大同煤田太原组9号煤底板高岭岩成因研究

利用偏光显微镜对大同煤田太原组9号煤层底板高岭岩的岩石学特征和成因进行了研究。在显微镜下识别出碎屑(包括陆源碎屑、火山石英晶屑、火山黑云母晶屑、脱玻化的"燧石状"玻屑)、隐晶高岭石团块、高岭石晶屑、高岭石基质四大结构组分;研究认为组成此层高岭岩的岩石类型主要为凝灰质团块状高岭岩,在顶部发育有薄层长石假象型晶粒高岭岩和凝灰质隐晶高岭岩,中间夹薄层凝灰质砂岩;该层高岭岩是经盆底水流改造的沉凝灰物质蚀变而成。特别是首次提出:该层高岭岩中大量发育的团块是由硅铝质玻屑蚀变而来的隐晶质高岭石集合体,由于经受了流水改造作用,其火山成因证据已经消失殆尽。

Origin of kaolinite rocks under Coal No.9 of Taiyuan formation in Datong coalfeld

The petrology and origin of kaolinite rocks under coal No.9 of Taiyuan Formation in Datong coalfield were studied based on the polarized microscope. Four texture components, i.e. clast (including terrigenous clast,volcanic quartz crystal pyroclast,volcanic biotite crystal pyroclast,devitrified"flint-like" vitric clast), cryptocrystalline kaolinite graupe, kaolinite crystal clast and kaolinite matrix, were identified under polarized microscope. The research shows that the main rock types of this bed of kaolinite rock were tuffaceous graupe kaolinite rock with thin feldspar pseudomorphic crystal kaolinite rock on the top, and intercalated with tuffaceous sandstone bed at middle part. This bed of kaolinite rock was originated from the tuffaceous sediments reworked by water current at the basin bottom. Especially, the new formation mechanism of abundant graupe were firstly submitted:that is, the cryptocrystalline kaolinite graupe is the altered products of silica-alumna vitric clast, which was reworked by water current in the basin bottom and show no evidence of volcanic origin.