Fluids in the Earth
May 10-14th, 2014
R. J. Bodnar
Virginia Tech, Blacksburg, VA, U.S.A.
L. V. Danyushevsky
Tasmania University, Hobart, Australia
B. De Vivo
University of Napoli Federico II
M. L. Frezzotti
University of Milano Bicocca
J. D. Webster
American Museum Natural History, N.Y., USA
May 10th, 2014
Introduction to the course (Bodnar; 1 hour)
The geohydrologic cycle (Bodnar; 1 hour)
The whole Earth system can be divided into the following reservoirs for H2O: atmosphere, biosphere, oceans, surface water, groundwater, glaciers and polar ice, continental crust, oceanic crust, upper mantle, transition zone, lower mantle and core. The amount of H2O contained in each of these reservoirs will be discussed, as well as the fluxes of H2O between reservoirs and residence times for H2O in the different reservoirs.
Introduction to phase equilibria and thermodynamics' (All; 2 hours)
The Gibbs Phase Rule; the Clausius-Clapeyron relationship; activity, fugacity; chemical potential and equilibrium; the definition of free energy and how it can be estimated from PVT data; solubility and saturation of volatiles in melts and fluids; melting diagrams for solid solutions; equilibrium between melts and simple solid solutions, the effects of changing melt/crystal proportions on the compositional evolution of solid solutions during crystallization; the effect of volatiles on crystallization temperatures of primitive magmas as a function of pressure
Introduction to phase equilibria and thermodynamics (continued) (All; 3 hours)
May 11th, 2014
Introduction to fluid Inclusions and fluid phase equilibria (Bodnar; 4 hours)
Identification, analysis and application of fluid inclusions to geologic problems.
Introduction to micro-Raman spectroscopy (Frezzotti; 2 hours): Raman spectroscopy is a non-destructive technique for fluid inclusion analysis, with a wide field of applications ranging from qualitative detection of solid, liquid and gaseous components to identification of polyatomic ions in solution. The main advantages of this technique are the minimal sample preparation and the high versatility. The procedures to calculate the density of CO2 fluids, the chemistry of aqueous fluids, and the molar proportions of gaseous mixtures present as inclusions, will be described.
Applications of fluid inclusions in ore-forming environments (Bodnar; 1 hour)
May 12th, 2014
Fluid inclusions in UHP metamorphic rocks (Frezzotti; 1 hour): The chemistry of fluid inclusions in high ultrahigh-pressure (UHP) metamorphic suites that experienced P–T conditions similar to those occurring in deep subduction zones (> 80-100 km) provide insight regarding the geochemical effects of fluid/melt addition to mantle wedges, and to the geochemical evolution of arc lavas. Examples from the Alps (Italy) and the Dabie-Sulu (China) UHP rocks will be presented.
CO2, carbonate melts, and brines and in the Earth’s upper-mantle (Frezzotti; 1 hour): Fluid inclusions in peridotite xenoliths provide a framework for interpreting the chemistry of fluids in the upper mantle in the different geodynamic settings. In the lithospheric mantle, the dominant fluid phase is CO2 (± brines), changing through carbonate melts at rising pressures. Mantle degassing liberates fluxes of CO2 (± brines), which may eventually reach upper crustal levels, including the atmosphere.
Introduction to melt inclusions (Danyushevsky; 3 hours)
Melt inclusions are small portions of melt trapped by crystals growing during magma evolution, and thus can represent ‘snapshot’ of the conditions that existed during crystallisation. In this lecture, trapping mechanisms of melt inclusions, their post-entrapment modifications, and experimental studies of melt inclusions will be discussed.
Applications of FI & MI on Vesuvius and Campi Flegrei volcanoes (De Vivo; 2 hours)
May 13th, 2014
Thermodynamics and physics of melt-fluid ± mineral systems (Webster; 4 hours)
Water and carbon dioxide are the primary magmatic volatile constituents, but sulfur and chlorine are also important magmatic volatiles. The phase relations of fluid exsolution from silicate melt, and the influences of these volatiles on magma evolution, fluid geochemistry, and the generation of mineralizing magmatic-hydrothermal fluids will be addressed.
Thermodynamics and physics of melt-fluid ± mineral systems, continued (Webster; 3 hours)
Volatile components in silicate melts influence melting temperatures and melt viscosity. Volatile components also influence the stability of minerals and fluids and consequently control larger processes including magma rheology and explosivity. The role of H2O and CO2 in these processes will be discussed.
May 14th, 2014
Using melt inclusions to constrain the origin of phenocrysts in strongly-phyric volcanic rocks (Danyushevsky; 1 hour)
An important implication of melt inclusions is to assess whether crystals in volcanic rocks crystallised from the same magma type as represented by the transporting melt (i.e., the groundmass of the rock), or are xenocrysts. Different examples from subduction-related volcanic suites will be shown.
Timing crystallisation processes using melt inclusions; Using melt inclusions to determine komatiite melt compositions; Melt inclusion studies on Vesuvius (Danyushevsky; 2 hours)
Post-entrapment re-equilibration of melt inclusions with their hosts can be used to assess crystallisation rates of individual phenocrysts. Melt inclusions can be a powerful tool for recovering melt compositions in ancient volcanic suites, when the groundmass in the lavas is chemically modified by alteration. A summary of melt inclusion studies of Vesuvius will be presented.
Melt inclusions in intermediate to felsic magmas (Webster; 2 hours)
The use and misuse of geochemical data from silicate melt inclusions of felsic continental and subduction-zone magmas will be described. Interpreting magma behaviour with melt inclusion compositions and experimentally determined volatile solubilities.
Exam on material covered in the short course (2 hours)