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Gene Whitney

Publications and source records attributed to Gene Whitney.

9 recordsLinked to original sources
USGS2024

Hydrothermal reactivity of saponite

Saponite crystallizes from amorphous gel having an ideal saponite composition within 7 days at all experimental temperatures between 300° and 550°C at 1 kbar pressure. Reactions subsequent to this initial crystallization vary in type and degree, depending on the temperature of reaction and the type of interlayer cation. Above 450°C the intitially crystallized K-saponite dissolves, and talc and phlogopite nucleate and grow as discrete phases. At 450°C the initial K-saponite reacts to form talc and phlogopite layers, but the reaction proceeds via intracrystalline layer transformations rather than via dissolution and precipitation, producing a mixture of fully ordered, interstratified talc/saponite and fully ordered saponite/ phlogopite. The K-saponite shows subtle signs of reaction at 400°C after 200 days: this temperature is at least 150°C lower than experimental reaction temperatures previously reported for saponites. No reactions beyond the initial crystallization of saponite were observed below 400°C. K-saponite reacts more rapidly than either Na-saponite or Ca-saponite above 400°C and the Na-saponite and Ca-saponite produce no mica iayers during their transformation to mixed-layer clays. Interstratified talc/saponite formed in the Na-saponite system, and the Ca-saponite system produced both talc/saponite and chlorite/saponite.

Clays and Clay Minerals↗
USGS2024

Vanadium chlorite from a sandstone-hosted vanadium-uranium deposit, Henry basin, Utah

An unusual vanadium chlorite precipitated during the formation of a vanadium-uranium ore deposit in the Henry Basin, southeastern Utah. The ore deposit formed by reduction and precipitation of U and V in the presence of organic matter at the interface between a stagnant brine and overlying, circulating meteoric water. Some samples of the vanadium chlorite (heated before analysis) contain > 10% V 2 O 5 . In fresh samples, most of the vanadium is in the trivalent oxidation state. X-ray powder diffraction data suggest that Fe and V are concentrated preferentially in the interlayer hydroxide sheets of the chlorite. A d(060) value of 1.52 Å indicates that the chlorite probably has a dioctahedral structure which is distended by the presence of octahedral Fe and V. The vanadium ore zone is flanked by peripheral zones containing perfectly ordered chlorite/smectite. This chlorite/smectite contains much less V than the pure chlorite. This chlorite may have formed by the progressive precipitation of vanadium-rich interlayer hydroxide sheets in the mixed-layer chlorite/smectite in the most reducing portion of the ore zone. The pure chlorite is a IIb polytype, which, for nonvanadiferous analogs, is ordinarily found in high-temperature environments; however, no evidence exists to show that these rocks have ever been exposed to elevated temperatures. In fact, the presence of unreacted smectite in a potassium-rich setting and the low vitrinite reflectance of coalified plant debris indicate a low-temperature history for these sediments.

Utah↗
USGS2024

Role of water in the smectite-to-illite reaction

A series of hydrothermal experiments was performed to determine the effect of fluid abundance on the reaction of smectite to illite. Experiments were conducted on K-saturated montmorillonite (<0.1-µm fraction) in a closed system at 250° to 400°C using run times of 1, 7, 14, 30, and 60 days at 100 MPa (1 kbar) pressure. In fluid-deficient systems (pore spaces not saturated), the rate and extent of illitization was significantly inhibited. A rock:water ratio of 20:1 (mass:mass) produced an R0 illite/smectite (I/S) having 82% smectite layers after 60 days at 250°C, whereas a rock:water ratio of 1:1 produced an I/S having 57% smectite layers under the same conditions. The effect became less pronounced at higher temperatures, with the 20:1 and the 1:1 experimental products differing by only 11% expandability at 400°C after 60 days. In addition, the low-fluid experiments produced fewer crystalline byproducts (quartz, cristobalite, chlorite) than did the fluid-rich runs, and the I/S was more difficult to disperse and orient in the fluid-deficient samples, suggesting enhanced cementation at grain contacts or the production of particle morphologies that did not lend themselves to orientation. The difference in reactivity of the smectite and I/S as a function of water content appears to be attributable to the reduced capacity for low volumes of water to mediate the dissolution, solute transport, and precipitation reactions that make up the series of reactions collectively termed illitization. Of these variables, solute transport is likely to be affected most by reduction of fluid.

