Ion microprobe analysis of a potassium self-diffusion experiment in biotite

Self-diffusion of potassium in biotite has been measured by inducing isotopic exchange between the potassium in the biotite and potassium enriched in ⁴¹K in a hydrothermal alkali chloride solution at 650°C and 2000 bars pressure, and then analyzing the resulting distribution of the K isotopes in the mica using an ion microprobe mass analyzer. The distribution of K isotopes in one mica flake was studied by three-dimensional mapping. The results show the diffusivity in the a or b directions to be greater than in the c direction by 2 to 4 orders of magnitude. In the c direction, the isotopic profile yields a diffusion coefficient of D = 1 × 10^?17cm²sec^?1 with an estimated error of a factor of ten. These results are in good agreement with bulk isotopic transport measurements on the same experiment reported by A.W. Hofmann and B.J. Giletti (1970). It is thus shown that diffusivities involving very slow net transport can be measured using an isotopic exchange technique and measuring the effect using an ion microprobe mass analyzer.     

Field pond as a sink for nutrients migrating from agrocenoses to freshwaters

Nutrients migrating from agrocenoses through drainage effluents are retained in a field pond. Studies were carried out concerning the effectiveness of this process in an aquatic environment in the conditions of development of phytoplankton and submersed and floating-leaved macrophytes (1987), in the state of phytoplankton dominance (1988), and, in a swamp environment, in the state of dominance of emergent macrophytes (1991).The greatest effectiveness of this process was found in the conditions of development of aquatic plants, i.e. submersed and folating-leaved macrophytes and phytoplankton. In the warm season of 1987 the retention of nutrients (in g · m^–2) was: TN — 7.20, TP — 3.5, K — 3.80, Ca — 119, and Mg — 8.2. When the euglenoid phytoplankton dominated, the level of retention was slightly higher and the export of N_org was also noted (3.27 g · m^–2 season^–1). In the case of dominance of emergent macrophytes, a reduction in the TN load, particularly in N-NO₃ (by 3.67 m^–2 season^–1), occurred, though at the same time a release of P, K, and Mg was noted. The export exceeded the import of TP by 0.44, K by 15.3, and Mg by 1.4 g · m^–1. The conditions for the functioning of a field pond as a sink for nutrients migrating from agroecosystems to surface waters were determined.     

Analysis of Diffusion and Adsorption of Volatile Organic Compounds in Zeolites by a Single Pellet Moment Technique

The diffusion and adsorption of two common volatile organic compounds, i. e., methanol and benzene, in different zeolite pellets were studied experimentally by using the single pellet moment technique. The experiments were conducted in a one‐sided single pellet adsorption cell at different temperatures in the range between 303 and 343 K. The results showed that both volatile organic tracers were adsorbed reversibly onto all zeolite samples. The overall adsorption equilibrium constants of both volatile organic compounds decreased with increasing temperature. The adsorption of the tracers onto the zeolite samples were found to increase in the order of NaY > clinoptilolite > 4A. In the range between 303 and 343 K, the adsorption constants of benzene range from 10.51 to 5.52 for zeolite 4A, from 11.90 to 6.37 for clinoptilolite and from 20.32 to 9.82 for NaY. The adsorption constants of methanol range from 19.05 to 8.26 for zeolite 4A, from 38.40 to 9.12 for clinoptilolite and from 74.21 to 14.70 for NaY at temperatures between 303 and 333 K. The effective diffusivities for benzene varied from 2.20·10^–6 to 13.01·10^–6 m²/s, whereas for methanol, they varied from 9.80·10^–6 to 15.60·10^–6 m²/s at the temperatures studied.     

