FLUIDS AND PETROGENESIS
Learning outcomes of the course unit
The aim of the course is to evidence the importance of fluids in the formation and evolution of magmatic and metamorphic rocks, to get the condition of rock formation through thermodynamic equilibria between solid phases and volatiles, to briefly describe the analytical methods for volatile identification and quantification in glass and inclusions (fluid and melt inclusions) occurring in the rocks. Small outlines on the relations between fluids and metallogenic deposits will be provided.
Course contents summary
1. Volatile in magmas
Solubility of H2O, CO2, fluorine, chlorine, and sulfur in silicate liquids. Effects of volatiles on magma density and viscosity. Effects of volatiles (H2O, CO2, F) on melting in silicate systems. Fractional crystallization in hydrous magma. Identification methods of volatiles in silicate glass.
2. Fluid and melt inclusions
Classification, origin and post-entrapment variations of fluid inclusions l.s.. Fluid inclusions: microscope description and identification, microthermometric measurement, trapping temperature and pressure (equations of state). Melt inclusions: microscope description and identification, microthermometric measurement, data interpretation. Outlines of Raman and infrared spectroscopy.
3. Geothermometry and geobarometry.
Thermodynamic considerations and general equation for geothermobarometers. Main geothermometers. Geobarometers: lithostatic pressure, fluid pressure. Buffer reactions and main oxygen buffers. Role of oxygen fugacity in phase equilibria. Fugacity of other volatile species (equations of state).
4. Effects of fluids on metamorphic reactions
Solid and fluid phases in metamorphic reactions. Kinetics of metamorphic reactions. Mass transfer during metamorphism. Pressure-volume-temperature relations in metamorphic fluids. Thermodynamics of mineral reactions with H2O - CO2 fluids.
5. Fluid composition and metamorphic reactions
Fluid composition and mineral equilibria. Buffering and the internal control of fluid composition. Infiltration and the external control of fluid composition. Fluid composition controlled by combined infiltration and buffering.
6. Fluids and metallogenesis
Magmatic-hydrothermal fluids. Role of fluids on metal transport and deposition. Effects of oxygen fugacity on the efficiency of metal removal from magmas. Source rocks, volatiles and metallogenic provinces.
Philpotts A.R. (1990) Principles of igneous and metamorphic petrology.
Shepherd T., Rankin A.K., Alderton D.H.M. (1985) A practical guide to fluid inclusion studies.
Carroll M.R., Holloway J.R. (1994) Volatiles in magmas. Reviews in Mineralogy, vol. 30
Rice J.M., Ferry J.M. (1982) Buffering, infiltration, and the control of intensive variables during metamorphism. In: Characterization of metamorphism through mineral equilibria (J.M. Ferry, editor), Reviews in Mineralogy vol. 10, 263-326
Rice J.M., Ferry J.M. (1982) Characterization of metamorphic fluid composition through mineral equilibria. In: Characterization of metamorphism through mineral equilibria (J.M. Ferry, editor), Reviews in Mineralogy vol. 10, 207-262
Candela P.A. (1989) Magmatic ore-forming fluids: thermodynamic and mass-transfer calculations of metal concentrations. In: Ore deposition associated with magmas (J.A. Whitney and A.J. Naldrett, eds.). Reviews in Economic Geology, 4, 203-221
Candela P.A. (1989) Felsic magmas, volatiles, and metallogenesis. In: Ore deposition associated with magmas (J.A. Whitney and A.J. Naldrett, eds.). Reviews in Economic Geology, 4, 223-233