Geochemical Problems Research Articles

Fluid Flow Equipment for Hydrothermal Investigations: Apparatus and Preliminary Results

During the last two decades, experimental dynamic systems have been developed to simulate geochemical mass transfer induced by fluid flow through various geological materials (PoseyDowty et al., 1986). Experiments using these fluid flow systems are conducted to investigate various environmental and geochemical problems. For several reasons, they are more attractive than batch experiments. For example, in fluid flow experiments the water/rock ratio is not affected by fluid sampling and the fluid chemistry can be monitored during the course of reaction without disturbing the temperature and pressure conditions. In addition, the control of fluid flow makes it easier to derive kinetic parameters. The extraction of useful energy from the so called 'Hot Dry Rock' (HDR) requires circulation of fluids through fractured rocks between two or more wells. This will induce mass transfers. The Soultz-sous-For~ts (Alsace, France) project consists of testing the feasibility of developing a heat exchanger in the deep granite basement. As part of this project, we designed and built fluid flow experimental equipment.

Some geochemical and environmental aspects of the Chernobyl nuclear accident

The Chernobyl nuclear accident took place on 1986-04-26, and resulted in radionuclide pollution of vast regions of Byelorussia. This has raised several geochemical problems: (1) investigation of the distribution and behaviour of radionuclides in the natural and technogenic landscapes (which were examined as a result of a 5-a study); (2) modes of occurence of radioactive elements in the environment; and (3) preliminary estimation of radionuclide migration in the future. As background information, geochemical studies carried out within Byelorussia, as well as landscape investigations in the period 1953–1987 made under the guidance of K.I. Lukashev were very important for solving the above questions. According to the results of these investigations, the lithogeochemical and hydrogeochemical zoning of Byelorussia is understood and the radioactive background of the republic was studied in the 1960s, as well as the distribution and peculiarities of clay minerals, carbonates, Fe Mn oxides, organic matter, pH-Eh, and the contents of many elements in the surficial deposits of Byelorussia. All these factors are of great importance for understanding the behaviour of radionuclides. Radionuclide fallout on Byelorussia in the first days after the accident was mainly dependent on the mass movement of air and rain. In cities, fallout was confined to regions with intensive industrial dust emissions, as well as to river valleys, where degassing of deep-seated zones through faults occurred side by side with evaporation. Radionuclide washout from upland territories can be related to secondary processes. After 5 a, the radioactive emission near the surface of the Earth decreased due to the decay of short-lived isotopes and penetration of radionuclides deeper into the soil, although the major part still occurs at a depth of 1–5 cm. Bogs, peat-bog soils, aquifers with fluctuating groundwater levels, variable pH-Eh conditions and a igh biological activity are all factors contributing to radionuclide migration in the Byelorussian landscape. A part of the radionuclides is gradually removed from eluvial landscape and accumulated in subareal landscape (e.g. lakes, oxbow-lakes, water-storage basins). The Chernobyl debris are represented by the following substances: “hot” particles, pseudocolloids, aerosols and gaseous compounds. Study of the modes of occurrence of radionuclides by different methods (e.g. extracts, sorbents) made it possible to estimate the migration capacity of some radionuclides (Cs, Sr, Ce, Ru), and to distinguish two zones around the reactor—the nearest and remote ones—differing in the ratio of “hot” particles and condensate fallout, which causes a different migration capcity of radionuclides. A very important part is assigned to biological processes and organic matter, which cause the destruction of “hot” paricles, the formation of organomethallic complexes, and water migration of nuclides. In the future (within 300 and more years), the redistribution of radionuclides in the landscape involves processes of weathering, erosion and sedimentation which will strongly depend on climatic conditions, Side by side with a gradual decay of Cs and Sr, an appreciable accumulation of 241Am, which is very mobile in landscape, should be expected due to decaying 241Pu. A considerable development of scientific and applied exploration should also be expected in the future and this will help in solving problems of radioactive pollution of landscapes.

