Compositional evidence regarding the origins of rims on Semarkona chondrules
Compositional evidence regarding the origins of rims on Semarkona chondrules
复制标题
关于塞马科纳球粒边缘起源的组成证据
DOI：
10.1016/0016-7037(87)90373-5
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发表时间：
1987
影响因子：
5
通讯作者：
J. Wasson
中科院分区：
文献类型：
--
作者：
J. Grossman;J. Wasson
用中子活化分析方法测定了塞马尔科纳公司生产的7种球粒(LL3.0)的内部成分和磨损表面的成分。对于非挥发性元素，表面的亲石和亲铁元素丰度模式通常与相应内部的相似。亲铁性和亲碳性在表面上的浓度要高得多，而亲石性在这两个组分中的浓度是相似的。表面和内部亲石模式的大部分相似之处和亲铁模式的一些相似之处可能反映了实验室中各组分的不完全分离，但对于3或4个球粒陨石来说，亲铁相似是固有的，这意味着表面和内部的金属是由单一的前体组合形成的。当熔化过程中迁移到球粒表面的这些相的液滴被重新加热并结合到附着在表面上的类似基质的材料中时，可能形成了金属和富含硫化物的球粒边缘。与其他类似矿物亲和力的元素相比，中等挥发性至挥发性元素K、As和Zn倾向于在表面富集物；其他中等挥发性元素既有富集性，也有贫化现象。一小部分球粒在熔化时经历了部分蒸发。
The compositions of the interiors and abraded surfaces of 7 chondrules from Semarkona (LL3.0) were measured by neutron activation analysis. For nonvolatile elements, the lithophile and siderophile element abundance patterns in the surfaces are generally similar to those in the corresponding interiors. Siderophile and chalcophile concentrations are much higher in the surfaces, whereas lithophile concentrations are similar in both fractions. Most of the similarities in lithophile patterns and some of the similarities in siderophile patterns between surfaces and interiors may reflect incomplete separation of the fractions in the laboratory, but for 3 or 4 chondrules the siderophile resemblance is inherent, implying that the surface and interior metal formed from a single precursor assemblage. Metal and sulfide-rich chondrule rims probably formed when droplets of these phases that migrated to the chondrule surface during melting were reheated and incorporated into matrix-like material that had accreted onto the surface. The moderately-volatile to volatile elements K, As and Zn tend to be enriched in the surfaces compared with other elements of similar mineral affinity; both enrichments and depletions are observed for other moderately volatile elements. A small fraction of chondrules experienced fractional evaporation while they were molten.