David R Janecky
Los Alamos National Laboratory, PT-5 Guest Scientist, Department Member
- Los Alamos National Laboratory, NonDestructive Testing & Evaluation, Department Memberadd
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ABSTRACT Lattice Boltzmann (LB) techniques are being applied to models of reactive transport processes in groundwaters with the purpose of modeling small scale (mm) interactions between water and rock in complex solid media. This method... more
ABSTRACT Lattice Boltzmann (LB) techniques are being applied to models of reactive transport processes in groundwaters with the purpose of modeling small scale (mm) interactions between water and rock in complex solid media. This method was used to create a simple porous media structure in which chemical reactions including sorption, dissolution and precipitation occur. A pre-existing lattice Boltzmann code developed at LANL for physical fluid flow was used as the basis for overlaying chemical exchange controls at each lattice node. Initially, Langmuir sorption isotherms were applied on open channel models varying from 10x4000 to 30x1000 nodes. The resulting breakthrough curves from these chemical slug models are compatible with analytical solutions that apply the isotherm equations on larger scales. The model was then further developed to include multiple solid compositions and dissolution and precipitation reactions to study the small scale spatial and temporal distributions of materials in porous media. Mineral nodes of varying composition which undergo specific chemical reactions can be created in the open channels or among evenly spaced blocks of solid nodes which simulate homogeneous porous media. This model structure is being used to investigate millimeter scale Sr isotopic variations observed in the K-metasomatized Lemitar Tuff from Southern New Mexico. Multiple samples of the adularia will provide an isochron age that may represent the time of K-metasomatism. Physical microsampling of this tuff has demonstrated the secondary adularia has a unique Sr isotopic characteristic (87}Sr/{86Sr near 0.727) relative to the fresh plagioclase and sanidine phenocrysts (0.709). The model is being used to discern between the possibilities of the Sr now present in the altered material originating from the surround matrix or alternatively from an outside source in the altering fluids. An outside source of Sr in the K-metasomatic groundwater would be likely with the failure of the model to recreate the correct Sr characteristic in the altered material while relying on in situ Sr from dissolution and precipitation.
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ABSTRACT We have analyzed trace elements in two types of hydrothermal precipitates using the Los Alamos Nuclear Microprobe. Chlorites and epidotes in basalt were analyzed from the Samail Ophiolite of Oman. Sulfide and sulfate minerals... more
ABSTRACT We have analyzed trace elements in two types of hydrothermal precipitates using the Los Alamos Nuclear Microprobe. Chlorites and epidotes in basalt were analyzed from the Samail Ophiolite of Oman. Sulfide and sulfate minerals were analyzed from samples of active chimney walls from 21/degree/N. East Pacific Rise. These samples are ideal for our study because of the extensive background information available on processes and component characteristics. Initial results indicate significant differences in mobile trace elements between chlorites associated with and those distinctly separate from major stockwork flow zones, consistent with greater water-rock reaction within stockworks. Trace element concentrations across chimney walls also exhibit distinctive patterns which can be correlated with mineral/chemical zonation and possible also with variations in elemental source. 9 refs., 2 figs., 1 tab.
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The Rocky Flats Environmental Technology Site (RFETS) was a U.S. Department of Energy (DOE) environmental cleanup site for a previous manufacturing plant that made components for the U.S. nuclear weapons arsenal. The facility was shut... more
The Rocky Flats Environmental Technology Site (RFETS) was a U.S. Department of Energy (DOE) environmental cleanup site for a previous manufacturing plant that made components for the U.S. nuclear weapons arsenal. The facility was shut down in 1989 to address environmental and safety concerns, and left behind a legacy of contaminated facilities, soils, surface and ground water. In 1995, the
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The instrumentation, the luminescence microprobe, and synchronously scanned luminescence spectroscopy technique described here can be used to classify microliter quantities of oil such as those in fluid inclusions in cements from... more
The instrumentation, the luminescence microprobe, and synchronously scanned luminescence spectroscopy technique described here can be used to classify microliter quantities of oil such as those in fluid inclusions in cements from petroleum reservoirs. It is primarily constructed to obtain synchronously scanned luminescence spectra from microscopic sized samples to characterize the organic classes of compounds that predominate. At present no other technique can so readily analyze a single oil-bearing fluid inclusion. The data collected from the technique are pertinent to evaluating systems and providing quantitative data for solving problems in oil migration and maturation determinations, oil-to-oil and oil-to-source correlations, oil degradation, and episodes and chemistry of cementation.
