内蒙古阿拉善北部好比如地区下石炭统好比如组时代修订及其地质意义

内蒙古阿拉善北部好比如地区地层研究程度较低,好比如组时代久有争议,制约了该区地层层序、沉积建造及构造演化的深入研究。测得好比如地区原定为早石炭世的好比如组碎屑岩LA-ICP-MS锆石U-Pb最小峰值年龄为279Ma,火山岩LA-ICP-MS锆石U-Pb年龄为270.3±2.2Ma,时代应修订为早二叠世空谷期—中二叠世罗德期。结合区域上岩性特征、地层对比及锆石年龄谱对比,将好比如组中段修订为船山统隆林阶—罗甸阶埋汗哈达组(P1-2m),将其上段修订为阳新统祥播阶—冷坞阶阿其德组(P2a)。好比如组的时代修订为研究区晚古生代地层层序、沉积建造及构造演化的研究提供了新的依据。

Chronology of the Haobiru Formation in the Haobiru area of northern Alxa, Inner Mongolia and its geological implications

Due to the low level of stratigraphic study of the Haobiru area in northern Alxa, Inner Mongolia, the age of the Haobiru Formation is controversial, and this limits the further discussion on the sequence stratigraphy, sedimentary construction and tectonic evolution.The authors revealed that the LA-ICP-MS zircon U-Pb age of the Early Carboniferous Haobiru Formation from the Haobiru area is 270.3±2.2Ma, and the youngest peak age of detrital zircons is 279Ma, and hence the age should be reassigned to Early Permian Kungurian-Middle Permian Roadian. According to the regional lithological characteristics, stratigraphic contrast and comparison of zircon age spectra, the Haobiru Formation should be reassigned to Lower-Middle Permian Maihanhada Formation(P_1-2m)- Middle Permian Aqide Formation(P₂a). The age revision of the Haobiru Formation provides new evidence for the discussion on the Late Paleozoic sequence stratigraphy, sedimentary construction and tectonic evolution.