摘要
内蒙古北山造山带北部黑红山-园包山地区新厘定的石炭纪白山组火山岩对研究北山地区晚古生代构造演化具有重要意义。分布于晚古生代额勒根乌兰乌拉蛇绿岩带两侧的石炭纪白山组火山岩无明显差异,该火山岩主要由玄武安山质、安山质、英安质、流纹质火山岩组成,在安山岩、英安质角砾熔岩中分别获得342±5.0 Ma、313±2.9 Ma的LA-ICP-MS锆石U-Pb同位素年龄,时代为早石炭世-晚石炭世。该套火山岩相对富集Ba、K等大离子亲石元素和轻稀土元素,相对亏损Nb、Ta、P、Ti等高场强元素,具有典型大陆岛弧火山岩地球化学特征。黑红山-园包山地区石炭纪白山组火山岩与额勒根乌兰乌拉蛇绿岩带代表的有限洋盆关系较小,该火山岩代表晚古生代北山北侧古亚洲洋洋壳向南俯冲过程中形成的火山弧,该火山弧的演化至少持续到晚石炭世。石炭纪白山组玄武安山岩、安山岩的岩浆源区是受俯冲带流体交代的地幔楔,酸性火山岩主要为大陆地壳物质熔融的产物。
The discovery of Carboniferous Baishan Formation volcanic rocks in the Heihongshan-Yuanbaoshan area in the Northern Beishan orogenic belt of Inner Mongolia is considerably significant to study the Late Paleozoic tectonic evolution in the Beishan area.There is no distinct difference for the volcanic rocks of Carboniferous Baishan Formation distributed on both sides of the Late Paleozoic Ergenwulanwula ophiolite belt.These volcanic rocks mainly comprise basaltic andesite,andesite,dacite,and rhyolitic volcanic rocks.Laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb isotopic ages were obtained at 342±5.0 and 313±2.9 Ma for andesite and dacitic breccia lava,respectively,dating at the Early Carboniferous-Late Carboniferous.The volcanic rocks are relatively enriched in large-ion lithophile elements(LILE)Ba,K,and LREE and relatively depleted in high field-strength elements(HFSE)Nb,Ta,P,and Ti.They exhibit typical geochemical characteristics associated with the continental-island-arc volcanic rocks.The Carboniferous volcanic rocks in the Heihongshan-Yuanbaoshan area are only slightly related with the limited oceanic basin represented by the Elegenwulanwula ophiolite.The volcanic rocks represent the volcanic arc formed during the southward subduction of the paleo-Asian oceanic crust on the northern side of the Beishan area during the Late Paleozoic.The volcanic arc evolution occurred at least until the Late Carboniferous.The magma source area of basalt andesite and andesite in the Baishan Formation is a mantle wedge metasomatized by fluid in the subduction zone.The melting of the continental crustal materials is responsible for the formation of numerous acidic volcanic rocks.
作者
程海峰
张正平
段先乐
刘广
李慧
孟庆涛
杨菊
朱炜
提振海
冯翼鹏
苏朋涛
范超
CHENG Haifeng;ZHANG Zhengping;DUAN Xianle;LIU Guang;LI Hui;MENG Qingtao;YANG Ju;ZHU Wei;TI Zhenhai;FENG Yipeng;SU Pengtao;FAN Chao(The Institute of Regional Geological Survey of Hebei Province,Langfang 065000;China Institute of Geo-Environment Monitoring,Beijing 100081;China University of Geoscience,Beijing 100083)
出处
《地质与勘探》
CAS
CSCD
北大核心
2022年第2期335-351,共17页
Geology and Exploration
基金
中国地质调查局项目(编号:DD20160039、1212011220464、1212011220463)资助。
