中国黄土物质来源的初步探讨——石英粉砂颗粒表面结构的电子显微镜研究

Loess of China, regardless of its ageexhibites similarity in the surface textures of silt quartz grains, all of them having conchoidal fractures, flat cleavage planes(or plates) and mechanical cracks, and having been rewrked by silica precipitation and chemical dissolution. Silica precipitation an different-degree chemical etching and dissolution are commonly found on thes silt quartz grains indicating that they would be separated from source rocks, such as granite, gneiss, etc. ; or they might have been subjected to relatively long weathering in situ before transported to loessic accumulation areas; or they probably underwent diagenesis when brought into the sedimentation system, followed by weathering and erosion, and then transported to loess accumulation areas. It is evident from the relationship between loess of China, deserts and Gobi, loessic cimposition and its regional distribution that MesozoicCenozoic land detrital sediments widely spreaded in the Ordos and Alxa regions are the principal material source of loessic materials in China.