Major element composition of stratospheric micrometeorites
Major element composition of stratospheric micrometeorites
复制标题
平流层微陨石的主量元素组成
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
M. M. Wheelock
中科院分区：
文献类型：
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作者：
L. Schramm;D. Brownlee;M. M. Wheelock
- 用能量色散X射线（EDX）分析方法测定了200个在平流层收集的行星际尘埃粒子（IDPs）的元素组成。这些结果合理地定义了平均尺寸为10微米的行星间尘埃颗粒的正常组成范围，并构成了一个数据库，用于与来自彗星和小行星的单个IDP，陨石和航天器数据进行比较。分析的所有IDP的平均元素组成与CI方解石的平均元素组成最相似，但数据显示平均IDP组成与CI标准之间存在微小但可辨别的差异。单个颗粒被分类为广泛的形态组，两个主要的组显示明确的组成差异。“多孔”组是一个紧密的匹配散装CI丰度，但“光滑”组有系统的Ca和Mg的耗尽，并包含化学计量的“过量”的氧与含水相的存在一致。在CI和CM矩阵中的Ca和Mg的类似的消耗已被归因于浸出，并通过类比，我们建议，在顺利组的颗粒也被处理的水蚀变。碳酸盐岩、磁铁矿framboids和层状硅酸盐的出现提供了额外的证据，表明至少有相当数量的光滑类IDP已经被水活性充分处理。在一个粒子亚类的成员中是否存在水性改性是其起源的重要线索。虽然它不能被证明，我们假设，广泛的水活动只发生在小行星，因此，顺利类的国内流离失所者有一个小行星的起源。如果彗星和小行星都是行星际尘埃的主要来源，那么默认情况下，多孔颗粒被推断为由彗星物质主导。
— The elemental compositions of 200 interplanetary dust particles (IDPs) collected in the stratosphere have been determined by energy dispersive X-ray (EDX) analysis. The results reasonably define the normal compositional range of chondritic interplanetary dust particles averaging 10 micrometers in size, and constitute a database for comparison with individual IDPs, meteorites, and spacecraft data from comets and asteroids. The average elemental composition of all IDPs analyzed is most similar to that of CI chondrites, but the data show that there are small yet discernable differences between mean IDP composition and the CI norm. Individual particles were classified into broad morphological groups, and the two major groups show unambiguous compositional differences. The “porous” group is a close match to bulk CI abundances, but the “smooth” group has systematic Ca and Mg depletions, and contains stoichiometric “excess” oxygen consistent with the presence of hydrous phases. Similar depletions of Ca and Mg in CI and CM matrix have been attributed to leaching, and by analogy we suggest that particles in the smooth group have also been processed by aqueous alteration. The occurrence of carbonates, magnetite framboids, and layer silicates provides additional evidence that at least a significant number of the smooth-class IDPs have been substantially processed by aqueous activity. The presence or absence of aqueous modification in members of a particle sub-class is an important clue to the origin. Although it cannot be proven, we hypothesize that extensive aqueous activity only occurs in asteroids and that, accordingly, the smooth class of IDPs has an asteroidal origin. If both comets and asteroids are major sources of interplanetary dust, then by default the porous particles are inferred to be dominated by cometary material.