Fig. 5.

Oxygen isotope and major element composition. (A) Oxygen three-isotope diagram showing silicate minerals collected by the Hayabusa spacecraft and representative compositions of major primary components of solar system matter. This plot includes bulk-rock data for refractory Ca-Al-rich inclusions (CAIs), carbonaceous, ordinary, enstatite, and R chondrites, and Mars. Ion microprobe data for Ol, Pl, Di, and low-Ca Px are indicated by the colored symbols (blue, light blue, green, and orange, respectively). Overlapping data for multiple phases are shown by the pie charts. The relative dimensions of the probed areas are expressed in the charts accordingly. The data for the minerals from Itokawa grains scatter around the range for whole-rock ordinary-chondrites and form an elongated cluster with a slope of approximately 0.5. The means of the analyses for each phase fall into the region for LL-ordinary chondrites defined by Clayton (15). Variation observed in O-isotope compositions is consistent with that observed by Yurimoto, et al. (5) although they interpreted the variation as possibly reflecting analytical ambiguity. (B) A diagram to show relative abundance of Mg-Mn-Fe and Na-K-Ca of silicate minerals from Itokawa grains plotted with those in equilibrated (4–6) ordinary chondrites (L and LL).