Abstract:

Bulk concentrations of Ir,Os,Co and the other siderophile elements of metal phase in chondrites increase significantly with degree of oxidation,Which,together with Co-Content of kamacite and Fa-content of olivine,reveal a continuous trend of variation of redox among chondrites.Intermediate groups of E/H,H/L,L/LL,and LL/C,lying between E and H,H and L,L and LL,LL and C,respectively,are proposed based on Co-content of kamacite,Fa-content of olivine,Fs-content of low Ca pyroxene,bulk concentrations of Ir,Os and Co of the metal phase and other criteria of classification.The discovery of intermediate groups increases the number of groups of chondrites from 9 to 13.Both the variation of redox among chondrites and the existence of intermediate groups of chondrites suggest a continuous chemical fractionation in the primordial solar nebula.