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F.W. Clarke award
0016.:037/91/$3.00
+
.oo
F. W. CLARKE AWARD Introduction of Richard J. Walker for the 1990 F. W. Clarke Award JOHN W. MORGAN*
Great stuff! Hammer films would love it. At the end of it all, however, there is good, exciting science, and such is the work for which Rich is being cited today. It is rare for the recipient of an award for a young scientist to have participated in the whole development of a technique. Although Rich is not a physicist, he played a major role in tailoring RIMS to the simultaneous measurement of Re and OS isotopic ratios. Although Rich is not a chemist, he mastered the chemistry of Re and the very difficult chemistry of OS and reduced blanks to the picogram level. He is a geologist, however, and, having established his technical base, he was quick to seize upon the important topics for study. Of his many publications on Re-0s systematics, let me mention just three. Rich’s first application of Re-0s isotopes was to the Pyke Hill komatiites from the Abitibi Belt of Superior Province. He demonstrated a very large variation in Re/Os ratio and derived an age of 2126 + 93 Ma for these rocks-the first terrestrial Re-0s isochron published. He then applied the technique to carbonaceous chondrites and iron meteorites and published the first Re-0s isotopic data on whole-rock chond~tes. These results showed that carbonaceous chondrites, like the ordinary chondrite metal studied by the Allegre group, lie systematically above the iron meteorite isochron, suggestive of an older age or, perhaps, an isotopically distinct source. In addition, some unequilibrated ehondrites appear inhomogeneous with respect to OS isotopes, su~esting the presence of components from isotopically variable reservoirs. An important application of Re-0s isotopics to economic geology with particular respect to the platinum-group elements has been the study of the Stillwater Complex. The Ultramafic Series yields a Re-0s isochron with an age of 2743 t 76 Ma and a near-chond~tic initial ‘*70s/‘860s. Chromitite seams from within the Ultramafic Series have initials ranging from near chondritic (0.87) to radiogenic (1.13). Chromitites with chondritic initial ratios may be related to the mantlederived “boninitic” magmas parental to the Ultramafic Series. On the other hand, the radiogenically enriched chromitites, as well as the economically important J-M Reef, may be related to the “A-type” magmas that seem to derive from the lower crust or from crustally contaminated mantle material. The very high sensitivity of the Re-0s system to the presence of a crustal component makes it particularly valuable for such studies. Richard Walker, through a single, sharply focused research effort, has made important cont~b~tions to the analytical instrumentation, the chemical technology, and the geoscience of this area of research. Mr. President, I am honored and delighted to present the recipient of the 1990 F. W. Clarke Award.
Mr. President, honored guests, ladies and gentlemen: Today it is a pleasant duty to introduce Dr. Richard J. Walker, the 1990 winner of the F. W. Clarke Medal. As is well known, Frank Wi~leswo~h Clarke was Chief Chemist of the USGS from 1883 through 1924. Perhaps I was asked to introduce Rich today because, about 100 years later, I held the same position. Needless to say, my tenure was much shorter and afterwards 1 needed an occupation for my declining years. As a result of the pivotal work of Luck and Allegre, Re-0s systematics looked like a topic whose time finally had come. Instead of being an almost insurmountable task, there were at least four promising ways of doing the difficult mass spectrometry. I was particularly intrigued by the possibilities of resonance ionization mass spectrometry (RIMS). One afternoon, Bruce Doe took me over to the then National Bureau of Standards (NBS) (now National Institute of Standards and Technology (NIST)) to meet a bright young fellow who was interested in applying RIMS technology to the problem of Re-0s isotope systematics. That bright young fellow was, of course, Rich Walker, and the Re-OS business hasn’t been the same since. Already, NBS had a working RIMS machine, and, in conjunction with Jack Fassett and others, Rich Walker had developed techniques for measuring picogram quantities of Re and OS with good precision. Rich’s ambition was to use the extreme sensitivity of RIMS to put Re-0s systematics on a par with other isotope methods, so that the technique could be applied to ordinary rocks as well as to meteorites and enriched minerals. To do so, it was impo~ant to have a chemical separation technique that could quantitatively separate picogram amounts of the two elements from large samples with low blanks. Rich had begun working on the chemistry and was at that point having a frustrating time. Now, elderly ex-Chief Chemists have one outstanding characteristic, and that is that they are extremely free with gratuitous advice. I suggested to Rich that perhaps it might be better to start out with such enriched materials as sulfides and chromites and gradually ease into low-abundance samples. Rich did what all bright young fellows do under such circumstances; he listened politely and then went on to do what he was going to do in the first place. Within a few weeks, he had hit upon the idea of using ceric sulfate as a low blank oxidant and was in business. Incidentally, for aficionados of early Frankenstein and other sci-fi movies, Re-0s is the only way to go. It has all the major ingredients, strangely colored liquids boiling away, complicated glass apparatus with bubbles passing through, and then (the pi&e de rt%istance) the mass spectrometer with the green and blue laser beams flashing away.
