UNIVERSITY OF MARYLAND

ISOTOPE GEOCHEMISTRY LABORATORY

Professor Richard J. Walker: Director (rjwalker@umd.edu)

Senior Research Scientist Igor S. Puchtel: Laboratory Manager (ipuchtel@umd.edu)

(left) Peridotite xenolith from a quarry near Yangyuan, China was erupted onto the surface approximately 38 million years ago. Materials like this are examined in order to study the evolution of the lithospheric mantle underlying the North China Craton. Evidence suggests that the ancient lithospheric mantle that underlay China as late as the mid-Ordovician has been replace by younger mantle represented by the rock shown.

(right) Apollo 16 pristine lunar anorthosite 65035. This rock likely formed during the creation of the lunar crust, possibly via flotation from a magma ocean. The anorthositic portion of this rock is characterized by very low abundances of highly siderophile elements, indicating that the Moon's long history of meteorite bombardment did not chemically modify the rock. The rock is, however, coated with a glass splash, consistent with impact melting near the rock.

Overview & History

The Isotope Geochemistry Laboratory (IGL) is part of the Geochemistry Laboratories of the Department of Geology, University of Maryland. The IGL was created in 1991 by Profs. R. J. Walker and E. J. Krogstad in order to pursue state of the art isotopic and trace element analysis of geological and cosmochemical materials. Currently, the IGL comprises a set of five laboratories for the preparation and isotopic analysis of a wide range of geological materials. These laboratories include separate mass spectrometry, chemistry, mineral separation and rock preparation facilities. The IGL began operations in 1991 with the acquisition of a 12 inch radius of curvature NBS single-collector, solid source mass spectrometer. In 1992 a VG Sector 54 mass spectrometer with 7 faraday collectors, was added to the complement of analytical tools. A third thermal ionization mass spectrometer, a Thermo Fisher Triton, with 9 Faraday cups was installed in 2007. The NBS and VG mass spectrometers were retired from UMd service during the summer of 2014, ending their careers with us with 10,261 and 14,479 individual analyses, respectively. The NBS instrument was donated to Miami University, and the VG was donated to the University of Alabama. In their place a new Thermo Fisher Triton Plus was installed in the fall of 2014. A second mass spectrometry laboratory, shared with the Plasma Laboratory, houses a Nu Plasma multi-collector inductively coupled plasma mass spectrometer, as well as an Element 2 single collector ICP-MS. Operations of the IGL are primarily supported via the University of Maryland, and grants from the NSF and NASA. An overview of the types of research conducted within the IGL at be found at our research homepage.

The mission of the IGL is to produce the highest quality isotope data, to innovate in techniques development and applications, to train students and visitors the techniques involved in gathering such data, and to maintain itself as a world-class isotope measurement facility.

Facilities

The Thermal Ionization Mass Spectrometry Laboratory (CHEM 0218) of the IGL currently houses two solid source mass spectrometers, two filament degassing apparatuses, and laminar flow benches for sample loading. Each mass spectrometer has dedicated ion optics sources for Re and Pt filaments.

Photos show the UMd Thermo Fisher Triton mass spectrometers.

The Thermo Fisher Tritons were installed in 2007 and 2014. These instruments are primarily used for high precision measurement of W, Nd, Sr, Os, Ru and Mo isotopes as applied to geological/cosmochemical projects.

The Nu Plasma multi-collector ICP-MS uses high temperature plasma to ionize elements that have been either chemically separated and purified from a material, or liberated from a solid matrix via laser ablation. The relative intensities of the different isotopes of a given element are quantified using either the multiple faraday cups or multiple electron multipliers. This instrument is commonly used to measure the isotopic compositions of Mo, Li, W, Pt, Ru, Ir, Pd and Re.

Photo of Nu Plasma multi-collector ICP-MS, part of the UMd Plasma Laboratory.

Most samples for isotopic analysis are processed (elements of interest are purified from matrix) in the Chemistry Clean Laboratories. Two 500 sq. ft. laboratories are supplied with HEPA filtered air. Each contains class-100 vented laminar flow hoods, chemical fume hoods and multiple work stations (with fume extraction). The facility also utilizes two Milli-Q water purification systems, and currently operates eight sub-boiling stills (quartz and teflon).

(left) Air-lock entrance foyer to the "old" and "new" clean rooms (CHEM0216 & CHEM 0214). (right) Vented work stations (foreground) and 2 of 4 class 100 laminar flow hoods (background) present in the "old" chemical clean laboratory.

A 500 ft2 clean lab in CHEM 0214 was opened in 2007. Left photo shows all plastic cabinetry and work stations. Right photo shows perchloric acid scrubber hood.

Photo of a first stage rhenium elution accomplished using disposable anion exchange columns.

The Sample Digestion Laboratory (CHEM0221) and Rock Preparation (CHEM0219) laboratories were most recently renovated in 2002-2003. The Rock Preparation lab houses, short-term sample storage, a ceramic jaw crusher and disk mill, alloy mortar and pestle, rock splitter, SPEX Industries Shatterbox and Mixer Mill (both with agate and alumina grinding chambers), and a Leco diamond slow-speed saw for cutting iron meteorites. The Sample Digestion lab houses two ovens (one can achieve temperatures as high as 380°C), one muffle furnace, both oxy-propane and oxy-hydrogen torches (for sealing Pyrex and quartz Carius tubes) and an Anton-Paar high pressure asher (HPA). The asher is used for high temperature digestions of samples for Os isotope and highly siderophile element measurement.

Images of the Anton Paar high-pressure asher (HPA) at the University of Maryland. (a) The HPA as installed beneath its custom built extraction hood. The bench-top size of the HPA (b) and simple operational controls make it ideal for processing precious materials, where time and simple methods are of the essence. (c) Wrapping tool for closing the optically perfect caps to high-purity 50mL capacity quartz digestion vessels prior to loading in the HPA. (d) Rack containing 6 quartz vessels being prepared for cleaning. 7 high purity quartz digestion vessels can be loaded into the HPA for digestion at a time.

(left) Sample Digestion Laboratory. This lab is used for flux fusions, HPA digestions, oven digestions, and torch work associated with the closure of Carius tubes. (right) Torchbox for sealing Carius tubes. An oxygen-propane torch is used for sealing Pyrex tubes, and an oxygen-hydrogen torch is used to seal quartz tubes.

(left) Rock crushing/short-term storage room. (right) Nickel-sulfide fire assays are used for concentrating highly siderophile elements from large quantities of matrix.

Current Research in the IGL

Some of the main thrusts of research in the IGL include studies of the mantle and crust, the isotopic evolution of the oceans, and the evolution of the early solar system. Applications also target tectonic and environmental problems. The range of specific research topics currently active in the IGL include:

  • The evolution of siderophile elements in Earth's mantle and crust through time. Recent targets of interest include mafic-ultramafic rocks (including komatiites and ophiolites) from South Africa (Barberton Greenstone Belt komatiites), Zimbabwe (Belingwe komatiites), Finland (various komatiites and ophiolites), Canada (Abitibi Greenstone Belt komatiites), United Kingdom (Unst Ophiolite), Norway (Leka ophiolite), Chile (Taitao ophiolite), Switzerland (Totalp Massif) and Russia (Vetreny and Kostomuksha komatiites), as well as oceanic rocks including abyssal peridotites.
  • Use of 182Hf-182W, 187Re-187Os and 190Pt-186Os isotope systems to study mantle heterogeneities resulting from primordial planetary differentiation processes and possible interactions between the Earth's core and lowermost mantle. Targeted rocks include ancient komatiites and modern ocean island basalts.
  • The chronology and chemical evolution of solar system materials. Specific targets include iron meteorites, pallasites, chondrites, lunar volcanic glasses and basalts, lunar highland breccias, martian meteorites and presolar grains. These studies include the application of short- and long-lived chronometers based on radioactive decay, and research on isotopic heterogeneities in meteorites and their implications for stellar nucleosynthesis, nebular mixing and early evolution of the solar system.
  • Study of peridotite xenoliths plucked from the subcontinental lithospheric mantle as a means of constraining the age of lithospheric mantle creation, assemblage and possible destruction (in some regions, such as underlying the North China Craton). Work is currently centered mostly on samples from China and Antarctica.

A more detailed overview of the types of research conducted within the IGL at be found at our research homepage.

Staff

The faculty/staff presently engaged in research in the IGL currently include: Katherine Bermingham, Sarah Penniston-Dorland, Rich Gashnig, Jay Kaufman, Igor Puchtel, Roberta Rudnick, Richard Walker.

