- Email: [email protected]
Highly siderophile elements in the Earth and meteorites
Chemical Geology 196 (2003) 1 – 3 www.elsevier.com/locate/chemgeo
Preface
Highly siderophile elements in the Earth and meteorites: A volume in honor of John Morgan An area of publication growth in Earth Sciences in the past decade, with no sign of abating, is the geochemistry of the highly siderophile elements (Pt, Pd, Ir, Os, Ru, Rh, Au, Re and including the 187Re – 187Os and 190 Pt– 186Os decay schemes)—specifically as applied to large-scale problems in the early history and evolution of the Earth, meteorites and the moon. Siderophile elements generate much excitement among geochemists, and even geophysicists, as their signatures provide tantalising hints of deep Earth processes, including possible core – mantle interactions, and may provide the elusive links between chemical structure and geophysical observations in both the upper mantle and in the deeper Earth. Much of the analytical and intellectual foundation underlying today’s innovative results is a direct outgrowth of painstaking earlier work. John Morgan, among his diverse scientific accomplishments, was a pioneer in siderophile element geochemistry and has been a key player in the establishment, development and promotion of this field for more than 40 years. John hails from the United Kingdom, but immigrated to the colonies completing his PhD in 1966 at the Australian National University under the supervision of John Lovering. His thesis research centered on the development of neutron activation methods for the precise measurement of trace element compositions, including Re and Os, in a range of planetary and terrestrial materials. This work set the pattern for the rest of John’s long and productive career—technique development followed by meticulous leading-edge analytical work aimed at acquiring new types of data to address first-order problems in the solid Earth Sciences. Highlights include some of the first precise measurements of Re and Os in stony meteorites, chondrites, achondrites and various terrestrial rock
suites (e.g. Morgan and Lovering, 1964; 1967a,b). Much of this early work prefaced today’s active fields including the use of siderophile elements to address the role of impacts on the Earth (e.g. Morgan, 1968; Morgan and Ehmann, 1970; Morgan et al., 1979). During the Apollo era, John was very active in the analysis of returned lunar samples and used siderophile element compositions to search for evidence of impact events and to characterise the impactors forming the great nearside lunar basins (e.g. Morgan et al., 1971, 1973, 1974, 1975). These projects were conducted with various international collaborators including Ed Anders’ group at the University of Chicago. From 1977– 1995 John was employed at the United States Geological Survey and was active in a wide range of geochemical studies including those aimed at radiochemical determinations of low-level volatile and siderophile elements, the geochemical evolution of the Earth’s upper mantle and chemical composition of the planets and asteroids. He combined knowledge of meteorite compositions with work on terrestrial mantle samples to address questions of the siderophile composition of the Earth’s mantle (Morgan et al., 1981) and Earth’s late accretionary history (Morgan, 1985, 1986; Morgan et al., 2001). During the late 1980s and 1990s, John collaborated with researchers both at the USGS and the University of Maryland, pushing the boundaries of the Re – Os system and initiating work in the Pt – Os system. This resulted in a range of analytical advances (e.g. Morgan et al., 1991) combined with new, highprecision results on topics as diverse as the ages of iron meteorites (e.g. Morgan et al., 1992) and new methods of tracing ore deposition (e.g. Morgan et al., 2002). In recent years, John was in residence at Colorado State University with collaborative research
0009-2541/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0009-2541(02)00403-5
2
Preface