Clays and Clay Minerals↗
USGS2024

Changes in particle morphology during illitization: An experimental study

Smectite was reacted at several temperatures between 200°C and 500°C to produce interstratified illite/smectite (I/S) with different proportions of expandable layers. Dispersed and sedimented products were examined using a transmission electron microscope. Particle size and aspect ratio showed no systematic change as a function of reaction extent during R0 illitization. However, particles exhibited rounded edges during the early stages of the reaction, suggesting some dissolution of primary smectite. Additionally, increasing particle contrast in the electron beam suggests thickening of particles with increasing reaction extent. The thickening of particles is thought to be produced by the nucleation and precipitation of secondary illite layers on primary smectite layers. In the most extensively reacted I/S, particles have become aggregated into clumps or quasicrystals by lateral growth of illite layers. Internal uniformity of crystallographic alignment of individual growing crystals within each aggregate was reflected in the increasing frequency of 60° and 120° interfacial angles within each aggregate. In highly illitic I/S, these aggregates took on an overall euhedral form and became crystallographically contiguous, producing single crystal electron diffraction patterns.

Clays and Clay Minerals↗
USGS1992

Dioctahedral smectite reactions at elevated temperatures: Effects of K-availability, Na/K ratio and ionic strength

Hydrothermal experiments were conducted to measure the effects of K availability, Na / K ratio and ionic strength in chloride solutions on the rate and extent of the reaction of smectite to interstratified illite/smectite. The < 2 μm fraction of a bentonite was treated hydrothermally at temperatures of 200, 250, 300, 350, 400 and 450°C for run times of up to 30 days in the presence of 0.33, 0.66 and 1.00 equivalents of K per O 10 (OH) 2 . The effect of K-content on reaction progress is dramatic at low (0.33 eq.) K concentrations, but diminishes above a concentration of 0.66 equivalents. The effect of K-content is also more important at lower temperatures than at higher temperatures. Addition of K above that required to satisfy the cation exchange capacity of the smectite reduced the amount of chlorite byproduct and produced authigenic K-feldspar at the highest K-concentration. Similar experiments were run using Na / K equivalent ratios of 0 to 25 and total solution molalities of 0 to 3.75 molal. Because these experiments were small fixed-volume experiments, it was necessary to vary two of the three key variables (K-content, Na / K ratio, ionic strength simultaneously. The data suggest, however, that K-content has a much stronger effect than either Na / K ratio or ionic strength on illitization reaction progress.

Applied Clay Science↗
USGS1990

Genesis of the tabular-type vanadium-uranium deposits of the Henry Basin, Utah

Tabular-type vanadium-uranium deposits occur in fluvial sandstones of the Salt Wash Member of the Morrison Formation of Late Jurassic age The mineralized intervals and the weakly mineralized lateral extensions are bounded both above and below by zones rich in dolomite cement. Carbon isotope values of dolomite cements indicate that at least two sources of carbon existed. One source appears to be the same as that which formed the bedded carbonates in the evaporites in the Tidwell Member of the Morrison Formation stratigraphically below the mineralized interval. The second carbon source is typical of terrestrially deposited carbonates generally associated with meteoric water-dominated environments. Oxygen isotope values of these dolomites show the same trend of isotopically light values above the mineralized interval and isotopically heavier values in and below that interval; they indicate that two isotopically distinct fluids were involved in the mineralizing process. Some aspects of the origin of gangue and ore phases are explainable on the basis of processes which occurred solely within the saline fluid, but key aspects of ore genesis involved the interaction of the saline and meteoric waters. It is postulated that the solution interface migrated vertically within the stratigraphic section. -from Authors

Utah↗