The main mineralogical characteristics of a large light-colored clast within the Murchison CM breccia are discussed in detail including data on the mineralogy, bulk chemistry, organics, and oxygen isotopes. Petrographic study shows that the white clast consists of two areas with different granoblastic textures: (1) a coarse-grained (average grain size: ∼200 μm) and (2) a fine-grained lithology (average grain-size: ∼20 μm). The Fa-content of olivine in the clast is the same as Fa within olivine from Rumuruti (R) chondrites (Fa: ∼38 mol%); however, the concentrations of the elements Ni and Ca in olivine are significantly different. The fragment also contains Ca-rich pyroxene, ∼An_30-38-plagioclase/maskelynite, Cr-rich spinel, several sulfide phases, a nepheline-normative glass, and traces of merrillite and metal. The occurrence of maskelynite and nepheline-normative amorphous phase in restricted areas of the well-recrystallized rock may indicate remarkable P-T-excursions during shock metamorphism. The O-isotope composition of the clast falls below the terrestrial fractionation line (TFL), lying in the field of CM chondrites and is significantly different from data for bulk R chondrites. The study of the soluble organic matter revealed a highly-oxidized carbon chemistry and organomagnesium compounds reflecting high temperature and pressure processes.

详细讨论了Murchison CM角砾岩中大型浅色碎屑的主要矿物学特征，包括有关矿物学，本体化学，有机物和氧同位素的数据。岩石学研究表明，白色碎屑包括两个具有不同粒状纹理的区域：（1）粗粒（平均粒径：〜200μm）和（2）细粒岩性（平均粒径：〜20μm） ）。碎屑中橄榄石中的Fa含量与Rumuruti（R）球粒陨石中的橄榄石中的Fa相同（Fa：〜38 mol％）；然而，橄榄石中镍和钙元素的含量差异很大。该片段还含有钙丰富的辉石，~An _30-38-斜长石/ maskelynite，富Cr的尖晶石，多个硫化物相，霞石规范的玻璃以及痕量的蒙脱石和金属。在充分重结晶的岩石限制区域中发生的辉绿岩和霞石规范的非晶相可能表明，在冲击变质过程中，PT出现了明显的偏移。地幔的O同位素组成低于地面分馏线（TFL），位于CM球粒陨石领域，与大块R球粒陨石的数据明显不同。对可溶性有机物的研究揭示了反映高温和高压过程的高度氧化的碳化学物质和有机镁化合物。