Another look at the constant sum problem in geochemistry

AbstractCompositional data—that is data where concentrations are expressed as proportions of a whole, such as percentages or parts per million—have a number of peculiar mathematical properties which make standard statistical tests unworkable. In particular correlation analysis can produce geologically meaningless results. Aitchison (1986) proposed a log-ratio transformation of compositional data which allows inter-element relationships to be investigated. This method was applied to two sets of geochemical data—basalts from Kilauea Iki lava lake and grantic gneisses from the Limpopo Belt—and geologically 'sensible' results were obtained. Geochemists are encouraged to adopt the Aitchison method of data analysis in preference to the traditional but invalid approach which uses compositional data.

Analytical electron microscopy (AEM) of core/rim structure in titanium carbonitride

The Chernobyl nuclear accident took place on 1986-04-26, and resulted in radionuclide pollution of vast regions of Byelorussia. This has raised several geochemical problems: (1) investigation of the distribution and behaviour of radionuclides in the natural and technogenic landscapes (which were examined as a result of a 5-a study); (2) modes of occurence of radioactive elements in the environment; and (3) preliminary estimation of radionuclide migration in the future. As background information, geochemical studies carried out within Byelorussia, as well as landscape investigations in the period 1953–1987 made under the guidance of K.I. Lukashev were very important for solving the above questions. According to the results of these investigations, the lithogeochemical and hydrogeochemical zoning of Byelorussia is understood and the radioactive background of the republic was studied in the 1960s, as well as the distribution and peculiarities of clay minerals, carbonates, FeMn oxides, organic matter, pH-Eh, and the contents of many elements in the surficial deposits of Byelorussia. All these factors are of great importance for understanding the behaviour of radionuclides.Radionuclide fallout on Byelorussia in the first days after the accident was mainly dependent on the mass movement of air and rain. In cities, fallout was confined to regions with intensive industrial dust emissions, as well as to river valleys, where degassing of deep-seated zones through faults occurred side by side with evaporation. Radionuclide washout from upland territories can be related to secondary processes.After 5 a, the radioactive emission near the surface of the Earth decreased due to the decay of short-lived isotopes and penetration of radionuclides deeper into the soil, although the major part still occurs at a depth of 1–5 cm. Bogs, peat-bog soils, aquifers with fluctuating groundwater levels, variable pH-Eh conditions and a igh biological activity are all factors contributing to radionuclide migration in the Byelorussian landscape. A part of the radionuclides is gradually removed from eluvial landscape and accumulated in subareal landscape (e.g. lakes, oxbow-lakes, water-storage basins).The Chernobyl debris are represented by the following substances: “hot” particles, pseudocolloids, aerosols and gaseous compounds. Study of the modes of occurrence of radionuclides by different methods (e.g. extracts, sorbents) made it possible to estimate the migration capacity of some radionuclides (Cs, Sr, Ce, Ru), and to distinguish two zones around the reactor—the nearest and remote ones—differing in the ratio of “hot” particles and condensate fallout, which causes a different migration capcity of radionuclides.A very important part is assigned to biological processes and organic matter, which cause the destruction of “hot” paricles, the formation of organomethallic complexes, and water migration of nuclides.In the future (within 300 and more years), the redistribution of radionuclides in the landscape involves processes of weathering, erosion and sedimentation which will strongly depend on climatic conditions, Side by side with a gradual decay of Cs and Sr, an appreciable accumulation of241Am, which is very mobile in landscape, should be expected due to decaying241Pu.A considerable development of scientific and applied exploration should also be expected in the future and this will help in solving problems of radioactive pollution of landscapes.