Thermal diffusivity of olivine

The thermal diffusivity of a naturally occurring polycrystalline olivine (Fo₉₁Fa₀₉) was measured by the Flash technique in the temperature range of 450–1500 K. At 450 K the thermal diffusivity was 10.7 × 10^?7 m²/s and decreased as a function of reciprocal temperature to 7.0 × 10^?7 m²/s at 800 K. From that temperature, the values gradually increased to a maximum of 7.8 × 10^?7 m²/s at 1000 K, and then steadily decreased to 5.6 × 10^?7 m²/s at 1500 K. The unusual decrease above 1000 K was caused by a reduction of the previously oxidized samples. The olivine's oxidation state plays a significant role in the value of thermal diffusivity at high temperatures.     

Comment on “The July 9 and 23, 1905, Mongolian earthquakes,a surface-wave investigation” by Emile Okal

K-Ar ages have been determined for sulfide minerals for the first time. The occurrence of adequate amounts of potassium-bearing sulfides with ideal compositions K₃Fe₁₀S₁₄ (～10 wt.% K) and KFe₂S₃ (～16 wt.% K) in samples from a mafic alkalic diatreme at Coyote Peak, California, prompted an attempt to date these materials. K₃Fe₁₀S₁₄, a massive mineral with conchoidal fracture, gives an age of 29.4 ± 0.5m.y.(⁴⁰Ar/³⁹Ar), indistinguishable from the 28.3 ± 0.4m.y.(⁴⁰Ar/³⁹Ar) and 30.2 ± 1.0m.y.8 (conventional K-Ar) ages obtained for associated phlogopite (8.7 wt.% K). KFe₂S₃, a bladed, fibrous sulfide, gives a younger age, 26.5 ± 0.5m.y.(⁴⁰Ar/³⁹Ar), presumably owing to Ar loss.     

Petrogenesis of the late Cretaceous K‐rich volcanic rocks from the Central Pontide orogenic belt,North Turkey

Subduction‐related volcanic rocks are widespread in the Central Pontides of Turkey, and represented by the Hamsaros volcanic succession in the Sinop area to the north. The volcanic rocks display high‐K calc‐alkaline, shoshonitic and ultra‐K affinities. ⁴⁰Ar/³⁹Ar age data indicate that the rocks occurred during the Late Cretaceous (ca 82 Ma), and the volcanic suites were coeval. Primitive mantle‐normalized trace element patterns of all the lavas are characterized by strong enrichments in large ion lithophile elements (LILE) (Rb, Ba, K, and Sr), Th, U, Pb, and light rare earth elements (LREE; La, Ce) and prominent negative Nb, Ta, and Ti anomalies, all typical of subduction‐related lavas. There is a systematic increase in the enrichment of incompatible trace elements from the high‐K calc‐alkaline lavas through the shoshonitic to the ultra‐K lavas. In addition, the shoshonitic and ultra‐K lavas have significantly higher ⁸⁷Sr/⁸⁶Sr (0.70666–0.70834) and lower ¹⁴³Nd/¹⁴⁴Nd (0.51227–0.51236) initial ratios than coexisting high‐K calc‐alkaline lavas (⁸⁷Sr/⁸⁶Sr 0.70576–0.70613, ¹⁴³Nd/¹⁴⁴Nd 0.51245–0.51253). Geochemical and isotopic data show that the shoshonitic and ultra‐K rocks cannot be derived from the high‐K calc‐alkaline suite by any shallow level differentiation process, and point to a derivation from distinct mantle sources. The shoshonitic and ultra‐K rocks were derived from metasomatic veins related to melting of recycled subducted sediments, but the high‐K calc‐alkaline rocks from a lithospheric source metasomatized by fluids from subduction zone.     

