Friedrich Jon M, Chen Matthiew M, Giordano Stephanie A, Matalka Olivia K, Strasser Juliette W, Tamucci Kirstin A, Rivers Mark L, Ebel Denton S
Department of Chemistry, Fordham University, Bronx, New York, USA.
Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA.
Microsc Res Tech. 2022 May;85(5):1814-1824. doi: 10.1002/jemt.24043. Epub 2021 Dec 27.
Within this work, we present the first true three-dimensional (3D) analysis of chondrule size. Knowledge about the physical properties of chondrules is important for validating astrophysical theories concerning chondrule formation and their aggregation into the chondritic meteorites (known as chondrites) that contain them. The classification of chondrites into chemical groups also relies on chondrule properties, including their dimensions. Within this work, we quantify the diameters of chondrules in five ordinary chondrites (OCs; comprised of the H, L, and LL chondrites) and one low-iron enstatite (EL) chondrite. To extract the chondrule size data, we use x-ray computed microtomography to image small (~1-2 cm ) chondrite samples followed by manual digital segmentation to isolate chondrules within the volumes or subvolumes. Our data yield true 3D results without stereographic corrections necessary for two-dimensional (2D) or petrographic thin section-based determinations of chondrule sizes. Our results are completely novel, but are consistent with previous surface analysis (2D) data for OCs. Within our OC chondrule diameter data, we find the trend of mean chondrule diameters increasing in the order H < L < LL. We also present the first detailed EL chondrite chondrule size-frequency distribution. Finally, we examine the shapes and collective orientations of the chondrules within the chondrites and show that chondrite petrofabrics can be explored with our methodology. Chondrule shape-preferred orientations are identical to the orientations of the metal and sulfide grains in the chondrites and this is likely due to impact-related compaction. HIGHLIGHTS: We present a first true three-dimensional analysis of chondrule size. Our ordinary chondrite chondrule diameter data demonstrate the trend of mean chondrule diameters increasing in the order H chondrites < L chondrites < LL chondrites. We also present the first detailed low-iron enstatite chondrite chondrule size-frequency distribution. We examine the shapes and collective orientations of the chondrules and show that chondrite petrofabrics can be explored with our methodology.
在这项工作中，我们展示了对球粒大小的首次真正的三维（3D）分析。了解球粒的物理性质对于验证有关球粒形成及其聚合成包含它们的球粒陨石（称为球粒陨石）的天体物理理论非常重要。将球粒陨石分类为化学群也依赖于球粒的性质，包括它们的尺寸。在这项工作中，我们量化了五块普通球粒陨石（OCs；由H、L和LL球粒陨石组成）和一块低铁顽火辉石（EL）球粒陨石中球粒的直径。为了提取球粒大小数据，我们使用X射线计算机断层扫描对小（约1 - 2厘米）的球粒陨石样本进行成像，然后通过手动数字分割来分离体积或子体积内的球粒。我们的数据产生了真实的3D结果，无需进行二维（2D）或基于岩石薄片的球粒大小测定所需的立体校正。我们的结果是全新的，但与之前OCs的表面分析（2D）数据一致。在我们的OC球粒直径数据中，我们发现平均球粒直径按H < L < LL的顺序增加的趋势。我们还展示了首个详细的EL球粒陨石球粒大小频率分布。最后，我们研究了球粒陨石中球粒的形状和集体取向，并表明可以用我们的方法探索球粒陨石的岩石组构。亮点：我们展示了对球粒大小的首次真正的三维分析。我们的普通球粒陨石球粒直径数据表明平均球粒直径按H球粒陨石 < L球粒陨石 < LL球粒陨石的顺序增加的趋势。我们还展示了首个详细的低铁顽火辉石球粒陨石球粒大小频率分布。我们研究了球粒的形状和集体取向，并表明可以用我们的方法探索球粒陨石的岩石组构。