Powder characterization by adsorption

The Chernobyl nuclear accident took place on 1986-04-26, and resulted in radionuclide pollution of vast regions of Byelorussia. This has raised several geochemical problems: (1) investigation of the distribution and behaviour of radionuclides in the natural and technogenic landscapes (which were examined as a result of a 5-a study); (2) modes of occurence of radioactive elements in the environment; and (3) preliminary estimation of radionuclide migration in the future. As background information, geochemical studies carried out within Byelorussia, as well as landscape investigations in the period 1953–1987 made under the guidance of K.I. Lukashev were very important for solving the above questions. According to the results of these investigations, the lithogeochemical and hydrogeochemical zoning of Byelorussia is understood and the radioactive background of the republic was studied in the 1960s, as well as the distribution and peculiarities of clay minerals, carbonates, FeMn oxides, organic matter, pH-Eh, and the contents of many elements in the surficial deposits of Byelorussia. All these factors are of great importance for understanding the behaviour of radionuclides.Radionuclide fallout on Byelorussia in the first days after the accident was mainly dependent on the mass movement of air and rain. In cities, fallout was confined to regions with intensive industrial dust emissions, as well as to river valleys, where degassing of deep-seated zones through faults occurred side by side with evaporation. Radionuclide washout from upland territories can be related to secondary processes.After 5 a, the radioactive emission near the surface of the Earth decreased due to the decay of short-lived isotopes and penetration of radionuclides deeper into the soil, although the major part still occurs at a depth of 1–5 cm. Bogs, peat-bog soils, aquifers with fluctuating groundwater levels, variable pH-Eh conditions and a igh biological activity are all factors contributing to radionuclide migration in the Byelorussian landscape. A part of the radionuclides is gradually removed from eluvial landscape and accumulated in subareal landscape (e.g. lakes, oxbow-lakes, water-storage basins).The Chernobyl debris are represented by the following substances: “hot” particles, pseudocolloids, aerosols and gaseous compounds. Study of the modes of occurrence of radionuclides by different methods (e.g. extracts, sorbents) made it possible to estimate the migration capacity of some radionuclides (Cs, Sr, Ce, Ru), and to distinguish two zones around the reactor—the nearest and remote ones—differing in the ratio of “hot” particles and condensate fallout, which causes a different migration capcity of radionuclides.A very important part is assigned to biological processes and organic matter, which cause the destruction of “hot” paricles, the formation of organomethallic complexes, and water migration of nuclides.In the future (within 300 and more years), the redistribution of radionuclides in the landscape involves processes of weathering, erosion and sedimentation which will strongly depend on climatic conditions, Side by side with a gradual decay of Cs and Sr, an appreciable accumulation of241Am, which is very mobile in landscape, should be expected due to decaying241Pu.A considerable development of scientific and applied exploration should also be expected in the future and this will help in solving problems of radioactive pollution of landscapes.

Order parameter functional method for calculation of phase diagrams for hardmetals

The Chernobyl nuclear accident took place on 1986-04-26, and resulted in radionuclide pollution of vast regions of Byelorussia. This has raised several geochemical problems: (1) investigation of the distribution and behaviour of radionuclides in the natural and technogenic landscapes (which were examined as a result of a 5-a study); (2) modes of occurence of radioactive elements in the environment; and (3) preliminary estimation of radionuclide migration in the future. As background information, geochemical studies carried out within Byelorussia, as well as landscape investigations in the period 1953–1987 made under the guidance of K.I. Lukashev were very important for solving the above questions. According to the results of these investigations, the lithogeochemical and hydrogeochemical zoning of Byelorussia is understood and the radioactive background of the republic was studied in the 1960s, as well as the distribution and peculiarities of clay minerals, carbonates, FeMn oxides, organic matter, pH-Eh, and the contents of many elements in the surficial deposits of Byelorussia. All these factors are of great importance for understanding the behaviour of radionuclides.Radionuclide fallout on Byelorussia in the first days after the accident was mainly dependent on the mass movement of air and rain. In cities, fallout was confined to regions with intensive industrial dust emissions, as well as to river valleys, where degassing of deep-seated zones through faults occurred side by side with evaporation. Radionuclide washout from upland territories can be related to secondary processes.After 5 a, the radioactive emission near the surface of the Earth decreased due to the decay of short-lived isotopes and penetration of radionuclides deeper into the soil, although the major part still occurs at a depth of 1–5 cm. Bogs, peat-bog soils, aquifers with fluctuating groundwater levels, variable pH-Eh conditions and a igh biological activity are all factors contributing to radionuclide migration in the Byelorussian landscape. A part of the radionuclides is gradually removed from eluvial landscape and accumulated in subareal landscape (e.g. lakes, oxbow-lakes, water-storage basins).The Chernobyl debris are represented by the following substances: “hot” particles, pseudocolloids, aerosols and gaseous compounds. Study of the modes of occurrence of radionuclides by different methods (e.g. extracts, sorbents) made it possible to estimate the migration capacity of some radionuclides (Cs, Sr, Ce, Ru), and to distinguish two zones around the reactor—the nearest and remote ones—differing in the ratio of “hot” particles and condensate fallout, which causes a different migration capcity of radionuclides.A very important part is assigned to biological processes and organic matter, which cause the destruction of “hot” paricles, the formation of organomethallic complexes, and water migration of nuclides.In the future (within 300 and more years), the redistribution of radionuclides in the landscape involves processes of weathering, erosion and sedimentation which will strongly depend on climatic conditions, Side by side with a gradual decay of Cs and Sr, an appreciable accumulation of241Am, which is very mobile in landscape, should be expected due to decaying241Pu.A considerable development of scientific and applied exploration should also be expected in the future and this will help in solving problems of radioactive pollution of landscapes.

