摘要
对吉中蛟河地区大河深组火山岩进行了锆石LA-ICP-MSU-Pb定年和岩石地球化学研究,以探讨其构造属性。火山岩岩石组合以流纹岩为主,少量安山岩及流纹质晶屑凝灰岩,流纹岩中锆石均呈自形—半自形,粒径在90~120μm,长宽比1∶2到1∶4,普遍具有震荡生长环带结构,Th/U为0.46~1.14,表明其为岩浆成因。锆石LA-ICP-MSU-Pb定年结果显示大河深组流纹岩形成于(296.5±2.2)Ma,即早二叠世。火山岩样品w(SiO_(2))约为54.12%~75.56%,w(K_(2)O)为0.39%~4.12%,均属于中钾钙碱性—高钾钙碱性系列,里特曼指数δ介于1.72~2.47,岩石富集大离子亲石元素(LILEs)和轻稀土元素(LREEs),亏损Nb、Ta和Ti等高场强元素(HFSEs)和重稀土元素(HREEs)。结合区域研究成果认为,火山岩岩浆来源于中—新元古代增生的玄武质下地壳的部分熔融,形成于古亚洲洋向北(松嫩地块)俯冲的活动大陆边缘环境。
Zircon LA-ICP-MS U-Pb dating and petrogeochemical study of the volcanic rocks of the Daishen Formation in Jiaohe area,central Jilin Province were carried out to explore the tectonic attribute.The volcanic rock assemblages are dominated by rhyolite,with a small amount of andesite and rhyolitic crystal tuff.Zircons in the rhyolite are euhedral to semi-euhedral,with particle sizes of 90-120μm and aspect ratios of 1∶2-1∶4.They generally have oscillating growth zone structure,and Th/U ranges from 0.46 to 1.14,indicating that they are of magmatic origin.Zircon LA-ICP-MS U-Pb dating indicates that the rhyolite of the Daishen Formation was formed at(296.5±2.2)Ma,namely the Early Permian.The contents of SiO_(2) in volcanic rock samples are 54.12-75.56 wt.%,and the contents of K_(2)O are 0.39-4.12 wt.%.They all belong to medium-K to high-K calc-alkaline series.The Rittmann Index(δ)is between 1.72 and 2.47.The volcanic rocks are enriched in large ion lithophilic elements(LILEs)and light rare earth elements(LREEs),and depleted in high field strength elements(HFSEs;e.g.,Nb,Ta,and Ti)and heavy rare earth elements(HREEs).Combined with the regional research results,it is concluded that the volcanic magma originated from the partial melting of the juvenile basaltic lower crust in Meso-Neoproterozoic and formed in an active continental margin environment where the Paleo-Asian Ocean plate was subducted northward(to Songnen Block).
作者
张旭
肖永春
ZHANG Xu(Institute of Geologic Survey of Jilin Province,Changchun 130102,China)
出处
《长春工程学院学报（自然科学版）》
2022年第3期52-58,共7页
Journal of Changchun Institute of Technology：Natural Sciences Edition
