江西吉水炉下环形构造坑底混杂堆积层的发现与成因解析

Discovery and Cause Analysis of Breccia Complex Layer at the Bottom of Luxia Ring Structure in Jishui County,Jiangxi Province

通过野外地质调查,在江西省吉水县炉下环形构造坑底部出现混杂堆积层,它是由大小不等泥砂岩角砾及河流沉积物砂砾在高温作用下烧结而形成的集块岩石,富含熔岩玻璃,气孔构造发育。经化学分析、X衍射以及镜下鉴定等一系列室内研究,发现集块岩的砂岩角砾中SiO_2的含量明显减少,Al_2O_3、Fe_2O_3的含量明显增加;砂岩角砾呈现典型的冲击变质特征,其中包括面型微裂隙(PFs)、面型微页理(PDFs)及击变矿物玻璃等。集块岩外部形貌特征和结构构造分析,完全符合"击变岩"的标准,初步判断陨石撞击形成了混杂堆积层及炉下环形构造。

Through field geological surveys, there is a breccia complex layer at the bottom of the Luxia ring structure in Jishui County, Jiangxi Province. It is an agglomerated rock rich in lava vitreous and vesicular structure well-developed, and is formed by the sintering of mud sandstone breccia and river sediment gravel under the effect of high temperature. Through a series of studies include chemical analysis, X-ray diffraction, microscopic identification, electron probes, and Raman spectroscopy, it shows that the content of SiO 2 in the sandstone breccia of agglomerates was significantly reduced, and the contents of Al 2O 3 and Fe 2O 3 were significantly increased. Sandstone brecciated quartz particles exhibit typical impact metamorphic features, including planar fissures(PFs),planar deformation features(PDFs) and diaplectic glass. The analysis of the external morphological characteristics and texture structure of the agglomerate rock is in full compliance with the criteria of “impactite”. The preliminary judgment of the impact of meteorites has formed a breccia complex layer and Luxia ring structure.