Past members of the IGL have included (with present affiliation): Harry Becker (Freie University), Al Brandon (University of Houston), Eirik Krogstad (Battelle Northwest), Christina Gallup (Univ. Minnesota, Duluth), Mary Horan (Carnegie Institution), Thomas Meisel (Leoben University), Seung Ryeol Lee (Korea Institute of Geoscience and Mineral Resources), Diane McDaniel (Montgomery College), Bill Minarik (McGill University), Tim Mock (Carnegie Institution), Sonia Esperança (NSF), John Morgan (retired), and Paul Tomascak (SUNY Oswego), Tod Waight (University of Copenhagen), Tetsuya Yokoyama (Tokyo Institute of Technology), James Day (Scripps Oceanographic Institute), Mathieu Touboul (ENS de Lyon).

Former IGL Postdocs (and current affiliation)

Thomas Meisel (1995-1996) (University of Leoben)

Alan Brandon (1997-1999) (University of Houston)

Tod Waight (1998-1999) (University of Copenhagen)

Harry Becker (1998-2001) (Freie University)

Diane McDaniel (2000-2003) (Montgomery College)

Aaron Pietruszka (2002-2003) (U. S. Geological Survey, Denver)

Seung Ryeol Lee (2004-2006) (Korea Institute of Geoscience and Mineral Resources)

Tetsuya Yokoyama (2006-2008) (Tokyo Institute of Technology)

James Day (2006-2010) (Scripps Oceanographic Institution)

Jingao Liu (2011-2012) (University of Alberta)

Mathieu Touboul (ENS de Lyon)

Students

Theses/dissertations completed:

  • Jerry L. Burgess (M.S., 1994-with LCP) Pressure-temperature-time-deformation (P-T-t-D) history of high-grade gneisses of the Port aux Basques area, southwest Newfoundland, Canada.
  • Jeffrey D. Jarriel (M.S., 1994) Use of Sr isotopic, hydrophysical, and other Geochemical data to delineate catchment flow paths during baseflow and storm events.
  • Paul B. Tomascak (Ph.D., 1995) The petrogenesis of granitic rocks in southwestern Maine.
  • Alison B. Schwab (M.S., 1995) Li isotope variability in ground and surface water in a first order agricultural catchment, eastern Maryland.
  • Michael I. Smoliar (Ph.D., 1996) Re-Os isotopic studies of magmatic iron meteorites.
  • Asuka Tsuru (M.S., 1997) The Os isotopic evolution of the upper mantle: the Jormua ophiolite complex, Finland.
  • Sarah E. Libeau (M.S., 1997) Pb isotope tracers in oyster shells from historic native American middens around the Chesapeake Bay.
  • Rachel A. Pressley (M.S.-with LCP, 1997) Petrogenesis of the Phillips pluton, Maine.
  • Gary S. Solar (Ph.D.-with LCP, 1999) Tracing melt migration and dating deformation, west-central Maine.
  • Donna Gunderson (M.S., 1999) Paleorecords of climate change.
  • Jinmei Tian (M.S.-with LCP, 2000) Petrogenesis of the Moose-lookmeguntic plutonic complex, Maine.
  • Ji Li (M.S., 2001) Use of the Re-Os isotope system to trace the origin of gold mineralizing fluids in the Allegheny District, California.
  • David Cook (M.S., 2001) Re-Os and Pt-Os isotopic systematics of evolved iron meteorites.
  • Stephen Lynton (Ph.D.-with LMDR, 2003) An experimental study of the isotopic fractionation and partitioning of lithium among quartz, muscovite, and fluids.
  • Amitava Gangopadhyay (Ph.D., 2004) Petrologic, geochemical and Os isotope studies of selected Precambrian komatiites.
  • Feng-Zhen Teng, (Ph.D., 2005) Quantifying the Li isotope composition of the upper continental crust.
  • Jacqueline L. Mann (Ph.D., 2005) Determination of sulfur isotope composition in sulfate from two high elevation snowpits by multi-collector thermal ionization mass spectrometry using a double spike.
  • Nick Geboy (M.S., 2006) Re-Os geochronology of organic-rich sediments.
  • Ruth Thompson Schulte (M.S., 2007) Isotopic systematics of mafic-ultramafic rocks of the Taitao ophiolite, Chile.
  • Tom Ireland (Ph.D., 2009) Highly siderophile element and tungsten systematics of Hawaiian picrites.
  • Kathleen Scheiderich (Ph.D., 2010) Stable Mo isotopes as tracers of redox conditions in modern and ancient oceans and estuaries.
  • Jingao Liu (Ph.D., 2011) Investigations of the history of the lithospheric mantle underlying the North China Craton.
  • Gregory Archer (M.S., 2012) Highly siderophile elements and the rhenium-osmium system in chondritic components.
  • Caitlin Brown (M.S., 2013) Petrogenesis of peraluminous granites from the Fosdick Mountains, Marie Byrd Land, West Antarctica
  • Julia Gorman (M.S., 2013) The role of mechanical mixing in the formation of reaction zones in subduction-related mélange.
  • Miriam Sharp (Ph.D., 2014) Determination of siderophile element characteristics throughout lunar history: implications for the lunar magma ocean and late heavy bombardment.

Theses/dissertations in progress:

  • Gregory Archer (Ph.D.)
  • Emily Worsham (Ph.D.)
  • Huan Cui (Ph.D.)
  • Willie Nicklas (Ph.D.)

As of 2015, the IGL has hosted research for a total of 23 senior undergraduate student theses.

Guest Users of the IGL have included (with affiliation at the time of visit):

Peter Ashley (Johns Hopkins University), Julie Bartley (West Georgia College), Lars Borg (Johnson Space Center), Chris Fedo (Virginia Tech), Robert Frei (Geologisk Institut Kobenhavns Universitet), Shan Gao (Key Laboratory of Continental Dynamics, Department of Geology, Northwestern University, Xi'an), Jenny Hall (Yale University), Eero Hanski (Geological Survey of Finland), Debra Hassler (Harvard University), Melissa Hicks (University of Nevada, Las Vegas), Steve Lev (Towson University), Gabriela Mora-Klepeis (University of Vermont), Brent Owens (College of William and Mary), Marcio Pimentel (Universidade de Brasilia), John Rakovan (Miami University of Ohio), Paula Shafer (Indiana University), Susanna Sichel (Universidade Federal Fluminense, Brazil), Michael Smoliar (Carnegie Institution of Washington), Ilona Suominen (University of Helsinki), Yasutaka Terakado (Kobe University), Malissa Washburn (University of Maine), Manuel Schilling (University of Chile), Elizabeth Widom (Miami University of Ohio), Lukas Ackerman (University of Prague), Curtis Williams (Indiana University), Joyashish Thakurta (Indiana University), Fu-yuan Wu (Changchun Univ. of Science and Tech., and Institute of Geology and Geophysics, Chinese Academy of Sciences), Hong-Lin Yuan (Key Laboratory of Continental Dynamics, Department of Geology, Northwestern University, Xi'an), Zhu-Yin Chu (Institute of Geology and Geophysics, Chinese Academy of Sciences), David van Acken (Freie University, Berlin), Brian O'Driscoll (Keele University), Robert Vocke (NIST), Zu Watanabe (Miami University of Ohio), Lorne Loudin (Keene State University), Christophe Robin (Univ. of Grenoble), Frederick Moynier (Washington University), Lynnette Pitcher (Stony Brook University), Eduardo Rocha (University of São Paulo), Amy Riches (University of Tennessee), Iva Gerasimenko (Randolph College), Eric Stifter (Indiana University), Brittany Sacco (James Madison University), Alex McCoy-West (Australian National University), Donal Ngonge (University of Sao Paolo).

