- Blacksburg, Virginia, United States
robert bodnar
Virginia Tech, Geosciences, Faculty Member
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Thus far, we have emphasised the common features of crustal fluids by discussing them in general terms, but of course the specific fluid compositions and processes may be quite different in different geological settings. One of the main... more
Thus far, we have emphasised the common features of crustal fluids by discussing them in general terms, but of course the specific fluid compositions and processes may be quite different in different geological settings. One of the main reasons that we are interested in fluids (other than
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In the course of this Perspectives we tried to outline a wide range of science with which we have been involved, and provide some insight into some related areas that are outside our personal experience. Now that we have advanced our... more
In the course of this Perspectives we tried to outline a wide range of science with which we have been involved, and provide some insight into some related areas that are outside our personal experience. Now that we have advanced our understanding of crustal fluids to the point that we understand
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Introduction: Zag and Monahans (1998) are H chondrite regolith breccias containing 4.5 giga-year-old halite crystals which contain abundant inclusions of aqueous fluids, solids and organics. These all originated on a... more
Introduction: Zag and Monahans (1998) are H chondrite regolith breccias containing 4.5 giga-year-old halite crystals which contain abundant inclusions of aqueous fluids, solids and organics. These all originated on a cryo-volcanically-active C class asteroid, probably 1 Ceres; the halite was transported to the regolith of the H chondrite parent asteroid, potentially 6 Hebe. Detailed analysis of these solids will thus potentially reveal the mineralogy of Ceres. Mineralogy of solids in the Monahans Halite Solid grains are present in the halites, which were entrained within the mother brines during eruption, including material from the interior and surface of the erupting body. The solids include abundant, widely variable organics that could not have been significantly heated (which would have resulted in the loss of fluids from the halite). Our analyses by Raman microprobe, SEM/EDX, synchrotron X-ray diffraction, UPLC-FD/QToF-MS, C-XANES and TEM reveal that these trapped grains includ...
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Zag (H3-6) and Monahans (1998) (H5) are regolith breccias that contain 4.5 GY old halite crystals which in turn contain abundant inclusions of aqueous fluids, solids and organics [1-4]. We have previously proposed that these halites... more
Zag (H3-6) and Monahans (1998) (H5) are regolith breccias that contain 4.5 GY old halite crystals which in turn contain abundant inclusions of aqueous fluids, solids and organics [1-4]. We have previously proposed that these halites originated on a hydro-volcanically-active C-class asteroid, probably Ceres [3-7]. We have begun a detailed analysis of the included solids and organics and are re-examining the related carbonaceous (C)) chondrite clast we previously reported in Zag [5-7]. These new investigations will potentially reveal the mineralogy of asteroid Ceres. We report here on potentially identical C chondrite clasts in the H chondrite regolith breccias Tsukuba (H5-6) and Carancas (H4-5). The clast in Tsukuba was known before [8], but the Carancas clast is newly recognized.
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Fluvial sediment pulses are associated with a sudden and major increase in sediment supply to riverine environments. Their occurrence can be triggered by natural or anthropogenic factors or processes, including landslides, debris flows... more
Fluvial sediment pulses are associated with a sudden and major increase in sediment supply to riverine environments. Their occurrence can be triggered by natural or anthropogenic factors or processes, including landslides, debris flows from tributaries, volcanic eruptions, dam removals, and mining‐related activities. To predict their propagation, decoupled (clear‐water) models are commonly used, despite shortcomings identified when simulating the initial propagation phase and the existence of coupled (sediment‐laden) models. Herein, a framework for improving the accuracy of modeling efforts that simulate fluvial sediment pulse propagation dynamics is presented. The framework is centered on a physics‐based criterion formed by a dimensionless parameter ξ and its threshold condition ξcr. Comparison with laboratory and field studies shows that ξ indicates the relative importance of the terms neglected in decoupled models and that its threshold condition ξcr effectively sets an upper lim...
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Research Interests: Geology and Geochemistry
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The objective of this research is to assess the effect that extreme hydrologic events have on the propagation of sediment pulses in river corridors. These sediment-flow hazards are associated with large amounts of loose material suddenly... more
The objective of this research is to assess the effect that extreme hydrologic events have on the propagation of sediment pulses in river corridors. These sediment-flow hazards are associated with large amounts of loose material suddenly deposited in rivers by the action of external factors or processes of natural or anthropogenic origin, including landslides, debris flows from tributaries, dam removal projects, and mining-related activities. Their occurrence is associated with severe channel aggradation and degradation, floodplain deposition, damage of infrastructure, and impairment of riparian and aquatic ecosystems. Given that the intensity of rainfall events have been significantly enhanced due to the influence of various human activities, sediment pulses are expected to become more common, with a more pronounced downstream impact as such climatic changes directly affect the magnitude, duration, and frequency of flows in riverine environments. Herein, numerical simulations were ...