How SIMS microscopy can be used in medicine

The identification, localization and quantification of intracellular chemical elements is an area of scientific endeavour which has not ceased to develop over the past 30 years. Secondary Ion Mass Spectrometry (SIMS) microscopy is widely used for elemental localization problems in geochemistry, metallurgy and electronics. Although the first commercial instruments were available in 1968, biological applications have been gradual as investigators have systematically examined the potential source of artefacts inherent in the method and sought to develop strategies for the analysis of soft biological material with a lateral resolution equivalent to that of the light microscope. In 1992, the prospects offered by this technique are even more encouraging as prototypes of new ion probes appear capable of achieving the ultimate goal, namely the quantitative analysis of micron and submicron regions. The purpose of this review is to underline the requirements for biomedical applications of SIMS microscopy.Sample preparation methodology should preserve both the structural and the chemical integrity of the tissue.

Reconstruction of human diet from σ 13C and σ 15N in contemporary Japanese hair: a stochastic method for estimating multi-source contribution by double isotopic tracers

A stochastic method has been proposed for estimating contributions of multi-sources based on a simultaneous measurement of C and N stable isotope compositions of a mixture. Double isotope tracer analyses essentially allow a determination of the mixing proportion of up to three sources by mass balance calculations. For more than three sources, a stochastic approach may provide a possible range of mixing proportions. In this work, a stochastic method using the Monte Carlo simulation was employed for reconstructing the dietary consumption of contemporary Japanese. The mean σ 13C and σ 15N values of contemporary Japanese scalp hair were found to be − 18.2 ± 0.4 and 10.3 ± 0.4‰ relative to PDB and the atmospheric N 2, respectively. A dietary model was constructed by using mean isotope ratios of five major food groups and hair for modern Japanese. Based on this model, a stochastic method was applied to simulate human feeding. A range of dietary patterns, consistent with reasonable energy/protein uptake ratio, was estimated for fitting C and N isotope distributions of hair. The estimated mean dietary pattern has protein contributions of 35, 9, 16, 14, 27% from C3 plants, legumes, C4 plants, land animal products, and fish products, respectively, in good agreement with the observed food consumption in the National Statistics Report. The contribution of C4 type plant was estimated to range from 10 to 20% in protein, indicating much higher consumption than the statistical estimation. Thus, this stochastic method is useful in dietary analysis based on C and N isotope ratios. If the isotopic compositions of source materials are sufficiently different and each source is not isotopically reproducible by mixing of others, the stochastic simulation may indicate accurately the different source contributions. This method is applicable also to many geochemical problems where mixing occurs.

NMRのケイ酸塩への応用

The application of high resolution NMR in mineralogical and geochemical sciences has been developed deeply in a recent decade. It gives new insights into the structures and dynamic properties of silicates, aluminosilicates and zeolites. This review will briefly summarize some fundamental aspects of the theory and experimental practice of NMR spectroscopy and application of NMR methods to mineralogical and geochemical problems. Although cited examples are limited, the detailes could be found in excellent textbooks and review papers referenced in this paper.