Groundwater cation concentrations in the riparian zone of a forested headwater stream

Groundwater cation concentrations in relation to hydrologic flow paths were studied in the riparian forest zone of a small headwater catchment near Toronto, Ontario. Groundwater entering the riparian zone from uplands showed significant differences in cation concentrations between slope-foot and near-stream locations. Mean Ca, Mg, K, and Na concentrations in shallow groundwater at the upland perimeter of the riparian forest were 65-0, 11-2, 0-7, and 1-8 mg L^?1 respectively. Mean Ca, Mg, K, and Na concentrations in deep groundwater flowing upwards through glacial sands beneath the riparian zone were 52-1, 15-1, 1-3, and 2-6 mg L^?1 respectively. Shallow groundwater emerged as slope-foot springs producing surface rivulets which crossed the riparian zone to the streams. Deep groundwater flowed upward through organic soils into the rivulets and also discharged directly to the streams as bed and bank seepage. Springs had higher Ca concentrations and lower Mg, K, and Na values than rivulets entering the streams. Conversely, Mg, K, and Na concentrations were higher and Ca concentrations were lower in bank seeps in comparison to rivulets. These results suggest that differences in cation concentrations in groundwater entering the streams result from initial contrast in the chemistry of shallow and deep groundwater rather than from the effects of riparian soils and vegetation.     

Controls of concentration and loadings of major ions in a stream draining intermediate igneous rocks

Some 300 measurements under a wide range of flow conditions were used to construct regression models to predict concentrations of six major ions in a moorland stream draining intermediate-basic lavas in Scotland. Ca, Mg, and HCO₃ were very closely related to discharge in log-log regressions (r² > 90 percent). Na and Cl required inclusion of seasonal functions for best prediction (r₂ = 76 per cent in both cases). K concentrations were predicted from discharge, direction of stage change, and a seasonal function. Annual losses of Ca, Mg, and HCO₃ were 252, 36, and 871 kg ha ^?1, substantially larger than those for upland catchments on acid rocks. Losses of K, Na, and Cl were of a similar order to other upland sites.     

The control of alkalies and uranium in seawater by ocean crust alteration

Alteration of the oceanic crust during hydrothermal circulation of seawater produces fluxes of K, Rb and Cs between these reservoirs which are significant compared to the river input of these elements. The ocean crust U flux, on the other hand, is probably not significant. The upper crust, altered at low temperature, is a sink for all of these elements (as shown by direct analysis of upper crustal materials). The lower crust is a source for K, Rb, and Cs, based on the observation that high-temperature fluids exiting the crust as “host springs” are enhanced over seawater in K, Rb and Cs concentration. While the sign of the hot spring fluxes may be correct, the absolute magnitudes cannot be, as the calculated yearly hot spring flux of Rb and Cs significantly exceeds the total Rb and Cs inventory of newly formed unaltered crust. By modelling the crust as a melt/cumulate combination, we show that the crust as a whole is a sink for K, Rb, Cs, and probably U, with yearly fluxes of1.1 × 10¹³, 2.6 ×10¹⁰, 6.0 × 10⁸ and 1.0 × 10⁹g, respectively (com to yearly river dissolved fluxes of7.4 × 10¹³, 3.5 × 10¹⁰, 6.4 × 10⁸and1.0 × 10¹⁰g, respectively). The alteratio oceanic crust appears capable of quantitatively balancing the river inputs of Rb and Cs. For K, an additional sink comprising～ 85% of the river input is necessary. Because this missing K sink cannot be arbitrarily manipulated without destroying the Rb and Cs balances, a sink with K/Rb higher than the continental crust is required, and may possible be found in the sediments of the continental shelves.     

Caesium-137: Its accumulation in a littoral community

The low-level radioactive liquid wastes which arise at the U.K. nuclear fuel reprocessing plant at Windscale on the Cumbria coast are discharged into the Irish Sea. These wastes are initially dispersed but they can also become reconcentrated in marine organisms. The present work discusses the concentrations of ¹³⁷Cs relative to those of potassium in the various stages of marine food chains and shows that discrimination occurs in favour of ¹³⁷Cs over potassium during the transfer between the different trophic levels.     