Research Interests: Engineering, Physics, Materials Science, Petroleum, Spectroscopy, and 13 moreScientific Instruments, Scientific, fluid Inclusions, Physical sciences, Microanalysis, Luminescence, CHEMICAL SCIENCES, Crude Oil, Optical Emission Spectroscopy, Fluid Inclusion, Microprobe, Gulf of California, and Organic Compound
Research Interests: Mechanical Engineering, Chemical Engineering, Mathematics, Physics, Kinetics, and 14 morePattern Formation, Cellular Automata, Statistical Physics, Spectral method, PARTIAL DIFFERENTIAL EQUATION, Lattice Boltzmann, Fluid flow, Navier Stokes, Lattice Boltzmann Method, Parallel Machines, Chemical Reaction, Lattice Boltzmann Methods, Cellular automaton, and Finite Difference Scheme
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Crystalline basalt, diabase and basalt glass have been reacted with a Na-Ca-K-Cl fluid of seawater ionic strength at 350-425°C, 375-400 bars pressure and fluid/rock mass ratios of 0.5-1.0, to assess the role of temperature, basalt/diabase... more
Crystalline basalt, diabase and basalt glass have been reacted with a Na-Ca-K-Cl fluid of seawater ionic strength at 350-425°C, 375-400 bars pressure and fluid/rock mass ratios of 0.5-1.0, to assess the role of temperature, basalt/diabase chemistry and texture on heavy metal and sulfur mobility during hydrothermal alteration. Alteration of basalt/diabase is characterized by cation fixation and hydrolysis reactions which show
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Abstract The geochemical changes associated with the experimental serpentinization of peridotite are due to reaction with sea water and to the growth of new mineral phases. Since the rare earth elements (REE) and Sr are primarily... more
Abstract The geochemical changes associated with the experimental serpentinization of peridotite are due to reaction with sea water and to the growth of new mineral phases. Since the rare earth elements (REE) and Sr are primarily ensconced in clinopyroxene, it is the unreactive nature of this phase in the presence of sea water that determines the REE content, the 87Sr/86Sr and 143Nd/144Nd ratio of the experimentally produced serpentinites. Serpentinites (after lherzolite and dunite) have chondrite-normalized REE abundance patterns similar to the initial peridotite indicating that the light REE (LREE) are not selectively mobilized by peridotite-sea water interaction at 300°C. However, the serpentinites produced as a result of harzburgite-sea water experiments show an increase in LREE content. Despite the sporadic behaviour of the LREE, the 143Nd/144Nd ratios in experimentally produced serpentinites (after lherzolite and harzburgite) are identical to primary clinopyroxene in the unaltered peridotite. In contrast, a marked change in the strontium isotopic composition of the peridotites occurs during experimental serpentinization due to the growth of hydrous and Ca-rich phases which facilitates the uptake of sea water Sr. Whereas harzburgite and dunite alter to produce serpentinites with high Sr contents and 87Sr/86Sr > 0.709, lherzolites tend to alter to serpentinites with 87Sr/86Sr < 0.709. This behaviour invalidates the use of Rb-Sr data in understanding the origin of oceanic and ophiolitic peridotites, but the relative immobility of the light REE (in clinopyroxene-bearing peridotites) and the low REE content of sea water encourages the careful use of the REE and neodymium isotopes as a petrogenetic indicator for elucidating the origin of serpentinized abyssal peridotites.
