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George B. MORGAN VIElectron Microprobe Operator
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| gmorgan@ou.edu |
Click here to visit Electron Microprobe Laboratory
Electron Microscopy and Microanalysis, Igneous Petrology, Experimental Geochemistry, Materials Science
I am responsible for the day-to-day operation of the electron microprobe laboratory (see our website), and consider a modern electron microprobe to be the most useful tool for characterizing multi-component solid materials. One of the joys of working with such a versatile analytical platform is the exposure to materials problems from a great variety of scientific disciplines including not only samples from numerous geological settings, but also diverse materials problems spanning the gamut from identifying the constituents of human kidney stones to investigating the nature or failure of fabricated metallic or electronic components. Within the School of Geology and Geophysics, I teach courses in electron microbeam methods and digital image analysis.
Association with the School of Geology and Geophysics has provided the opportunity to continue research on the genesis and evolution of silicic magmas. Collaborative work with David London and a group of students and postdoctoral associates is helping to constrain the time-temperature paths along which granitic magmas acquire their chemical signatures from their source regions, some of the mechanisms that promote chemical and textural variability in granitic rocks (expressed by products as diverse as simple granites or rhyolites to complexly-zoned pegmatites), and near- to sub-solidus processes in evolved granites and granitic pegmatites. Research has involved the examination of natural igneous systems coupled with experimental petrologic study. Experiments to date have centered mostly on four areas: (1) the effects of volatile and fluxing components (e.g., H2O, CO2, B, P and F) on phase equilibria, melt structure, and crystallization behavior; (2) the kinetic response of silicic liquids to various cooling paths; (3) the dissolution of minerals and diffusion of their chemical constituents in granitic liquids; and (4) the effect of liquidus undercooling on crystal-melt elemental distributions. I returned to OU in 1992, after 2-1/2 years of operating the microsampling Raman spectroscopy laboratory in the Department of Earth and Planetary Sciences at Washington University, St. Louis. There, study was centered on fluid inclusions, which represent samples of fluids trapped within crystals either during or after growth of the mineral host. That research included applied studies of natural fluid inclusions, experimental studies examining how inclusions re-equilibrate in response to changes in the chemical environment of the host crystal, and basic research on synthetic fluid systems toward refining analytical methods.
SELECTED PUBLICATIONS
Morgan GB VI and London D (2005) Phosphorus distribution between potassic alkali feldspar and metaluminous haplogranitic liquid at 200 MPa (H2O): The effect of undercooling on crystal-liquid systematics. Contributions to Mineralogy and Petrology, in press.
Morgan GB VI and London D (2005) The effect of current density on the electron microprobe analysis of alkali aluminosilicate glasses. American Mineralogist, 90, 1131-1138.
Acosta-Vigil A, London D, and Morgan GB VI (2005) Contrasting interactions of sodium and potassium with H2O in haplogranitic liquids and glasses at 200 MPa from hydration-diffusion experiments. Contributions to Mineralogy and Petrology, 149, 276-287.
Acosta-Vigil A, London D, Morgan GB VI, and Dewers TA (2003) Solubility of excess alumina in hydrous granitic melts in equilibrium with peraluminous minerals at 700o-800oC and 200 MPa, and applications of the aluminum saturation index. Contributions to Mineralogy and Petrology, 146, 100-119.
Morgan GB VI and London D (2003) Trace element partitioning at conditions far from equilibrium: Ba and Cs distributions between alkali feldspar and undercooled hydrous granitic liquid at 200 MPa. Contributions to Mineralogy and Petrology, 144, 722-738.
Acosta-Vigil A, London D, Dewers TA, and Morgan GB VI (2002) Dissolution of corundum and andalusite in H2O-saturated haplogranitic melts at 800 C and 200 MPa: Constraints on diffusivities and the generation of peraluminous melts. Journal of Petrology, 43, 1885-1908.
Morgan, GB VI and London, D (1999) Crystallization of the Little Three layered pegmatite-aplite dike, Ramona District, California. Contributions to Mineralogy and Petrology, 136, 310-330.
London, D, Wolf, MB, Morgan, GB VI, and Garrido, MG (1999) Experimental silicate-phosphate equilibria in peraluminous granitic magmas, with a case study of the Albuquerque Batholith at Tres Arroyos, Badajoz, Spain. Journal of Petrology, 40, 215-240.
Morgan, GB VI, London, D, and Luedke, RG (1998) Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia. Journal of Petrology, 39, 601-632.
Morgan, GB VI and London, D (1996) Optimizing the electron microprobe analysis of hydrous alkali aluminosilicate glasses. American Mineralogist, 81, 1176-1185.
London, D, Morgan, GB VI, and Wolf, M (1996) Boron in granitic rocks and their contact aureoles. Invited chapter for: Grew, ES (ed) Boron Mineralogy, Petrology, and Geochemistry. Mineralogical Society of America, Reviews in Mineralogy, 33, 299-330.
Morgan, GB VI, Chou, I-M, Pasteris, JD, and Olsen, SN (1993) Re-equilibration of CO2 fluid inclusions at controlled hydrogen fugacities. Journal of Metamorphic Geology, 11, 155-164.
Seitz, JC, Pasteris, JD, and Morgan, GB VI (1993) Quantitative analysis of mixed volatile fluids by Raman microprobe spectroscopy: a cautionary note on spectral resolution and peak shape. Applied Spectroscopy, 47, 816-820.
Morgan, GB VI, Chou, I-M, and Pasteris, JD int(1992) Speciation in experimental C-O-H fluids produced by the thermal dissociation of oxalic acid dihydrate. Geochimica et Cosmochimica Acta, 56, 281-294
Morgan, GB VI, London, D, and Kirkpatrick, RJ (1990) Reconnaissance spectroscopic study of hydrous sodium aluminum borosilicate glasses. (abstr) Geological Society of America, Abstracts with Programs, 22, A167.
London, D, Morgan, GB VI, and Hervig, RL (1989) Vapor-undersaturated experiments with macusanite glass + H2O at 200 MPa, and the internal differentiation of granitic pegmatites. Contributions to Mineralogy and Petrology, 102, 1-17.
Morgan, GB VI and London, D (1989) Experimental reactions of amphibolite with B-bearing aqueous fluids at 200 MPa: implications for tourmaline stability and partial melting in mafic rocks. Contributions to Mineralogy and Petrology, 102, 281-297.
Morgan, GB VI and London, D (1987) Alteration of amphibolitic wallrocks around the Tanco rare-element pegmatite, Manitoba. American Mineralogist, 72, 1097-1121.
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