Effet de la composition des micas trioctaedriques sur les distributions de Rb et Cs a l'etat de traces

An experimental study is reported on the distributions of trace amounts of Rb and Cs between some trioctahedral micas and a hydrothermal solution at 600°C and 1000 bars. The equilibrium constant K_X^min = (X/K)_aq/(X/K)_min varies considerably with the composition of micas. K_Cs^min is equal to 4.2 for phlogopite of theoretical composition, whereas it becomes equal to 8 for a mica close to eastonite. It reaches up to 17 for a mica in which Mg is largely substituted by Al. In annite, Fe(II) analogue of phlogopite, K_Cs^min becomes equal to 1.8. With Rb, the variations of the equilibrium constant are smaller than with Cs. K_Rb^min is 0.65 for phlogopite and increases up to 1.9 for a more aluminous mica. It is 0.44 for annite.The distributions depend very much on the ratios Mg/Fe and Si/Al of the trioctahedral micas. Consequences in geothermometrical interpretation of alkali trace element distributions in natural rocks are considered.     

Sources and sinks of sea salt in a newfoundland blanket bog

Over an oceanic peatland, the concentration of Na in fog averaged 38.1 mgl^?1 compared with 1.8 mgl^?1 in rain, resulting in a significant flux of mineral elements to the surface. Between 16 May and 20 June 1990 the average mass flux of Na to the bog surface by fog, rain, and dry deposition was 21.9, 10.4 and 7.0 mg m^?2 d^?1. There was little long-term storage of Na within the peatland system, where Na losses measured in stream runoff averaged 34.8 mg m² d^?1, and deep groundwater losses 4 mg m^?2 d^?1. Calcium and Mg were preferentially retained in the organic soil, whereas K was relatively mobile. Potassium tended to become concentrated in the unsaturated zone. Stream runoff had a consistently higher pH than groundwater, corresponding to higher Ca and Mg concentrations, which may have been from mineral sources in the headwater ponds. Otherwise, the stream water chemistry was closely related to groundwater in the upper layers of the peat deposit.     

The Antarctic meteorite Yamato 74123 — a new ureilite

The rare gases He, Ne, Ar, Kr and Xe were measured in bulk samples of Yamato 74123. The ³He and ²¹Ne exposure ages are found to be 5.50 Ma and 2.83 Ma, respectively. In addition to the cosmogenic component the samples contain primordial rare gases of the fractionated type in amounts typical of ureilites. In a three-isotope plot neon turns out to be a mixture of planetary neon and cosmogenic neon.The elements Na, Mg, Al, Si, P, S, K, Ca, Cr, Mn, Fe, Co, and Ni have been determined by spark source mass spectrometry in Yamato 74123 and for comparison in the ureilites Haveröand Kenna. The chemical composition as well as the noble gas abundance pattern identify Yamato 74123 as an ureilite.     

K/Rb and (Sr/Sr)0 ratios of dredged submarine basalts

K/Rb and (⁸⁷Sr/⁸⁶Sr)₀ ratios were measured for 14 submarine basalts dredged from seamounts in the Pacific Ocean. The K/Rb ranges from 200 to 700, which is significantly lower than that of oceanic ridge tholeiites. Petrographic examination and the low value of K/Rb indicate that seamount basalts are alkaline.     

Neutron capture logging calibration and data analysis for environmental contaminant assessment

