Department of Geology

CURRICULUM VITAE: RICHARD J. WALKER

Business Address: Department of Geology, University of Maryland, College Park, Maryland 20742. (301) 405-4089. rjwalker AT umd.edu

Education
1981-1984: State University of New York, Stony Brook. Completed Ph.D. Geochemistry,
December 1984. Dissertation Title: "The Origin of the Tin Mountain Pegmatite, Black Hills, South Dakota".
Advisors: J.J. Papike and G.N. Hanson.

1979-1981: State University of New York, Stony Brook. Completed M.S. Geology,
May 1981. Thesis Title: "A Study of Apollo 15 Regolith and Agglutinate Glass".
Advisor: J.J. Papike.

1975-1979: College of William and Mary, Williamsburg, Virginia. Completed B.S. Geology, May 1979.

Employment

1998-present: Professor of Geology, Department of Geology, University of Maryland, College Park
1997: Visiting Scientist, Max Planck Institut für Chemie, Mainz, Germany
1993-1998: Associate Professor of Geology, Department of Geology, University of Maryland, College Park.
1990-1993: Assistant Professor of Geology, Department of Geology, University of Maryland, College Park.
1989-1990: Geologist, U.S. Geological Survey, Isotope Branch, Reston, Virginia.
1987-1989: Research Associate, Carnegie Institution of Washington, Department of Terrestrial Magnetism, Washington D.C.
1985-1987: National Research Council Postdoctoral Fellow, National Bureau of Standards, Gaithersburg, Maryland.
1981-1984: Research Assistant, SUNY, Stony Brook.
1979-1981: Teaching Assistant, SUNY, Stony Brook.

Awards

2009 Fellow, American Geophysical Union
2009 Fellow, Geochemical Society
2005 College of Computer, Mathematics and Physical Science Board of Visitors Distinguished Faculty Award
1997 Alexander von Humboldt Fellowship.
1990 Geochemical Society Clarke Medal.

Peer Reviewed Publications (1981-2009)

1. Walker R.J. and Papike J.J. (1981) The relationship of the lunar regolith <10 micron fraction and agglutinates. Part 2: Chemical composition of agglutinate glass as a test of the fusion of the finest fraction model. Proc. 12th Lunar and Planet. Sci. Conf., 421-432.

2. Walker R.J. and Papike J.J. (1981) The Apollo 15 regolith: Comparative petrology of drive tube 15010/15011 and drill core section 15003. Proc. 12th Lunar and Planet. Sci. Conf., 485-508.

3. Walker R.J. and Papike J.J. (1981) The Apollo 15 regolith: Chemical modelling and mare/highland mixing. Proc. 12th Lunar and Planet. Sci. Conf., 509-517.

4. Laul J.C., Walker R.J., Shearer C.K., Papike J.J. and Simon S.B. (1984) Chemical migration by contact metamorphism between pegmatite and country rocks: Natural analogs for radionuclide migration. Mat. Res. Soc. Symp. Proc. 26, 951-958.

5. Shearer C.K., Papike J.J. and Walker R.J. (1985) Mineral chemistry of the Harney Peak Granite and associated pegmatites. In Geology of the Black Hills, South Dakota and Wyoming, F.J. Rich (Ed.), American Geological Institute, Alexandria, VA 241-260.

6. Walker R.J., Hanson G.N., Papike J.J., O'Neil J.R. and Laul J.C. (1986) The internal evolution of the Tin Mountain pegmatite, Black Hills, South Dakota. Am. Min. 71, 440-459.

7. Walker R.J., Hanson G.N., Papike J.J. and O'Neil J.R. (1986) Nd, O and Sr isotope constraints on the origin of Precambrian rocks, Black Hills, South Dakota. Geochim. Cosmochim. Acta 50, 2833-2846.

8. Walker R.J. and Fassett J.D. (1986) Isotopic measurement of subnanogram quantities of rhenium and osmium by resonance ionization mass spectrometry. Anal. Chem. 58, 2923-2927.