efforts focussed on the application of the Pt – Os system to various terrestrial and meteorite problems including the search for core signatures in plume basalts, and in the use of the Re – Os system to determine the timing and origin of Archean Au mineralisation. John has now relocated to begin a long-deferred career in music at the University of Indiana. In addition to John’s copious analytical and scientific contributions, he is a rarity in the isotope geochemistry community in being both universally respected and well liked. The reasons for this are many, not the least of which is his intellectual generosity. John is a consummate analyst who is willing to share his insights. Many of the contributors to this volume have stories of John providing the answers to tricky analytical questions and taking the time for detailed technique discussions. Most owe him a debt of gratitude whether they realise it or not. John is the author or co-author of more than 160 publications, many of them landmarks in the field. John’s papers are classics not only from the scientific, but also often from a literary standpoint, containing the well-turned phrase combined with wry wit. This volume grew out of an enthusiastically attended special session in John’s honor organised at the American Geophysical Union held in December 2001. The diverse topics of the 14 papers comprising this volume, all under the heading of highly siderophile element geochemistry, are a reflection of the vitality of the field and encompass many, but certainly not all, of the range of John’s scientific interests. The first three papers focus on aspects of highly siderophile elements in meteorites: Horan et al. present new high-quality PGE patterns yielding evidence for the subtle yet distinct differences among chondritic meteorite classes; Jones et al. provide a review and synthesis of Martian highly siderophile element geochemistry; Becker and Walker use Ru – Tc decay schemes to examine early solar system chronologies. The next four papers are focussed on highly siderophile elements in upper mantle samples, with Lorand et al. and Schmidt et al. addressing some of the complex melt and metasomatic processes that can affect highly siderophile element signatures in the upper mantle; Wu et al. and Handler et al. use Re – Os systematics to determine the ages and processes of upper mantle architecture in two very different set-
tings, Northeastern China and Marie Byrd Land, Antarctica. The next two contributions use initial 187 Os compositions determined from ancient ultramafic samples to examine late Archean (Gangopadhyay and Walker) and early Archean mantle compositions (Frei et al.). Gannoun et al. apply the Re – Os system to determining the age and source of massive sulphide deposits. The final four papers use modern basalts to examine the range of sources and processes contributing to highly siderophile characteristics observed in different tectonic environments. These include the Iceland Rift (Momme et al.), the Ontong Java Plateau (Ely and Neal) with possible evidence of core influences, comparative MORB and back-arc basin basalt Re chemistries (Sun et al.) and detailed Re – Os systematics within oxidising arc environments (Widom et al.). All the editors gratefully thank the authors and reviewers for their conscientious efforts allowing this volume to be brought to fruition. Finally, it is with the acknowledgement and appreciation of John’s large, continuing and enduring contributions to the field of highly siderophile geochemistry that we dedicate this volume to him.
References Morgan, J.W., 1968. Estimate of the influx of extraterrestrial material during the Silurian. Nature 219, 147. Morgan, J.W., 1985. Earth’s late accretionary history: osmium isotopic constraints. Nature 317, 703 – 705. Morgan, J.W., 1986. Ultramafic xenoliths: clues to Earth’s late accretionary history. J. Geophys. Res. 91, 12375 – 12387. Morgan, J.W., Ehmann, W.D., 1970. Twin terrestrial impact craters. Nature 225, 255. Morgan, J.W., Lovering, J.F., 1964. Rhenium and osmium abundances in stony meteorites. Science 144, 835 – 836. Morgan, J.W., Lovering, J.F., 1967a. Rhenium and osmium abundances in chondritic meteorites. Geochim. Cosmochim. Acta 31, 1893 – 1909. Morgan, J.W., Lovering, J.F., 1967b. Rhenium and osmium abundances in some igneous and metamorphic rocks. Earth Planet. Sci. Lett. 3, 219 – 224. Morgan, J.W., Laul, J.C., Ganapathy, R., Anders, E., 1971. Glazed lunar rocks: origin by impact. Science 172, 556 – 558. Morgan, J.W., Ganapathy, R., Laul, J.C., Anders, E., 1973. Lunar crater Copernicus: search for debris of impacting body at Apollo 12 site. Geochim. Cosmochim. Acta 37, 141 – 154. Morgan, J.W., Ganapathy, R., Higuchi, H., Krahenbuhl, U., Anders, E., 1974. Lunar basins: tentative characterization of projectiles,
