The Allan Hills 76005 polymict eucrite pairing group consists of 15 paired masses recovered during six different field seasons in the Transantarctic Mountains. Although this group has been well studied in general, most of the meteorites contain a significant portion of dark clasts that have not been well characterized. The Dawn mission to Vesta discovered dark materials that provide insight into its evolution. The ALH dark clasts are thus of great interest to understanding the evolution of Vesta. Here, 45 different dark clasts from 15 different thin sections from the pairing group are characterized in detail to better understand their nature and origin. Five different textural types of dark clasts are recognized among this group—skeletal, vitrophyric, pilotaxitic, fan spherulitic, and troilite‐silica‐plagioclase‐rich clasts with aphyric or blobby textures. Mineralogy of the clasts is dominated by plagioclase and pyroxene, with minor troilite, silica, ilmenite, chromite, and rare Fe‐Ni metal. All of the textures can be produced by rapid cooling rates on the order of 60–2500°C h⁻¹. Bulk compositions of the clasts are demonstrably eucritic, and not chondritic, howarditic, or diogenitic. The combination of mineralogy, composition, and textures strongly suggests that the dark clasts are eucritic impact melts. Several craters on Vesta have associated orange deposits that have been proposed as impact melt breccias. The ALH pairing group may thus represent material that originated near Oppia or Octavia craters.

中文翻译：

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艾伦希尔斯（Allan Hills）76005多微米真绿岩配对组中的深色碎屑的矿物学和岩石学

艾伦·希尔斯（Allan Hills）76005多微生物真绿岩配对组由15个成对的团块组成，这些团块在跨南极山脉的六个不同田间季节中回收。尽管对这组陨石进行了全面的研究，但大多数陨石都含有相当一部分尚未明确表征的深色碎屑。前往维斯塔（Vesta）的Dawn任务发现了深色材料，可以洞悉其演变过程。因此，ALH黑暗碎片对了解Vesta的演变非常感兴趣。在此，对来自配对组15个不同薄片的45个不同深色碎片进行了详细表征，以更好地了解其性质和来源。在这组中，我们识别出五种不同质地的深色碎屑-骨骼，玻璃体，飞行员，扇形，富含三叶草，二氧化硅和斜长石的碎屑，带有仿生或过钝的质地。板屑的矿物学特征主要是斜长石和辉石，以及次要的三叶草，二氧化硅，钛铁矿，铬铁矿和稀有的Fe-Ni金属。可以通过约60–2500°C h的快速冷却速率来产生所有纹理^-1。碎屑的大块组成显然是优生的，而不是软骨的，怪异的或双生的。矿物学，组成和质地的结合有力地表明，深色碎屑是共生冲击熔体。维斯塔（Vesta）上的几个陨石坑伴有橙色沉积物，这些沉积物已被提议为冲击熔融角砾岩。因此，ALH配对基团可以代表起源于Oppia或Octavia陨石坑附近的物质。