Some sedimentary aspects of lateritic weathering profile development in the major bioclimatic zones of tropical Africa

Models of the accumulation of lateritic and bauxitic residua in the more humid parts of Africa, and the more sandy residua in drier parts, are outlined. The overhead source, both in the case of interfluve and slope-bottom accumulations, gives many of these monocyclic residual mantles a variety of features which are similar to and very difficult to distinguish from sedimentary features of polycyclic mantles whose development during periods of tectonic quiescence was periodically interrupted by erosion. Mechanisms for the evacuation of the materials, removal of which is essential for the accumulations to develop, are discussed. Evacuation of intact quartz and kaolinite by surface or shallow groundwater faces serious problems. Even greater problems face removal in solution and related geochemical problem apply to the limited mobilisition of the lateritic and bauxitic components, which is an integral process of accumulation. Nevertheless, the silicate karst features of profile and landsurface development indicate that evacuation is essentially by groundwater. Biochemical leaching is indicated to be capable of causing the necessary breakdown of minerals, rendering the dissolution products in forms which may have the necessary mobility. The recognition that materials can be mobilised, which are theoretically immobile if strictly geochemical constraints apply, facilitates genetic interpretation of sedimentary materials in groundwater discharge situations, dambo infill being cited as an example.

Calculation of multicomponent ionic diffusion from zero to high concentration: I. The system Na-K-Ca-Mg-Cl-SO 4-H 2O at 25°C

A model is described for the calculation of diffusion coefficients and other vector transport processes for the six component seawater system Na-K-Ca-Mg-Cl-SO 4-H 2O at 25 °C, from low to high ionic strengths. The model is based upon an extension of the empirical equations of Miller (1967a) for the calculation of Onsager phenomenological coefficients and upon an accurate thermodynamic model utilizing the ion-interaction method of Pitzer (1979) and coworkers. The necessary parameters for the activity derivatives and the Onsager coefficients may be evaluated from binary and ternary data. Additional data are not required for applications in more complex systems. The present model parameterization accurately reproduces all of the relevant, binary mutual diffusion coefficients to high ionic strength. In common-ion ternary systems, the model with the present parameterization does well for solutions in which the concentrations of the component electrolytes are approximately equal and for the dominant electrolyte in systems in which one of the electrolytes is in excess. The model may not be as accurate for the minor components of mixed electrolyte systems, because the required ternary experimental data are not available; however, even in these cases errors do not exceed 20%. The model is also used to calculate diffusion coefficients at the composition of seawater. Our calculated values are supported by the measured conductivities, partial molal conductivities, and mutual diffusion coefficients of neutral components at seawater composition. The importance of coupling between diffusive flows is illustrated by application to a hypothetical geochemical problem which could result from a salt dome penetrating an overlying formation saturated with seawater. The large diffusive flux of NaCl creates significant gradients in all of the minor species (i.e., K +, Ca 2+, Mg 2+, SO 4 2−), even though there were no initial concentration gradients for these species. The use of tracer diffusion coefficients is also discussed. The use of such coefficients in simplified forms of Fick's law is shown to be fundamentally inapplicable for electrolyte systems even at infinite dilution. When used in more comprehensive electrolyte diffusion models, isotope-isotope coupling effects complicate the use of tracer diffusion coefficients, especially at higher concentrations.

Novel biomarkers found in South Florida Basin

Several novel series of aryl isoprenoids, have been observed in the Sunniland Limestone of South Florida Basin (U.S.A.). All of these compounds have the same series of homologous key ions, m/ z 91 + 14 n ( n = 0–10). The compositions and distributions of trimethylalkylbenzenes (1-alkyl-2,3,6-trimethylbenzenes) are reported and discussed in this paper. Their application to various organic geochemical problems are also discussed, particularly their use as indicators of organic facies and maturity of sedimentary organic matter.

NORMOD: A program for modal norm calculation and evaluation of other component transformations

NORMOD is a program to solve component transformations in petrologic and geochemical problems focusing to modal norms calculations. Most component transformations are carried out by multiple linear regression, using the least-squares method. In addition, an empirical approximation is used to calculate the “best subset” in transformations, as a CIPW norm, where the set of unknown components is independent from known components. Each specific application is presented by a subroutine involving a data file. Three applications actually are written to calculate two modal norms for peraluminous granitoids and a CIPW norm for oversaturated rocks.

