大兴安岭阿尔山地区宝力高庙组浅变质岩年代学、地球化学特征及原岩建造探讨

Chronology, geochemical characteristics and protolith formation of low-grade metamorphic rocks from Baoligaomiao Formation in Aershan area,Da Hinggan Ling(Mts.)

大兴安岭阿尔山地区宝力高庙组为一套以沉积碎屑岩、安山岩为主的陆相沉积-火山岩系,经历了区域变质作用后转变为低绿片岩相。笔者对宝力高庙组浅变质岩开展了锆石U-Pb定年、地球化学的研究,结合岩性岩相学和变质变形特征,试图恢复其原岩建造,并在此基础上,探讨了沉积背景。结果表明,阿尔山地区变质安山岩LA-ICP-MS锆石U-Pb年龄为(312.1±1.2)Ma,地质时代属晚石炭世—早二叠世,将其厘定为宝力高庙组,原岩组合属典型的滨湖相陆源中酸性火山-沉积建造,沉积构造环境为活动大陆边缘的弧内盆地,与区域上二连—贺根山蛇绿—增生杂岩带晚石炭世—早二叠世时期的构造环境一致。

The Baoligaomiao Formation,located in the Arshan area of the Da Hinggan Ling(Mts.),comprises a continental sedimentary-volcanic rock series,predominantly formed of sedimentary clastic rocks and andesites,which have undergone regional metamorphism and have been converted into the low greenschist facies.This study focuses on the zircon U-Pb dating and geochemical analysis of the low-grade metamorphic rocks of Baoligao-miao Formation.By integrating lithologic petrographosed and metamorphic deformation characteristics,the research aims to reconstruct the protolith structure and explore the sedimentary setting.The results indicate that the LA-ICP-MS zircon U-Pb age of the metamorphic andesites in the Arshan area is approximately(312.1±1.2)Ma,belonging to the Late Carboniferous and Early Permian periods,and it is identified as part of Baoligaomiao Formation.The protolith assemblage of Baoligaomiao Formation in the Arshan area is a typical terrigenous intermediate-acidic volcano-sedimentary lacustrine facies.The sedimentary tectonic environment is the intra-arc basin of the active continental margin,which is consistent with the tectonic environment of the Late Carboniferous-Early Permian in Erlian-Hegenshan ophiolite-accretionary complex.