9. Fassett J.D. and Walker R.J. (1987) Ultratrace elemental and isotopic analysis of osmium and rhenium using resonance ionization mass spectrometry and thermal vaporization. Resonance Ionization Spectroscopy 1986, G.S. Hurst and C.G. Morgan (Eds.), Inst. of Phys. Conf. Ser 84, 115-120.

10. Fassett J.D., Walker R.J., Travis J.C. and Ruegg F.C. (1987) Quantification of pulsed ion currents produced in resonance ionization mass spectrometry. Int. J. Mass Spectrom. Ion Proc. 75, 111-126.

11. Shearer C.K., Papike J.J., Redden J.A., Simon S.B., Walker R.J. and Laul J.C. (1987) Origin of pegmatitic granite segregations, Willow Creek, Black Hills, South Dakota. Can. Mineral. 25, 159-171.

12. Walker R.J., Shirey S.B. and Stecher O. (1988) Comparative Re-Os, Sm-Nd and Rb-Sr isotope and trace element systematics for Archean komatiite flows from Munro Township, Abitibi Belt, Ontario. Earth Planet. Sci. Lett. 87, 1-12.

13. Walker R.J. (1988) Low-blank chemical separation of osmium and rhenium from gram quantities of silicate rock for measurement by resonance ionization mass spectrometry. Anal. Chem. 60, 1231-1234.

14. Fassett J.D., Walker R.J., Travis J.C. and Ruegg F.C. (1988) Measurement of low abundance isotopes by laser resonance ionization mass spectrometry. Anal. Chem. 60, 1231-1234.

15. Walker R.J., Fassett J.D. and Travis J.C. (1988) The use of resonance ionization mass spectrometry for measuring the isotopic compositions of rhenium and osmium extracted from silicate rocks. Resonance Ionization Spectroscopy 1988, G.S. Hurst and C.G. Morgan (Eds.), Inst. of Phys. Conf. Ser. 94, 337-342.

16. Walker R.J. and Morgan J.W. (1989) Rhenium-osmium isotope systematics of carbonaceous chondrites. Science 243, 519-522.

17. Walker R.J., Hanson G.N. and Papike J.J. (1989) Trace element constraints on pegmatite genesis: Tin Mountain pegmatite, Black Hills, South Dakota. Contrib. Mineral. Petrol. 101, 290-300.

18. Lambert D.D., Morgan J.W., Walker R.J., Shirey S.B., Carlson R.W., Zientek M.L. and Koski M.S. (1989) Rhenium-osmium and samarium-neodymium isotopic systematics of the Stillwater Complex. Science 244, 1169-1174.

19. Walker R.J., Carlson R.W., Shirey S.B. and Boyd F.R. (1989) Os, Sr, Nd, and Pb isotope systematics of southern African peridotite xenoliths: Implications for the chemical evolution of subcontinental mantle. Geochim. Cosmochim. Acta 53, 1583-1595.

20. Morgan J.W. and Walker R.J. (1989) Isotopic determinations of rhenium and osmium using fusion, distillation and ion exchange separations, as applied to meteorites. Anal. Chim. Acta 222, 91-9300.

21. Walker R.J., Shirey S.B., Hanson G.N., Rajamani V. and Horan M.F. (1989) Re-Os, Rb-Sr and O isotopic systematics of the Archean Kolar schist belt, Karnataka, India. Geochim. Cosmochim. Acta 53, 3005-3013.

22. Mayo S., Fassett J.D., Kingston H.M. and Walker R.J. (1990) Measurement of vanadium impurity in SIMOX material by isotope dilution and resonance ionization mass spectrometry. Anal. Chem. 62, 240-244.