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Plagioclase‐hosted melt inclusions are infrequently used to investigate magmatic processes owing to the perception that they are less robust than olivine‐hosted inclusions. Based on a set of time series experiments ranging from 30 min to... more
Plagioclase‐hosted melt inclusions are infrequently used to investigate magmatic processes owing to the perception that they are less robust than olivine‐hosted inclusions. Based on a set of time series experiments ranging from 30 min to 4 days, we demonstrate that plagioclase‐hosted melt inclusions can preserve the original (primitive) magmatic signal if steps are taken to correct for post entrapment crystallization. Diffusion within plagioclase‐hosted melt inclusions is sufficiently fast that the melt inclusions can be homogenized within 30 min through heating experiments. As heating time increases, the composition of melt inclusions drifts. We attribute this longer‐term phenomenon to plastic deformation of the host plagioclase (crystal relaxation) inducing a decrease in the internal pressure in the melt inclusion combined with diffusion of elements across the host/melt inclusion interface. The rate of chemical reequilibration within melt inclusions is limited by the much slower r...
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Research Interests: Geology, Geochemistry, Geophysics, Peridotite, Metasomatism, and 4 moreKimberlite, Xenolith, Craton, and Mantle plume
The need for accurate modeling of fluid-mineral processes over wide ranges of temperature, pressure and composition highlighted considerable uncertainties of available property data and equations of state, even for the CO2 + H2O binary... more
The need for accurate modeling of fluid-mineral processes over wide ranges of temperature, pressure and composition highlighted considerable uncertainties of available property data and equations of state, even for the CO2 + H2O binary system. In particular, the solubility, activity, and ionic dissociation equilibrium data for the CO2-rich phase, which are essential for understanding dissolution/precipitation, fluid-matrix reactions, and solute transport, are uncertain or missing. In this paper we report the results of a new experimental study of volumetric and phase equilibrium properties of CO2 + H2O, to be followed by measurements for bulk and confined multicomponent fluid mixtures. Mixture densities were measured by vibrating tube densimetry (VTD) over the entire composition range at T = 200 and 250 C and P = 20, 40, 60, and 80 MPa. Initial analysis of the mutual solubilities, determined from volumetric data, shows good agreement with earlier results for the aqueous phase, but finds that the data of Takenouchi and Kennedy (1964) significantly overestimated the solubility of water in supercritical CO2 (by a factor of more than two at 200 C). Resolving this well-known discrepancy will have a direct impact on the accuracy of predictive modeling of CO2 injection in geothermal reservoirs and geologicalmore » carbon sequestration through improved equations of state, needed for calibration of predictive molecular-scale models and large-scale reactive transport simulations.« less
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sky, M. Fries, Q.H.-S. Chan, Y. Kebukawa, A. Steele, R.J. Bodnar, M. Ito, D. Nakashima, T. Nakamura, R. Greenwood, Z. Rahman, L. Le, D.K. Ross, K. Ziegler, W. Bottke, J. Martinez.NASA Johnson Space Center, Houston, TX 77058, USA... more
sky, M. Fries, Q.H.-S. Chan, Y. Kebukawa, A. Steele, R.J. Bodnar, M. Ito, D. Nakashima, T. Nakamura, R. Greenwood, Z. Rahman, L. Le, D.K. Ross, K. Ziegler, W. Bottke, J. Martinez.NASA Johnson Space Center, Houston, TX 77058, USA (michael.e.zolensky@nasa.gov); Open Univ., Milton Keynes, UK; Yokohama Nat. Univ., Yokohama 240-8501, Japan; Carnegie Geophys. Lab, Washington, DC 20015, USA; Virginia Tech, Blacksburg, VA 24061, USA; JAMSTEC, Kochi, 783-8502, JAPAN; Tohoku University, Sendai 980-8577, JAPAN; Jacobs ESCG, Houston, TX 77058 USA; Inst. Of Meteoritics, Univ. New Mexico, Albuquerque, NM, 87801 USA; Southwest Research Inst., Boulder CO, 80302 USA.
