额济纳旗大狐狸山地区干泉组火山岩锆石U-Pb测年及其意义

银额盆地干泉组火山岩段和碎屑岩段在大狐狸山地区出露较全,火山岩段由含晶屑玄武岩和中酸性火山岩构成双峰式火山岩组合。本次研究在含晶屑玄武岩中获得(305.2±3.9)Ma(MSWD=7.9)的LA-ICP-MS单颗粒锆石微区U-Pb同位素年龄,表明干泉组火山岩时代为晚石炭世,结合地层间接触关系,将干泉组时代定为晚石炭世一早二叠世。这一资料对于分析银额盆地北部红石山-黑鹰山坳陷充填演化意义重大,晚石炭世盆地属于裂谷盆地,发生快速裂解沉积巨厚的碎屑岩-火山岩。

Zircon U-PbDating about Volcanic Rocks of Ganquan Formation in Dahulishan Area,Ejina Banner and Its Geological Implication

Volcanic and clastic rock members of Ganquan Formation within Yin'e basin hasoutcropped in Dahulishan area very well. The volcanic rock member is consists of basalt with crystal pyroclast and intermediate-acidic volcanic rocks, forming a bimodal volcanic rock assemblage.Through using LA-ICP-MS zircon U-Pb dating, the isotopic ages of (305.2±3.9)Ma(MSWD=7.9) for basalt with crystal pyroclast have been obtained in this paper, indicating the age for the strata of Ganquan Formation is Late Carboniferous. Combining with the contact relationships among these strata, it's determined that the age of Ganquan Formation is Late Carboniferous-Early Permian. This data has a great significance for analyzing the depression and filling evolution process of Hongshishan-Heiyingshan in the northern part of Yin'e basin. Thus, this Late Carboniferous basin belongs to the rift basin, developing a rapid cleavage and depositing a giant thick clastic rocks and volcanic rocks.