Microstructural Record of Evolving Condensation Processes in Fine-Grained Ca-Al-Rich Inclusions from the Reduced CV3 Chondrites

[摘要] Fine-grained, spinel-rich Ca-Al-rich inclusions (FGIs) in carbonaceous chondrites consist of numerous layered nodules having cores of spinel, hibonite, and/or perovskite surrounded by multiple thin layers of melilite, anorthite, diopside, and/or olivine. They are interpreted as aggregates of direct high-temperature condensates from an 16O-rich nebular gas that escaped significant melting. However, FGIs are very complex objects composed of intimate intergrowths of fine-grained refractory phases and show extremely large variations in mineralogy, modal abundance, and textures. Thus, detailed FIB/TEM analyses of FGIs are required to fully characterize their micro-to-nanometer scale textures, mineralogy, and chemical compositions and hence elucidate their formation processes and conditions in the early solar nebula. Here, we present our on-going study of pristine FGIs from the reduced CV3 chondrites Efremovka and Thiel Mountains (TIL) 07003 and 07007 that have minimal evidence for secondary parent body alteration.

[发布日期] 2019-07-07

[学科分类] 空间科学

[关键词] ALUMINUM OXIDES;CHONDRITES;CONDENSATES;FELDSPARS;HIGH TEMPERATURE;INCLUSIONS;MINERALOGY;NODULES;NUCLEATION;PEROVSKITES;PYROXENES;SOLAR NEBULA;THERMODYNAMICS;X RAY SPECTROMETERS