* US Geological Survey, National Center, Reston, VA 22092, USA. 1205
Acceptance Speech for the 1990 F. W. Clarke Award RICHARD J. WALKER* John Morgan, decided to pursue Re-0s concentration studies in “normal” rocks. The composition data that John has produced over a more than a twenty-five year period are still the basis for many of our interpretations. I really didn’t know John or much about his work when I decided to work on the system in 1985. My own interest in OS isotopes stemmed from the pioneering work of JeanMarc Luck, who during the late 1970s and early 1980s published a series of papers on the application of the system to a number of terrestrial and extraterrestrial problems. His was really the work that got the ball rolling in OS isotopes and I hope that people recognize that fact. In 1985 I was offered a postdoc to work on a new type of mass spectrometer at the National Bureau of Standards. I knew it had the capability of making high-sensitivity measurements of Re and OS, and that is what really pushed me, naively, into the field of Re-0s isotopes, At NBS I was given free reign to do anything I wanted with this mass spectrometer, even if I was silly enough to want to use it on rocks, as long as it lead to a refinement of the instrument and produced papers. I quickly sized up the situation and figured I would be making isotopic measurements of very low quantities of OS within about two or three weeks. I anticipated quickly solving all geologic problems with the Re-0s system, and wasn’t sure what I would do with the rest of my postdoc. As things turned out, it took more than two years before I was able to correctly analyze my first rock. Various problems led to the creation of the RIMS creed: “Lasers, you can’t live with ‘em, you can’t live without ‘em.” During this period of time I received a tremendous amount of help and inspiration from the members of the Mass Spectrometry group at the National Bureau of Standards (now NIST). Jack Fassett, for example, was the primary mover in directing the development of the RIMS instrument at NBS, and I’d still be waiting for the laser repairman if John Travis had not kept the laser going through various catastrophic failures. Some ivory tower people like to complain about “government science” in the US, but the Ea,rth Sciences would be much less developed if it were not for people like them at government facilities. I’d also like to acknowledge and thank the people I have collaborated with in the last five years. Laboratory development projects don’t permit one much time for developing field projects on their own. Fortunately I was able to tie-in with people like Steve Shirey, Rick Carlson, and David Lambert at the Department of Terrestrial Magnetism, and John Morgan at the USGS. These collaborators either had rocks, or knew people that had “perfect rock suites” that could be sacrificed to a relatively unproven isotope system. Their insights and suggestions have kept me busy and out of trouble for the last six years. Finally, I’d like to thank my wife, Mary, who listened to me curse resonance ionization mass spectrometry and Re-0s isotopes for more than two years before meeting with success. In retrospect, I guess it was pretty dull dinner conversation.
