Geochemical exploration

Total arsenic, dissolved organic carbon (DOC), iron, major cations and anions were measured in tube-well waters used for drinking by people to investigate the geochemical condition of subsurface aquifer, source of arsenic and mechanism of arsenic release to groundwater of Bangladesh. Solid phases of total arsenic, iron, manganese and aluminum oxide and organic carbon (TOC) content in sediments were determined to find out their interrelationships. Arsenic concentrations in groundwaters vary from 0.03 to 0.75 mg/l with the mean value of 0.41 mg/l that exceed the maximum permissible limit of WHO (0.01 mg/l) and Bangladesh (0.05 mg/l) for drinking water. Arsenic concentrations demonstrate negative covariation with the concentrations of sulfate and nitrate but correlate weakly with iron concentrations and positively with those of ammonium ions. Dissolved iron exhibits a negative covariance with the concentrations of sulfate. Very low concentrations of nitrate and sulfate and high concentrations of dissolved iron and ammonium ions demonstrate the reducing condition of subsurface aquifer. These relationships suggest that oxidation of arsenic-rich pyrite is not responsible for the increased concentrations of arsenic but reflect the dependence of As concentration on the reductive processes. Arsenic is strongly correlated with DOC concentrations. Borehole data demonstrate the arsenic enrichment in organic matter-rich fine-grained clayey silt and silty sand than in sandy sediments. Arsenic contents are well correlated with those of iron, manganese and aluminum oxides in fine particle fraction of sediments, whereas arsenic is significantly correlated with TOC in large particle fraction. Sequential chemical leaching exhibits that arsenic is mainly present in three phases: (1) oxide phase of Fe and Mn, (2) organic matter and (3) sulfide and silicate phases. Since the distribution of arsenic in the subsurface sediments is not solely controlled by a single solid phase, the dissolution -desorption from different phases contributes to the total arsenic concentrations in groundwater. Microbial oxidation of organic matter (including localized peat layer) and reductive dissolution of Fe and Mn oxyhydroxide are the important processes to mobilize arsenic. The combined effects of NaHCO 3 and high pH values also play a significant role to mobilize arsenic from surface of iron oxides, other minerals and subsurface sediments. The very strong relationship between arsenic and 0375-6742/02/$ -see front matter D bicarbonate concentrations in groundwater of Bangladesh and high pH values (8.03 -8.7) of the Ganges sediments support the hypothesis. This paper reports first about arsenic leaching by the combined effects of NaHCO 3 and high pH values in Bangladesh. D

Elements of demonstrated immobility in hydrothermal alteration and metamorphism provide useful lithogeochemical parameters for mineral exploration in greenstone terranes. They yield precise identifications of precursor volcanic rock type and magmatic affinity, and quantitative estimates of mass, volume and mineralogical changes. Immobile incompatible elements (Zr, Y, Nb, REE) establish affinities, and monitor fractionation of compatible elements in tholeiitic and transitional volcanic suites. Mass changes in mobile components can be determined for a homogeneous rock unit or a continuous volcanic series. Mass change results also bear directly on the interpretation of REE profiles in altered rocks. Normative calculations allow chemical analyses to be portrayed as alteration minerals, which are also useful in interpreting oxygen isotope data. Immobile element techniques produce a large number of parameters that can be illustrated on maps and diagrams, and otherwise used in exploration. Usage of these techniques brings deeper insight to the evolution of volcanic stratigraphy and the hydrothermal processes that formed the alteration zones and ore deposits.

