新疆阿尔金喀腊大湾地区拉配泉组流纹岩年龄和地球化学特征及其对阿尔金北缘构造演化的启示  

Chronology and geochemical characteristics of the Lapeiquan Formation rhyolite in the Altun Kaladawan area,Xinjiang,and implications for tectonic evolution of the northern margin of Altun

作　　者：武彬[1] 王爱国[1] 彭博[1] 王继龙 张艺武 鲍晓明[1] 叶现韬[2] 于俊杰[1] WU Bin;WANG Aiguo;PENG Bo;WANG Jilong;ZHANG Yiwu;BAO Xiaoming;YE Xiantao;YU Junjie(Nanjing Center,China Geological Survey,Nanjing 210016,Jiangsu,China;College of Oceanography,Hohai University,Nanjing 210098,Jiangsu,China)

机构地区：[1]中国地质调查局南京地质调查中心,江苏南京210016 [2]河海大学海洋学院,江苏南京210098

出　　处：《地质通报》2023年第11期1894-1908,共15页Geological Bulletin of China

基　　金：国家科技支撑计划项目《甜水海-塔什库尔干地块基底演化与成矿》(编号:2015BAB05B01-02)。

摘　　要：由于新疆阿尔金拉配泉组研究程度较低,其沉积时代及构造成因仍存在疑问。以拉配泉组流纹岩为研究对象,开展年代学、地球化学等方面的研究。LA-ICP-MS锆石U-Pb测年结果显示,拉配泉组二段流纹岩年龄为497±2.0 Ma、三段流纹岩年龄为483.4±1.9 Ma。岩石地球化学研究显示,样品具有富硅(70.07%~78.55%)、低镁(0.32%~0.58%)、低Mg#(24~30)等特征。稀土元素分析结果显示,样品呈现富集轻稀土元素,相对亏损重稀土元素的特征,(La/Yb)_(N)=10.23~12.73,负Eu异常明显(δEu=0.10~0.19);微量元素分析结果显示,样品明显富集La、Nd、Zr、Ce、Sm、U、Th、Hf等,相对亏损Sr、Nb、Ti等。结合前人研究成果,厘定拉配泉组沉积时代为晚寒武世—早奥陶世。二段流纹岩具有A型花岗岩特征,可能主要来源于地壳物质的部分熔融,构造环境为北阿尔金洋回转引起的弧后伸展环境。Due to the low level studies on the Altun Lapeiquan Formation in Xinjiang,its depositional age and tectonic genesis are still in doubt.Chronological and geochemical studies were carried out on the rhyolites of the Lapeiquan Formation.The results of zircon LA-ICP-MS U-Pb dating show that the ages of the second and third member rhyolites of the Lapaiquan Formation are 497±2.0 Ma and 483.4±1.9 Ma,respectively.The petrogeochemical studies show that the samples are Si-rich(70.07%~78.55%),Mg-poor(0.32%~0.58%),and Mg#-low(24~30).The rare earth elements exhibit the characteristics of enrichment of light rare earth elements and relatively deficient in heavy rare earth elements((La/Yb)_(N)=10.23~12.73),and the negative Eu is abnormally obvious(δEu=0.10~0.19);the analysis of trace elements shows that the samples are obviously enriched in La,Nd,Zr,Ce,Sm,U,Th,Hf,etc.,and relatively deficient in Sr,Nb,Ti,etc.Combined with the previous researches,the depositional age of the Lapeiquan Formation is determined to be Late Cambrian-Early Ordovician.The second member of rhyolite has the characteristics of A-type granite,and it most likely came from partial melting of crustal materials,and the tectonic environment is a post-arc extensional environment caused by the reversal of the North Altun Ocean.

关 键 词：拉配泉组 流纹岩 U-PB年龄 地球化学 阿尔金 

分 类 号：P588.141[天文地球—岩石学] P597.3[天文地球—地质学]