Trace analysis by degrees - An academic perspective

The increasing awareness of the important role of very small amounts of chemical species in chemical, physical, and biological systems has greatly stimulated the refinement and extension of analyses at these levels. The analytical requirements imposed by the minute quantities and typically complex systems involved has led to the development of methodology and instrumentation so specialized as to warrant consideration as a distinct field of analytical chemistry-trace analysis. One of the aims of this symposium is to gain an accurate assessment of the current state of this field, and this paper is an attempt to present this status from an academic perspective. In order to discuss any specialty in analytical chemistry as carried on in colleges and universities, it is necessary to first review the current status of the whole discipline. It must be stated that the main missions of universities are teaching and research, and chemistry, one of the basic sciences, is an essential discipline in most colleges and universities. How does analytical chemistry fare in academe? A review of the American Chemical Society Directory of Graduate Research lists faculties, publications and theses in chemistry and other related disciplines at universities in the United States and Canada. A review of the 1985 edition, the latest available, reveals that of the 315 chemistry departments listed, 201 include analytical chemistry with 510 analytical faculty members. It is obvious that these departments cover a wide range of sizes, so that some of the smaller institutions are less structured. Of these 201 departments, 80 have at least three or more analytical chemistry faculty members. What becomes quite apparent from a review of the data is that while analytical chemistry is not formally included in every department, there are a significant number of strong analytical departments in the United States and Canada to advance the science adequately. In this environment we can now turn our attention to trace analysis. With regard to trace analysis research, two major approaches are evident: development of new techniques and methodology, and application to important problems. Because the field of trace analysis is so broad, I have chosen to limit my evaluation to trace element analysis, the area of my expertise. This specialty can be conveniently divided into three categories: bulk analysis, spatially resolved analysis, and speciation. In the area of applications, trace analytical research is being pursued by a good number of faculty to solve important biomedical, environmental, solid state materials, and geochemical problems. Among the techniques currently being employed for bulk trace analysis, electroanalytical, atomic spectroscopy, x-ray fluorescence, activation analysis, and mass spectrometry are the most advanced and most used. A review of bulk trace techniques over the past 40 years indicates continuous progress in each of these categories. See figure 1. Thus, each of these techniques has continuously been used and kept viable with novel research advances. The current exciting areas in each of these categories include modified electrodes, inductively coupled plasma spectroscopy (ICP), proton induced x-ray emission spectroscopy (PIXE), charged particle and prompt gamma activation analyses, and ICP-mass spectroscopy. While there will always be a need for more sensitive bulk trace methods of broad scope, there has been increased interest in recent years in localization of elements in solid samples. These spatially resolved methods of trace analysis can establish the distribution of many elements with spatial resolutions at the micrometer level or better. Table I lists

The association of major, minor and trace inorganic elements with lignites. III. Trace elements in four lignites and general discussion of all data from this study

Fourteen trace elements (La, Cr, Sc, Y, Yb, Ga, Ni, V, Be, Zr, Ge, Pb, Sn, Ce) have been determined by emission spectroscopy in the ash from 7–17 levels within four early Tertiary lignite seams from Wyoming, Texas and Alabama, and two elements (Cu, Zn) in the acid-soluble and acid-insoluble fractions of the samples by inductively coupled plasma arc emission spectrometry. These elements were also determined in the roof and floor strata enclosing the seams. The concentrations of a number of elements ( e.g. Be, V, Cu, Y, Yb) were considerably higher in the coal ash than in the adjacent inorganic layers, and these elements are most probably associated with organic matter as coordination complexes. Several elements (Be, Y, Yb, Ga, Sc) were frequently found to be concentrated near the margins of the seam relative to the main body. One of the seams has a 6 cm “rider” separated from the top of the main seam by 9 cm of clayey sand. Analysis of fractions separated by specific gravity and solubility in acid showed this to be rich in trace elements, of which V, Be, Cu, Ni, Ge, Cr, Y, Yb, Ga and Sc appeared to be partly complexed with organic matter, and Sn and Pb were present only in minerals. The rider evidently acted as an efficient trap for unusually large amounts of many trace elements. Cluster analysis showed that the distributions of elements with depth in three of the seams represent three very distinctly separate populations of data; each seam constitutes a different geochemical problem. In a general discussion of the results of the whole series of three papers, a model describing the incorporation of inorganic components in peats is presented, based on the erosion of rocks by chelating organic acids and other agents, followed by transport in water and trapping of mineral grains and dissolved ions by the organic matter of peat. Inorganic materials in peat thus constitute the principal input of mineral matter into coals. The elements that tend to be enriched near the margins of lignite seams are mostly those that have complexed with organic matter. However, the data on this enrichment from our own and previously published work are quite variable, no doubt depending on the nature and efficiency of transport of the incoming cations.