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... D. Wes Efurd, Wolfgang Runde,* Joe C. Banar ... of the filtrates were made by counting aliquots that were stippled onto stainless steel disks, evaporated to dryness under a heat lamp, flamed to dull red, and counted on an... more
... D. Wes Efurd, Wolfgang Runde,* Joe C. Banar ... of the filtrates were made by counting aliquots that were stippled onto stainless steel disks, evaporated to dryness under a heat lamp, flamed to dull red, and counted on an α-scintillation counter (Eberline Instrument Corporation ...
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Research Interests: Earth Sciences, Geology, Salinity, Physical sciences, Plume, and 3 moreAttenuation, Ridge, and panache
Summary Groundwater–peatland interactions were assessed by a regional survey in the Hudson Bay Lowlands, where the rapid rate of isostatic uplift has perturbed hydrological flow systems across a 6000‐year chronosequence. A 24 000 km2... more
Summary Groundwater–peatland interactions were assessed by a regional survey in the Hudson Bay Lowlands, where the rapid rate of isostatic uplift has perturbed hydrological flow systems across a 6000‐year chronosequence. A 24 000 km2 study area along the Albany River consists of 55% fen, 35% bog and 10% mineral soil. The peatland vegetation may be further subdivided into 11 noda, which are closely related to different water levels, ranges in water chemistry, and peat landform type. Species richness generally declines with increasing water level and acidity, whereas the gradient from bog to extremely rich fen is marked by the changing abundance and occurrence of fen‐indicator species. Bog landforms are restricted to physiographic settings where surface waters flow downwards and the bog vegetation is therefore isotated from the influence of geogenous waters. In contrast, fens are located in areas where mineral solutes are transported to the peat surface either by upwelling groundwater or by advective/dispersion along lateral flow paths. Peatlands spread across the study area between 6000 and 3000 bp, coinciding with the emergence of new land from the sea. The release of organic acids from the nearly continuous peat cover acidified this calcareous landscape, leading to the convergence of the surface‐water chemistry into four discrete groupings of pH vs. calcium. Isostatic uplift, however, continues to alter the topography, fluvial geometry and groundwater flow systems of the lowlands, maintaining diverse peatland types on land surfaces of similar age. The formation of water‐table mounds under the interfluvial divides and rising moraine system spurred the development of raised bogs, whereas the formation of regional seepage faces for goundwater on the margins of the moraine and rivers of the till plain maintains large areas of fen. Although peatland succession seems to follow predictable pathways within a given hydrogeological setting, these pathways are locally altered by tectonic drivers that continually modify surface and groundwater flow systems. In this large peat basin the pace and pathway of peatland succession seems to be driven by tectonic rather than climatic forcing.
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Research Interests: Engineering, Terrorism, Natural Resource Management, Risk Management, Waste Management, and 15 moreStakeholder participation, Medicine, Multidisciplinary, Risk Analysis, Case Study, United States, Natural disaster, Harm, Adaptive Management, Natural Resource, Office Building, Post Disaster Planning, Initial Condition, Public Facilities, and Disaster planning
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ABSTRACT Equilibrium path calculations have been used to model mixing between hot (350°C) hydrothermal solutions and ambient seawater, in an attempt to simulate mineral precipitation at seafloor vents. These calculations predict... more
ABSTRACT Equilibrium path calculations have been used to model mixing between hot (350°C) hydrothermal solutions and ambient seawater, in an attempt to simulate mineral precipitation at seafloor vents. These calculations predict temperatures of precipitation, paragenetic sequence of minerals, and chemical composition of chimney deposits associated with vents on the seafloor at 21°N, EPR. Assuming sulfate-sulfide disequilibrium during mixing, the paragenetic sequence revealed is: chalcopyrite, anhydrite, pyrrhotite, pyrite, sphalerite, graphite, and barite. When sulfate-sulfide equilibria is permitted during mixing, however, reduction of small amounts of sulfate results in early precipitation of pyrite and a sequence of Cu-rich sulfide minerals (chalcopyrite-bornite-chalcocite-covellite). This sequence is analogous to that observed in thin chimney walls. The calculations indicate that sulfide mineral