大兴安岭北部红水泉组碎屑锆石LA-ICP-MS U-Pb年代学及其地质意义

红水泉组广泛出露于大兴安岭北部地区，主要由杂砂岩、砂板岩、碳酸盐岩和凝灰岩组成，含腕足、珊瑚和苔藓虫化石，时代为早石炭世。对额尔古纳右旗和扎兰屯地区的红水泉组砂岩样品进行了LA-ICP-MS锆石U-Pb测年。结果显示,87个谐和-近谐和年龄主要分布在4个年龄区间：353~379 Ma，峰值年龄约为366 Ma；428~473 Ma，峰值年龄约为441 Ma和464 Ma；487~521 Ma，峰值年龄约为502 Ma；1 790~1 943 Ma，峰值年龄约为1 848 Ma。其中:约366、441、464和502 Ma的峰值年龄与额尔古纳、兴安地块的岩浆事件基本吻合，1 848 Ma的峰值年龄普遍存在于2个地块，说明红水泉组的沉积物主要来自额尔古纳－兴安地块；约366 Ma的峰值年龄反映沉积物部分来自大兴安岭北部晚泥盆世火山弧，物源区具有双向性（古老陆壳和火山弧）。结合区域早石炭世沉积特征认为红水泉组为一套弧后盆地沉积。

LA-ICP-MS U-Pb Geochronology of Detrital Zircon from the Hongshuiquan Formation in the Northern Da Hinggan Area and Its Tectonic Significance

The Hongshuiquan Formation,widely exposed in the northern Da Hinggan area,consistsmainly of greywacke,sand-slate,carbonate rocks and tuffs,in which brachiopods,corals and bryozoansflourished in Early Carboniferous.LA-ICP-MS zircon U-Pb dating of the sandstones from theHongshuiquan Formation in Ergun and Zhalantun area is carried out in order to discuss the EarlyCarboniferous basin type.Results show that 87zircon concordant ages give four age groups:353-379Mawith peak age at 366Ma,428-473Ma with peak age at 441Ma and 464Ma,487-521Ma with peak ageat 502Ma and 1 790-1 943Ma with peak age at 1 848Ma.In this frame,the peak ages of 366Ma,441Ma,464Ma and 502Ma are consistent with the magmatic events in Ergun and Xing’an blocks,and the peak age of 1 848Ma is widely existed in the two blocks,suggesting that sediments of the HongshuiquanFormation mainly derive from Ergun-Xing’an blocks.The youngest peak age of 366Ma indicates thatthe sediments come partly from the Late Devonian volcanic arc.The sandstones from the HongshuiquanFormation have bidirectional sources(continent and volcanic arc).Combined with regional sediments inEarly Carboniferous,we believe that the Hongshuiquan Formation is a suite of sedimentary sequenceformed in a back-arc basin setting.