I feel extremely fortunate to have been selected for this year’s Clarke medal and I thank the Geochemical Society for selecting me. To set the record straight, 1 have been assured by insiders that the decision to so honor me was in no way related to the fact that my dissertation advisor, Jim Papike, is the current President of the Geochemical Society. Actually, although Jim has never mentioned it, he probably considered disowning me when, upon receiving my doctorate, I (temporarily) shifted my energies from the study of granites and granitic pegmatites to the development of a noisy type of mass spectrometer and applying it to an eccentric isotope system comprised of elements with rather funny names. I hope he has forgiven me for this transgression into analytical chemistry and for taking the traitorous step of working on rocks with distastefully low silica contents. Having read previous Clarke medalist acceptance speeches, I see that it is proper to acknowledge one’s “upbringing.” My earliest exposure to the science of geology was as an undergraduate at the College of William and Mary. I enjoyed geology classes and especially field trips so much that I convinced myself that geology would make an interesting career. In retrospect I think I made a wise decision, although at the time I didn’t realize how difficult it would be to find “permanent” employment in the Earth sciences during the 1980s. Similarly, my graduate career at Stony Brook, especially interactions with faculty like Jim Papike and Gil Hanson, and a variety of stimulating fellow students, pushed my research interests in the direction that made this award possible. It’s important for me to mention that the successes I’ve had with resonance ionization mass spectrometry and the Re-0s isotope system have been highly dependent on the pioneering works of a number of people. The development of the Re-0s system has been a long and arduous process that has involved, and currently involves, many people. Although it is a bit of a cliche in science to say that one’s work “rests on the achievements of many predecessors,” in the case of both RIMS and Re-0s isotopes it is especially true. I’d therefore like to use this opportunity to acknowledge the work that came before my own, in many cases long before my own, and also acknowledge the help that I have received during the past five years. The background work for OS studies was accomplished by Nier, who published the isotopic composition of a sample of OS in 1937. His numbers have held up quite well considering that 53 years have passed since then. Re-0s work on geologic samples passed its first important milestone during the late 1950s and early 1960s when Herr and colleagues analyzed meteorites and molybdenites. Their data gave geologists the first hints regarding how the system “works” in real rocks. Also during this time frame, the fellow that introduced me,
* Department of Geology, University of Maryland, College Park, MD 20742, USA. 1206
+
.oo
F. W. CLARKE AWARD Introduction of Richard J. Walker for the 1990 F. W. Clarke Award JOHN W. MORGAN*
Great stuff! Hammer films would love it. At the end of it all, however, there is good, exciting science, and such is the work for which Rich is being cited today. It is rare for the recipient of an award for a young scientist to have participated in the whole development of a technique. Although Rich is not a physicist, he played a major role in tailoring RIMS to the simultaneous measurement of Re and OS isotopic ratios. Although Rich is not a chemist, he mastered the chemistry of Re and the very difficult chemistry of OS and reduced blanks to the picogram level. He is a geologist, however, and, having established his technical base, he was quick to seize upon the important topics for study. Of his many publications on Re-0s systematics, let me mention just three. Rich’s first application of Re-0s isotopes was to the Pyke Hill komatiites from the Abitibi Belt of Superior Province. He demonstrated a very large variation in Re/Os ratio and derived an age of 2126 + 93 Ma for these rocks-the first terrestrial Re-0s isochron published. He then applied the technique to carbonaceous chondrites and iron meteorites and published the first Re-0s isotopic data on whole-rock chond~tes. These results showed that carbonaceous chondrites, like the ordinary chondrite metal studied by the Allegre group, lie systematically above the iron meteorite isochron, suggestive of an older age or, perhaps, an isotopically distinct source. In addition, some unequilibrated ehondrites appear inhomogeneous with respect to OS isotopes, su~esting the presence of components from isotopically variable reservoirs. An important application of Re-0s isotopics to economic geology with particular respect to the platinum-group elements has been the study of the Stillwater Complex. The Ultramafic Series yields a Re-0s isochron with an age of 2743 t 76 Ma and a near-chond~tic initial ‘*70s/‘860s. Chromitite seams from within the Ultramafic Series have initials ranging from near chondritic (0.87) to radiogenic (1.13). Chromitites with chondritic initial ratios may be related to the mantlederived “boninitic” magmas parental to the Ultramafic Series. On the other hand, the radiogenically enriched chromitites, as well as the economically important J-M Reef, may be related to the “A-type” magmas that seem to derive from the lower crust or from crustally contaminated mantle material. The very high sensitivity of the Re-0s system to the presence of a crustal component makes it particularly valuable for such studies. Richard Walker, through a single, sharply focused research effort, has made important cont~b~tions to the analytical instrumentation, the chemical technology, and the geoscience of this area of research. Mr. President, I am honored and delighted to present the recipient of the 1990 F. W. Clarke Award.
