8.17,平均7.34,(La/Yb)N=2.93~10.81,平均8.33,其呈现轻稀土富集,重稀土亏损,具弱的Eu正异常(δEu=1.26~1.58);富集Ba、Sr、U等元素,亏损高场强元素(如Nb、Ta、Ti),与典型的火山弧玄武岩地球化学特征相似,属于典型的岛弧岩浆岩,形成于与俯冲有关的岛弧环境。获得谢米斯台山火山岩中玄武安山岩的LA-ICP-MS锆石U-Pb年龄为(413.6±6.9)Ma,表明其形成于晚志留世-早泥盆世。结合前人的研究资料,认为博什库尔-成吉斯岩浆弧可能是早古生代末-早泥盆世古亚洲洋俯冲的地质记录。
In this paper,the geochemical and isotopic geochronological research is carried out on the Devonian volcanic rocks of the Shemistai Mountain range within the Boshkur-Gengis magmatic arc in the northern part of West Junggar Basin.It is shown that the volcanic rocks are composed of calcium-alkaline basalt and basalt andesite,with SiO 2 content of 50.44%–56.35%,TiO2 content of 0.79%–1.53%,P2O5 content of 0.05%–0.27%,high Al2O3 content of 15.92%–18.07%,MgO content of 2.66%–5.55%and Mg#value of 47–57.In addition,these rocks have total REE content of 41.73×10^-6–116.72×10^-6,with an average of 77.34×10^-6,the LREE/HREE ratios are 6.45–8.17 and(La/Yb)N=2.93–10.81,with an average of 8.33,which means that all the samples in the REE spider diagram show an enrichment of LREE(light rare-earth elements)and a depletion of HREE(heavy rare-earth elements).The Eu positive anomalies are in the range of 1.26–1.58.This is closely similar to the typical arc volcanic feature(enriched in Ba,Sr,U and depleted in Nb,Ta,Ti),and it is indicated that these rocks are formed in the subduction related to island arc environment.Moreover,the LA-ICP-MS zircon U-Pb dating age of basaltic andesite is(413.6±6.9)Ma,showing that the volcanic rocks of the Xiemisitai mountain range are formed in the Early Devonian.Consequently,the volcanic rocks of the Xiemisitai Mountain range is derived from the island arc environment related to the subduction of the Early Devonian.It is believed that the formation of Boshchekul-Chingiz magmatic arc might have an intimate relationship with the subduction of the Early Paleozoic(Early Devonian)ocean.
作者
谭震江
刘希军
张治国
李锐
刘鹏德
肖尧
宋宇嘉
张兆祺
TAN Zhenjiang;LIU Xijun;ZHANG Zhiguo;LI Rui;LIU Pengde;XIAO Yao;SONG Yujia;ZHANG Zhaoqi(Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration and Guangxi Collaborative Innovation Centre ofHidden Non–ferrous Metallic Ore Deposits Exploration and Development of Materials,Guilin University of Technology,Guilin 541006,Guangxi,China;Xinjiang Research Center for Mineral Resources,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Urumqi 830011,Xinjiang,China)
出处
《矿产与地质》
2020年第2期278-286,共9页
Mineral Resources and Geology
基金
国家自然科学基金(41772059)
2019年广西硕士研究生创新项目(YCSW2019155)共同资助。
