Earth
and Space Sciences Faculty |
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I.
Stewart McCallum |
Areas of Interest:
Igneous Petrology
Research Group:
Petrology/Mineralogy/Geochemistry
Education:
Ph.D., University of Chicago,
1968
Background and Current
Research:
Stewart McCallum received
his Ph.D. from the University of Chicago in 1968 and joined the University of
Washington faculty in 1970 after a two-year NASA post-doctoral fellowship at
the University of Oregon. At Oregon his research was primarily in the study
of the first samples returned from the moon during the manned Apollo missions.
McCallum has continued his study of not only lunar samples but also eucritic
meteorites with the goal of reconstructing the stratigraphy and thermal evolution
of the lunar crust and the eucrite parent body (4Vesta) using thermobarometry,
cooling rates based on simulations of exsolution processes, and cooling rates
based on cation ordering in pyroxenes. Techniques used include single crystal
x-ray methods, transmission electron microscopy, electron probe, ion probe,
experimental studies, and computer modeling. These studies are supplemented
by mineralogical, geochemical, and textural studies to elucidate the extent
and effect of partial melting and subsolidus recrystallization. The results
are interpreted in terms of global evolution models based in large part on data
from Clementine (1994) and Prospector (1998-99) missions. This work is carried
out in collaboration with Dr. Chiara Domeneghetti at the Centro di Studio per
la Crystallochimica e la Crystallografia at the Universita di Pavia, Italy.
For the past two and a half decades McCallum and his students have been involved in a major effort directed towards understanding the petrogenesis of the Stillwater Complex, a classic layered mafic intrusion. Key areas have been mapped in detail, several representative stratigraphic sections have been measured and sampled and over 1000 samples have been collected and are being analyzed by electron microprobe, ion microprobe, INAA, ICPMS and thermal ionization mass spectrometry (TIMS). A narrow zone within the complex (J-M Reef) contains economically important concentrations of sulfides rich in platinum group elements that are presently being mined. The origin of these important deposits is controversial. McCallum and Professor Alan Boudreau at Duke University have proposed that the PGE-rich sulfides are the product of high temperature hydromagmatic fluids rich in chlorine that were generated by outgassing of melts trapped lower in the cumulate pile. The Stillwater Mining Company, which is responsible for extracting the Pt-Pd ore, has recently driven two 5 kilometer long adits through that part of the complex above the reef. These adits provide an unprecedented opportunity to study in detail the petrology and geochemistry of a large fraction of the stratigraphic section and we are in the early stages of this study.
Additional interests include the volcanic and plutonic rocks of the Cascade magmatic arc, specifically, the Chilliwack and Index batholiths and the volcanic rocks associated with the Indian Heaven and Simcoe Volcanic fields.
Selected Publications:
McCallum, I.S. (1996) The
Stillwater Complex. In: Cawthorn, R. G. (ed.) “Layered Intrusions”
Developments in Petrology, vol. 15, p. 441-483, Elsevier, Amsterdam.
McCallum, I.S. and O'Brien, H.E. (1996) Stratigraphy of the lunar highland crust: Depths of burial of lunar samples from cooling rate studies. American Mineralogist, 81, 1166-1175.
Jolliff, B. L., Floss, C., McCallum, I.S. and Schwartz, J.M. (1999) Geochemistry, petrology and cooling history of lunar sample 14161,7373, a plutonic rocklet with textural evidence of granitic-fraction separation by liquid immiscibility. American Mineralogist, 84, 821-837
McCallum, I.S., Thurber, M.W., Nelson, B.K. and O’Brien, H. E. (1999) Lead isotopes in sulfides from the Stillwater Complex, Montana: Evidence for subsolidus remobilization. Contrib. Mineral. Petrol., 137, 206-219.
McCallum, I. S., Thurber, M. W., Bosch, D., and Nelson, B. K., 1992, Lead isotopic compositions of plagioclases and sulfides in the Stillwater Complex: Evidence for isotopic disequilibrium and remobilization, Lunar and Planetary Sciences XXXIII, p. 867-868.
McCallum, I.S. (2001) A new view of the Moon in light of data from Clementine and Prospector missions. Proceedings of the Conference on Earth-Moon Relationships, Padua, Italy. Earth, Moon, and Planet, 85/86, 253-269.
McCallum, I.S. and Schwartz, J.M. (2001) Lunar Mg suite: Thermobarometry and petrogenesis of parental magmas. Jour. Geophys. Res. (Planets), 106, 27969-27984.
Graduate Research (2001):Kim E. Gerke: The role of fluids in the petrogenesis of the recent volcanics and mantle xenoliths of the Simcoe Volcanic Field, Southern Washington Cascades.
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