Preface from meteoritic elements in Apollo 17 boulders. Proceedings of Fifth Lunar Science ConferenceGeochim. Cosmochim. Acta, vol. 5, pp. 1703 – 1736. Morgan, J.W., Higuchi, H., Anders, E., 1975. Meteoritic material in a boulder from the Apollo 17 site: implications for its origin. The Moon 14, 373 – 384. Morgan, J.W., Janssens, M.J., Hertogen, J., Gros, J., Takahashi, H., 1979. Ries impact crater, Southern Germany: search for meteoritic material. Geochim. Cosmochim. Acta 43, 803 – 815. Morgan, J.W., Wandless, G.A., Petrie, R.K., Irving, A.J., 1981. Composition of the Earth’s upper mantle—1. Siderophile trace elements in ultramafic nodules. Tectonophysics 75, 47 – 67. Morgan, J.W., Golightly, D.W., Dorrazpf, A.F., 1991. Methods for the separation of rhenium, osmium, and molybdenum in isotope geochemistry. Talanta 38, 259 – 265. Morgan, J.W., Walker, R.J., 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. Morgan, J.W., Walker, R.J., Brandon, A.D., 2001. Siderophile elements in Earth’s upper mantle and lunar breccias: data synthesis suggests manifestations of the same late influx. Meteorit. Planet. Sci. 36, 1257 – 1275. Morgan, J.W., Walker, R.J., Horan, M.F., Beary, E., Naldrett, A.J., Li, C., 2002. 190Pt – 186Os and 187Re – 187Os systematics of the Sudbury Igneous Complex, Ontario. Geochim. Cosmochim. Acta. 66, 273 – 290.
3
Vickie C. Bennett* Research School of Earth Sciences, The Australian National University, Canberra ACT 0200, Australia Email address: [email protected]. Mary F. Horan Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC, 20015, USA Alan D. Brandon NASA—Johnson Space Center, Houston, TX 77058, USA Clive R. Neal Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA * Corresponding author. Tel.: +61-2-6125-5509; fax: +61-26125-0738.
Preface
Highly siderophile elements in the Earth and meteorites: A volume in honor of John Morgan An area of publication growth in Earth Sciences in the past decade, with no sign of abating, is the geochemistry of the highly siderophile elements (Pt, Pd, Ir, Os, Ru, Rh, Au, Re and including the 187Re – 187Os and 190 Pt– 186Os decay schemes)—specifically as applied to large-scale problems in the early history and evolution of the Earth, meteorites and the moon. Siderophile elements generate much excitement among geochemists, and even geophysicists, as their signatures provide tantalising hints of deep Earth processes, including possible core – mantle interactions, and may provide the elusive links between chemical structure and geophysical observations in both the upper mantle and in the deeper Earth. Much of the analytical and intellectual foundation underlying today’s innovative results is a direct outgrowth of painstaking earlier work. John Morgan, among his diverse scientific accomplishments, was a pioneer in siderophile element geochemistry and has been a key player in the establishment, development and promotion of this field for more than 40 years. John hails from the United Kingdom, but immigrated to the colonies completing his PhD in 1966 at the Australian National University under the supervision of John Lovering. His thesis research centered on the development of neutron activation methods for the precise measurement of trace element compositions, including Re and Os, in a range of planetary and terrestrial materials. This work set the pattern for the rest of John’s long and productive career—technique development followed by meticulous leading-edge analytical work aimed at acquiring new types of data to address first-order problems in the solid Earth Sciences. Highlights include some of the first precise measurements of Re and Os in stony meteorites, chondrites, achondrites and various terrestrial rock
suites (e.g. Morgan and Lovering, 1964; 1967a,b). Much of this early work prefaced today’s active fields including the use of siderophile elements to address the role of impacts on the Earth (e.g. Morgan, 1968; Morgan and Ehmann, 1970; Morgan et al., 1979). During the Apollo era, John was very active in the analysis of returned lunar samples and used siderophile element compositions to search for evidence of impact events and to characterise the impactors forming the great nearside lunar basins (e.g. Morgan et al., 1971, 1973, 1974, 1975). These projects were conducted with various international collaborators including Ed Anders’ group at the University of Chicago. From 1977– 1995 John was employed at the United States Geological Survey and was active in a wide range of geochemical studies including those aimed at radiochemical determinations of low-level volatile and siderophile elements, the geochemical evolution of the Earth’s upper mantle and chemical composition of the