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R.J. Bodnar1, A. Dolocan2, M.E. Zolensky3, H. Lamadrid4, Y. Kebukawa5, Q.H.-S. Chan6, Z. Rahman7; 1Dept. of Geosciences, Virginia Tech, Blacksburg VA 24061 USA; 2Texas Materials Institute, Univ. of Texas, Austin, TX 78712 USA; 3ARES, NASA... more
R.J. Bodnar1, A. Dolocan2, M.E. Zolensky3, H. Lamadrid4, Y. Kebukawa5, Q.H.-S. Chan6, Z. Rahman7; 1Dept. of Geosciences, Virginia Tech, Blacksburg VA 24061 USA; 2Texas Materials Institute, Univ. of Texas, Austin, TX 78712 USA; 3ARES, NASA JSC, Houston TX 77058, USA; 4Dept. of Geological Sci., Univ. of Missouri Columbia, Columbia MO 75211, USA; 5Faculty of Engineering, Yokohama National Univ., Yokohama 240-8501, Japan; 6Dept. of Physical Sciences, The Open Univ., Milton Keynes, MK7 6AA, UK; 7Jacobs JETS, Houston, TX 77058 USA.
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Abstract Basalt formations are potentially attractive targets for carbon capture and sequestration (CCS) on the basis of favorable CO2-water-rock reactions, which result in permanent CO2 isolation through mineral trapping. Recent... more
Abstract Basalt formations are potentially attractive targets for carbon capture and sequestration (CCS) on the basis of favorable CO2-water-rock reactions, which result in permanent CO2 isolation through mineral trapping. Recent pilot-scale experiments in Iceland and Washington state, USA, provide promising results that indicate rapid carbon mineralization occurs within basalt reservoirs. Nevertheless, transitioning these pilot-scale results to large-scale industrial CCS operations is fraught with uncertainty because fluid flow in basalt formations is governed by fracture-controlled hydraulic properties that are highly heterogeneous and difficult to map in situ. This uncertainty is exacerbated by feedbacks between multi-phase fluid dynamics (CO2 and water) and fluid-rock reactions, which may result in a reinforcing feedback comprising CO2 mineralization, permeability alteration, and fluid mobility. To begin to understand the feedbacks between multi-phase fluid flow and mineralization in fractured basalt, this study uses reactive transport simulation methods to model CO2 infiltrating a meter-scale, synthetic basalt fracture overlying a storage reservoir while accounting for porosity change due to mineralization and its corresponding effect on permeability and fluid mobility. Results show that (i) carbonate and clay mineralization tends to occur downgradient of a fracture intersection, (ii) mineralization reduces porosity, which leads to permeability reduction and slows free-phase CO2 migration, (iii) stronger porosity-permeability coupling increases the proportion of mineralized carbon while reducing CO2 mass that can enter fracture, which may lead to self-sealing behavior as fluid mobility approaches nil, and (iv) errors caused by unknown porosity-permeability relationships are small in comparison to errors that arise by omitting mineralization-induced permeability reduction when simulating CO2 sequestration scenarios in basalt reservoirs.
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Several recent models that have been put forth to explain bradyseism at Campi Flegrei (CF), Italy, are discussed. Data obtained during long-term monitoring of the CF volcanic district has led to the development of a model based on... more
Several recent models that have been put forth to explain bradyseism at Campi Flegrei (CF), Italy, are discussed. Data obtained during long-term monitoring of the CF volcanic district has led to the development of a model based on lithological-structural and stratigraphic features that produce anisotropic and heterogeneous permeability features showing large variations both horizontally and vertically; these data are inconsistent with a model in which bradyseism is driven exclusively by shallow magmatic intrusions. CF bradyseism events are driven by cyclical magmatic-hydrothermal activity. Bradyseism events are characterized by cyclical, constant invariant signals repeating over time, such as area deformation along with a spatially well-defined seismogenic volume. These similarities have been defined as “bradyseism signatures” that allow us to relate the bradyseism with impending eruption precursors. Bradyseism is governed by an impermeable shallow layer (B-layer), which is the cap ...
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Research Interests: Geology and Systematics
Inclusions of basaltic melt trapped inside of olivine phenocrysts during igneous crystallization provide a rich, crystal-scale record of magmatic processes ranging from mantle melting to ascent, eruption, and quenching of magma during... more
Inclusions of basaltic melt trapped inside of olivine phenocrysts during igneous crystallization provide a rich, crystal-scale record of magmatic processes ranging from mantle melting to ascent, eruption, and quenching of magma during volcanic eruptions. Melt inclusions are particularly valuable for retaining information on volatiles such as H2O and CO2 that are normally lost by vesiculation and degassing as magma ascends and erupts. However, the record preserved in melt inclusions can be variably obscured by postentrapment processes, and thus melt inclusion research requires careful evaluation of the effects of such processes. Here we review processes by which melt inclusions are trapped and modified after trapping, describe new opportunities for studying the rates of magmatic and volcanic processes over a range of timescales using the kinetics of post-trapping processes, and describe recent developments in the use of volatile contents of melt inclusions to improve our understandin...
