James D. Webster
Curator, Department of Earth and Planetary Sciences; Chairman, Division of Physical Sciences
Ph.D., Arizona State University, 1987 "Experimental Investigation of Phase Equilibria, Water and Chlorine Solubility, and the Behavior of Lithophile Ore Metals and Trace Elements in Fluorine-Rich Siliceous Aluminosilicate Melts."
James D. Webster studies geochemistry, petrology, and volcanology, relying on laboratory and field-based investigations of igneous rocks and ore samples to study how volatile elements and compounds of water, fluorine, chlorine, sulfur, and carbon dioxide influence the formation of metallic ore deposits. Dr. Webster is particularly interested in the role fluids play in transporting and depositing ore metals to create mineral deposits, and in how the violent escape of volatile compounds from magmas drives explosive volcanic eruptions. Dr. Webster studies the influence of these volatiles on melting behavior and the stability of minerals, and on how and when fluids are released from magma. Specifically, he is interested in how these volatiles in magmas lead to volcanic eruptions at such sites as Mt. Vesuvius, Italy, and Augustine Volcano, Alaska. These data are needed to help predict volcanic eruptions worldwide. With colleague Senior Research Scientist, Dr. Charles W. Mandeville, he has focused on chlorine, sulfur, carbon dioxide, and water because they represent the primary media for transporting metals, and because they drive explosive volcanic eruptions. Using equipment in the Department's Experimental Petrology Laboratory, Dr. Webster melts rock samples at pressures and temperatures equivalent to those in the Earth's crust. In the lab, he also reacts molten rocks with volatile compounds to understand how hot fluids and magma interact in nature.
Dr. Webster served as a NATO post-doctoral fellow at the University of Edinburgh before joining the Museum in 1990.
RECENT SIGNIFICANT PUBLICATIONS
Mathez, E.A., and J.D. Webster. "Partitioning Behavior of Chlorine and Fluorine in the System Apatite-Silicate Melt-Fluid." Geochimica et Cosmochimica Acta 69 (2005): 1275-1286.
Pettke, T., W.E. Halter, J.D. Webster, M. Aigner-Torres, and C.A. Heinrich. " Accurate Quantification of Melt Inclusion Chemistry by LA-ICPMS: A Comparison with EMP and SIMS and Advantages and Possible Limitations of Either Method". Lithos 78 (2004): 333-361.
Webster, J.D. "The Exsolution of Magmatic Hydrosaline Melts". Chemical Geology 210 (2004): 33-48.
Webster, J.D., R. Thomas, H.-J. Förster, R. Seltmann, and C. Tappen. "Geochemical Evolution of Halogen-Enriched, Granite Magmas and Mineralizing Fluids of the Zinnwald Tin-Tungsten Mining District, Erzgebirge, Germany". Mineralium Deposita 39 (2004): 452-472.
Godon, A., J.D. Webster, G.D. Layne, and F. Pineau. "Secondary Ion Mass Spectrometry for the Determination of ?37Cl. Part II. Intercalibration of SIMS and IRMS for Aluminosilicate Glasses". Chemical Geology 207 (2004): 291-303.
Webster, J.D., and B. DeVivo. "Experimental and Modeled Solubilities of Chlorine in Aluminosilicate Melts, Consequences of Magma Evolution, and Implications for Exsolution of Hydrous Chloride Melt at Mt. Somma-Vesuvius, Italy". American Mineralogist 87 (2002): 1046-1061.
Thomas, R., J. D. Webster, and W. Heinrich. "Melt Inclusions in Pegmatite Quartz: Complete Miscibility Between Silicate Melts and Hydrous Fluids at Low Pressure." Contributions to Mineralogy and Petrology 139 (2000): 394-401.
Webster, J. D., R. J. Kinzler, and E. A. Mathez. "Chloride and Water Solubility in Basalt and Andesite Liquids and Implications for Magmatic Degassing." Geochimica et Cosmochimica Acta 63 (1999): 729-738.
Webster, J. D., and C. R. Rebbert. "Experimental Investigation of H2O and Cl Solubilities in F-Enriched Silicate Liquids: Implications for Volatile Saturation of Topaz Rhyolite Magmas." Contributions to Mineralogy and Petrology 132 (1998): 198-207.
Webster, J. D., R. Thomas, D. Rhede, H.-J. Förster, and R. Seltmann. "Melt Inclusions in Quartz From an Evolved Peraluminous Pegmatite: Geochemical Evidence for Strong Tin Enrichment in Fluorine-Rich and Phosphorus-Rich Residual Liquids." Geochimica et Cosmochimica Acta 61 (1997): 2589-2604.
Carroll, M. R., and J. D. Webster. "Solubilities of Sulfur, Noble Gases, Nitrogen, Chlorine, and Fluorine in Magmas." In "Volatiles in Magmas." Reviews in Mineralogy 30 (1994): 231-279.
POSTDOCTORAL FELLOWS, GRADUATE STUDENTS, AND SCIENTIFIC ASSISTANTS