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Richard J. Walker
University of Maryland, College Park
ChondriteGeologyMeteoriteGeochemistryMantle (geology)
383Publications
67H-index
15.8kCitations
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Publications 380
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#1J. R. Reimink (PSU: Pennsylvania State University)H-Index: 7
#2Andrea Mundl‐Petermeier (UMD: University of Maryland, College Park)H-Index: 1
Last. D. Graham Pearson (U of A: University of Alberta)H-Index: 23
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#1Connor D. Hilton (UMD: University of Maryland, College Park)H-Index: 2
#2Richard J. Walker (UMD: University of Maryland, College Park)H-Index: 67
Abstract The origin of the IAB main group (MG) iron meteorites is explored through consideration of 182W isotopic compositions, thermal modeling of 26Al decay, and mass independent (nucleosynthetic) Mo isotopic compositions of planetesimals formed in the noncarbonaceous (NC) protosolar isotopic reservoir. A refined 182W 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...
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#1Connor D. Hilton (UMD: University of Maryland, College Park)H-Index: 2
#2Richard D. Ash (UMD: University of Maryland, College Park)H-Index: 24
Last. Richard J. Walker (UMD: University of Maryland, College Park)H-Index: 67
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#1A. Mundl-Petermeier (UMD: University of Maryland, College Park)H-Index: 1
#2Richard J. Walker (UMD: University of Maryland, College Park)H-Index: 67
Last. Mark D. Kurz (WHOI: Woods Hole Oceanographic Institution)H-Index: 54
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Abstract The short-lived 182Hf-182W isotope system (t1/2 = 9 Ma) left evidence in both ancient and modern terrestrial rock record of processes that took place during the earliest stages of Earth’s accretionary and differentiation history. We report µ182W values (the deviation of 182W/184W of a sample from that of laboratory standards, in parts per million) and corresponding 3He/4He ratios for rocks from 15 different hotspots. These rocks are characterized by µ182W values that range from ∼0 to as...
1 CitationsSource
#1Simone Marchi (SwRI: Southwest Research Institute)H-Index: 48
#2Richard J. Walker (UMD: University of Maryland, College Park)H-Index: 67
Last. Robin M. Canup (SwRI: Southwest Research Institute)H-Index: 29
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The approximately chondritic estimated relative abundances of highly siderophile elements (HSE) in the bulk martian mantle suggest that these elements were added after Mars’ core formed. The shergottite-nakhlite-chassigny (SNC) meteorites imply an average mantle Pt abundance of ≈3 to 5 parts per billion, which requires the addition of 1.6 × 1021 kilograms of chondritic material, or 0.25% martian masses, to the silicate Mars. Here, we present smoothed particle hydro-dynamics impact simulations th...
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#1Emmanuel Donald Ngonge (USP: University of São Paulo)H-Index: 2
#2Maria Helena Bezerra Maia de Hollanda (USP: University of São Paulo)H-Index: 16
Last. Carlos José Archanjo (USP: University of São Paulo)H-Index: 18
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Abstract The northeastern part of the Borborema Province, NE Brazil is noteworthy for its history of crust formation from the Archean to Cenozoic, which certainly resulted in chemical changes in the lithospheric mantle beneath. Here we examine the chemical evolution of the subcontinental lithospheric mantle (SCLM) in the northeastern Borborema Province using the Re–Os isotopic system combined with major and trace element, including highly siderophile element (HSE) data for 23 mantle xenoliths. T...
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#1Richard J. WalkerH-Index: 67
Last. Mary F. HoranH-Index: 31
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#2Richard J. WalkerH-Index: 67
Last. Eero HanskiH-Index: 19
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#1A. Mundl-Petermeier (UMD: University of Maryland, College Park)H-Index: 1
#2Richard J. Walker (UMD: University of Maryland, College Park)H-Index: 67
Last. S. A. Halldorsson (University of Iceland)H-Index: 15
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Abstract Studies of short-lived radiogenic isotope systems and noble gas isotopic compositions of plume-derived rocks suggest the existence of primordial domains in Earth's present-day mantle. Tungsten-182 anomalies together with high 3He/4He in Phanerozoic rocks from large igneous provinces and ocean island basalts demonstrate the preservation of early-formed (within the first 60 Ma of solar system history) mantle domains tapped by modern mantle plumes. It has proven difficult to link the evide...
6 CitationsSource
#1J. K. Gorman (UMD: University of Maryland, College Park)H-Index: 3
#2Sarah C. Penniston-Dorland (UMD: University of Maryland, College Park)H-Index: 16
Last. Richard J. Walker (UMD: University of Maryland, College Park)H-Index: 67
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Abstract Traverses across amphibole-chlorite schist metamorphic reaction zones at contacts between meta-igneous and ultramafic rocks in high-pressure melange zones were analyzed for highly siderophile element (HSE) concentrations and 187 Os/ 188 Os in two melange zones (Catalina Schist, Santa Catalina Island, CA, and Attic-Cycladic Complex, Syros, Greece) in order to investigate the relative effects of mechanical mixing and diffusive and advective transport by fluids in subduction-related reacti...
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