Petrology of "Equilibrated" Chondrites. 2. Metamorphism and Thermal History

• Main Author: Hiroko Nagahara
• Format: Report
• Language: English
• Published: Geological Institute, Faculty of Science, University of Tokyo 1980
• Subjects: Yamato; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=1088; http://id.nii.ac.jp/1291/00001088/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1088&item_no=1&attribute_id=18&file_no=1

Petrological studies based mainly on the microprobe analyses have been made on nine ordinary chondrites, Yamato-74115 (H5), -74155 (H4), ALHA77148 (H6), Yamato-74007 (L6), -74190 (L6), -74354 (L6), -74362 (L6), -74445 (L6), and -74646 (LL6) and preliminary studies on the "unequilibrated" chondrites, ALHA77015 (L) and 77033 (LL). Detailed microprobe analyses of minerals of chondrites indicate that some chondrules became rich in FeO from the surface after their formation and before accretion to form a parental body or bodies. Based on the textural and petrochemical data, thermal history of "equilibrated" chondrites has been inferred. It is suggested that highly recrystallized chondrites were derived from the relatively inner part of the parental body and weakly recrystallized ones from near the surface.