内蒙古扎兰屯市浩绕山地区白音高老组时代归属探讨

亚洲东北部、蒙古共和国以及俄罗斯外贝加尔地区广泛发育着一套侏罗纪—白垩纪的火山—沉积地层,尤以我国的冀北—辽西地区研究程度最高,该区是中国东北地区乃至东北亚地区早白垩世地层区域对比的标尺。内蒙古扎兰屯市浩绕山地区发育的白音高老组为一套火山岩—沉积序列,但其地层时代归属一直存在着争议,有晚侏罗世和早白垩世2种观点,给区域地层对比造成了较大的困难。利用LA-ICP-MS锆石U-Pb测年法,在该组火山碎屑岩中分别获得了(139.84±0.78)Ma,(134.84±0.78)Ma两个年龄,将其地层时代限定为早白垩世,在区域上可以与冀北地区的张家口组进行对比,进一步完善了冀北—辽西地区晚中生代火山-沉积地层格架,具有重要的研究意义。

Study on Age Attribution of Baiyingaolao Formation in Haoraoshan Area in Zhalantun City of Inner Mongolia

A set of JurassicCretaceous volcanicsedimentary strata widely distributed in the northeastern of the Asia, the Republic of Mongolia, and the Transbaikalia area of the Russia. Research has been carried out widely on the similar strata in the northern Hebei province and the western Liaoning province . It can be regarded as typical strata for the regional comparison between early Cretaceous sedimentary sequence in the northeastern of China and the northeastern of the Asia. The Baiyingaolao formationdeveloped in Haoraoshan area in Zhalantun city of Inner Mongolia is a series of volcanicsedimentary rock sequence. However, it still remains a debute about the age attribution whether it developed in late Jurassic or early Cretaceous. By using LAICPMS zircon UPb dating, two ages as (139.84± 0.78)Ma and (134.84±0.78)Ma of the subvolcanic rocks in Baiyingaolao formation have been obtained. Therefore, the sedimentary time of Baiyingaolao formation can be limited to early Cretaceous, and compared with Zhangjiakou formation in the northern of Hebei province more precisely. It has great significance to improve the late Mesozoic volcanicsedimentary framework.