Extension of the specific interaction model to include gas solubilities in high temperature brines     

Leslie Barta  Daniel J. Bradley 《Geochimica et cosmochimica acta》1985,49(1):195-203

A semi-empirical model for gas solubilities in high temperature brines was developed by modification of the Pitzer interaction model (Pitzer, 1973) and evaluated by least-squares fitting to available P-T-X data for carbon dioxide, hydrogen sulfide, and methane in pure water and in aqueous sodium chloride solutions. Over the range of experimental data used (25°–350°C, NaCl concentration 0–6 m, P_CO2 1–150 atm. P_CH4 1–30 atm, P_CH4 1–1700 atm), standard deviations of fit in the natural logarithm of the Henry's law ratio were 0.096 for CO₂, 0.093 for H₂S and 0.116 for CH₄.The model has several advantages. First, it has a theoretical basis which can easily be extended for the inclusion of more than one salt or gas. Second, the equations simplify to the empirically derived equation of Setschenow, in the limit of infinite dilution. Finally, the model is easily integrated into a framework of equations which can yield all of the thermodynamic properties of the system.An example in which values of the model parameters for interaction of gas with salt may be used to estimate the effect of dissolved gas or salt solubility is given.  相似文献   

The geochemistry of Ca,Sr, Ba and Ra sulfates in some deep brines from the Palo Duro Basin,Texas     

Donald Langmuir  Daniel Melchior 《Geochimica et cosmochimica acta》1985,49(11):2423-2432

The geochemistry of Ca, Sr, Ba and Ra sulfates in some deep brines from the Palo Duro Basin of north Texas, was studied to define geochemical controls on radionuclides such as ⁹⁰Sr and ²²⁶Ra. Published solubility data for gypsum, anhydrite, celestite, barite and RaSO₄ were first reevaluated, in most cases using the ion interaction approach of Pitzer, to determine solubility products of the sulfates as a function of temperature and pressure. Ionic strengths of the brines were from 2.9 to 4.8 m, their temperatures and pressures up to 40°C and 130 bars. Saturation indices of the sulfates were computed with the ion-interaction approach in one brine from the arkosic granite wash fades and four from the carbonate Wolfcamp Formation. All five brines are saturated with respect to gypsum, anhydrite and celestite, and three of the five with respect to barite. All are undersaturated by from 5 to 6 orders of magnitude with respect to pure RaSO₄. ²²⁶Ra concentrations in the brines, which ranged from 10^?11.3 to 10^?12.7 m, are not controlled by RaSO₄ solubility or adsorption, but possibly by the solubility of trace Ra solid solutions in sulfates including celestite and barite.  相似文献   

Determination of Boron in 35 International Geochemical Reference Materials by Thermal Neutron Capture Prompt Gamma-ray Spectrometry     

Ernest S. GLADNEY  David B. CURTIS  Daniel R. PERRIN 《Geostandards and Geoanalytical Research》1984,8(1):43-46

Concentrations of boron in 35 silicate reference materials are measured by thermal neutron capture gamma-ray spectrometry. Results are compared for NBS, USGS, and CCRMP reference materials with values from the literature. The use of two prompt gamma facilities at Los Alamos are discussed.  相似文献   

A new parameterization of eddy diffusivities for nocturnal boundary-layer modeling     

Claude Estournel  Daniel Guedalia 《Boundary-Layer Meteorology》1987,39(1-2):191-203

Exchange coefficients and mixing lengths under stable stratification have been studied through measurements of mean wind velocity and temperature in the nocturnal boundary layer. For values of the gradient Richardson number lower than 0.15, our measurements fit well the relation of Delage (1974). Beyond Ri = 0.15, the decrease of mixing length is much slower. So a new parameterization of turbulent exchanges is suggested. When introduced in a model of the nocturnal boundary layer, it results in a thickening of the turbulent and inversion layers.  相似文献   