IGL Publications 1992-2015
    1992
  1. Horan M.F., Morgan J.W., Walker R.J. and Grossman J.N. (1992) Re-Os isotope constraints on the age of iron meteorites. Science 255, 1118-1121.
  2. Morgan J.W., Walker R.J. and Grossman J.N. (1992) Rhenium-osmium isotope systematics in meteorites I: Magmatic iron meteorite groups IIAB and IIIAB. Earth Planet. Sci. Lett. 108, 191-202.
  3. 1993
  4. Krogstad E.J., Walker R.J., Nabelek P.I. and Russ-Nabelek C. (1993) Pb isotopic constraints on the origin of Archean and Proterozoic granites, Black Hills, South Dakota. Geochim. Cosmochim. Acta 57, 4677-4685.
  5. 1994
  6. Walker, R.J., Morgan, J.W., Hanski, E.J. and Smolkin, V.F. (1994) The role of the Re-Os system in the study of magmatic sulfide ores: A tale of three ores. Proceedings of Sudbury-Norilsk Symposium, Ontario Geological Survey Spec. Pub. 5, 343-355.
  7. Horan M.F, Morgan J.W., Grauch R.I., Coveney R., Murowchick J., Hulbert L. (1994) Re-Os isotopes in black shales and Ni-Mo-PGE-rich sulfide layers, Yukon Territory, Canada and Guizhou and Hunan, China. Geochim. Cosmochim. Acta. 58, 257-265.
  8. Krogstad E.J. and R.J. Walker (1994) High closure temperatures of the U-Pb system in large apatites from the Tin Mountain pegmatite, Black Hills, South Dakota. Geochim. Cosmochim. Acta 58, 3845-3853.
  9. Walker, R.J., Morgan J.W., Horan M.F., Czamanske G.F., Krogstad E.J., Fedorenko V. and Kunilov V.E. (1994) Re-Os isotopic evidence for an enriched-mantle source for the Noril'sk-type ore-bearing intrusions, Siberia. Geochim. Cosmochim. Acta 58, 4179-4197.
  10. Lambert D.D., Walker R.J., Morgan J.W., Shirey S.B., Carlson R.W., Zientek M.L., Lipin B.R., Koski M.S. and Cooper R.L. (1994) Re-Os and Sm-Nd isotope geochemistry of the Stillwater Complex, Montana: Implications for the petrogenesis of the J-M Reef. Journ. Petrol. 35, 1717-1753.
  11. 1995
  12. Morgan J.W., Horan M.F., Walker R.J. and Grossman J.N. (1995) Rhenium-osmium concentration and isotope systematics in group IIAB iron meteorites. Geochim. Cosmochim. Acta 59, 2331-2344.
  13. Shirey S.B. and Walker R.J. (1995) Carius tube digestion for low-blank rhenium-osmium analysis. Anal. Chem. 34, 2136-2141.
  14. Krogstad E.J., Hanson G.N. and Rajamani V. (1995) Sources of continental magmatism adjacent to the later Archean Kolar Suture Zone, south India:distinct isotopic and elemental signatures of two late Archean magmatic series. Contrib. Mineral. Petrol. 122, 159-173.
  15. Walker R.J., Morgan J.W. and Horan M.F. (1995) 187Os enrichment in some mantle plume sources: Evidence for core-mantle interaction? Science 269, 819-822.
  16. Horan M.F., Walker R.J., Fedorenko V.A. and Czamanske G.K. (1995) Os and Nd isotopic constraints on the temporal and spatial evolution of Siberian flood basalt sources. Geochim. Cosmochim. Acta 59, 5159-5168.
  17. Burgess, J.L., Brown, M., Dallmeyer, R.D. and van Staal, C.R. (1995) Microstructure, metamorphism, thermochronology and P-T-t-deformation history of the Port aux Basques Gneisses, Southwest Newfoundland, Canada. Journal of Metamorphic Geology, 13, 751-776.
  18. 1996
  19. Smoliar M.I., Walker R.J. and Morgan J.W. (1996) Re-Os ages of group IIA, IIIA, IVA and IVB iron meteorites. Science 271, 1099-1102.
  20. Meisel T., Biino G.G. and Nagler T. (1996) Re-Os, Sm-Nd and rare earth element evidence for Proterozoic subcontinental and oceanic lithosphere in tectonized ultramafic lenses from the Swiss Alps. Geochim. Cosmochim. Acta 60, 2583-2593.
  21. Tomascak P.B., Krogstad E.J. and Walker R.J. (1996) U-Pb monazite geochronolgy of granitic rocks from Maine:implications for late Paleozoic tectonics in the northern Appalachians. J. of Geol. 104, 185-195.
  22. Koide M., Goldberg E.D. and Walker R. (1996) The analysis of seawater osmium. Deep-Sea Res. 43, 53-55.
  23. Walker R.J., Hanski E.J., Vuollo J. and Liipo J. (1996) The Os isotopic composition of Proterozoic upper mantle:evidence for chondritic upper mantle from the Outokumpu ophiolite, Finland. Earth Planet. Sci. Lett. 141, 161-173.
  24. Krogstad E.J. and Walker R.J. (1996) Evidence of heterogeneous crustal sources: the Harney Peak Granite, South Dakota, U.S.A. Trans. Roy. Soc. Edinburgh; Earth Sciences 87, 331-337.
  25. Meisel T., Walker R.J. and Morgan J.W. (1996) The osmium isotopic composition of the Earth's primitive upper mantle. Nature 383, 517-520.
  26. Fedo C.M., Eriksson K.A. and Krogstad E.J. (1996) Geochemistry of shales from the Archean (~3.0 Ga) Buhwa Greenstone Belt, Zimbabwe: implications for provenance and source-area weathering. Geochim. Cosmochim. Acta 60, 1751-1764.
  27. Tomascak P.B., Krogstad E.J. and Walker R.J. (1996) Nature of the crust in Maine, USA: evidence from the Sebago batholith. Contrib. Mineral. Pet. 125, 45-59.
  28. Carlson R.W., Esperança S. and Svisero D.P. (1996) Chemical and Os isotopic study of Cretaceous potassic rocks from southern Brazil. Contrib. Mineral. Pet. 125, 393-405.
  29. 1997
  30. Terakado Y., Fujitani T. and Walker R.J. (1997) Nd and Sr isotopic constraints on the origin of igneous rocks resulting from the opening of the Japan Sea, southwestern Japan. Contrib. Mineral. Pet. 129, 75-86.
  31. Walker R. J., Morgan J.W., Hanski E.J. and Smolkin V. (1997) Re-Os systematics of Early Proterozoic ferropicrites, Pechenga Complex, NW Russia:evidence for ancient 187Os-enriched plumes. Geochim. Cosmochim. Acta 61, 3145-3160.
  32. Meisel T., Lange J.-M. and Krähenbühl U. (1997) The chemical variation of moldavite tektites: simple mixing of terrestrial sediments. Meteoritics & Planetary Science 32, 493-502.
  33. Walker R.J., Morgan J.W., Smoliar M.I., Beary E., Czamanske G.K. and Horan M.F. (1997) Application of the 190Pt-186Os isotope system to geochemistry and cosmochemistry Geochim. Cosmochim. Acta 61, 4799-4807.
  34. Meisel T., Melcher F., Tomascak P., Dingeldey C. and Koller F. (1997) Re-Os isotopes in orogenic peridotite massifs in the eastern Alps, Austria. Chemical Geology 143, 217-229.
  35. Esperança S, Carlson R.W., Shirey S.B. and Smith D. (1997) Dating crust-mantle separation: Re-Os isotopic study of mafic xenoliths from central Arizona. Geology 25, 651-654.
  36. Ashley, P., Krogstad, E., Lees, P., Silbergeld, E., and Smith, D. (1997) The use of stable lead isotopes to identify and apportion sources of lead in urban house dust. in: Hazardous Waste: Impacts on Human and Ecological Health, (B. Johnson, C. Xintaras, and J. Andrews, eds.), Princeton Science Publications, p. 139-150.
  37. 1998
  38. Horan M.F., Smoliar M. and Walker R.J. (1998) 182W and 187Re-187Os systematics of iron meteorites: chronology for melting, differentiation and crystallization of asteroids. Geochim. Cosmochim. Acta 62, 545-554.
  39. Shirey S.B. and Walker R.J. (1988) Re-Os isotopes in cosmochemistry and high-temperature geochemistry. Annual Reviews of the Earth and Planetary Sciences 26, 423-500.
  40. Asmerom Y. and Walker R.J. (1998) Pb and Os isotopic constraints on the composition and rheology of the lower crust. Geology 26, 359-362.
