Publications by authors named "Gregory J Archer"

The abundances of highly siderophile elements (HSE; including Re, Os, Ir, Ru, Pt, and Pd) and Re-Os isotopic systematics were determined for two fragments from ungrouped achondrite NWA 7325. Rhenium-Os systematics are consistent with closed-system behavior since formation or soon after. The abundances of the HSE were therefore largely unaffected by late-stage secondary processes such as shock or terrestrial weathering.

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Northwest Africa (NWA) 6704 is a unique achondrite characterized by a near-chondritic major element composition with a remarkably intact igneous texture. To investigate the origin of this unique achondrite, we have conducted a combined petrologic, chemical, and Re-Os, O, and Ti isotopic study. The meteorite consists of orthopyroxene megacrysts (EnWoFs; Fe/Mn = 1.

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The abundances of highly siderophile elements (HSE: Re, Os, Ir, Ru, Pt, Pd), as well as Re-Os and Hf-W isotopic systematics were determined for separated metal, slightly magnetic, and nonmagnetic fractions from seven H4 to H6 ordinary chondrites. The HSE are too abundant in nonmagnetic fractions to reflect metal-silicate equilibration. The disequilibrium was likely a primary feature, as Re-Os data indicate only minor open-system behavior of the HSE in the slightly and non-magnetic fractions.

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Here we describe a new analytical technique for the high-precision measurement of W/W and W/W using negative thermal ionization mass spectrometry (N-TIMS). We improve on the recently reported method of Trinquier et al. (2016), which described using Faraday cup collectors coupled with amplifiers utilizing 10 Ω resistors to continuously monitor the O/O of WO and make per-integration oxide corrections.

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