planets and asteroids. He combined knowledge of meteorite compositions with work on terrestrial mantle samples to address questions of the siderophile composition of the Earth’s mantle (Morgan et al., 1981) and Earth’s late accretionary history (Morgan, 1985, 1986; Morgan et al., 2001). During the late 1980s and 1990s, John collaborated with researchers both at the USGS and the University of Maryland, pushing the boundaries of the Re – Os system and initiating work in the Pt – Os system. This resulted in a range of analytical advances (e.g. Morgan et al., 1991) combined with new, highprecision results on topics as diverse as the ages of iron meteorites (e.g. Morgan et al., 1992) and new methods of tracing ore deposition (e.g. Morgan et al., 2002). In recent years, John was in residence at Colorado State University with collaborative research
0009-2541/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0009-2541(02)00403-5
2
Preface
efforts focussed on the application of the Pt – Os system to various terrestrial and meteorite problems including the search for core signatures in plume basalts, and in the use of the Re – Os system to determine the timing and origin of Archean Au mineralisation. John has now relocated to begin a long-deferred career in music at the University of Indiana. In addition to John’s copious analytical and scientific contributions, he is a rarity in the isotope geochemistry community in being both universally respected and well liked. The reasons for this are many, not the least of which is his intellectual generosity. John is a consummate analyst who is willing to share his insights. Many of the contributors to this volume have stories of John providing the answers to tricky analytical questions and taking the time for detailed technique discussions. Most owe him a debt of gratitude whether they realise it or not. John is the author or co-author of more than 160 publications, many of them landmarks in the field. John’s papers are classics not only from the scientific, but also often from a literary standpoint, containing the well-turned phrase combined with wry wit. This volume grew out of an enthusiastically attended special session in John’s honor organised at the American Geophysical Union held in December 2001. The diverse topics of the 14 papers comprising this volume, all under the heading of highly siderophile element geochemistry, are a reflection of the vitality of the field and encompass many, but certainly not all, of the range of John’s scientific interests. The first three papers focus on aspects of highly siderophile elements in meteorites: Horan et al. present new high-quality PGE patterns yielding evidence for the subtle yet distinct differences among chondritic meteorite classes; Jones et al. provide a review and synthesis of Martian highly siderophile element geochemistry; Becker and Walker use Ru – Tc decay schemes to examine early solar system chronologies. The next four papers are focussed on highly siderophile elements in upper mantle samples, with Lorand et al. and Schmidt et al. addressing some of the complex melt and metasomatic processes that can affect highly siderophile element signatures in the upper mantle; Wu et al. and Handler et al. use Re – Os systematics to determine the ages and processes of upper mantle architecture in two very different set-
tings, Northeastern China and Marie Byrd Land, Antarctica. The next two contributions use initial 187 Os compositions determined from ancient ultramafic samples to examine late Archean (Gangopadhyay and Walker) and early Archean mantle compositions (Frei et al.). Gannoun et al. apply the Re – Os system to determining the age and source of massive sulphide deposits. The final four papers use modern basalts to examine the range of sources and processes contributing to highly siderophile characteristics observed in different tectonic environments. These include the Iceland Rift (Momme et al.), the Ontong Java Plateau (Ely and Neal) with possible evidence of core influences, comparative MORB and back-arc basin basalt Re chemistries (Sun et al.) and detailed Re – Os systematics within oxidising arc environments (Widom et al.). All the editors gratefully thank the authors and reviewers for their conscientious efforts allowing this volume to be brought to fruition. Finally, it is with the acknowledgement and appreciation of John’s large, continuing and enduring contributions to the field of highly siderophile geochemistry that we dedicate this volume to him.