Mr. President, honored guests, ladies and gentlemen: Today it is a pleasant duty to introduce Dr. Richard J. Walker, the 1990 winner of the F. W. Clarke Medal. As is well known, Frank Wi~leswo~h Clarke was Chief Chemist of the USGS from 1883 through 1924. Perhaps I was asked to introduce Rich today because, about 100 years later, I held the same position. Needless to say, my tenure was much shorter and afterwards 1 needed an occupation for my declining years. As a result of the pivotal work of Luck and Allegre, Re-0s systematics looked like a topic whose time finally had come. Instead of being an almost insurmountable task, there were at least four promising ways of doing the difficult mass spectrometry. I was particularly intrigued by the possibilities of resonance ionization mass spectrometry (RIMS). One afternoon, Bruce Doe took me over to the then National Bureau of Standards (NBS) (now National Institute of Standards and Technology (NIST)) to meet a bright young fellow who was interested in applying RIMS technology to the problem of Re-0s isotope systematics. That bright young fellow was, of course, Rich Walker, and the Re-OS business hasn’t been the same since. Already, NBS had a working RIMS machine, and, in conjunction with Jack Fassett and others, Rich Walker had developed techniques for measuring picogram quantities of Re and OS with good precision. Rich’s ambition was to use the extreme sensitivity of RIMS to put Re-0s systematics on a par with other isotope methods, so that the technique could be applied to ordinary rocks as well as to meteorites and enriched minerals. To do so, it was impo~ant to have a chemical separation technique that could quantitatively separate picogram amounts of the two elements from large samples with low blanks. Rich had begun working on the chemistry and was at that point having a frustrating time. Now, elderly ex-Chief Chemists have one outstanding characteristic, and that is that they are extremely free with gratuitous advice. I suggested to Rich that perhaps it might be better to start out with such enriched materials as sulfides and chromites and gradually ease into low-abundance samples. Rich did what all bright young fellows do under such circumstances; he listened politely and then went on to do what he was going to do in the first place. Within a few weeks, he had hit upon the idea of using ceric sulfate as a low blank oxidant and was in business. Incidentally, for aficionados of early Frankenstein and other sci-fi movies, Re-0s is the only way to go. It has all the major ingredients, strangely colored liquids boiling away, complicated glass apparatus with bubbles passing through, and then (the pi&e de rt%istance) the mass spectrometer with the green and blue laser beams flashing away.
