吉林省南部宇宙尘的化学组成特征

在吉林省南部元古宇石英岩内发现磁性微球粒３９２枚，根据其产状，形貌及一般特征，微结构和化学组成表明为陨石消融型宇宙尘，由４亚４小类组成一个宇宙尘系列，（１）金属球粒；（２）纯铁球粒，（ｂ）ＦＣＮ型（天然不锈钢）球粒；（２）氧化物球粒（ａ）普通铁质宇宙尘（ｂ）铬铁氧化物球粒；（３）玻璃质球粒；（４）氧化物－金属过渡型球粒，其母体要能是一分异的ＦＣＮ型石－铁陨石质陨星体，核部为ＦＣＮ合金，经消融分异作

CHEMICAL COMPOSITION OF PROTEROZOIC COSMIC DUSTS IN SOUTHERN JILIN PROVINCE, CHINA

Three hundred and ninety-two magnetic spherules were discovered in Proterozoic quartzite in southern Jilin Province, China. These spherules are demonstrated as cosmic dusts of fusion type, based on their characteristics of occurrence, shape feature,general physical property, microstructure and chemical composition. The spherules were divided into 4 subtypes, including 4 sorts in two subtypes of them, and the spherules in southern Jilin could be refered as a series of cosmic dusts. They are: (1) metal spherules, including pure iron spherules and FCN (Fe-Cr-Ni alloy, natural stainless steel) spherules; (2) oxide spherules, including Si-Fe oxide spheruls (common iron cosmic dusts) and Cr-Fe oxide spherules; (3) glassy spherules and (4) the oxide-metal spherules. Both the Si-Fe oxide spherules and pure iron spherules are very similar to common magnetic iron cosmic dusts. FCN spherules are a sort of natural stainless steel,which contain ca 18% Cr and average 5.85% Ni. The Cr-Fe oxide spherules contain 10.43% to 26.70% Cr2O3. The parent body of this sort of cosmic dust series may be a differential stone-iron meteorite of FCN type. The inner part (i.e. the core) of the parent, which consists of a Fe-Cr-Ni alloy originally, has turned into pure iron spherules and natural stainless steel spherules by fusion differentiation. The outer part of the parent, which is a crust of Fe-Cr silicate composed of fayalite, ferrosilite and chromite etc., has turned into the common iron cosmic dust, Cr-Fe oxide spherules and glassy spherules by fusion differentiation. The oxide-metal spherules are generated from the boundary zone between the core and the crust of parent body. In a word,the chemical compositions of the cosmic dust series are charcterized by higher ischromiun and less magnesium.