Fig. 1. Backscattered electron image of (a) Bencubbin and (b) Weatherford. In the clast on the left of (a), metal grains that are sulfide free and that contain rounded sulfide blebs are sintered together with arcuate sulfide occurring at the grain margins. The clast on the right of (a) contains few sulfides. The Weatherford clast in (b) has a similar texture to the large Bencubbin clast on the left in (a). Scale bars are (a) 2 mm and (b) 0.5 mm.

Fig. 2. Siderophile element abundances in Bencubbin, Weatherford, and Gujba metal clasts, normalized to Fe and CI abundances (Anders and Grevesse, 1989). Data below detection limits are not shown. Open circles are bulk instrumental neutron activation analysis data from Bencubbin (Kallemeyn et al., 1978).

Fig. 3. Abundance ratios of Mo, Ru, Rh, Pd, W, Re, Os, Pt, and Au to Ir in Bencubbin (circles), Gujba (squares), and Weatherford (triangles) metal clasts. The dashed lines are chondritic values (Anders and Grevesse, 1989). The refractory siderophiles strongly correlate with one another in nearly chondritic proportions, although Mo and W show more scatter than the others. The nonrefractory siderophiles Pd and Au are fractionated from Ir at high Ir concentrations.

Fig. 4. Ir/Fe vs. Ni/Fe (top) and Pd/Fe vs. Ni/Fe (bottom) for metal clasts in Bencubbin (circles), Gujba (squares), and Weatherford (triangles). The chondritic abundances (Anders and Grevesse, 1989) are represented by the solid square. The addition or removal of Fe during redox processing is represented by the thin solid line. Calculated equilibrium condensation trajectories, at nebular pressures of 10⁻⁶ (bottom), 10⁻⁴ (middle), and 10⁻² (top) bar are indicated by heavy dotted lines. The condensation trajectory of a gas that is metal enriched by a factor of 10⁷, relative to the nebular conditions, is shown as a heavy solid line. Data from within a single zoned metal grain in QUE 94411 (Campbell et al., 2001a) are shown as solid diamonds; 2σ errors on these points are 20%. Note that the QUE 94411 data and the Bencubbin data follow different trends in Pd/Fe vs. Ni/Fe.

Fig. 5. Mo/Ir vs. W/Ir for metal clasts in Bencubbin (circles), Gujba (squares), and Weatherford (triangles). Scaling these elements against Ir allows the effect of oxidation to be observed independently of the refractory behavior of Mo and W. The chondritic abundances are represented by the solid square. Solid curves represent condensation paths in a metal-enriched (10⁷×) gas, with various oxidation fugacities indicated by their difference in log units from the iron-wüstite (IW) buffer.

Fig. 6. Condensation curves for Fe, Cu, Pd, and Ir under nebular and metal-rich conditions. Gray curves, at lower temperatures, represent condensation of solid metal alloy from a solar gas at 10⁻⁴ bar total pressure. Black curves, at higher temperatures, represent condensation of liquid metal alloy from a gas that is uniformly enriched in the siderophile elements by a factor of 10⁷ relative to the solar gas. Note that Pd is significantly more refractory than Fe in the metal-rich gas, in contrast to its behavior in solar gas, while Ir is highly refractory relative to Fe in both cases.

Fig. 7. Volatile element abundances in Bencubbin, Weatherford, and Gujba metal clasts, compared to the calculated condensation paths for a solar nebula at 10⁻⁴ bar (dashed curves) and a gas that is metal enriched by a factor of 10⁷ relative to the nebular conditions (solid curves). Upper figure: Cu (solid circles/black curves), Ga (open circles/gray curves); lower figure: Sb (solid circles/black curves), Au (open circles/gray curves). Chondritic compositions are indicated by solid squares.

Table 1. Laser ablation ICP-MS standards. Underlined entries indicate values used in calibration. Italicized entries denote detection limits. Data in ppm unless otherwise indicated. Errors are 2σ. Literature values from Buchwald; Wasson; Sylvester and Campbell. Reference values for SRM 1263a and SRM 1158 are values certified by the National Institute of Standards and Technology.

Table 2. Laser ablation ICP-MS data from metal in the bencubbinites Bencubbin, Weatherford, and Gujba. Italicized entries denote detection limits. Errors are 2σ.