23. Walker R.J., Echeverría L.M., Shirey S.B. and Horan M.F. (1991) Re-Os isotopic constraints on the origin of volcanic rocks, Gorgona Island, Colombia: Os isotopic evidence for ancient heterogeneities in the mantle. Contrib. Mineral. Petrol. 107, 150-162.

24. Walker R.J., Morgan J.W., Naldrett A.J., Li C. and Fassett J.D. (1991) Re-Os isotope systematics of Ni-Cu Sulfide Ores, Sudbury Igneous Complex, Ontario: Evidence for a major crustal component. Earth Planet. Sci. Lett. 105, 416-429.

25. 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.

26. 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.

27. 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.

28. 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.

29. Krogstad E.J. and Walker R. J. (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.

30. 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.

31. 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.

32. 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.

33. Shirey S.B. and Walker R.J. (1995) Carius tube digestion for low-blank rhenium-osmium analysis. Anal. Chem. 34, 21362141.

34. 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.

35. 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.

36. *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.

37. *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.

38. Koide M., Goldberg E.D. and Walker R. (1996) The analysis of seawater osmium. Deep-Sea Res. 43, 53-55.

39. 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.

40. 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.

41. 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.

42. *Tomascak P.B., Krogstad E.J. and Walker R.J. (1996) Mixed crustal sources for the late Paleozoic Sebago batholith, Maine, U.S.A. Contrib. Mineral. Pet. 125, 45-59.

43. 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.

44. 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.

45. Walker R.J., Morgan J.W., Beary E., Smoliar M.I., Czamanske G.K. and Horan M.F. (1997) Applications of the 190Pt-186Os isotope system to geochemistry and cosmochemistry. Geochim. Cosmochim. Acta 61, 4799-4808.

46. Shirey S.B. and Walker R.J. (1998) Re-Os isotopes in cosmochemistry and high-temperature geochemistry. Annual Reviews of the Earth and Planetary Sciences 26, 423-500.

47. Horan M.F., *Smoliar M.I. and Walker R.J. (1998) 182W and 187Re-187Os systematics of iron meteorites: chronology for melting, differentiation and crystallization in asteroids. Geochim. Cosmochim. Acta 62, 545-554.

48. 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.

49. Brandon A., Walker R.J., Morgan J.W., Norman M.D. and Prichard H.M. (1998) Coupled 186Os and 187Os evidence for core-mantle interaction. Science 280, 1570-1573.

50. *Tomascak P.B., Krogstad E.J. and Walker R.J. (1998) Nd isotope systematics and the derivation of granitic pegmatites in southwestern Maine, USA. Canadian Mineralogist 36, 327-337.

51. *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.

52. Walker R.J., Storey M., Kerr A., Tarney J. and Arndt N.T. (1999) Implications of 187Os heterogeneities in mantle plumes: evidence from Gorgona Island and Curaçao. Geochim. Cosmochim. Acta 63, 713-728.

53. Tomascak P., Tera F., Helz R. and Walker R. (1999) The absence of lithium isotope fractionation during basalt differentiation: New measurements by multi-collector sector ICP-MS. Geochim. Cosmochim. Acta 63, 907-910.

54. 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.

55. *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.

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. 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.

58. 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.

59. Borisov A. and Walker R.J. (2000) Os solubility in silicate melts: new efforts and results. American Mineralogist 85, 912-918.

60. 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.

61. 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.

62. 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.

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 an 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. Chem. Geol. 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. 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.

72. 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.

73. Becker H., Dalpe C. and Walker R.J. (2002) High precision Ru isotopic measurements by multi-collector ICP-MS. The Analyst 127, 775-780.

74. Walker R.J. and Nisbet E. (2002) 187Os isotopic constraints on Archean mantle dynamics. Geochim. Cosmochim. Acta 66, 3317-3325.

75. 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.

76. 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.

77. 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.

78. 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.

79. 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.

80. *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.

81. 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.

82. Becker H. and Walker R.J. (2003) Efficient mixing of the solar nebula from uniform Mo isotopic composition of meteorites. Nature 425, 152-155.