  41. Brandon A., Walker R.J., Morgan J.W., Norman M.D. and Prichard H. (1998) Coupled 186Os and 187Os evidence for core-mantle interaction. Science 280, 1570-1573.
  42. Tomascak P.B., Krogstad E.J. and Walker R.J. (1998) Nd isotope systematics and the derivation of granitic pegmatites in southwestern Maine, USA. Can. Min. 36, 327-337.
  43. 1999
  44. Tomascak P.B., Krogstad E.J. and Walker R.J. (1999) Clues to the significance of the Norumbega Fault Zone in southwestern Maine from the geochemistry of granitic rocks. In, The Norumbega Fault Zone, eds. A. Ludman and D.P. West, G.S.A. Special Paper 331, 105-119.
  45. Pressley, R.A. and Brown, M. (1999) The Phillips Pluton, Maine, USA: Evidence of heterogeneous crustal sources, and implications for granite ascent and emplacement mechanisms in convergent orogens. Lithos 46, 335-366.
  46. Brown, M. and Pressley, R.A. (1999) Crustal melting in nature: Prosecuting source processes. Physics and Chemistry of the Earth 24, 305-316.
  47. Walker R.J., Storey M., Kerr A. and Tarney J. (1999) Implications of 187Os heterogeneities in mantle plumes: evidence from Gorgona Island and Curaçao. Geochim. Cosmochim. Acta 63, 713-728.
  48. Tomascak P.B., Tera F., Helz R. and Walker R.J. (1999) The absence of lithium isotope fractionation during basalt differentiation: New measurments by multicollector sector ICP-MS. Geochim. Cosmochim. Acta 63, 907-910.
  49. Brandon A.D., Norman M.D., Walker R.J. and Morgan J.W. (1999) 186Os-187Os systematics of Hawaiian picrites. Earth Planet. Sci. Lett., 172, 25-42.
  50. 2000
  51. Tsuru A., Walker R.J., Kontinen A., Peltonen P. and Hanski E. (2000) Re-Os isotopic systematics of the Jormua Ophiolite Complex, NW Finland. Chemical Geology 164, 123-141.
  52. Böhlke J.K. and Horan M. (2000) Strontium isotope geochemistry of groundwaters and streams affected by agriculture, Locust Grove, MD. Applied Geochemistry 15, 599-609.
  53. Righter K., Walker R.J. and Warren P.H. (2000) Significance of highly siderophile elements and Os isotopes in the lunar and terrestrial mantles. in Origin of the Earth and Moon, R. Canup and K. Righter eds., Univ. of Arizona Press, Tucson, 291-322.
  54. Borisov A. and Walker R.J. (2000) Os solubility in silicate melts: new efforts and results. American Mineralogist 85, 912-918.
  55. Brandon A.D., Snow J.E., Walker R.J., Morgan J.W. and Mock T.D. (2000) 190Pt-186Os and 187Re-187Os systematics of abyssal peridotites. Earth Planet. Sci. Lett. 177, 319-335.
  56. Borg L.E., Brandon A.D., Clynne M.A. and Walker R.J. (2000) Re-Os isotopic systematics of primitive basalts from the Lassen region of the Cascade arc, California. Earth Planet. Sci. Lett. 177, 301-317.
  57. Helz G.R., Adelson J.M., Miller C.V., Cornwell J.C., Hill J.M., Horan M. and Walker R.J. (2000) Osmium isotopes demonstrate distal transport of contaminated sediments in Chesapeake Bay. Environmental Science and Technology 34, 2528-2534.
  58. Becker H. (2000) Re-Os isotopic systematics of eclogites: Implications for crustal recycling. Earth Planet. Sci. Lett. 177, 287-300.
  59. Walker R.J. (2000) News & Views: The extraterrestrial wedding ring. Nature 406, 359-360.
  60. Brandon A.D., Walker R.J., Morgan J.W. and Goles G.G. (2000) Re-Os isotopic evidence for early differentiation of the Martian mantle. Geochim. Cosmochim Acta. 64, 4083-4095.
  61. Czamanske G.K., Wooden J.L., Walker R.J., Fedorenko V.A., Simonov O.N., Budahn J.R. and Siems D.F. (2000) Geochemical, isotopic and SHRIMP age data for Precambrian basement rocks, Permian volcanic rocks, and sedimentary host rocks to the ore-bearing intrusions, Noril'sk-Talnakh District, Siberian Russia. International Geology Review, 42, 895-927.
  62. 2001
  63. Begemann F., Ludwig K.R., Lugmair G.W., Min K.W., Nyquist L.E., Patchett P.J., Renne P.R., Shih C.-Y., Villa I.M. and Walker R.J. (2001) Towards and improved set of decay constants for geochronological use. Geochim. Cosmochim Acta 65, 111-121.
  64. Meisel T., Walker R.J., Irving A.J., and Lorand J.-P. (2001) Osmium isotopic compositions of mantle xenoliths: a global perspective. Geochim. Cosmochim Acta. 65, 1311-1323.
  65. Walker R.J. and Stone W.R. (2001) Os isotope constraints on the origin of the 2.7 Ga Boston Creek flow, Ontario, Canada. Chemical Geology 175, 567-579.
  66. Hanski E., Walker R.J., Huhma H. and Suominen I. (2001) The Os and Nd isotopic systematics of the 2.44 Ga Akanvaara and Koitelainen mafic layered intrusions in northern Finland. Precambrian Research 109, 73-102.
  67. Horan M.F., Morgan J.W., Walker R.J. and Cooper R. (2001) Re-Os isotopic constraints on magma mixing in the peridotite zone of the Stillwater Complex, Montana. Contrib. Mineral. Petrol. 141, 446-457.
  68. Becker H., Walker R.J., MacPherson G.J., Morgan J.W. and Grossman J.N. (2001) Rhenium-osmium systematics of calcium-aluminum-rich inclusions in carbonaceous chondrites. Geochim. Cosmochim. Acta 65, 3379-3390.
  69. Morgan J.W., Walker R.J., Brandon A.D. and Horan M.F. (2001) Siderophile elements in Earth's upper mantle and lunar breccias: Data synthesis suggests manifestations of the same late influx. Meteoritics and Planetary Science 36, 1257-1275.
  70. Waight T.E., Wiebe R.A., Krogstad E.J. and Walker R.J. (2001) Isotopic responses to basaltic injections into silicic magma chambers: a whole rock and microsampling study of macrorhythmic units in the Pleasant Bay layered gabbro-diorite complex, Maine, USA. Contrib. Mineral. Petrol. 142, 323-335.
  71. Becker H., Shirey S.B. and Carlson R.W. (2001) Effects of melt percolation on the Re-Os systematics of peridotites from a Paleozoic convergent plate margin. Earth Planet. Sci. Lett. 188, 107-121.
  72. Meisel T., Moser J. and Wegscheider W. (2001) Recognizing heterogeneous distribution of platinum group elements (PGE) in geological materials by means of the Re-Os isotope system. Fresenius J. Anal. Chem. 370, 566-572.
  73. Dorais, M. J., Wintsch, R. P., Becker H. (2001) The Massabesic gneiss complex, New Hampshire: a study of a portion of the Avalon terrane. American Journal of Science 301, 657-682.
  74. 2002
  75. Morgan J.W., Walker R.J., Horan M.F. and Beary E.S. (2002) 190Pt-186Os and 187Re-187Os systematics of the Sudbury Igneous Complex, Ontario. Geochim. Cosmochim. Acta 66, 273-290.
  76. Walker R.J., Prichard H.M., Ishiwatari A. and Pimentel M. (2002) The osmium isotopic composition of convecting upper mantle deduced from ophiolite chromitites. Geochim. Cosmochim. Acta 66, 329-345.
  77. Tomascak P.B., Widom E., Benton L.D., Goldstein S.L. and Ryan J.G. (2002) The control of lithium budgets in island arcs. Earth Planet. Sci. Lett. 196, 227-238.
  78. Owens B.E. and Tomascak P.B. (2002) Mesoproterozoic lamprophyres in the Labrieville Massif, Quebec: Clues to the origin of alkalic anothosites? Can. J. Earth Sci. 39, 983-997.
  79. Zack T., Tomascak P.B., Rudnick R.L., Dalpe C. and McDonough W.F. (2003) Extremely light Li in orogenic eclogites: The role of isotope fractionation during dehydration in subducted oceanic crust. Earth and Planetary Science Letters 208, 279-290.
  80. Walker R.J. and Nisbet E. (2002) 187Os isotopic constraints on Archean mantle dynamics. Geochim. Cosmochim. Acta 66, 3317-3325.