Over 700 apatite grains from a range of rock types have been analysed by laser-ablation microprobe ICPMS for 28 trace elements, to investigate the potential usefulness of apatite as an indicator mineral in mineral exploration. Apatites derived from different rock types have distinctive absolute and relative abundances of many trace elements (including rare-earth elements (REE), Sr, Y, Mn, Th), and chondrite-normalised trace-element patterns. The slope of chondrite-normalised REE patterns varies systematically from ultramafic through mafic/intermediate to highly fractionated granitoid rock types. (Ce/Yb) cn is very high in apatites from carbonatites and mantle-derived lherzolites (over 100 and over 200, respectively), while (Ce/Yb) cn values in apatites from granitic pegmatites are generally less than 1, reflecting both HREE enrichment and LREE depletion. Within a large suite of apatites from granitoid rocks, chemical composition is closely related to both the degree of fractionation and the oxidation state of the magma, two important parameters in determining the mineral potential of the magmatic system. Apatite can accept high levels of transition and chalcophile elements and As, making it feasible to recognise apatite associated with specific types of mineralisation. Multivariate statistical analysis has provided a user-friendly scheme to distinguish apatites from different rock types, based on contents of Sr, Y, Mn and total REE, the degree of LREE enrichment and the size of the Eu anomaly. The scheme can be used for the recognition of apatites from specific rock types or styles of mineralisation, so that the provenance of apatite grains in heavy mineral concentrates can be determined and used in geochemical exploration. D

A sequential extraction scheme for application to soils, tills and surficial sediments is described that elucidates the form in which an element is held and provides information as to its provenance. The phases selected for extraction have been categorised as: adsorbed/exchangeable/carbonate (using CH ,COONa as extractant); amorphous Fe oxyhydroxide (0.25 M ' GSC contribution #21 895

The technique of phytomining involves growing a crop of a metal-hyperaccumulating plant species, harvesting the biomass and burning it to produce a bio-ore. The first phytomining experiments were carried out in California using the Ni-hyperaccumulator Streptanthus polygaloides and it was found that a yield of 100 kg=ha of sulphur-free Ni could be produced. We have used the same technique to test the phytomining potential of the Ni-hyperaccumulators Alyssum bertolonii from Italy and Berkheya coddii from South Africa. The effect of different fertiliser treatments on growth of Alyssum bertolonii was established in situ in Tuscany and showed that the biomass of the plant could be increased by a factor of nearly 3 (4.5 t=ha to 12 t=ha) without significant loss of the Ni concentration (7600 mg=kg) in the plant. Analogous experiments have been carried out on Berkheya coddii where a biomass yield of over 20 t=ha can readily be achieved though the Ni concentration is not as high as in A. bertolonii. The total yield is, however, much greater. We have also been able to induce plants to hyperaccumulate Au by adding ammonium thiocyanate to the substrate. Up to 57 mg=kg Au (dry mass) could be accumulated by Indian mustard (Brassica juncea). Unusual hyperaccumulation (>500 mg=kg dry mass) of Tl has been determined in Iberis intermedia and Biscutella laevigata (Brassicaceae) from southern France. The Iberis contained up to 0.4% Tl (4000 mg=kg) in the whole-plant dry matter and the Biscutella over 1.5%. This unusually high accumulation of Tl has significance for animal and human health, phytoremediation of contaminated soils, and phytomining for Tl. We calculate that using Iberis, a net return of $ US 1200=ha (twice the return from a crop of wheat) would be possible with a biomass yield of 10 t=ha containing 0.08% Tl in dry matter. The break-even point (net yield of $ US 500=ha) would require 170 mg=kg (0.017%) Tl in dry matter. A model of a phytomining operation and its economics is presented and its advantages and disadvantages discussed.

The non-stoichiometric compounds of iron sulphide named pyrrhotite (Fe 1 À x S) are often associated with pyrite (FeS 2 ) in sulphidic ores and their waste products. The factors affecting pyrite and pyrrhotite oxidation are similar but the latter has received much less attention. As it is the case for pyrite, an increase in temperature has an increasing effect on the oxidation of pyrrhotite and the process follows the Arrhenius behaviour. Both ferric iron and bacteria act as catalysts in the oxidation reactions and play a significant role in the oxidation kinetics. Several spectroscopic techniques are used to study the oxidation mechanisms and products of pyrrhotite oxidation. This paper presents and discusses the main factors controlling pyrrhotite oxidation and the proposed mechanisms of oxidation under normal conditions of temperature and pressure. D Abbreviations: AES, Auger electron spectroscopy; AMD, acid mine drainage; EPR, electron paramagnetic resonance; FTIR, Fourier transform infrared; NL, non-equilibrium layer; SEM, secondary electron microscopy; SLS, sequential layer sputtering; ToF SIMS, time of flight-secondary electron mass spectrometry; XES, X-ray electron spectrometry; XRD, X-ray diffraction; XPS, X-ray photoelectron spectrometry.