Submarine lava tubes and channels     

Daniel J. Fornari 《Bulletin of Volcanology》1986,48(5):291-298

High-resolution, side-looking sonar surveys of the East Pacific rise and seamounts in the eastern Pacific have revealed the common presence of lava tubes and channels in seafloor volcanic terrains. Tube and channel systems commonly issue from small volcanic cones or domes, are continuous for distances of 1–3 km, and are considered to be important in distributing lavas around seafloor extrusive sites and creating characteristic morphology. Eruption rate and volume are probably the most important controlling factors in determining whether tubes or channels will form. Volatile content and state, slope angle, and preeruption surface morphology are secondary factors that influence the ease with which a tube or channel may form and its direction and shape. Seafloor tubes and channels may also have a profound influence on the structure and evolution of the upper oceanic crust. Tubes and channels are likely to form intracrustal horizontal pathways for circulating hydrothermal fluids. Flow differentiation processes acting within tubes and channels may affect the chemical composition of lavas and could be partially responsible for the chemical diversity of rocks along accretionary boundaries. Seafloor tubes and channels that are either partially water-filled or contain volcaniclastics which are then buried within the volcanic pile can lower the compressional velocity and seismic response of the upper oceanic crustal layer along spreading axes.  相似文献   

Organic Acid Derivatization Techniques Applied to Petroleum Hydrocarbon Transformations in Subsurface Environments     

Michael J. Barcelona  Jie Lu  Daniel M. Tomczak 《Ground Water Monitoring & Remediation》1995,15(2):114-124

Evidence for the natural microbial remediation of subsurface fuel contamination situations should include identification and analysis of transformation or degradation products. In this way. u mass balance between fuel constituents and end products may be approached to monitor cleanup progress. Application of advanced organic acid metabolite derivatization techniques to several known sites of organic compounds and fuel mixture contamination provide valuable information on the pathways and progress of microbial transformation. Good correlation between observed metabolites and transformation pathways of aromatic fuel constituents were observed at the sites.  相似文献   

Book review     

William D. Stuart  Kacper Rybicki  Brian J. Mitchell  Daniel Moos  Jeanne Sauber  Bernard Vonnegut  Ross J. Salawitch  David S. Gutzler 《Pure and Applied Geophysics》1987,125(5):853-855

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Rhyolites contaminated with metapelite and gabbro,Lipari, Aeolian Islands,Italy: products of lower crustal fusion or of assimilation plus fractional crystallization?     

Daniel S. Barker 《Contributions to Mineralogy and Petrology》1987,97(4):460-472

Pleistocene lavas from Monte S. Angelo and Chiesa Vecchia volcanoes on Lipari contain two suites of inclusions. A metapelitic suite consists of gneisses and granulites with combinations of cordierite, garnet, corundum, hercynite, andalusite, sillimanite, orthopyroxene, ilmenite, magnetite, biotite, plagioclase, and quartz. A gabbroic suite has cumulus texture and contains plagioclase, orthopyroxene, clinopyroxene, and magnetite. All megacryst phases in the lavas appear to be derived from rock fragments, with the exception of euhedral strongly zoned calcic plagioclase, and none has grown by homogeneous nucleation from liquid represented by the groundmass, which is peraluminous rhyolite (>70 wt% SiO₂, >6 wt% K₂O). Ground-mass microcrysts were nearly all derived from disaggregated metapelites; overgrowths of alkali feldspar on plagioclase and of orthopyroxene on clinopyroxene, and quartz intergrown with alkali feldspar, are the only phases that grew from the rhyolitic liquid. Euhedral cordierite, hercynite, and plagioclase at the margins of some rock fragments grew by reaction of metapelite with liquid.For grains in contact within metapelite inclusions, geothermometers and geobarometers yield estimates of equilibration conditions in the range of 800±100° C and 5±1 kbar. Compositions of phases in the same thin section, but not in the same inclusion, yield broadly erratic P and T estimates indicating disequilibrium among metapelite inclusions. Pyroxene thermometry in the gabbro suite indicates a crystallization temperature of 1020±50° C and a lack of subsequent thermal equilibration with the rhyolitic liquid.The metapelite suite may partly be restite, but much is xenolithic, derived from a vertical interval of perhaps several kilometers, and may have undergone a much earlier episode of melting. The gabbro fragments are accidental xenoliths incorporated as the magma rose. Contaminants (metapelite and gabbro) account for 50 vol.% of the lavas, and cause them to be classified as high-K andesite according to whole-rock major element analysis.The rhyolitic liquid may have originated by partial fusion of metapelites in the lower crust, or by fractional crystallization of mafic mantle-derived magma combined with assimilation of metapelite; the bulk of the evidence favors assimilation-fractional crystallization. Miocene and younger metapelite-contaminated rhyolites also occur in Tuscany, SE Spain, E Morocco, and NW Tunisia, and are associated in each region with mafic silica-undersaturated lavas, implying crustal underplating around the western Mediterranean before, during, and after formation of the Tyrrhenian basin.  相似文献   