  81. Walker R.J., Horan M.F., Morgan J.W., Becker H., Grossman J.N. and Rubin A. (2002) Comparative 187Re-187Os systematics of chondrites: Implications regarding early solar system processes. Geochim. Cosmochim. Acta 66, 4187-4201.
  82. Becker H., Dalpe C. and Walker R.J. (2002) High precision Ru isotopic measurements by multi-collector ICP-MS. The Analyst 127, 775-780.
  83. 2003
  84. Brandon A.D., Walker R.J., Puchtel I.S., Becker H, Humayun M. and Revillon S. (2003) 186Os-187Os systematics of Gorgona Island komatiites: implications for early growth of the inner core. Earth Planet. Sci. Lett. 206, 411-426.
  85. Horan M.F., Walker R.J., Morgan J.W., Grossman J.N. and Rubin A. (2003) Highly siderophile elements in chondrites. Chem. Geol. 196, 5-20.
  86. Becker H. and Walker R.J. (2003) The 98Tc-98Ru and 99Tc-99Ru chronometers: new results on iron meteorites and chondrites. Chem. Geol. 196, 43-56.
  87. Wu F., Walker R.J., Ren X-w, Sun D-y and Zhou X-h. (2003) Osmium isotopic constraints on the age of lithospheric mantle beneath northeastern China. Chem. Geol. 196, 107-129.
  88. Gangopadhyay A. and Walker R.J. (2003) Re-Os systematics of the ca. 2.7 Ga Alexo komatiites, Ontario, Canada. Chem. Geol. 196, 147-162.
  89. Tomascak P.B., Hemming N.G., and Hemming S.R. (2003) The lithium isotopic composition of waters of the Mono Basin, California. Geochim. Cosmochim. Acta 67, 601-611.
  90. Arndt N.T., Czamanske G.K., Walker R.J., Chauvel C. and Fedorenko V.A. (2003) Geochemistry and origin of the intrusive hosts of Noril'sk-Talnakh Cu-Ni-PGE deposits. Econ. Geol. 98, 495-515.
  91. Becker H. and Walker R.J. (2003) Efficient mixing of the solar nebula from uniform Mo isotopic composition of meteorites. Nature 425, 152-155.
  92. 2004
  93. Lazar G.C., Walker D. and Walker R.J. (2004) Experimental partitioning of Tc, Mo, Ru and Re between solid and liquid during crystallization in Fe-Ni-S. Geochim. Cosmochim. Acta 68, 643-651.
  94. McDaniel D.K., Walker R.J., Hemming S.R., Horan M.F., Becker H. and R. I Grauch (2004) Sources of osmium to the modern oceans: New evidence from the 190Pt-186Os system. Geochim. Cosmochim. Acta 68, 1243-1252.
  95. Cook D.L. Walker R.J., Horan M.F., Wasson J.T. and Morgan J.W. (2004) Pt-Re-Os systematics of group IIAB and IIIAB iron meteorites. Geochim. Cosmochim. Acta 68, 1413-1431.
  96. West, D.P., Jr., Coish, R.A., and Tomascak, P.B. (2004) Tectonic setting and regional correlation of Ordovician metavolcanic rocks of the Casco Bay Group, Maine: Evidence from trace element and isotope geochemistry: Geol. Mag. 141, 125-140.
  97. Hanski E.J., Walker R.J. Huhma H., Polyakov, G.V., Glotov, A.I., Tran Trong Hoa, Ngo Thi Phuong (2004) Origin of Permo-Triassic komatiites, northwestern Vietnam. Contrib. Mineral. Petrol. 147, 453-469.
  98. Balykin, P.A., Polyakov, G.V., Hanski, E., Walker, R.J., Huhma, H., Glotov, A.I., Trang Trong Hoa, Ngo Thi Phuong, Hoang Huu Thanh, Tran Quoc Hung, Petrova, T.E. (2004) Late-Permian komatiite-basalt complex in the Song Da rift, northwestern Vietnam. Journal of Geology (Vietnam), Series B, No. 23, 52-64.
  99. Gornostayev S.S., Walker R.J., Hanski E.J. and Popovchenko S.E. (2004) Evidence for the emplacement of ca. 3.0 Ga lithospheric mantle in the Ukrainian Shield. Precamb. Res. 132, 349-362.
  100. Gelinas A., Kring D.A., Zurcher L., Urrutia-Fucugauchi J., O. Morton and Walker R.J. (2004) Osmium isotope constraints on the proportion of bolide component in Chicxulub impact meltrocks. Meteoritics Planet. Sci. 39, 1003-1008.
  101. Teng F.Z., McDonough W.F., Rudnick R.L., Dalpé C., Tomascak P.B., Gao S., Chappell B.W. (2004) Lithium isotopic composition and concentration of the upper continental crust. Geochim. Cosmochim. Acta 68, 4181-4192.
  102. Tomascak P.B. (2004) Developments in the understanding and application of lithium isotopes in the Earth and planetary sciences. In: Johnson CM, Beard BA, and Albarede F (eds) Geochemistry of Non-Traditional Isotope Systems, Min. Soc. Amer. Reviews Mineralogy Geochemistry. 55, 153-195.
  103. Walker R. J., Horan M.F., Shearer C.K. and Papike J.J. (2004) Depletion of highly siderophile elements in the lunar mantle: evidence for prolonged late accretion. Earth Planet. Sci. Lett. 224, 399-413.
  104. Rudnick R.L., Tomascak P.B., Njo H.B. and Gardner L.R. (2004) Extreme lithium isotopic fractionation during continental weathering revealed in saprolites from South Carolina. Chem. Geol. 212, 45-57.
  105. 2005
  106. Hulbert L.J., Hamilton M.A., Horan M.F. and Scoates R.F.J. (2005) U-Pb zircon and Re-Os isotope geochronology of mineralized ultramafic intrusions and associated nickel ores from the Thompson nickel belt, Manitoba, Canada. Econ. Geol. 100, 29-41.
  107. Tomascak P.B., Brown M., Solar G.S., Becker H., Centorbi T.L., and Tian J. (2005) Source contributions to Devonian granite magmatism near the Laurentian border, New Hampshire and Western Maine, USA. Lithos 80, 75-99.
  108. Walker R. J., Brandon A.D., Bird J.M., Piccoli P.M., McDonough W.F. and Ash R.D. (2005) 186Os-187Os systematics of Os-Ir-Ru alloy grains, southwestern Oregon. Earth Planet. Sci. Lett 230, 211-226.
  109. Brandon A. D. and Walker R.J. (2005) The debate over core-mantle interaction. Earth Planet. Sci. Lett. Frontiers 232, 211-225.
  110. Terakado Y. and Walker R.J. (2005) Nd, Sr and Pb isotopic and REE geochemical study of Miocene submarine hydrothermal deposits (Kuroko deposits), Japan, Contrib. Mineral. Petrol. 149, 388-399.
  111. Walker R.J. and Walker D. (2005) Does the core leak? EOS 86, 237-242.
  112. Lynton S.J., Walker R.J. and Candela P.A. (2005) Lithium isotopes in the system Qz-Ms-fluid. Geochim. Cosmochim. Acta 69, 3337-3347.
  113. Puchtel I.S., Brandon A.D., Humayun M., and Walker, R.J. (2005) Evidence for the early differentiation of the core from Pt-Re-Os isotope systematics of 2.8-Ga komatiites. Earth Planet. Sci. Lett. 237, 118-134.
  114. Gangopadhyay A., Sproule R.A., Walker R.J. and Lesher M. (2005) Re-Os systematics of komatiites and komatiitic basalts at Dundonald Beach, Ontario, Canada: Evidence for a complex alteration history and implications of a late-Archean chondritic mantle source. Geochim. Cosmochim. Acta 69, 5087-5098.
  115. Mann J.L. and Kelly W.R. (2005) Measurement of sulfur isotope composition (δ34S) by multiple-collector thermal ionization mass spectrometry using a 33S-36S double spike. Rapid Commun. In Mass Spectrom. 19, 3429-3441.
  116. 2006
  117. Brandon A.D., Humayun M., Puchtel I.S., Leya I. and Zolensky M. (2006) Osmium isotope evidence for an s-process carrier in primitive chondrites. Science 309, 1233-1236.
  118. Pietruszka A.J., Walker R.J. and Candela P.A. (2006) Determination of mass dependent molybdenum isotopic variations by MC-ICP-MS: an evaluation of matrix effects. Chem. Geol. 225, 121-136.
  119. Gangopadhyay A., Walker R.J., E. Hanski, and P. Solheid (2006) Origin of Paleoproterozoic Ti-enriched komatiitic rocks from Jeesiörova, Kittilä Greenstone Complex, Finnish Lapland. Journal of Petrology 47, 773-789.