83. 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, 643-652.

84. 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.

85. *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.

86. 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.

87. 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.

88. 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.

89. **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 melt rocks. Meteoritics Planet. Sci .39, 1003-1008.

90. 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.

91. 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.

92. Brandon A. D. and Walker R.J. (2005) The debate over core-mantle interaction. Earth Planet. Sci. Lett. Frontiers 232, 211-225 (invited).

93. 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.

94. Walker R.J. and Walker D. (2005) Does the core leak? EOS 86, 237-242.

95. *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.

96. 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.

97. *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.

98. 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.

99. *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.

100. *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.

101. 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.

102. 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.

103. 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.

104. 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.

105. *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.

106. 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.

107. 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.

108. 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 Planet. Sci. Lett. 259, 567-580.

109. 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.

110. 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.

111. Walker R.J., McDonough W.F., Honesto J., Chabot N.L., McCoy T.J., Ash R.D. and Bellucci J.J. (2008) Origin and chemical evolution of group IVB iron meteorites. Geochim. Cosmochim. Acta 72, 2198-2216.

112. *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 Planet. Sci. Lett. 268, 171-181.

113. 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.

114. 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.

115. 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.

116. *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. Chem. Geol. 260, 112-128.

117. **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. Chem. Geol. 260, 196-210.

118. 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.

119. Yokoyama D., Walker D. and Walker R.J. (2009) Low osmium solubility in silicate at high pressures and temperatures. Earth Plan. Sci. Lett. 279, 165-173.

120. 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? Chem. Geol. 262, 391-405.

121. 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. Invited Review.

122. *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.

123. Rudnick R.L. and Walker R.J. (2009) Ages from Re-Os isotopes in peridotites. Proceedings of the 9th Kimberlite Conference, Lithos. Invited Review, in press.

124. *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, in press.

125. O’Driscoll B.O., 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., in press.

126. 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. in press.

127. *Van Acken D., Becker H. and Walker R.J., McDonough W.F., Wombacher F., Ash R.D. and Piccoli P.M. (2009) Formation of pyroxenite layers in the Totalp ultramafic massif (Swiss Alps) – insights from highly siderophile elements and Os isotopes. Geochim. Cosmochim. Acta, in revision.

128. Horan M.F., Alexander C.M.O’D. and Walker R.J. Highly siderophile element evidence for early solar system processes in components from ordinary chondrites. Geochim. Cosmochim. Acta, in revision.

129. Puchtel I.S., Walker R.J., Brandon A.D. and Nisbet E.G. Pt-Re-O isotope and HSE systematics of the 2.7 Ga Belingwe and Abitibi komatiites. Geochim. Cosmochim. Acta, in revision.

130. Geboy N.J., Kaufman A.J., Walker R.J., Misi A., de Oliviera T. F., Miller K., Brody K.B., Sievers N., Azmy K., Kendall B. and Poulton S. Evidence for Mesoproterozoic ice ages in Brazil. Science, in review.

131. Scheiderich K., Helz G.R. and Walker R.J. Century-long record of Mo isotopic composition in sediments of a seasonally anoxic estuary (Chesapeake Bay). Earth Planet. Sci. Lett., in review.

132. Yokoyama T., Alexander C.M.O’D. and Walker R.J. Osmium isotope anomalies in chondrites: results for acid residues enriched in insoluble organic matter. Earth and Planet. Sci. Lett., in review.

Unrefereed Review Articles

Walker R.J. (2000) News & Views: The extraterrestrial wedding ring. Nature 406, 359-360.

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) Replying to; R. Arculus, I.H. Campbell, S.M. McLennan and S.R. Taylor. Nature 459, doi:10.1038/nature08077.

* - Work published as part of a M.S. or Ph.D. thesis/dissertation project.
** - Work published as part of a B.S. senior research project.

Last Revised: July 2009