John W. Shervais

Professor and Director of Undergraduate Studies
Director, USC Electron Microprobe Laboratory and X-ray Flourescence Laboratory

Igneous Petrology and Geochemistry

B.Sc., 1971, San Jose State University, California
Ph.D.,1979, University of California, Santa Barbara

Research Areas: Petrology, major and trace element geochemistry of basic and intermediate igneous rocks. Mantle plumes, ophiolites and island arcs, mantle metasomatism, and lunar petrology.

For laboratory facilities, see the USC Electron Microprobe Facility and the Department of Geological Sciences X-ray Flourescence Laboratory.

Mantle Plumes and Continental Volcanism: Our current work in the Snake River Plain of southern Idaho focuses on the role of mantle plumes ("Hot Spots") and their interactions with continental lithosphere. Mantle plumes are thought to represent the upwelling of hot, enriched material from the core-mantle boundary towards the surface. Volcanic rocks which form by passage of lithosphere over a mantle plume will display chemical and isotopic compositions which vary in response to plume dynamics and interactions between the plume and the overlying lithosphere. Our work in the Snake River Plain uses both surface samples and drill core samples from existing scientific and geothermal test wells. These samples document variations in the chemistry of the plume-related basalts back to 6 Ma in the eastern SRP and back to 11 Ma in the western SRP. Our goal is to reconstruct the geochemical and geodynamical history of the Yellowstone plume and its interactions with the overlying continental lithosphere.

Ophiolites, Arcs, and Accreted Terranes: Ophiolites are distinctive assemblages of mafic, ultramafic, and felsic igneous rocks that are commonly thought to represent oceanic crust and mantle that has been accreted to a continental margin. The accretion of ophiolite and island arc terranes has been the primary mechanism of continental growth since the Proterozoic. My work focuses in several areas: the Coast Range ophiolite (CRO) of California, the Carolina arc terrane in the southern Appalachians, and the Kohistan arc terrane of NW Pakistan.

Metasomatism and Magma Evolution in the Upper Mantle: Most basalts erupted at the Earths surface originate by partial melting of the Earth's upper mantle. The chemical and isotopic composition of magmas erupted in different tectonic settings reflect differences in mantle composition, in melting process, and in subsequent magma evolution. Understanding the roles of metasomatism (which modifies mantle composition) and magma evolution (which modifies the resulting melts) is crucial to our understanding of how the Earth evolves chemically and thermally through time.

Lunar Mare Volcanism and Highlands Crust: Deciphering the origin and evolution of the lunar highland crust is crucial to our understanding of the Moon's early magmatic history and, by inference, the early history of other terrestrial planets. This task is especially difficult in the western lunar highlands because of the small size of the highland rock clasts recovered from breccias, and because it is impossible to calculate parent magma compositions from whole rock chemical data on cumulate rocks. My current work on lunar samples avoids these problems by analyzing the major and trace element composition of primary cumulus phases (with an electron microprobe and an ion microprobe) and using equilibrium crystal/liquid partition coefficients to calculate possible parent magma compositions. These data offer new insights into the evolution of the moon's crust and into the general processes of cumulate rock formation.

Selected Publications

Shervais, J.W. and McGee, J.J. (1998) Ion & electron microprobe study of Mg suite troctolites, norite, and anorthosites from Apollo 14: Evidence for urKREEP assimilation during Petrogenesis of Apollo 14 Mg-suite rocks. Geochim. Cosmochim. Acta, 62/17, 3009-3023.

Shervais, J.W. and McGee, J.J. (1999) KREEP cumulates in the western lunar highlands: Ion & electron microprobe study of Alkali anorthosites and norites from Apollo 14. American Mineralogist, vol 84, #5/6, 806-820.

Shervais, J.W. (1999) Highlands crust at the Apollo 14 site: Surfing the Fra Mauro shoreline. In Planetary Geology and Geochemistry, G.A. Snyder, C.R. Neal, and W.G. Ernst (eds), Geological Society of America, International Book Series, v. 2, 194-206.

Shervais, J.W. and McGee, J.J. (1999) Petrology of the western Highlands Province: Ancient crust formation at the Apollo 14 site. Journal Geophysical Research, Vol. 104 , No. E3 , 5891-5920.

Shervais, J.W. (1999) Highlands crust at the Apollo 14 site: Surfing the Fra Mauro shoreline. International Geology Review, 41, 141-153.

Shervais, J.W., Shelley, S.A., and Secor, D.T. Jr.: The Carolina terrane: A rifted volcanic arc in the southeastern Piedmont; accepted for publication in "Avalonian and Related Terranes of the Circum-Atlantic, D. Nance (ed), Geol. Soc. America Special Publication.

Dennis and Shervais, J.W.: The Corolina terrane in northwestern South Carolina: Insights into the development of an evolving island arc; accepted for publication in RAvalonian and Related Terranes of the Circum-Atlantic, D. Nance (ed), Geol. Soc. America Special Publication.

Shah, M.T., Shervais, J.W. , and Ikrammudin, M. (1994) The Dir meta-volcanic sequence: calc-alkaline magmatism in the Kohistan arc terrane, northern Pakistan; Geol. Bull. Univ. Peshawar, 27, 9-27.

Shah, M.T., Ikrammudin, M., and Shervais, J.W. (1994) Behaviour of Tl relative to K, Rb, Sr, and Ba in mineralized and unmineralized metavolcanics from the Dir area, northern Paksitan; Mineralum Deposita, 29, 422-426.

Shervais, J.W., Vetter, S.K., and Hackett, W.R. (1994) Chemical Stratigraphy of Basalts in Coreholes NPR-E and WO-2, Idaho National Engineering Laboratory, Idaho: Implications for Plume Dynamics in the Snake River Plain, in Proceedings of the VIIth International Symposium on the Observation of Continental Crust Through Drilling, Santa Fe, New Mexico, 1994, 93-96.

Vetter, S.K. and Shervais, J.W. (1992) Continental Basalts of the Boise River Group near Smith Prairie, Idaho. Jour. Geophys. Res., 97/B6, 9043-9061.

Shervais, J.W., and Mukasa, S.B. (1991) The Balmuccia Orogenic Lherzolite Massif, Italy. Jour. Petrology, Special Lherzolites Issue, 155-174.

Mukasa, S.B., Shervais, J.W., Wilshire, H.G., and Nielsen, J.E. (1991) Intrinsic Nd, Pb, and Sr isotopic heterogeneities exhibited by the Lherz alpine peridotite massif, French Pyrenees. Jour. Petrology, Special Lherzolites Issue, 117-134.

Dennis, A.J. and Shervais, J.W. (1991) Arc rifting of the Carolina terrane in northwestern South Carolina. Geology, 19, 226-229.

Shervais, J.W. (1990), Island arc and ocean crust ophiolites: contrasts in the petrology, geochemistry, and tectonic style of ophiolite assemblages in the California coast ranges. Ophiolites: Oceanic Crustal Analogues, J.C. Malpas, E.M. Moores, A. Panayiotou, and C. Xenophontos (eds.), The Geological Survey Department, Nicosia, Cyprus, 507-520.

Shervais, J.W. and Hanan, B.B. (1989) Jurassic volcanic glass from the Stonyford volcanic complex, Franciscan assemblage, northern California coast ranges, Geology, 17, 510-514.

John Shervais
Department of Geological Sciences
University of South Carolina
Columbia, SC 29208

Phone: 803 777-2669
FAX: 803 777-6610
email: shervais@geol.sc.edu