precipitation occurs in response to both cooling and change in composition of the hydrothermal solutions as a result of mixing. Varying the amount of mixing with respect to temperature, simulating conductive heating of seawater prior to mixing, results in only minor variations in the sequence and abundance of precipitated phases.Anhydrite precipitation during mixing occurs early, which is consistent with formation of an anhydrite leading edge of chimney structures. Similarly, extrapolation of warm spring data from Galapagos to zero SO4 concentration suggests anhydrite formation due to mixing with seawater beneath the seafloor, most likely below the level of reactive calcareous sediments. Subsequent interaction of the mixed hydrothermal solution with those sediments results in elevated and variable Ca concentrations estimated for end-member solutions from the Galapagos.Precipitation of Mg hydroxide sulfate hydrate in the walls of the vent chimneys at 21°N, EPR, occurs as a result of conductive heating of ambient seawater with only very minor amounts of mixing. In contrast, precipitation of amorphous silica in the vents must be due to conductive cooling of the hydrothermal solutions.Thus, incremental reaction calculations demonstrate that reactions occurring in and associated with venting ridge crest hydrothermal solutions can be effectively modeled using the thermodynamic data and reaction modeling codes available today. Departures from equilibrium required to accurately model the mixing process are easily accommodated and consistent with data from the vents and vent forming materials.
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Research Interests: Geology, Geochemistry, Geothermal Energy, Mid Ocean Ridge, Quartz, and 15 moreHydrothermal Alteration, Basalt, Olivine, Energy System, Plagioclase, Pacific ocean, Volcanic Rock, Trace element, Chemical Composition, Mid-Atlantic Ridge, Ridge, Experimental Data, Supercritical Fluid, albite, and epidote
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ABSTRACT Fresh tholeiitic basalt glass has been reacted with seawater at 150°C, (water/rock mass ratio of 10), and fresh diabase has been reacted with a Na-K-Ca-Cl fluid at 375°C (water/rock mass ratios of 1, 2, and 5) to understand... more
ABSTRACT Fresh tholeiitic basalt glass has been reacted with seawater at 150°C, (water/rock mass ratio of 10), and fresh diabase has been reacted with a Na-K-Ca-Cl fluid at 375°C (water/rock mass ratios of 1, 2, and 5) to understand better the role of temperature, basalt composition, and water/rock mass ratio on the direction and magnitude of B and Li exchange during basalt alteration. At 150°C, slight but nevertheless significant amounts of B and Li were removed from seawater and incorporated into a dominantly smectite alteration phase. At 375°C, however, B and Li were leached from basalt. B behaved as a “soluble” element and attained concentrations in solution limited only by the B concentration in basalt and the water/rock mass ratio. Li, however, was less mobile. For example, at water/rock mass ratios of 1, 2, and 5, the percent of Li leached from basalt was 58, 70, and 92% respectively. This suggests some mineralogic control on Li mobility during hydrothermal alteration of basalt, especially at low-water/rock mass ratios. In general, these results, as well as those for B, are consistent with the temperature-dependent chemistry of altered seafloor basalt and the chemistry of ridge crest hydrothermal fluids.Based on the distribution and chemistry of products of seafloor weathering, low (≤ 150°C) and high-temperature hydrothermal alteration of basalt, and the chemistry of ridge crest hydrothermal fluids, it was estimated that alteration of the oceanic crust is a Li source for seawater. This is not true for B, however, since the hot spring flux estimated for B is balanced by low-temperature basalt alteration. These data, coupled with B and Li flux estimates for other processes (e.g., continental weathering, clay mineral adsorption, authigenic silicate formation and formation of siliceous skeletal material) yield new insight into the B and Li geochemical cycles. Calculations performed here indicate relatively good agreement between the magnitude of B and Li sources and sinks. The geochemical cycle of B, however, may be affected by serpentinization of mantle derived peridotite in oceanic fracture zones. Serpentinites are conspicuously enriched in B and if the B source for these rocks is seawater, then an additional B sink exists which must be integrated into the B geochemical cycle. However, until more data are available in terms of areal extent of serpentinization, serpentite chemistry and isotopic composition, the importance of B in these rocks with respect to the B geochemical cycle remains speculative at best.
