In order to understand the nature of the dust that accreted onto chondrules in the nebula and to unravel the conditions of formation of fine grained rims (FGRs), we studied three of the least altered chondrites from different chondrite groups (LL3.00 Semarkona, CO3.0 DOM 08006, CR2.8 QUE 99177) and compared the results with our previous work on the Paris CM chondrite (Zanetta et al., 2021). For each sample, we selected representative rimmed chondrules showing minimal traces of aqueous alteration. We performed high-resolution SEM X-ray chemical mapping to obtain relevant phase abundances and grain size distributions. Four FIB sections were then extracted from each meteorite, two in the rims and two in their adjacent matrix for quantitative TEM analysis. At the microscale, texture, modal abundances and grain size differ depending on the chondrite but also between FGRs and their adjacent matrix. At the nanoscale (i.e. TEM observations), matrices of the four chondrites consist mostly of domains of amorphous silicate associated with Fe-sulfides, Fe-Ni metal, Mg-rich anhydrous silicates and an abundant porosity. The related FGRs in Semarkona (LL) and DOM 08006 (CO) exhibit more compact textures with a lower porosity while FGRs in QUE99177 (CR) are similar to the matrix in terms of porosity. In the three chondrites, FGRs are made of smooth and chemically homogeneous amorphous (or nanocrystalline) silicate with no porosity that encloses domains of porous amorphous silicate bearing Mg-rich anhydrous silicates, Fe-sulfides, Fe-oxides and sometimes metal and Fe-rich olivines. The average compositions in major elements of the amorphous regions are similar for the FGRs and the matrix within a given chondrite (but differ between chondrites). The texture and the chemical homogeneity of the smooth silicate and the fact that it encloses domains of porous amorphous silicate bearing other mineral phases similar to matrix-like material suggests a formation by condensation. Areas that are enclosed in this smooth silicate exhibit Fe-rich olivine formed through Fe interdiffusion that also suggest a thermal modification of the dust accreted to form FGRs. These characteristics indicate a transformation process for the modification of the FGR material similar to the one proposed in our previous work on Paris. We conclude that matrix and FGRs accreted a similar type of dust but FGR material was affected by thermal modification and compaction contemporary with their accretion. For each chondrite, dust accreted onto chondrules under different conditions (dust density, temperature) which led to diverse degrees of compaction/thermal modification of the sub-domains and explain the textural differences observed in FGRs. They accreted on chondrules in a warm environment related to the chondrule formation episode, whereas matrix accreted later in a cooler environment.

为了了解在星云球粒上堆积的尘埃的性质并解开细粒边缘 (FGR) 的形成条件，我们研究了来自不同球粒陨石群的三种变化最小的球粒陨石（LL3.00 Semarkona，CO3 .0 DOM 08006、CR2.8 QUE 99177）并将结果与​​我们之前在巴黎 CM 球粒陨石上的工作（Zanetta 等人，2021 年）进行比较。对于每个样品，我们选择了具有代表性的边缘球粒，显示出最小的水性改变痕迹。我们进行了高分辨率 SEM X 射线化学映射以获得相关的相丰度和晶粒尺寸分布。然后从每个陨石中提取四个 FIB 部分，两个在边缘，两个在它们相邻的矩阵中，用于定量 TEM 分析。在微观尺度上，质地，模态丰度和晶粒尺寸因球粒陨石而异，但在 FGR 及其相邻基质之间也不同。在纳米尺度上（即 TEM 观察），四种球粒陨石的基质主要由与 Fe-硫化物、Fe-Ni 金属、富含镁的无水硅酸盐和丰富的孔隙度相关的无定形硅酸盐域组成。Semarkona (LL) 和 DOM 08006 (CO) 中的相关 FGRs 表现出更紧密的纹理和更低的孔隙率，而 QUE99177 (CR) 中的 FGRs 在孔隙率方面与基质相似。在这三个球粒陨石中，FGR 由光滑且化学均质的无定形（或纳米晶）硅酸盐制成，没有孔隙，包围着含有富镁无水硅酸盐、铁硫化物、铁氧化物，有时还有金属和富铁的多孔无定形硅酸盐区域橄榄石。对于 FGR 和给定球粒陨石内的基质，无定形区域主要元素的平均成分相似（但在球粒陨石之间有所不同）。光滑硅酸盐的质地和化学均质性以及它包围多孔无定形硅酸盐区域的事实，该区域带有类似于基质状材料的其他矿物相，表明是通过冷凝形成的。封闭在这种光滑硅酸盐中的区域表现出通过 Fe 相互扩散形成的富含 Fe 的橄榄石，这也表明堆积形成 FGR 的灰尘发生了热改性。这些特征表明 FGR 材料的改造过程类似于我们之前在巴黎的工作中提出的过程。我们得出结论，基质和 FGR 吸积了类似类型的灰尘，但 FGR 材料受到与其吸积同时发生的热改性和压实的影响。对于每个球粒陨石，尘埃在不同条件（尘埃密度、温度）下吸积到球粒上，导致子域发生不同程度的压实/热改性，并解释了在 FGR 中观察到的结构差异。它们在与球粒形成事件相关的温暖环境中附着在球粒上，而基质则在较冷的环境中附着。