This paper describes a method to calibrate a neutron capture sonde equipped with a high resolution γ-ray detector, and analyze log data. The method utilizes the 1460.8-keV passive γ-ray of ⁴⁰K, the 770.3-keV capture γ-ray of ³⁹K, and a capture γ-ray from a target element. An equation containing the spectral line intensities for the two capture γ-rays, nuclear capture data, and the detector efficiency function expresses the concentration of the target element as a multiple of the ³⁹K concentration. The concentration of ³⁹K is easily deduced from the ⁴⁰K concentration, which is calculated directly from the line intensity for the 1460.8-keV γ-ray in a passive γ-ray spectrum.The calibration automatically adjusts to changes in the neutron transport properties of the logged medium that may result, for example, from variations in the H density and the concentrations of neutron poisons. Fluctuations in the neutron source output are similarly accommodated. The calibration utilizes U.S. Department of Energy (DOE) passive γ-ray calibration standards that contain well established concentrations of K, U, and Th. The passive γ-rays from K, U, and Th (and the U and Th decay progenies) provide data for the detector efficiency function determination.Data for proof-of-principle demonstrations of the method were acquired by logging boreholes penetrating the shallow subsurface at a DOE waste site with a simple, reliable neutron capture logging system. The system had a ²⁵²Cf source and a high purity germanium (HPGe) detector. Time gating could not be used to sort signals originating from capture and activation, but the excellent energy resolution permitted capture γ-ray identifications based solely on the γ-ray energies. Cl, H, and other elements were detected and assessed.A conventional calibration and data analysis method was also employed. The method was specific to Cl and was based on measurements in two Cl-impregnated concrete blocks. Cl concentrations inferred with this method were often consistent with the concentrations determined with the new method. When the two methods produced different Cl concentrations, the discrepancies could be explained by variations in formation parameters.     

Seasonal mixing from intermittent flow drives concentration-discharge behaviour in a stream affected by coal mine drainage

Abandoned mining operations continue to severely degrade many ecosystems worldwide by releasing acidic water and/or heavy metals into surface and groundwater. Contaminant concentrations in affected streams vary with discharge in patterns that reflect both geochemical reactions and variable mixing of contaminated and non-contaminated waters. However, controls on concentration-discharge (C-Q) patterns remain unclear, particularly for constituents that experience changing solubility across redox and pH gradients. Understanding the C-Q behaviour of contaminants aids in predicting both downstream transport and effects on aquatic life under variable flow. Here, we examined the C-Q behaviours of non-reactive (Na, K, Ca, Mg, Cl⁻) and reactive (Fe, Mn, Al, H⁺, SO₄²⁻) solutes in a stream contaminated with acid mine drainage in northeastern Ohio, USA. Concentration-discharge patterns at the watershed outlet primarily reflected mixing of contaminated baseflow with intermittent inputs of high pH water draining from a passive limestone treatment system into the stream. The treatment system acted as an ephemeral tributary that mitigated contamination in the stream by diluting solutes, raising pH, and driving metal precipitation, but only when flow was present during wet seasons. Consequently, AMD-derived reactive solutes (H⁺, Fe, Mn, Al) decreased with increasing stream discharge while relatively conservative solutes (e.g., Ca, Mg, K, Na) decreased only slightly or were chemostatic. This study highlights both the unique C-Q patterns of reactive solutes when compared to those of non-reactive solutes and the potential for intermittent streams to control C-Q behaviour in headwater catchments.     

Comprehensive Combustion Performances of Water Hyacinth and Pistia stratiotes Pellet Fuels

For efficient combustion of aquatic biomass, the effects of heating rate on the combustion and dynamic characteristics of two typical aquatic species (water hyacinth, Pistia stratiotes), and the effects of temperature and additives on ash K and Cl concentrations are studied. The two types of pellets have ignition temperatures of 252.7 and 250.3 °C, respectively. At a heating rate of 10 °C min⁻¹, where combustion is most stable, the comprehensive combustion efficiencies reach their maximum at 4.7 × 10⁻⁶ and 2.2 × 10⁻⁶ mg²min⁻¹°C⁻², respectively. The K and Cl concentrations in the ash decrease steadily with increasing temperature, falling to 10.3% and 0.41% for water hyacinth and 11.1% and 1.85% for P. stratiotes, respectively. X-ray diffraction (XRD)shows that abundant Ca minerals form in the ash after the addition of CaO, which inhibit KCl formation, and K and Al silicates form in the ash after the addition of kaoline, which reserve K in the ash. These findings provide a starting point for the development of efficient aquatic biomass combustion.     