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ABSTRACT The potential significance of two fluid phases (excluding air and hydrocarbons) has been established for a limited number of geochemical processes. Of note are phase equilibria in metacarbonate rocks for low to moderate prograde... more
ABSTRACT The potential significance of two fluid phases (excluding air and hydrocarbons) has been established for a limited number of geochemical processes. Of note are phase equilibria in metacarbonate rocks for low to moderate prograde metamophism, flow and transport in metamorphic rocks, and fluid inclusions. However, the reactive properties of a supercritical carbon dioxide phase that may coexist at relatively low temperatures and pressures with brine has implications not evaluated or appreciated in the a broad range of geologic systems. Flexible cell hydrothermal experiments are being used to evaluate reactions with supercritical carbon dioxide and 5.5 molal NaCl brine during hydrothermal alteration of sandstone and shale. Experimental brine-aquifer-aquitard systems approach steady state (32 to 59 days) before injection of carbon dioxide and continued reaction (45 to 80 days). Separate experiments without injection of carbon dioxide provide baseline reactions and kinetics. Concentrations of Na in the brine decrease, and Si, Mg, Fe and Mn increase, following injection of carbon dioxide. Carbon dioxide concentration in the brine increases from 5 to about 270 millimole/Kg following injection to supersaturation at 200C and 200bars. Silicate minerals (quartz, oligoclase, microcline and biotite) display textures (etch pits, mineralization) indicating significant reaction. Pressure decrease (about 30 bars over 72 hours) following injection of carbon dioxide is indicative of a decrease in the volume of the system due to the phase change of supercritical carbon dioxide to dissolved carbonate, and finally to mineral carbonate. Development of approaches to calculate reaction paths, including phase equilibria of immiscible carbon dioxide and water allows exploration of reaction processes and insight into influence of two fluid phases on mineral equilibria. Using EQ3/6, brine chemistry of degassed samples at STP (pH 6.5) has been evaluated for carbon dioxide-saturated conditions at 200C (pH 3.5). Brine samples from experiments with low carbon dioxide concentrations do not exhibit such large pH swings between STP and in-situ conditions. Our results bear on the developing issues of sequestration of anthropogenic carbon dioxide and classic questions of the origin and distribution of carbonate cements and veins in sedimentary basin sandstones.
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Quartz-carbonate veins are common in a variety of moderate temperature hydrothermal systems and ore deposits. Associated fluid inclusions have a wide range of compositions, including liquid carbon dioxide fillings. Examination of chemical... more
Quartz-carbonate veins are common in a variety of moderate temperature hydrothermal systems and ore deposits. Associated fluid inclusions have a wide range of compositions, including liquid carbon dioxide fillings. Examination of chemical and physical conditions which result precipitation of quartz and carbonate in veins raises several key questions about multiphase fluid processes and reaction rates. We have been experimentally investigating physical-chemical reaction processes of mixed brine-carbon dioxide fluids for the shallow crust. Synthetic arkose (microcline + oligoclase + quartz + biotite) plus argillaceous shale were reacted with 5.5 molal NaCl brine. The system was held at 200 C and 200 bars for 32 days to approach steady state, then injected with carbon dioxide and allowed to react for an additional 45 days. In a parallel experiment, the system was allowed to react for 77 days without injection of carbon dioxide. Trace ions initially absent from NaCl brine appeared in solution at mM (K, Ca, and silica) to uM (Mg, Al, Fe and Mn) quantities, reflecting reaction of brine with rock. Without carbon dioxide injection, the silica concentration (2.4 mM) was stable below calculated quartz solubility (3.9 mM). Injection of carbon dioxide resulted in decreased pH and increased silica concentration to a level near calculated chalcedony solubility (5.4 mM). Dissolution of silicate minerals is apparently coupled to the acidity, and concomitant inhibition of the precipitation of quartz (and other silicates). A significant increase in concentration of trace metals is consistent with in-situ pH decrease and increased carbon dioxide dissolved in brine. Multi-phase fluid reaction relationships between supercritical carbon dioxide and brine-rock systems allow formation of carbonate vein precipitates in substantial quantities. Brine and continued rock reactions provide a substantial reservoir for Ca, Mg and Fe components. A separate carbon dioxide liquid allows precipitation from relatively small volumes of total fluid, with coupled increases in pH and mineral stability. The doubling of silica concentration in the experimental system containing acidic brine and supercritical carbon dioxide indicates that precipitation of silica can occur in parallel to carbonate minerals when pH increases. Emplacement of silica super-saturated brine into a rock-dominated reaction system buffered to more neutral pH conditions may enhance precipitation of quartz, chalcedony, or amorphous silica as veins or cements, depending on the permeability structure of the host rock. Phase separation or loss of carbon dioxide with decreasing pressure can substantially shift pH upwards, with potential for creating massive vein or scale formation.
