摘要
内蒙古东南部巴林右旗地区发育晚二叠世埃达克质火山岩,岩石组合为安山岩、粗安岩、英安岩及辉石安山岩,其LA-ICP-MS锆石U-Pb测年结果为256.7±2.7Ma,指示其形成于晚二叠世。地球化学特征显示,该套火山岩属准铝质-弱铝质中钾钙碱性岩石系列,具富Si(SiO_2>56%)、高Al(Al_2O_3>15%)、富Na、贫K、高Sr、低Yb和Y等特征,Na_2O/K_2O值为2.33~3.90,Mg~#值为35.3~60.8;稀土元素总量为96.69×10^(-6)~192.4×10^(-6)、轻重稀土元素分馏较明显((La/Yb)_N值为6.27~13.82),具正的Eu(δEu=1~1.67)异常,在原始地幔标准化蛛网图中,富集大离子亲石元素Rb、Ba、U,亏损高场强元素Nb、Ta,为O型(大洋型)埃达克质火山岩地球化学特征。综合区域资料,巴林右旗埃达克质火山岩是残留在地幔中的古亚洲洋残余洋壳部分熔融并受到地幔橄榄岩混染形成的,暗示晚二叠世存在古亚洲洋向华北板块俯冲消亡事件。
Permian adakitic volcanic rocks are distributed in Bairin Right Banner, southeast Inner Mongolia. This set of adakitic volcanic rocks is mainly outcropped in Dayushu, Shanhoutun and Handaba, with rock association being andesite, trachyandesite, dacite and augite andesite. The LA-ICP-MS zircon U-Pb age is 256.7±2.7Ma, indicating that the rocks were formed in the Late Permian.This set of volcanic rocks belongs to the quasi-aluminum-weak aluminium and medium-K-Calc-alkaline rock series, with the following geochemical characteristics： rich Si （SiO2〉56%）, high Al （Al2O3〉15%）, rich Na, poor K （Na2O=4.32%-4.73%, K2O=4.32%-2.49%）, higher Sr and lower Yb and Y （Sr〉400×10^-6,Yb〈1.9×10^-6, Y〈18×10^-6） ,Na2O/K2O=2.33 - 3.90, Mg#=35.3 - 60.8, the total amount of rare earth elements 96.69×10^- 6 - 192.4×10^- 6, light and heavy REE exhibiting obvious fractionation （（La/Yb）N=6.27-13.82） and positive anomalies δEu （1-1.67）. Enrichment of LILE （Rb,Ba,U） and depletion of HFSE（Nb,Ta） are displayed in the primitive mantle normalized multi-element variation diagram, indicating geochemical characteristics of O-type adakitic volcanic rocks.Based on regional information, adakitic volcanic rocks distributed in Bairin Right Banner were formed by contamination of the partly molten remnants of Paleo-Asian oceanic crust and the mantle peridotite, suggesting the existence of subduction extinction event of Paleo-Asian oceanic crust toward the North China Plate in Late Permian.
作者
杨文鹏
张生旭
姜海洋
刘洪大
隋成禹
孙江军
张俭峰
吕石佳
李新鹏
YANG Wenpeng;ZHANG Shengxu;JIANG Haiyang;LIU Hongda;SUI Chengyu;SUN Jiangjun;ZHANG Jianfeng;Lü Shijia;LI Xinpeng(Geological Survey Institute of Heilongjiang,Harbin 150036,Heilongjiang,China)
出处
《地质通报》
CAS
CSCD
北大核心
2018年第9期1710-1721,共12页
Geological Bulletin of China
基金
中国地质调查局项目<大兴安岭成矿带突泉-翁牛特地区地质矿产调查>(编号:DD20160048)和<内蒙古1:5万查干沐沦
大板镇
古力古台
召胡都格幅区域地质调查>(编号:DD20160048-13)
