Phosphate-bearing microspherules in chondrules of unequilibrated ordinary chondrites

• Main Authors: Yabuki,Hideo, Goresy,Ahmed El
• Format: Report
• Language: English
• Published: The Institute of Physical and Chemical Research/Max-Planck-Institut fur Kernphysik 1986
• Subjects: Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=1967; http://id.nii.ac.jp/1291/00001967/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1967&item_no=1&attribute_id=18&file_no=1

Microspherules, up to ca. 200μm in size, composed mainly of metal cores and various amounts of phosphates usually at the rim are described in chondrules and igneous-textured clasts from ordinary chondrites of petrologic types 3 and 4 and one type 5 chondrite. Phosphates found in microspherules in petrologic types 3 and 4 are mostly whitlockite and those in type 5 include apatite as well. Their chemical composition is almost identical to those in equilibrated ordinary chondrites. One of those spherules in Chainpur shows quite complex texture with native copper and lawrencite-like phase. Though many points on the formation history of phosphate-bearing bodies are left as future problems, their xenolithic origin was indicated by the features of some of those spherules. They were probably formed from molten droplets of metal and schreibersite (in the same event as the chondrule formation?) followed by oxidation reaction in advance of their being captured by coarser silicate chondrule melt.