Compositional and thermal convection in magma chambers   总被引：7，自引：1，他引：7  

Daniel Martin  Ross W. Griffiths  Ian H. Campbell 《Contributions to Mineralogy and Petrology》1987,96(4):465-475

Magma chambers cool and crystallize at a rate determined by the heat flux from the chamber. The heat is lost predominantly through the roof, whereas crystallization takes place mainly at the floor. Both processes provide destabilizing buoyancy fluxes which drive highly unsteady, chaotic convection in the magma. Even at the lowest cooling rates the thermal Rayleigh number Ra is found to be extremely large for both mafic and granitic magmas. Since the compositional and thermal buoyancy fluxes are directly related it can be shown that the compositional Rayleigh number Rs (and therefore a total Rayleigh number) is very much greater than Ra. In the case of basaltic melt crystallizing olivine Rs is up to 10⁶ times greater than Ra. However compositional and thermal buoyancy fluxes are roughly equal. Therefore thermal and compositional density gradients contribute equally to convection velocities in the interior of the magma. Effects of thermal buoyancy generated by latent heat release at the floor are included.The latent heat boundary layer at the floor of a basaltic chamber is shown to be of the order of 1 m thick with very low thermal gradients whereas the compositional boundary layer is about 1 cm thick with large compositional gradients. As a consequence, the variation in the degree of supercooling in front of the crystal-liquid interface is dominated by compositional effects. The habit and composition of the growing crystals is also controlled by the nature of the compositional boundary layer. Elongate crystals are predicted to form when the thickness of the compositional boundary layer is small compared with the crystal size (as in laboratory experiments with aqueous solutions). In contrast, equant crystals form when the boundary layer is thicker than the crystals (as in most magma chambers). Instability of the boundary layer in the latter case gives rise to zoning within crystals. Diffusion of compatible trace elements through the boundary layer can also explain an inverse correlation, observed in layered intrusions, between Ni concentration in olivine and the proportion of Ni-bearing phases in the crystallizing assemblage.  相似文献   

Dynamics of lava flow fronts, Arenal Volcano, Costa Rica     

Andrea Borgia  Scott Linneman  Daniel Spencer  Luis Diego Morales  Jose Brenes Andre 《Journal of Volcanology and Geothermal Research》1983,19(3-4)

Arenal Volcano has effused basaltic andesite lava flows nearly continuously since September, 1968. The two different kinds of material in flows, lava and lava debris, have different rheologic properties and dynamic behavior. Flow morphology depends on the relationship between the amount and distribution of the lava and the debris, and to a lesser extent the ground morphology.Two main units characterize the flows: the channel zone and the frontal zone. The channel zone consists of two different units, the levées and the channel proper. A velocity profile in the channel shows a maximum value at the plug where the rate of shear is zero, and a velocity gradient increasing outward until, at the levées, the velocity becomes zero. Cooling produces a marked temperature gradient in the flow, leading to the formation of debris by brittle fracture when a critical value of shear rate to viscosity is reached. When the lava supply ceases, much of this debris and part of the lava is left behind after the flow nucleus drains out, forming a collapsed channel.Processes at the frontal zone include levée formation, debris formation, the change in shape of the front, and the choice of the flow path. These processes are controlled primarily by the rheological properties of the lava.Frontal zone dynamics can be understood by fixing the flow front as the point of reference. The lava flows through the channel into the front where it flows out into the levées, thereby increasing the length of the channel and permitting the front to advance. The front shows a relationship of critical height to the yield strength (τ₀) surface tension, and slope; its continued movement is activated by the pressure of the advancing lava in the channel behind. For an ideal flow (isothermal, homogeneous, and isotropic) the ratio of the section of channel proper to the section of levées is calculated and the distance the front will have moved at any time t_x can be determined once the amount of lava available to the front is known. Assuming that the velocity function of the front {G(t)} during the collapsing stage is proportional to the entrance pressure of the lava at the channel-front boundary, an exponential decrease of velocity through time is predicted, which shows good agreement with actual frontal velocity measurements taken on two flows. Local variations in slope have a secondary effect on frontal velocities.Under conditions of constant volume the frontal zone can be considered as a machine that consumes energy brought in by the lava to perform work (front advancement). While the front will use its potential energy to run the process, the velocity at which it occurs is controlled by the activation energy that enters the system as the kinetic energy of the lava flowing into the front. A relation for the energy contribution due to frontal acceleration is also derived. Finally the entrance pressure, that permits the front to deform, is calculated. Its small value confirms that the lava behaves very much like a Bingham plastic.  相似文献