References Morgan, J.W., 1968. Estimate of the influx of extraterrestrial material during the Silurian. Nature 219, 147. Morgan, J.W., 1985. Earth’s late accretionary history: osmium isotopic constraints. Nature 317, 703 – 705. Morgan, J.W., 1986. Ultramafic xenoliths: clues to Earth’s late accretionary history. J. Geophys. Res. 91, 12375 – 12387. Morgan, J.W., Ehmann, W.D., 1970. Twin terrestrial impact craters. Nature 225, 255. Morgan, J.W., Lovering, J.F., 1964. Rhenium and osmium abundances in stony meteorites. Science 144, 835 – 836. Morgan, J.W., Lovering, J.F., 1967a. Rhenium and osmium abundances in chondritic meteorites. Geochim. Cosmochim. Acta 31, 1893 – 1909. Morgan, J.W., Lovering, J.F., 1967b. Rhenium and osmium abundances in some igneous and metamorphic rocks. Earth Planet. Sci. Lett. 3, 219 – 224. Morgan, J.W., Laul, J.C., Ganapathy, R., Anders, E., 1971. Glazed lunar rocks: origin by impact. Science 172, 556 – 558. Morgan, J.W., Ganapathy, R., Laul, J.C., Anders, E., 1973. Lunar crater Copernicus: search for debris of impacting body at Apollo 12 site. Geochim. Cosmochim. Acta 37, 141 – 154. Morgan, J.W., Ganapathy, R., Higuchi, H., Krahenbuhl, U., Anders, E., 1974. Lunar basins: tentative characterization of projectiles,
Preface from meteoritic elements in Apollo 17 boulders. Proceedings of Fifth Lunar Science ConferenceGeochim. Cosmochim. Acta, vol. 5, pp. 1703 – 1736. Morgan, J.W., Higuchi, H., Anders, E., 1975. Meteoritic material in a boulder from the Apollo 17 site: implications for its origin. The Moon 14, 373 – 384. Morgan, J.W., Janssens, M.J., Hertogen, J., Gros, J., Takahashi, H., 1979. Ries impact crater, Southern Germany: search for meteoritic material. Geochim. Cosmochim. Acta 43, 803 – 815. Morgan, J.W., Wandless, G.A., Petrie, R.K., Irving, A.J., 1981. Composition of the Earth’s upper mantle—1. Siderophile trace elements in ultramafic nodules. Tectonophysics 75, 47 – 67. Morgan, J.W., Golightly, D.W., Dorrazpf, A.F., 1991. Methods for the separation of rhenium, osmium, and molybdenum in isotope geochemistry. Talanta 38, 259 – 265. Morgan, J.W., Walker, R.J., 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. Morgan, J.W., Walker, R.J., Brandon, A.D., 2001. Siderophile elements in Earth’s upper mantle and lunar breccias: data synthesis suggests manifestations of the same late influx. Meteorit. Planet. Sci. 36, 1257 – 1275. Morgan, J.W., Walker, R.J., Horan, M.F., Beary, E., Naldrett, A.J., Li, C., 2002. 190Pt – 186Os and 187Re – 187Os systematics of the Sudbury Igneous Complex, Ontario. Geochim. Cosmochim. Acta. 66, 273 – 290.
3
Vickie C. Bennett* Research School of Earth Sciences, The Australian National University, Canberra ACT 0200, Australia Email address: [email protected]. Mary F. Horan Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC, 20015, USA Alan D. Brandon NASA—Johnson Space Center, Houston, TX 77058, USA Clive R. Neal Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA * Corresponding author. Tel.: +61-2-6125-5509; fax: +61-26125-0738.