摘要
由于缺少对SSZ型蛇绿岩和洋内弧火成岩的系统研究,制约了古亚洲洋东段古生代洋内俯冲过程的进一步认识。本文报道了内蒙古迪彦庙SSZ型蛇绿岩带北部新发现的巴嘎哈尔早石炭世闪长岩。LA-ICP-MS锆石U-Pb定年显示,巴嘎哈尔闪长岩的侵位年龄为324.2±1.8 Ma,其形成时代为早石炭世末期。巴嘎哈尔闪长岩SiO_(2)含量为57.71%~61.24%;高铝(Al_(2)O_(3)含量为15.58%~16.68%);具有相对富钠(Na_(2)O含量为3.29%~4.15%)、低钾(K_(2)O含量为1.05%~1.69%)的特征,Na_(2)O/K_(2)O比值为2.18~3.95;MgO含量较高(3.30%~4.23%),Mg#为47.20~51.82;贫TiO_(2)(0.65%~0.76%)和P2O5(0.14%~0.15%);稀土元素总量(ΣREE为85.19×10^(-6)~98.21×10^(-6))较低,稀土元素分布曲线呈微右倾型,具弱的Eu异常;相对富集Rb、Ba、K等大离子亲石元素(LILE),亏损Nb、Ta、P和Ti等高场强元素(HFSE),显示俯冲带岛弧型岩浆岩特征。结合前人研究,认为巴嘎哈尔闪长岩与迪彦庙SSZ型蛇绿岩中的前弧岩石组合形成相对完整、连续的洋内俯冲作用成因的洋内弧火成岩岩石组合,揭示了古亚洲洋东段在早石炭世的洋内俯冲从初始俯冲到逐渐成熟的过程。
Due to the lack of reliable discovery and systematic study of SSZ ophiolite and Intra-oceanic arc igneous rock,which restricts the further understanding of the Paleozoic subduction extinction process of the eastern part of the paleo Asian ocean.The Bagahaer Early Carboniferous diorite distributed along the Hegenshan suture zone in the eastern part of the Xingmeng Orogenic Belt was discovered to be outcropped in the northern section of Diyanmiao SSZ ophiolite in Xiwuqi,Inner Mongolia.It belongs to Calc alka series,chemically characterized by 57.71%~61.24%of SiO_(2),15.58%~16.68%of Al_(2)O_(3),and 3.30%~4.23%of MgO,with relative rich in Na_(2)O(3.29%~4.15%)poor in K_(2)O(1.05%~1.69%)and high ratio of Na_(2)O/K_(2)O(2.18~3.95).The diorite relatively enriched large ion lithophile elements(LILE)Rb、Ba、K and depleted high field strength elements(HFSE)Nb、Ta、P and Ti,etc.In addition,it features lowΣREE(85.19×10^(-6)~98.21×10^(-6))and clear REE fractionation((La/Yb)N=3.08~3.99),without obvious Eu anomaly(δEu=0.61~0.82).Eighteen zircon grains from the diorite yielded a weighted mean 206Pb/238U age of 324.2±1.8 Ma,indicating an Early Carboniferous age.The petrological and geochemical characteristics of the diorite have obvious similarities and progressively evolved relationships with the fore-arc basalt(FAB)and boninite in the Diyanmiao SSZ-type ophiolite.The discovery and confirmation of Bagahaer Early Carboniferous intra-oceanic arc diorite in the Diyanmiao SSZ-type ophiolite reveal the transition from initial arc to mature arc of the eastern Paleo-Asian Ocean intra-oceanic subduction during the late Paleozoic.
作者
刘志斌
李英杰
曹侃
王金芳
董培培
张夏炜
王帅
LIU Zhibin;LI Yingjie;CAO Kan;WANG Jinfang;DONG Peipei;ZHANG Xiawei;WANG Shuai(College of the Earth Sciences,Heibei GEO University,Shijiazhuang,Hebei 050031,China;Hebei Province Collaborative Innovation Center for Strategic Critical Mineral Research,Hebei GEOUniversity,Shijiazhuang,Hebei 050031,China;The Geology of Inner Mongolia co.,Ltd,Huhhot,Inner Mongolia 010020,China;School of the Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2023年第10期3265-3277,共13页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号41972061)
中国地质调查局项目(编号1212011120701、1212011120711)联合资助的成果。
关键词
闪长岩
洋内俯冲作用
早石炭世
古亚洲洋
内蒙古西乌旗
diorite
intra-oceanic subduction
early Carboniferous
Paleo-Asian Ocean
Xi Ujimqin
Inner Mongolia
