Melting Experiments on a Yamato Chondrite

One-atmosphere melting experiments have been carried out on Yamato L6 chondrite 74354 at temperatures 1125°, 1200°and 1275℃ and at Po_2 (oxygen partial pressure) between (10)^<-16> and (10)^<-8> atm. The compositions of olivine, Ca-poor pyroxene, Fe-Ni metal and liquid have been determined as functions of temperature and Po_2; for example, the composition of olivine varies from Fo_<62> to Fo_<87> and that of metal varies from Fe_<20>Ni_<80> to Fe_<94>Ni_6 as Po_2 varies from (10)^<-12> to (10)^<-16> atm at 1125℃, and from Fo_<66> to Fo_<77> and from Fe_<40>Ni_<60> to Fe_<84>Ni_<16> respectively as temperature varies from 1125°to 1275℃ at (10)^<-14> atm Po_2. Based on these experimental data, Po_2 for equilibration of this chondrite is estimated as about (10)^<-20> atm. The compositions of liquids coexisting with olivine, Ca-poor pyroxene and Fe-Ni metal at Po_2 lower than (10)^<-8.5> atm are within the compositional ranges of howardite and eucrite, suggesting that chondrites may have a genetical relationship with these basaltic achondrites.