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The impact of bulk and surface defect states on the vibrational and optical properties of step-graded epitaxial GaAs1-ySby (0 ≤ y ≤ 1) materials with and without chemical surface treatment by (NH4)2S was investigated. Tunable antimony... more
The impact of bulk and surface defect states on the vibrational and optical properties of step-graded epitaxial GaAs1-ySby (0 ≤ y ≤ 1) materials with and without chemical surface treatment by (NH4)2S was investigated. Tunable antimony (Sb) composition GaAs1-ySby epitaxial layers, grown by solid source molecular beam epitaxy (MBE), were realized on GaAs and Si substrates by varying key growth parameters (e.g., Sb/Ga flux ratio, growth temperature). Raman and photoluminescence (PL) spectroscopic analysis of (NH4)2S-treated GaAs1-ySby epitaxial layers revealed composition-independent Raman spectral widths and enhanced PL intensity (1.3×) following (NH4)2S surface treatment, indicating bulk defect-minimal epitaxy and a reduction in the surface recombination velocity corresponding to reduced surface defect sites, respectively. Moreover, quantification of the luminescence recombination mechanisms across a range of measurement temperatures and excitation intensities (i.e., varying laser po...
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ABSTRACT The Jbel Tirremi fluorite-barite ± sulfide deposit in northeastern Morocco is hosted in a Jurassic-aged structurally high carbonate platform known as the Jbel Tirremi dome. The host rocks consist of unmetamorphosed, flat-lying... more
ABSTRACT The Jbel Tirremi fluorite-barite ± sulfide deposit in northeastern Morocco is hosted in a Jurassic-aged structurally high carbonate platform known as the Jbel Tirremi dome. The host rocks consist of unmetamorphosed, flat-lying early Jurassic dolomitized limestones, locally intruded by Eocene lamprophyre dikes. The orebodies consist mostly of fluorite and barite, and occur as open-space fillings and partial to massive replacement of the enclosing medium- to coarse-grained dolomitized limestones. The ore mineralogy is dominated by fluorite of different colors and habits, barite, and, to a lesser extent, sulfides. Rare earth element compositions along with fluid inclusion, halogen and isotopic data suggest that the fluorite barite mineralization and the spatially associated Eocene alkaline magmatism are petrogenetically unrelated, pointing instead to the regional circulation of hydrothermal basinal brines mixed to various degrees with meteoric water in a dominantly closed rock-buffered system at progressively higher temperatures and fluid/rock ratios. In this respect, fluid inclusion microthermometric measurements show that the ore-bearing hydrothermal system developed in two separate stages of fluorite-barite mineralization, as also revealed by isotopic data. Both stages precipitated from saline fluids at shallow crustal levels (i.e., <5 km), and were related, in varying degrees, to different stages of basin evolution and salt dome growth (salt mobilization and mineralization). During the first stage, the ore fluid was a highly saline aqueous brine with a total salinity up to 44.2 wt % NaCl + KCl equiv, at temperatures ≥82°C and possibly up to 218°C, whereas in the second stage the mineralizing fluid had a similar temperature range, but lower salinities (~20–10 wt % NaCl equiv). The recorded high salinities are interpreted to represent the involvement of a mixture of halite dissolution water and evaporated seawater component. Oxygen (δ18O = 21.7 to 29.6‰ V-SMOW) and carbon (δ13C = −7.9 to 0.2‰ V-PDB) isotope data along with strontium (87Sr/86Sr = 0.70300–070789) and lead (206Pb/204Pb = 17.961–20.96, 207Pb/204Pb = 15.511–15.697, 208Pb/204Pb = 37.784–39.993) isotope ratios suggest the involvement of a mixture of oil-bearing fluids, basinal brines, and meteoric fluids that interacted extensively with the early Jurassic host carbonates, the underlying Triassic salt-bearing diapir, associated siliciclastic rocks, and the highly fractionated and greisenized Hercynian granitic crystalline basement, resulting in the release of fluoride, metals, and other constituents to form the Jbel Tirremi deposit. Petroleum-bearing fluid, released from overpressured portions of the Guercif Basin at lithostatic pressures, and bittern brines dominated the first stage of mineralization. Mixing of saline, oxidized, CaCl2- and sulfate-rich bittern brine with oil-bearing fluid resulted in fluorite precipitation of stage I. Conversely, during the second stage of mineralization, the hydrothermal system was open to the influx of oxidized meteoric water as a consequence of the upward migration of the Triassic salt-bearing diapir and associated pressure decrease. The shift from stage I to stage II is associated with the evolution of the system from lithostatic to mostly hydrostatic pressure conditions. Stage I mineralization is thought to have occurred during the Late Miocene in response to rapid sedimentation and high subsidence rates and subsequent hydrocarbon migration associated with the outward migration of the Rif thrust front. Conversely, stage II mineralization occurred coevally with the uplift phase during Tortonian time.