Engineering topics
Righter, K.
Publications and source records attributed to Righter, K..
Experimental Determination of Spinel/Melt, Olivine/Melt, and Pyroxene/Melt Partition Coefficients for Re, Ru, Pd, Au, and Pt
Experimental studies have identified spinels as important hosts phases for many of the highly siderophile elements (HSE). Yet experimental studies involving chromite or Cr-rich spinel have been lacking. Experimental studies of partitioning of HSEs between silicate, oxides and silicate melt are plagued by low solubilities and the presence of small metallic nuggets at oxygen fugacities relevant to magmas, which interfere with analysis of the phases of interest. We have circumvented these problems in two ways: 1) performing experiments at oxidized conditions, which are still relevant to natural systems but in which nuggets are not observed, and 2) analysis of run products with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), allowing a combination of high sensitivity and good spatial resolution.
Diffusion of Siderophile Elements in Fe Metal: Application to Zoned Metal Grains in Chondrites
The distribution of highly siderophile elements (HSE) in planetary materials is controlled mainly by metal. Diffusion processes can control the distribution or re-distribution of these elements within metals, yet there is little systematic or appropriate diffusion data that can be used to interpret HSE concentrations in such metals. Because our understanding of isotope chronometry, redox processes, kamacite/taenite-based cooling rates, and metal grain zoning would be enhanced with diffusion data, we have measured diffusion coefficients for Ni, Co, Ga, Ge, Ru, Pd, Ir and Au in Fe metal from 1200 to 1400 C and 1 bar and 10 kbar. These new data on refractory and volatile siderophile elements are used to evaluate the role of diffusional processes in controlling zoning patterns in metal-rich chondrites.
What is the Earth Made Of?
Measurements made on materials from Earth, Mars, comets, and meteorites of Mg/Si, Al/Si, oxygen, Os, D/H, Ar/H2O, and Kr/Xe ratios, all lead to the conclusion that no primitive material similar to Earth mantle material is currently represented in our meteorite collections. Additional information is contained in the original extended abstract.
Nickel and Cobalt Partitioning Between Spinel and Basaltic Melt: Applications to Planetary Basalt Suites
New experimental spinel/melt partition coefficients for Ni and Co have been measured in basalt samples with natural levels of Ni and Co, are lower than previous high doping experiments, and are applied to several planetary basalt suites. Additional information is contained in the original extended abstract.
Rhenium and Iridium Partitioning in Silicate and Magmatic Spinels: Implications for Planetary Magmatism and Mantles
Highly siderophile elements Re, Ru and Ir partition strongly into spinel structures with large octahedral sites. New experimental results for both magmatic and silicate spinels will be presented with a few planetary implications. Additional information is contained in the original extended abstract.
Petrography, Mineralogy and Petrology of Two New HED Meteorites: Diogenite GRA98108 and Howardite GRA98030
Two new HED meteorites are described. GRA98108 is an olivine-bearing diogenite at the Mg-rich end of the diogenite clan. GRA98030 is a howardite with 30% eucritic and 70% diogenitic clasts, and contains an MgO-rich and CaO- and Al2O3-poor glassy spherule. Additional information is contained in the original extended abstract.
Interpreting HSE Contents of Planetary Basalts: The Importance of Sulfide Saturation and Under-Saturation
Highly siderophile elements provide important constraints on planetary differentiation due to their siderophile behavior. Their interpretation in terms of planetary differentiation models has so far overlooked the importance of sulfide saturation and under-saturation.
Tungsten Partitioning in Silicates. A Key to Understanding the Early Evolution of the Moon
We investigate the partitioning behavior of W in a variety of silicates that may have been stable during LMO crystallization, evaluate their role in generating W isotopic signatures, and speculate about the early differentiation of the Moon.