  120. Teng F.-Z., McDonough W.F., Rudnick R.L. and Walker R.J. (2006) Diffusion-driven extreme lithium isotopic fractionation in country rocks of the Tin Mountain pegmatite. Earth Planet. Sci. Lett. 243, 701-710.
  121. Brandon A.D., Walker R.J. and Puchtel I.S. (2006) Platinum-Os isotope evolution of the Earth's mantle: constraints from chondrites and Os-rich alloys. Geochim. Cosmochim. Acta 70, 2093-2103.
  122. Lee S. R., Horton J.W. and Walker R.J. (2006) Osmium-isotope and platinum-group element systematics of impact melt rocks, Chesapeake Bay Impact Structure, Virginia, USA. Meteoritics Planet. Sci. 41, 819-833.
  123. Teng F.-Z., McDonough W.F., Rudnick R.L. and Walker R.J. (2006) Lithium isotopic systematics of granites and pegmatites from the Black Hills, South Dakota. Am. Min. 91, 1488-1498.
  124. Lee S. R. and Walker R. J. (2006) Re-Os isotope systematics of mantle xenoliths from South Korea: evidence for complex growth and loss of lithospheric mantle beneath East Asia. Chem. Geol. 231, 90-101.
  125. Becker H., Horan M.F., Walker R.J., Gao S., Lorand J.-P. and Rudnick R.L. (2006) Highly siderophile element composition of the Earth's primitive upper mantle: Constraints from new data on peridotite massifs and xenoliths. Geochim. Cosmochim. Acta 70, 4528-4550.
  126. Wu F-Y., Walker R.J., Yang Y-H., Yuan H-L., and Yand J-H. (2006) The chemical-temporal evolution of lithospheric mantle underlying the North China Craton. Geochim. Cosmochim. Acta 70, 5013-5034.
  127. 2007
  128. Yuan H., Gao S., Rudnick R.L., Jin Z., Liu Y., Puchtel I., Walker R.J. and Yu R. (2007) Re-Os evidence for age and origin of peridotites from the Dabie-Sulu ultrahigh pressure metamorphic belt, China. Chem. Geol. 236, 323-338.
  129. West Jr. D.P., Tomascak P.B., Coish R.A., Yates M.G. and Reilly M.J. (2007) Petrogenesis of the ultrapotassic Lincoln syenite, Maine: late Silurian-early Devonian melting of a source region modified by subduction-driven metasomatism. Amer. J. Sci. 307, 265-310.
  130. Yokoyama T., Rai V.K., Alexander C.M.O'D., Lewis R.S., Carlson R.W., Shirey S.B., Thiemens M.H. and Walker R.J. (2007) Osmium isotope evidence for uniform distribution of s- and r-process components in the early solar system. Earth and Planet. Sci. Lett. 259, 567-580.
  131. Puchtel I., Humayun M. and Walker R.J. (2007) Os-Nd-Pb isotope and lithophile and siderophile trace element systematics of komatiitic rocks from the Volotsk suite, SE Baltic Shield. Precambrian Res. 158, 119-137.
  132. Walker R.J., Böhlke J.-K., McDonough W.F. and Li J. (2007) Combined Re-Os isotope, gold and platinum-group element study of epigenetic gold ores, Alleghany District, California. Economic Geology 102, 1079-1089.
  133. 2008
  134. Walker R.J., McDonough W.F., Honesto J., Chabot N.L., McCoy T.J., Ash R.D. and Bellucci J.J. (2008) Modeling fractional crystallization of group IVB iron meteorites. Geochim. Cosmochim. Acta 72, 2198-2216.
  135. Van Acken D., Becker H. and Walker R.J. (2008) Mantle refertilization processes and their impact on the Re-Os systematics of peridotites: a case study from the Totalp ultramafic massif, eastern Switzerland. Earth Planetary Sci. Lett. 268, 171-181.
  136. Gao S., Rudnick R.L., Xu W-L., Yuan H-L., Liu Y-S., Walker R.J., Puchtel I.S., Liu X., Huang H. and Wang X-R. (2008) Recycling deep cratonic lithosphere and generation of intraplate magmatism in the North China Craton. Earth Planet. Sci Lett. 270, 41-53.
  137. Puchtel I.S., Walker R.J., James O.B. and Kring D.A. (2008) Osmium isotope and highly siderophile element systematics of lunar impact melt rocks: Implications for the late accretion history of the Moon and Earth. Geochim. Cosmochim. Acta 72, 3022-3042.
  138. Sichel S.E., Espernca S., Motoki A., Maia M., Horan M.F., Szartman P., Alves E.dC. and Mello S.M. (2008) Geophysical and geochemical evidence for cold upper mantle beneath the equatorial Atlantic Ocean. Revista Brasileira de Goefisica 26, 69-86.
  139. 2009
  140. Day J.M.D., Ash R.D., Liu Y., Bellucci J.J., Rumble D., McDonough W.F., Walker R.J. and Taylor L.A. (2009) Early formation of evolved asteroidal crust. Nature 457, 179-182.
  141. Ireland T., Walker R.J. and Garcia M.O. (2009) Highly siderophile element and 187Os isotopes systematics of Hawaiian picrites: Implications for parental melt composition and source heterogeneity. Chemical Geology 260, 112-128.
  142. Pitcher L., Helz R.T., Walker R.J. and Piccoli P.M. (2009) Fractionation of the platinum-group elements and Re during crystallization of basalt in Kilauea Iki lava lake, Hawaii. Chemical Geology 260, 196-210.
  143. Yokoyama D., Walker D. and Walker R.J. (2009) Low osmium solubility in silicate at high pressures and temperatures. Earth Planetary Sci. Lett. 279, 165-173.
  144. Basu A., Day J.M.D., Liu Y., Rumble D. and Taylor L.A. (2009) Petrogenesis of olivine-phyric shergottite Larkman Nunatak 06319: Implications for enriched components in Martian basalts. Geochim. Cosmochim. Acta 73, 2190-2214.
  145. Walker R.J. (2009) Highly siderophile elements in the Earth, Moon and Mars: Update and implications for planetary accretion and differentiation. Chemie der Erde 69, 101-125.
  146. Ackerman L., Walker R.J., Puchtel I.S., Pitcher L., Jelínek E. and Strnad L. (2009) Effects of melt perolation on highly siderohile elements and Os isotopes in subcontinental lithospheric mantle: a study of the upper mantle profile beneath Central Europe. Geochim. Cosmochim. Acta 73, 2400-2414.
  147. Ireland T.J., Arevalo R.D., Walker R.J. and McDonough W.F. (2009) Tungsten in Hawaiian picrites: a compositional model for the source of Hawaiian lavas. Geochim. Cosmochim. Acta 73, 4517-4530.
  148. Puchtel I.S., Walker R.J., Anhaeusser C.R. and Gruau G. (2009) Re-Os isotope systematics and HSE abundances of the 3.5 Ga Schapenburg komatiites, South Africa: evidence for hydrous melting or prolonged survival of primordial heterogeneities in the mantle? Chemical Geology 262, 355-369.
  149. Rudnick R.L. and Walker R.J. (2009) Ages from Re-Os isotopes in peridotites. Proceedings of the 9th Kimberlite Conference, Lithos 112S, 1083-1095.
  150. Chu Z-Y., Wu F-Y., Walker R.J., Rudnick R.L., Pitcher L., Puchtel I.S., Yang Y-H. and Wilde S.A. (2009) Temporal evolution of the lithospheric mantle beneath the eastern North China Craton. Journ. Petrol. 50, 1857-1898.
  151. Schulte R.F., Schilling M., Horan M.F., Anma R., Komiya T., Farquhar J., Piccoli P.M., Pitcher L. and Walker R.J. (2009) Chemical and chronologic complexity in the convecting upper mantle: evidence from the Taitao Ophiolite, southern Chile. Geochim. Cosmochim. Acta 73, 5793-5819.
  152. O'Driscoll B., Day J.M.D., Daly J.S., Walker R.J. and McDonough W.F. (2009) Rhenium-osmium isotopes and platinum-group elements in the Rum Layered Suite, Scotland: implications for Cr-spinel seam formation and the longevity of the Iceland mantle anomaly. Earth Planet. Sci. Lett. 286, 41-51.
  153. Horan M.F., Alexander C.M.O'D. and Walker R.J. (2009) Highly siderophile element evidence for early solar system processes in components from ordinary chondrites. Geochim. Cosmochim. Acta 73, 6984-6997.
