论文标题
Chelyabinsk撞击角砾岩中的微作用揭示了软骨中磷 - 橄榄石分配的历史
Microtextures in the Chelyabinsk impact breccia reveal the history of Phosphorus-Olivine-Assemblages in chondrites
论文作者
论文摘要
软骨磷酸盐矿物质的地球化学和质地关联可以为父母小行星的地质历史提供见解,但是管理其形成和变形的过程仍然受到巨大约束。在这里,我们使用扫描电子显微镜,电子显微镜,patrodomineminess和电子背散射技术对Chelyabinsk(LL5)普通软骨的三种含磷矿物纹理进行定量评估。磷酸盐的相位关联,微纹理和微观结构在Chelyabinsk陨石中研究的不同震动的岩性之间的变化极高。我们观察到不断紧张以及重结晶,无应变的磷酸盐种群。重结晶的晶粒(无应变亚域)仅存在于更激烈的深色岩性中,表明Chelyabinsk中的磷酸盐生长早于原发性休克型超形态纹理的发展。这一破坏事件还通过陨石的部分融化来记录,以产生冲击熔融岩性,其中包含大量富含磷的橄榄石晶粒。我们解释了Chelyabinsk的质地和相位关联是通过替代橄榄石替代的初始磷酸盐生长而产生的,随后在早期的冲击熔点撞击和随后发生的轻微冲击事件中进行了重大变形。这个小事件似乎已经产生了磷酸盐的亚种群,这些磷酸盐在光线和深色岩性中都显示出斑驳的CL纹理。最后,我们提出了一种新的分类方案,以描述各种类型的磷 - 寡素组合(I-III型POA),该组合可用于对休克变质事件进行分类并定义相关的物理化学过程。
The geochemistry and textural associations of chondritic phosphate minerals can provide insights into the geological histories of parental asteroids, but the processes governing their formation and deformation remain poorly constrained. Here, we present a quantitative assessment of phosphorus-bearing mineral textures in the three variously-shocked lithologies (light, dark, and melt) of the Chelyabinsk (LL5) ordinary chondrite using scanning electron microscope, electron microprobe, cathodoluminescence, and electron backscatter diffraction techniques. Phase associations, microtextures, and microstructures of phosphates are extremely variable within and between the differently-shocked lithologies investigated in the Chelyabinsk meteorite. We observe continuously strained as well as recrystallized, strain-free phosphate populations. Recrystallized grains (with strain-free subdomains) are present only in the more intensely shocked dark lithology, indicating that phosphate growth in Chelyabinsk predates the development of primary shock-metamorphic textures. This disruption event is also recorded by complete melting of portions of the meteorite to produce the shock-melt lithology, which contains a population of phosphorus-rich olivine grains. We interpret the textures and phase associations of Chelyabinsk to have resulted from initial phosphate growth via metasomatic olivine replacement, followed by major deformation during an early shock-melting impact and a subsequent minor shock event. This minor event appears to have generated a sub-population of phosphates that display patchy CL textures, in both the light and dark lithology. Finally, we propose a new classification scheme to describe various types of Phosphorus-Olivine-Assemblages (Type I-III POAs), which can be used to classify shock metamorphic events and define the associated physicochemical processes.