Terrestrial fractionation line

Bulk meteorites, the Moon and Mars lie within a few percentile above or below the terrestrial fractionation line on a three-oxygen isotope plot (see Fig. 3.1). Therefore, the oxygen isotope composition of the Sun has been assnmed to be the same as that of the Earth. This view has changed with the suggestion of Clayton (2002) that the Sun and the initial composition of the solar system are 0-rich com-... 

Oxygen 3-isotope plot showing excesses of 160 in minerals from calcium-aluminum inclusions (CAIs). All samples from Earth rocks plot along the terrestrial fractionation line. Mass-dependent fractionation processes cannot move a composition off of this line, so the excesses of 160 were clearly isotopic anomalies. After Clayton et al. (1977). 

Most chondrite classes (ordinary, carbonaceous, and enstatite chondrites) plot in unique positions on a three-isotope oxygen plot (Figure 4). Carbonaceous and K chondrites fall below the terrestrial fractionation line (Cl chondrites are the only exception), whereas ordinary, enstatite, and R chondrites each form well-defined clusters on or above the terrestrial fractionation line. However,... 

Oxygen-isotopic data for Cl chondrites provide some constraints on the location of alteration. The bulk compositions of Cl chondrites lie close to the terrestrial fractionation line on a three-isotope plot, with a of 4-0.38 0.09%o... 

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