  154. Puchtel I.S., Walker R.J., Brandon A.D. and Nisbet E.G. (2009) Pt-Re-O isotope and HSE systematics of the 2.7 Ga Belingwe and Abitibi komatiites. Geochim. Cosmochim. Acta 73, 6367-6389.
  155. Liu Y., Floss C., Day J.M.D., Hill E. and Taylor L.A. (2009) Petrogenesis of lunar mare basalt meteorite Miller Range 05035. Meteoritics and Planet. Sci. 44, 261-284.
  156. 2010
  157. Van Acken D., Becker H. and Walker R.J., McDonough W.F., Wombacher F., Ash R.D. and Piccoli P.M. (2010) Formation of pyroxenite layers in the Totalp ultramafic massif (Swiss Alps) – insights from highly siderophile elements and Os isotopes. Geochim. Cosmochim. Acta 74, 661-683.
  158. Scheiderich K., Helz G.R. and Walker R.J. (2010) Century-long record of Mo isotopic composition in sediments of a seasonally anoxic estuary (Chesapeake Bay). Earth Planet. Sci. Lett. 289, 189-197.
  159. Day J.M.D., Walker R.J., James O.B. and Puchtel I.S. (2010) Osmium isotope and highly siderophile element systematics of the lunar crust. Earth Planet Science Lett. 289, 595-605.
  160. Yokoyama T., Alexander C.M.O'D. and Walker R.J. (2010) Osmium isotope anomalies in chondrites: results for acid residues enriched in insoluble organic matter. Earth Planet. Sci. Lett. 291, 48-59.
  161. Van Acken D., Becker H., Hammerschmidt K., Walker R.J. and Wombacher F. (2010) Highly siderophile elements and Sr-Nd isotopes in refertilized mantle peridotites – a case study from the Totalp ultramafic massif, Swiss Alps. Chem. Geol. 276, 257-268.
  162. Yang J-H., O'Reilly S., Walker R.J., Griffin W., Wu F-Y., Zhang M. and Pearson N. (2010) Diachronous decratonization of the Sino-Korean Craton: geochemistry of mantle xenoliths from North Korea. Geology 38, 799-802.
  163. Liu J., Rudnick R.L., Walker R.J., Gao S., Wu F. and Piccoli P. (2010) Processes controlling highly siderophile element fractionations in xenolithic peridotites and their influence on Os isotopes. Earth Planet. Sci. Lett. 297, 287-297.
  164. Scheiderich K., Zerkle A.L., Helz G.R., Farquhar J. and Walker R.J. (2010) Molybdenum isotope, multiple sulphur isotope, and redox-sensitive element behaviour in early Pleistocene Mediterranean sapropels. Chemical Geology 279, 134-144.
  165. Bottke W.F., Walker R.J., Day J.M.D., Nesvorny D. and Elkins-Tanton L. (2010) Stochastic late accretion to Earth, the Moon and Mars. Science 330, 1527-1530.
  166. Hanghøj K., Kelemen P.B., Hassler D., and Godard M. (2010) Composition and genesis of depleted mantle peridotites from the Wadi Tayin Massif, Oman Ophiolite; major and trace element geochemistry, and Os isotope and PGE systematics. Journ. of Petrol. 51, 201-227.
  167. Day J.M.D., Pearson D.G., Macpherson C.G., Lowry D. and Carracedo J.C. (2010) Evidence for distinct proportions of subducted oceanic crust and lithosphere in HIMU-type mantle beneath El Hierro and La Palma, Canary Islands. Geochim. Cosmochim. Acta 74, 6565-6589.
  168. Blichert-Toft J. and Puchtel I.S. (2010) Depleted mantle sources through time: evidence from Lu-Hf and Sm-Nd isotope systematics of Archean komatiites. Earth Planet. Sci. Lett. 297, 598-606.
  169. 2011
  170. Riches A.J.V., Liu Y., Day J.M.D., Puchtel I.S., Rumble D., McSween H.Y., Walker R.J. and Taylor L.A. (2011) The petrology and geochemistry of Yamato 984028: a cumulate lherzolitic shergottites with affinities to Y 000027, Y 000047, and Y 000097. Polar Sci. 4, 497-514.
  171. Yokoyama T., Alexander C.O'D. and Walker R.J. (2011) Assessment of nebular versus parent body processes on presolar components in chondrites: evidence from Os isotopes. Earth Planet. Sci. Lett. 305, 115-123.
  172. Liu J., Rudnick R.L., Walker R.J., Gao S., Wu F-y., Piccoli P.M., Yuan H., Xu W-L. and Xu Y-G. (2011) Mapping lithospheric boundaries using Os isotopes of mantle xenoliths: an example from the North China Craton. Geochim. Cosmochim. Acta 75, 3881-3902.
  173. Ireland T.J., Walker R.J. and Brandon A.D. (2011) 186Os-187Os systematics of Hawaiian picrites revisited: additional insights into the causes of Os isotopic variations in ocean island basalts. Geochim. Cosmochim. Acta 75, 4456-4475.
  174. Moskovitz N. and Walker R.J. (2011) Size of the group IVA meteorite core: constraints from the age and composition of Muonionalusta. Earth Planet. Sci. Lett. 308, 410-416.
  175. Hanski E.J., Luo Z-Y., Oduro H. and Walker R.J. (2011) The Pechenga Ni-Cu sulfide deposits, NW Russia: a review with new constraints from the feeder dikes. In: Li., C., Ripley, E.M. (eds.) Magmatic Ni-Cu and PGE Deposits: Geology, Geochemistry, and Genesis. Reviews in Economic Geology 17, 145-162.
  176. Connolly B.D., Puchtel I.S., Walker R.J., Arevalo R., Piccoli P.M., Byerly G., Robin-Popieul C. and Arndt N. (2011) Highly siderophile element systematics of the 3.3 Ga Weltevreden komatiites, South Africa: implications for early Earth history. Earth Planet. Sci. Lett. 311, 253-263.
  177. 2012
  178. McCoy T.J., Walker R.J., Goldstein J.I., Yang J., McDonough W.F., Rumble D., Chabot N.L., Ash R.D., Corrigan C.M., Michael J.R. and Kotula P.G. (2011) Group IVA irons: new constraints on the crystallization and cooling history of an asteroidal core with a complex history. Geochim. Cosmochim. Acta 75, 6821-6843.
  179. Touboul M. and Walker R.J. (2012) High precision tungsten isotope measurement by thermal ionization mass spectrometry. International Journal of Mass Spectrometry 309, 109-117.
  180. Brandon A.D., Puchtel I.S., Walker R.J., Day J.M.D., Irving A.J. and Taylor L.A. (2012) Evolution of the martian mantle inferred from the 187Re-187Os isotope and highly siderophile element systematics of shergottites meteorites. Geochim. Cosmochim. Acta 76, 206-235.
  181. Day J.M.D., Walker R.J., Ash R.D., Liu Y., Rumble D., Irving A.J., Goodrich C.A., Tait K., McDonough W.F. and Taylor L.A. (2012) Origin of Graves Nunataks 06128 and 06129, brachinites and brachinite-like achondrites by partial melting of volatile-rich primitive parent bodies. Geochim. Cosmochim. Acta 81, 94-128.
  182. Penniston-Dorland S. C., Walker R.J., Pitcher L. and Sorensen S. S. (2012) Mantle-crust interactions in a paleosubduction zone: evidence from highly-siderophile element systematics of eclogite and related rocks. Earth Planet. Sci. Lett. 319-320, 295-306.
  183. Touboul M., Puchtel I.S. and Walker R.J. (2012) 182W evidence for long-term preservation of early mantle differentiation products. Science 335, 1065-1069, DOI: 10.1126/science.1216351.
  184. O'Driscoll B., Day J.M.D., Walker R.J., Daly S., McDonough W.F. and Piccoli P.M. (2012) Chemical heterogeneity in the upper mantle recorded by peridotites and chromitites from the Shetland Ophiolite Complex, Scotland. Earth Planet. Sci. Lett. 333-334, 226-237.
  185. Hibbert K.E.J., Williams H.M. and Puchtel I.S. (2012) Iron isotopes in ancient and modern komatiites: evidence in support of an oxidised mantle from Archean to present. Earth Planet. Sci. Lett. 321-322, 198-207.
