Chondrites osmium isotopes

Osmium isotopic ratio of the bulk silicate Earth overlaps measurements of ordinary chondrites but is distinct from other chondrite groups. Adapted from Righter et al. (2006). 

Walker, R.J. and J.W, Morgan Rhenium-Osmium Isotope Systematics of Carbonaceous Chondrites, Science, 519 (January 27, 1989). 

The oldest samples that provide direct constraints on the osmium isotopic composition of the upper mantle are rare spinel peridotites contained within the Early Archean Itsaq gneiss complex of southwest Greenland that are interpreted to be —3.81 Ga abyssal peridotites (Friend et al., 2002). The measured and initial compositions determined from low-Re/Os spinel and olivine mineral separates from these peridotites are the most primitive, in the sense of closest to solar-system initial compositions, Os isotopic compositions yet obtained on any terrestrial material (Bennett et al., 2002). This shows that at least some, if not all, of the Early Archean upper mantle was characterized by chondritic Os/ Os isotopic compositions. Osmium isotopic constraints from this time period (—3.8-3.9 Ga) are of particular interest as they provide a rough constraint on the timing of the addition of the late veneer of... 

Walker, R.J. and Morgan, J.W. (1989) Rhenium-osmium isotope systematics of carbonaceous chondrites. Science,... 

---