87Rb-87Sr studies of waters in a geothermal area: The Cantal,France

We have determined K, Rb and Sr concentrations and⁸⁷Sr/⁸⁶Sr ratios in fresh surface waters, a rain water sample and five geothermal waters from the Cantal volcanic area in the Massif Central, France. A comparison with appropriate rock types of the region showed no apparent chemical and isotopic fractionation occurring in the fresh water-surface rock system. The thermo-mineral water results suggest that all springs discharge dissolved Sr from the following contributors: Hercynian granito-metamorphic basement, lacustrian sediments underlying the volcano, Miocene-Pliocene volcanic rocks of basaltic to rhyolitic composition.     

The thermal boundary-layer interpretation of D″ and its role as a plume source

The “anomalous” layer in the lowermost mantle, identified as D″ in the notation of K.E. Bullen, appears in the PREM Earth model as a 150 km-thick zone in which the gradient of incompressibility with pressure, $\text{d}\text{K}\text{d}\text{P}$, is almost 1.6, instead of 3.2 as in the overlying mantle. Since PREM shows no accompanying change in density or density gradient, we identify D″ as a thermal boundary layer and not as a chemically distinct zone. The anomaly in $\text{d}\text{K}\text{d}\text{P}$ is related to the temperature gradient by the temperature dependence of K_s, for which we present a thermodynamic identity in terms of accessible quantities. This gives the numerical result (?K_s/?T)_P=?1.6×10⁷ Pa K^?1 for D″ material. The corresponding temperature increment over the D″ range is 840 K. Such a layer cannot be a static feature, but must be maintained by a downward motion of the lower mantle toward the core-mantle boundary with a strong horizontal flow near the base of D″. Assuming a core heat flux of 1.6 × 10¹² W, the downward speed is 0.07 mm y^?1 and the temperature profile in D″, scaled to match PREM data, is approximately exponential with a scale height of 73 km. The inferred thermal conductivity is 1.2 W m^?1 K^?1. Using these values we develop a new analytical model of D″ which is dynamically and thermally consistent. In this model, the lower-mantle material is heated and softened as it moves down into D″ where the strong temperature dependence of viscosity concentrates the horizontal flow in a layer ～ 12 km thick and similarly ensures its removal via narrow plumes.     

Episodic mesozoic volcanism in Namibia and Brazil: A K—Ar Isochron study bearing on the opening of the south atlantic

An attempt is made to find a more objective and precise basis for the correlation of volcanics from southwestern Africa and South America than is possible by frequency diagrams of individual K—Ar ages. This leads to a critical appraisal of conventionally calculated K—Ar ages with the conclusion thata priori assumption regarding the isotopic composition of non-radiogenic argon and, hence, the standard atmospheric correction, are no longer tenable.K—Ar isotoopic data on Mesozoic basalts and dolerites from Namibia and Brazil are presented in terms of an isochron model. Plots for cogenetic rocks are unacceptably scattered on a “radiogenic”⁴⁰Ar vs. K diagram, but show a high degree of collinearity on⁴⁰Ar/³⁶Ar diagrams0K/³⁶Ar diagrams. Using the latter plots, a number of isochrons are generated which indicate that Mesozoic volcanism in these regions occured as several discrete episodes of fairly short duration. Effusion of the extensive Serra Geral basalts of Brazil and the Kaoko basalts of Namibia is shown to have occured simultaneeously at 121 m.y.B.P. Basalts from a series of boreholes along the central Parana Basin, as well as a group of dykes from Sao Paulo, yield isochrons of 128 m.y., which coincides with the postulated onset of separation of Africa and South America based on marine magnetic anomalies. Linear dyke swarms along the Namibian seaboard, interpreted as an expression of the earliest rift phase, have an isochron age of 134 m.y. Sills and dykes, mainly from southern Namibia, with isochron ages of 183 m.y. are considered to be the westernmost manifestation of Stormberg volcanism, not necessarily related to rifting. Most of the igneous suites examined have initial⁴⁰Ar/³⁶Ar ratios significantly different from the modern atmospheric value.