  186. Rocha E.R.V., Puchtel I.S., Marques L.S., Walker R.J., Machado F.B., Nardy A.J.R., Babinski M. and Figueiredo A.M.G. (2012) Re-Os isotope and highly siderophile element systematics of the Paraná continental flood basalts (Brazil). Earth Planet. Sci. Lett. 337-338, 164-173.
  187. Day J.M.D., Walker R.J., Qin L. and Rumble D. (2012) Early timing of late accretion in the solar system. Nature Geoscience 5, 614-617.
  188. Walker R.J. (2012) Evidence for homogeneous distribution of osmium in the protosolar nebula. Earth Planet. Sci. Lett. 351-352, 36-44.
  189. Riches A.J.V., Day J.M.D., Walker R.J., Simonetti A., Liu Y., Neal C.R., and Taylor L.A. (2012) Rhenium-osmium isotope and highly-siderophile element abundance systematics of angrite meteorites. Earth Planet. Sci. Lett. 353-354, 208-218.
  190. Moynier F., Day J.M.D., Okui W., Yokoyama T., Bouvier A., Walker R.J. and Podosek F.A. (2012) Planetary-scale strontium isotopic heterogeneity. Astrophys. Journ. 758, 45.
  191. Liu J., Carlson R.W., Rudnick R.L., Walker R.J., Gao S. and Wu F-y. (2012) Comparative Sr-Nd-Hf-Os-Pb isotopic systematics of xenolithic peridotites from Yangyuan, North China Craton: additional evidence for a Paleoproterozoic age. Chem. Geol. 332-333, 1-14.
  192. Jenniskens P., Fries M.D., Yin Q-Z., Zolensky M., Krot A.N., Sandford S.A., Sears D., Beauford R., Ebel D.S., Friedrich J.M., Nagashima K., Wimpenny J., Yamakawa A., Nishiizumi K., Hamajima Y., Cafee M.W., Welten K.C., Laubenstein M., Davis A.M., Simon S.B., Heck P.R., Young E.D., Kohl I.E., Thiemens M.H., Nunn M.H., Mikouchi T., Hagiya K., Ohsumi K., Cahil T.A., Lawton J.A., Barnes D., Steele A., Rochette P., Verosub K.L., Gattacceca J., Cooper G., Glavin D.P., Burton A.S., Dwrorkin J.P., Elsila J.E., Pizzarello S., Ogliore R., Schmitt-Koppin P., Harir M., Herkorn N., Verchovsky A., Grady M., Nagao K., Okazaki R., Takechi H., Hiroi T., Smith K., Silber E.A., Brown P.G., Albers J., Klotz D., Hankey M., Matson R., Fries J.A., Walker R.J., Puchtel I., Lee C-T. A., Erdman M.E., Eppich G.R., Roeske S., Gabelica Z., Lerche M., Nuevo M., Girten B. and Worden S.P. (2012) Radar enable recovery of the Sutter's Mill meteorite, a carbonaceous chondrite regolith breccia. Science 338, 1583-1587. DOI: 10.1126/science.1227163.
  193. 2013
  194. Ackerman L., Pitcher L., Strnad L., Puchtel I.S., Jelínek E. and Walker R.J. (2013) Highly siderophile element geochemistry of peridotites and pyroxenites from Horní Bory: implications for HSE behaviour in subduction-related upper mantle. Geochim. Cosmochim. Acta 100, 158-175.
  195. McCoy-West A.J., Puchtel I.S., Bennett V.C. and Walker R.J. (2013) Extreme persistence of cratonic lithosphere in the Southwest Pacific: Paleoproterozoic Os isotopic signatures in Zealandian mantle xenoliths. Geology, doi:10.1130/G33626.1.
  196. Puchtel I.S., Blichert-Toft J., Touboul M., Walker R.J., Byerly G.R., Nisbet E.G. and Anhaeusser C.R. (2013) Insights into early Earth from Barberton komatiites: evidence from lithophile isotope and trace element systematics. Geochim. Cosmochim. Acta 108, 63-90.
  197. Arevalo Jr. R., McDonough W.F., Stracke A., Willbold M., Ireland T.J. and Walker R.J. (2013) Simplified mantle architecture and distribution of radiogenic power. Geochem. Geophys Geosyst. 14, 2265-2285.
  198. Geboy N.J., Kaufman A.J., Walker R.J., Misi A., de Oliviera T.F., Miller K.E., Azmy K., Kendall B. and Poulton S. (2013) Re-Os age constraints and new observations of glacial deposits in the Mesoproterozoic Vazante Group, Brazil. Precamb. Res. 238, 199-213.
  199. 2014
  200. Walker R.J. (2014) Rhenium-Osmium Dating (Meteorites), Encyclopedia of Scientific Dating Methods. (W.J. Rink and J. Thompson eds.), Springer Science. 9 pp. DOI 10.1007/978-94-007-6326-5_85-1.
  201. Puchtel I.S., Walker R.J., Touboul M., Nisbet E.G. and Byerly G.R. (2014) Insights into early Earth from the Pt-Re-Os isotope and highly siderophile element abundance systematics of Barberton komatiites. Geochim. Cosmochim. Acta 125, 394-413.
  202. Sharp M., Gerasimenko I., Loudin L.C., Liu J., James O.B., Puchtel I.S. and Walker R.J. (2014) Characterization of the dominant impactor signature for Apollo 17 impact melt rock. Geochim. Cosmochim. Acta 131, 62-80.
  203. Archer G.J., Bullock E.S., Ash R.D. and Walker R.J. (2014) 187Re-187Os isotopic and highly siderophile element systematics of the Allende meteorite: evidence for primary nebular processes and late-stage alteration. Geochim. Cosmochim. Acta 131, 402-414.
  204. Kruijer T.S., Touboul M., Fischer-Gӧdde M., Bermingham K.R., Walker R.J. and Kleine T. (2014) Protracted core formation and rapid accretion of protoplanets. Science 344, 1150-1154.
  205. Touboul M., Liu J., O"Neil J., Puchtel I.S. and Walker R.J. (2014) New insights into the Hadean mantle revealed by 182W and highly siderophile element abundances of supracrustal rocks from the Nuvvuagittuq Greenstone Belt, Quebec, Canada. Chem. Geol. 383, 63-75.
  206. Penniston-Dorland S.C., Gorman J.K., Bebout G.E., Piccoli P.M. and Walker R.J. (2014) Reaction rind formation in the Catalina Schist: deciphering a history of mechanical mixing and metasomatic alteration. Chem. Geol. 384, 47-61.
  207. Walker R.J. (2014) Siderophile element constraints on the origin of the Moon. Phil. Trans. Roy. Soc. A 372, 20130258, DOI:10.1098/rsta.2013.0258.
  208. Stepanova A.V., Samsonov A.V., Salnikova E.B., Puchtel I.S., Larionova O., Larionov A.N., Stepanov V.S., Shapovalov Y.B. and Egorova S.V. (2014) Palaeoproterozoic continental MORB-type tholeiites in the Karelian Craton: petrology, geochronology, and tectonic setting. Journ. Petrol. 55, 1719-1751.
  209. González-Jiménez J.M., Barra F., Walker R.J., Reich M. and Gervilla F. (2014) Geodynamic implications of ophiolitic chromitites in the La Cabaña ultramafic bodies, Central Chile. Internat. Geology Rev. 56, 1466-1483.
  210. Brown S., Elkins-Tanton L. and Walker R.J. (2014) Effects of magma ocean crystallization and overturn on the development of 142Nd and 182W isotopic heterogeneities in the primordial mantle. Earth Planet. Sci. Lett. 408, 319-330.
  211. Antonelli M.A., Kim S-T., Peters M., Labidi J., Cartigny P., Walker R.J., Lyons J.R., Hoek J., and Farquhar J. (2014) An early inner Solar System origin for anomalous sulfur isotopes in differentiated protoplanets. Proc. Natl. Acad. Sci. 111, 17749-17754.
  212. 2015
  213. Liu J., Rudnick R.L., Walker R.J., Xu W-l, Gao S. and Wu Y-y. Big insights from tiny peridotites: evidence for persistence of Precambrian lithosphere beneath the eastern North China Craton. Tectonophysics, in press.
  214. Sharp M., Righter K. and Walker R.J. Estimation of trace element concentrations of the lunar magma ocean using mineral-melt and metal-silicate partition coefficients. Meteoritics and Planet. Sci., in press.
  215. Carlson R.W., Boyet M., O'Neil J., Rizo H. and Walker R.J. Early differentiation and its long term consequences for Earth evolution. AGU Monograph Series, in press.
  216. Liu J., Sharp M., Ash R.D., Kring D.A. and Walker R.J. Diverse impactors in Apollo 15 and 16 impact melt rocks: evidence from osmium isotopes and highly siderophile elements. Geochim. Cosmochim. Acta, in press.