Origin and Age of Metal Veins in Canyon Diablo Graphite Nodules.

Previous studies attributed the origin of metal veins penetrating graphite nodules in the Canyon Diablo IAB main group iron meteorite to condensation from vapor or melting of host metal. Abundances of 16 siderophile elements measured in kamacite within vein and host meteorite are most consistent with an origin by melting of the host metal followed by fractional crystallization of the liquid. The presence of the veins within graphite nodules may be explained by impact, as peak shock temperatures, and thus the most likely areas to undergo metal melting, are at metal-graphite interfaces.

Genetics, Age and Crystallization History of Group IIC Iron Meteorites.

The eight iron meteorites currently classified as belonging to the IIC group were characterized with respect to the compositions of 21 siderophile elements. Several of these meteorites were also characterized for mass independent isotopic compositions of Mo, Ru and W. Chemical and isotopic data for one, Wiley, indicate that it is not a IIC iron meteorite and should be reclassified as ungrouped.

New implications for the origin of the IAB main group iron meteorites and the isotopic evolution of the noncarbonaceous (NC) reservoir.

The origin of the IAB main group (MG) iron meteorites is explored through consideration of W isotopic compositions, thermal modeling of Al decay, and mass independent (nucleosynthetic) Mo isotopic compositions of planetesimals formed in the noncarbonaceous (NC) protosolar isotopic reservoir. A refined W model age for the meteorites Campo del Cielo, Canyon Diablo, and Nantan suggests that the IAB-MG parent body underwent some form of metal-silicate segregation as early as 5.3 ± 0.

Genetics, crystallization sequence, and age of the South Byron Trio iron meteorites: New insights to carbonaceous chondrite (CC) type parent bodies.

The nucleosynthetic Mo, Ru, and W isotopic compositions of the South Byron Trio iron meteorite grouplet (SBT) are consistent with all three meteorites originating on a single parent body that formed in the carbonaceous chondrite (CC) isotopic domain within the Solar nebula. Consistent with a common origin, the highly siderophile element (HSE) concentrations of the SBT can be related to one another by moderate degrees of fractional crystallization of a parental melt with initially chondritic relative abundances of HSE, and with initial S and P contents of ~7 and ~1 wt. %, respectively.

Excess W in IIAB iron meteorites: Identification of cosmogenic, radiogenic, and nucleosynthetic components.

The origin of W excesses in iron meteorites has been a recently debated topic. Here, a suite of IIAB iron meteorites was studied in order to accurately determine the contribution from galactic cosmic rays (GCR) and from potential decay of Os to measured excesses in the minor isotope W. In addition to W isotopes, trace element concentrations (Re, Os, Ir, Pt, W) were determined on the same samples, as well as their cosmic ray exposure ages, using Cl-Ar systematics.