Melting of a Yamato L3 chondrite (Y-74191) up to 30 kbar

• Main Author: Eiichi Takahashi
• Format: Report
• Language: English
• Published: Institute for Thermal Spring Research,Okayama University 1983
• Subjects: Yamato; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=1558; http://id.nii.ac.jp/1291/00001558/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1558&item_no=1&attribute_id=18&file_no=1

Melting phase relations of a Yamato L3 chondrite (Y-74191) have been studied in the pressure range 6 to 30 kbar. Solidus of the chondrite is defined by eutectic melting of Fe-Ni-S at about 950℃ regardless of pressure. At 15 kbar, silicate solidus of the chondrite is about 250℃ higher than the metal/sulfide eutectic solidus and the temperature interval between the two solidi widens as pressure increases. Composition of the metal/sulfide melt changes from FeS-rich to Fe-Ni-rich as temperature increases. Ferrobasaltic liquids containing 18 to 23wt% FeO and 0.2wt% sulfur are produced as partial melts over a large pressure and temperature interval. At low temperatures below the silicate solidus, the metal/sulfide melts are small isolated patches dispersed in grain boundaries of silicate minerals. At high temperatures, the metal/sulfide melts become numerous globules surrounded by silicate melts. Segregation of the ferrobasaltic partial melt on top of the residual olivines and the metal/sulfide globules has been observed. Gravitational settling of the dense metal/sulfide globules, however, did not take place under any experimental condition at least up to 10hr. Based on the partial melting experiments a model for genesis of pallasite meteorite is proposed.