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Lattice gas automata models are described, which couple solute transport with chemical reactions at mineral surfaces within pore networks. Diffusion in a box calculations are illustrated, which compare directly with Fickian diffusion.... more
Lattice gas automata models are described, which couple solute transport with chemical reactions at mineral surfaces within pore networks. Diffusion in a box calculations are illustrated, which compare directly with Fickian diffusion. Chemical reactions at solid surfaces, including precipitation/dissolution, sorption, and catalytic reaction, can be examined with the model because hydrodynamic transport, solute diffusion and mineral surface processes are all
Research Interests: Environmental Science, Geology, Geochemistry, Chemistry, Mass Transfer, and 15 moreDiagenesis, Crystal structure, Environmental Sciences, Porosity, Geosciences, Ground Water, Mathematical Models, Dissolution, Fluid flow, Chemical Reactions, Mathematical Model, Porous Material, Chemical Reaction, Cellular automaton, and Hydrodynamic Model
Current models indicate that catastrophic impacts by asteroids and comets capable of killing more than one quarter of Earth&amp;#x27;s human population have occurred on average once every million years; smaller impacts, such the 1908... more
Current models indicate that catastrophic impacts by asteroids and comets capable of killing more than one quarter of Earth&amp;#x27;s human population have occurred on average once every million years; smaller impacts, such the 1908 Tunguska impact that leveled more than 2,000 ...
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Experimental investigations of basalt-solution reactions at conditions inferred for generation of high temperature oceanic ridge crest hydrothermal solutions indicate the importance of pressure, solution-rock ratios, and rock composition... more
Experimental investigations of basalt-solution reactions at conditions inferred for generation of high temperature oceanic ridge crest hydrothermal solutions indicate the importance of pressure, solution-rock ratios, and rock composition for formation of these metal-bearing solutions. At temperatures above 350°C. 400 bars pressure. and under rock dominated conditions. Ca and Na-metasomatism results in acid pHs and significant transition metal mobility. For Fe, Mn, and H+, the concentrations are exponential functions of temperature. while Zn and Cu reach maximum concentrations at ~400°C. Variations in rock chemistry and mineralogy result in consistent variations in metasomatic reactions, aqueous SiO2 concentration, and thereby, pH and dissolved metal concentrations. At 425°C. Na and Cl are also effected by a separate process which results in their depletion in solution by up to ~40%. Silicate alteration minerals formed during these experiments include smectite/chlorite, tremolite-actinolite, clinozoisite, and possibly albitic plagioclase. Pyrite, growing from pyrrhotite, and magnetite were also observed, consistent with phase stability predicted from H2S and H2 compositions of the solutions. Solution compositions from sampled East Pacific Rise hydrothermal systems for metals. H2S, H2, pH, minor and major elements are best modeled by our experimental data as the result of reaction of olivine-normative diabase at ~400°C, 400 bars. Higher or lower temperatures and variations in rock composition (e.g., to ferrobasalt) produce significant variations in the solution chemistry which may be observed elsewhere.