Geology of the Sabie River Basalt Formation in the Southern Kruger National Park

The Sabie River Basalt Formation (SRBF) in the central Lebombo is a virtually continuous sequence of basaltic lavas some 2 500 m thick that was erupted 200 - 179 Ma ago. Flows are dominantly pahoehoe in character and vary from 2 m to 20 m in thickness. Dolerite dykes cross-cutting the basalt sequence probably represent feeders to this considerable volcanic event. Volcanological features observed within the SRBF are described. Two chemically distinct basaltic magma types are recognised, the simultaneous eruption of which presents an intriguing geochemical problem as to their origins.

Evaluation of dynamic ion exchanger for the isolation of metal ions for characterization by mass and .alpha.-spectrometry

A /sup 140/La tracer has been used to identify the sources of cross-contamination when conventional high-performance liquid chromatography was used to collect metal ion fractions for subsequent analysis by ..cap alpha.. spectrometry or mass spectrometry. Major sources of memory effects identified were normal band broadening, sorption onto metal surfaces, and retention within sample valves; secondary sorption effects within the column and isotopic exchange with sorbed metal ions were not important sources of memory effects. On the basis of these results a recommended procedure was developed that gives cross-contamination levels of less than or equal to 0.006%. Sample preparation techniques for the ..cap alpha.. spectrometric and mass spectrometric analyses of the collected fractions are discussed, and some examples are given of applications to analytical problems in geochemistry and the nuclear industry. Good sample recoveries were obtained for the sample range studied (0.1-500 ng).

Instrumental analytical techniques in geochemistry: Requirements and applications

Geochemists must analyse an extremely wide range of terrestrial and planetary materials. The instrumental techniques necessary to cope with this difficult task are considered. The most important analytical techniques in use by the geochemist today are AAS, ICP-OES, INAA, MSID and XRFS, and the electron microscope for in situ mineral analysis. Some applications of these techniques to solving major problems in geochemistry are discussed. The importance of certified reference materials and of high quality geochemical data are emphasized. It is concluded that the general quality of trace element data has improved over the past 25 years, as a direct result of the application of modern instrumental techniques. Surprisingly, the quality of data reported for certain major elements has deteriorated over that time, when compared with data obtainable by classical chemical methods. Predictions are made concerning the instrumentation needs of the next generation of geochemists.

環境地質調査への資源地質学からのアプローチ

It is emphasized that knowledges and experiences in economic geology are absolutely necessary for solving some environmental problems caused by the development of mineral deposits.Soil and water pollutions by minor elements of heavy metals are usually observed in the neighborhood of metal mines. Considering the basic geochemical problems on the origin, dispersion and concentration of heavy metal elements, environmental pollutions accompanied by the development of mineral deposits are usually composed of natural and artificial pollutions.It is very difficult to divide both these pollutions, however, making the most of knowledges and experiences in economic geology, collecting the various useful data, having a good command of high techniques, such as simulation analysis, step by step progress must be made for solution of the problems.In addition, examples of environmental geological survey by soil and water and outlines of environmental survey with development of geothermal energy are shown, and, importance of framing background data and prosperity of underground injection of mine drainage are also mentioned.

A lattice statistics model for the age distribution of air bubbles in polar ice

Measurements of CO2 in bubbles in polar ice have been used to establish a pre-industrial concentration1–4. Similar measurements have been made for other atmospheric constituents5,6. However, in order to use ice-core measurements to determine the increase in CO2 over the last 200 years, it is necessary to consider the time delay between the deposition of the original snow and the bubble trapping and also the distribution of trapping times over several decades7. The percolation model from lattice statistics describes the static geometrical aspects of trapping and reproduces various aspects of recent observations. The observations of large seasonal fluctuations in trapped bubble volume reflect the enhanced susceptibility to perturbations near the percolation transition. The critical exponent of the percolation probability largely determines the stability of the deconvolution of observed concentrations, indicating that the bubble deconvolution problem is less poorly posed than typical geochemical source deduction problems.