关键词: 特大尘暴沉积物, 重矿物, 兰州

Abstract: This paper studies the heavy minerals in the dustfall of a catastrophic duststorm that took place on May 5, 1993 in Lanzhou Area, Gansu Province. Detailed determination under,microscope reveals that there are totally 27 kinds of the heavy minerals, of which 3 kinds are of unstable,11kinds of less stable, 5 kinds of stable, and 8 kinds of extremely stable. According to the components and the conbination characteristics of heavy minerals and also the formation area of the duststorm,it suggests that the wind-blown deposits are mainly derived from the sedentary products of neutral and acidic granolite and some sedentary products of metamorphic rocks.Clearly,the main source area of the dustfall deposits must be Beishan mountains(in Gansu)and the adjacent desert areas to the east.The source areas of the duststorm deposists differ from those of the Malan loess deposited in the last glacial period.

Key words: Severe duststorm, Heavy minerals, Lanzhou