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Researchers in the Fluids Research Group are concerned with the distribution, properties and role of fluids in planetary processes.
This group is headed by Bob Bodnar.
Methods
Fluid inclusions provide the best source of information concerning the occurrence of fluids in natural samples. The distribution of fluids in the Earth and planetary systems is determined by studying fluid inclusions in earth materials and samples delivered to Earth from outer space.
The properties of geologic fluids are determined through experimental and theoretical studies of model fluid systems. The experimental technique that is used most commonly in the Fluids Research Laboratory is the synthetic fluid inclusion technique.
The role of fluids in geologic processes is studied by combining information obtained from natural fluid inclusions with PVTX data for model systems and with other geologic and geochemical information to interpret the results.
Research Areas
Fluid inclusions - general
Melt inclusions - general
Synthetic fluid inclusions
PVTX properties of model fluid systems, including H2O-NaCl, H2O-CO2, H2O-NaCl-KCl, H2O-NaCl-CaCl2, H2O-CO2-NaCl
Development of analytical techniques to study fluid and melt inclusions
Reequilibration of fluid inclusions
Fluid inclusions in low temperature and hydrocarbon systems
Fluid inclusions in ore deposits
Fluid inclusions in metamorphic environments
Mantle fluids
Fluid inclusions in meteorites and extraterrestrial environments
Volatiles in magmas
Geohydrologic Cycle
Volatile evolution of the Phlegrean Volcanic District (Italy) from studies of melt inclusions
Silicate-melt inclusions are small droplets (1-several 100 µm) of silicate melt entrapped in phenocryst minerals during their growth (Fig.1 and 2). Melt inclusions thus provide a sample of the melt that was present in the magma chamber when the phenocryst grew, and offer the possibility of reconstructing the chemical composition of the magma (silicate melt + volatiles) during its evolution from formation at mantle depth to its ascent and eruption at the surface. Moreover, MI provide the only reliable means of determining the volatile evolution before eruption. A basic assumption of melt inclusion studies is that the inclusions behave as closed (= isolated) systems after their formation; that is, after trapping the silicate melt remains isolated from the evolving melt in the magma chamber.
In populated areas in which active volcanoes are present, such as Campi Flegrei (Italy), understanding the role of volatiles in magmas provides important information on volcanic system dynamics. In particular, the volatile content in magmas (e.g. H2O, CO2, Cl, S and F) is of critical importance in determining the eruptive style and magma evolution, because degassing is usually one of the major phenomena before and during an eruption. The Phlegrean eruptive products were selected based on age, eruptive characteristic, mineralogical and chemical compositions, and structural position of the eruptive center to examine possible relationships between magma chemistry, especially the volatile content, and eruptive style. Melt inclusions were analyzed by Electron Microprobe (EMPA), Ion Microprobe (SIMS), Raman Spectroscopy, and Laser Ablation ICP-MS. Our study is a long term project that started in 2004 and is a joint program between Virginia Tech and the Università di Napoli Federico II, (Italy).
Melt inclusion hosted in sanidine from the Phlegrean Volcanic District. Note that the MI contain glass plus 5 bubbles. The picture is 50 x 60 μm.
Olivine phenocryst containing MI and glass embayments from the Phlegrean Volcanic District. Important to note is that MI are with or without bubble, and the olivine euhedral morphology. The size of the crystal is ~2 mm.
PT phase diagram for CO2, showing isochores in g/cm3, overlaid by the lithostatic and hydrostatic pressure gradients
Volumetric constraints on CO2 storage in a saline aquifer
In the effort to identify potential geological reservoirs for sequestration of CO2, one of the major types of targets is saline aquifers. Whereas there has been significant interest in CO2 solubility constraints, less attention has been given to the volumetric requirements of dissolving CO2 in saline brines in a confined aquifer. Dissolved CO2 has a finite partial molar volume in H2O and H2O-NaCl fluids, and thus injection of CO2 into an aquifer, even if coupled by complete dissolution of the CO2 into the brine, results in increase of the fluid volume, or reservoir pressure, or both. We incorporate the PVTX properties (solubilities, molar volumes and phase relations) of H2O-CO2 and H2O-NaCl-CO2 to investigate the volumetric effect of CO2 injection into a confined saline aquifer. As end member scenarios, we consider the pressure evolution if the pore volume in the aquifer remains constant (isochoric), and the volume evolution if the pore fluid pressure remains constant (isobaric). Under isochoric conditions, the fluid pressure increases whereas under isobaric conditions, fluid volume increases, with CO2 injection. Both scenarios result in breaching of the confining beds and CO2 escape. These results indicate that planning for CO2 storage in saline aquifers must consider not only CO2 solubility constraints and reservoir fluid volume, but must also consider the volumetric effect of dissolving CO2 in the brine, in order to ensure stability of the geologic reservoir.
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