* US Geological Survey, National Center, Reston, VA 22092, USA. 1205
Acceptance Speech for the 1990 F. W. Clarke Award RICHARD J. WALKER* John Morgan, decided to pursue Re-0s concentration studies in “normal” rocks. The composition data that John has produced over a more than a twenty-five year period are still the basis for many of our interpretations. I really didn’t know John or much about his work when I decided to work on the system in 1985. My own interest in OS isotopes stemmed from the pioneering work of JeanMarc Luck, who during the late 1970s and early 1980s published a series of papers on the application of the system to a number of terrestrial and extraterrestrial problems. His was really the work that got the ball rolling in OS isotopes and I hope that people recognize that fact. In 1985 I was offered a postdoc to work on a new type of mass spectrometer at the National Bureau of Standards. I knew it had the capability of making high-sensitivity measurements of Re and OS, and that is what really pushed me, naively, into the field of Re-0s isotopes, At NBS I was given free reign to do anything I wanted with this mass spectrometer, even if I was silly enough to want to use it on rocks, as long as it lead to a refinement of the instrument and produced papers. I quickly sized up the situation and figured I would be making isotopic measurements of very low quantities of OS within about two or three weeks. I anticipated quickly solving all geologic problems with the Re-0s system, and wasn’t sure what I would do with the rest of my postdoc. As things turned out, it took more than two years before I was able to correctly analyze my first rock. Various problems led to the creation of the RIMS creed: “Lasers, you can’t live with ‘em, you can’t live without ‘em.” During this period of time I received a tremendous amount of help and inspiration from the members of the Mass Spectrometry group at the National Bureau of Standards (now NIST). Jack Fassett, for example, was the primary mover in directing the development of the RIMS instrument at NBS, and I’d still be waiting for the laser repairman if John Travis had not kept the laser going through various catastrophic failures. Some ivory tower people like to complain about “government science” in the US, but the Ea,rth Sciences would be much less developed if it were not for people like them at government facilities. I’d also like to acknowledge and thank the people I have collaborated with in the last five years. Laboratory development projects don’t permit one much time for developing field projects on their own. Fortunately I was able to tie-in with people like Steve Shirey, Rick Carlson, and David Lambert at the Department of Terrestrial Magnetism, and John Morgan at the USGS. These collaborators either had rocks, or knew people that had “perfect rock suites” that could be sacrificed to a relatively unproven isotope system. Their insights and suggestions have kept me busy and out of trouble for the last six years. Finally, I’d like to thank my wife, Mary, who listened to me curse resonance ionization mass spectrometry and Re-0s isotopes for more than two years before meeting with success. In retrospect, I guess it was pretty dull dinner conversation.
I feel extremely fortunate to have been selected for this year’s Clarke medal and I thank the Geochemical Society for selecting me. To set the record straight, 1 have been assured by insiders that the decision to so honor me was in no way related to the fact that my dissertation advisor, Jim Papike, is the current President of the Geochemical Society. Actually, although Jim has never mentioned it, he probably considered disowning me when, upon receiving my doctorate, I (temporarily) shifted my energies from the study of granites and granitic pegmatites to the development of a noisy type of mass spectrometer and applying it to an eccentric isotope system comprised of elements with rather funny names. I hope he has forgiven me for this transgression into analytical chemistry and for taking the traitorous step of working on rocks with distastefully low silica contents. Having read previous Clarke medalist acceptance speeches, I see that it is proper to acknowledge one’s “upbringing.” My earliest exposure to the science of geology was as an undergraduate at the College of William and Mary. I enjoyed geology classes and especially field trips so much that I convinced myself that geology would make an interesting career. In retrospect I think I made a wise decision, although at the time I didn’t realize how difficult it would be to find “permanent” employment in the Earth sciences during the 1980s. Similarly, my graduate career at Stony Brook, especially interactions with faculty like Jim Papike and Gil Hanson, and a variety of stimulating fellow students, pushed my research interests in the direction that made this award possible. It’s important for me to mention that the successes I’ve had with resonance ionization mass spectrometry and the Re-0s isotope system have been highly dependent on the pioneering works of a number of people. The development of the Re-0s system has been a long and arduous process that has involved, and currently involves, many people. Although it is a bit of a cliche in science to say that one’s work “rests on the achievements of many predecessors,” in the case of both RIMS and Re-0s isotopes it is especially true. I’d therefore like to use this opportunity to acknowledge the work that came before my own, in many cases long before my own, and also acknowledge the help that I have received during the past five years. The background work for OS studies was accomplished by Nier, who published the isotopic composition of a sample of OS in 1937. His numbers have held up quite well considering that 53 years have passed since then. Re-0s work on geologic samples passed its first important milestone during the late 1950s and early 1960s when Herr and colleagues analyzed meteorites and molybdenites. Their data gave geologists the first hints regarding how the system “works” in real rocks. Also during this time frame, the fellow that introduced me,
* Department of Geology, University of Maryland, College Park, MD 20742, USA. 1206