The purpose of this study was to identify the various mineralization zones especially supergene enrichment and hypogene in two different Iranian porphyry Cu deposits, based on subsurface data and by using the proposed concentration-volume (C-V) fractal method. The Sungun and Chah-Firuzeh porphyry Cu deposits, which are situated in NW and SE Iran, respectively, were selected for this study. Straight lines fitted through log-log plots showing C-V relations for Cu were employed to separate supergene enrichment and hypogene zones from oxidation zones and barren host rocks in the two deposits and to distinguish a skarn mineralized zone from the hypogene zone in Sungun deposit. In the proposed C-V fractal method, the identification of mineralization zones is based on power-law relationships between Cu concentrations and the volume of rocks hosting porphyry Cu mineralization. Separate subsurface data from the two deposits were analyzed by C-V fractal method and the results have been compared with geological models which included alteration and mineralogical models. The comparison shows that the interpreted zones based on the C-V fractal method are consistent with the geological models. The proposed C-V method is a new approach to defining zones in a mineral deposit and there was no commercial software available to perform the relevant calculations; therefore, a fractal concentration-volume (FCV) software was designed by the authors to achieve this goal.

There is lack of research and documentation of actual (as opposed to theoretical) benefits (e.g., mineral deposit discovery) of developments in compositional data analysis and imputation of censored values to mineral exploration geochemistry. In the present study, analyses of logratio-and ln-transformed stream sediment geochemical data containing ca. 30% of samples with censored values of a pathfinder element for the mineral deposit-type of interest yielded the following findings. Exclusion of those samples supports interpretation of multi-element anomalies reflecting the presence of mineralization. However, the multielement anomaly maps obtained by exclusion of those samples are barely better than the multi-element anomaly maps derived by inclusion of those samples after replacing the censored values with 1/2 of detection limit or with imputed values. Logratio (i.e., alr, clr, or ilr) transformation, compared to ln-transformation, of stream sediment geochemical data does not improve mapping of pathfinder element anomalies reflecting the presence of mineralization. However, stream sediment geochemical data, excluding or including censored values (replaced with 1/2 of detection limit or with imputed values), should be clr-or ilr-transformed to enhance recognition of anomalous multi-element associations reflecting the presence of mineralization. The anomaly maps of multi-element associations derived from ilr-transformed data are better, albeit slightly, than the anomaly maps of multi-element associations derived from clr-transformed data. In the present study, the main benefit of either clr-or ilr-transformation, compared to either ln-or alr-transformation, of stream sediment geochemical data is the enhancement of anomalous multi-element associations reflecting the presence of mineralization. This is an important benefit because variations in trace element concentrations in regional-scale stream sediment geochemical data are mostly due to lithology and other factors (or processes) unrelated to mineralization. Further investigations of various exploration geochemical data are needed to demonstrate and document the actual (as opposed to theoretical) benefits of developments in compositional data analysis and imputation of censored values to mineral exploration.

This study reports the degree of heavy metal pollution (Cr, Cu, Ni, Pb, Zn and V) in 135 urban topsoil samples from the metropolitan area of Mexico City. Pollution indices (PI) were calculated to identify the metal accumulation with respect to the background values. The levels of heavy metals in the analyzed samples show a wide range of variation. Lead, Zn and Cu are the elements most enriched in the analyzed area, presenting pollution indexes of up to 23.8, 21.6 and 12.4, respectively. Geochemical maps were produced to assess the spatial distribution of pollution index. It is concluded that emissions from vehicles may be the major source of Pb urban contamination; furthermore, other small or large factories are possible sources for soil pollution (Cu, Zn). The concentration of Cr, Ni, and V in most of the analyzed samples do not appear to reach pollution levels. The assessment of the soil environmental quality in the metropolitan area Mexico City in terms of PI can be used as the basis for a regular monitoring program for implementing suitable pollution control measures.

The northern part of the Czech Republic ranks among the most industrially polluted areas of Europe due mainly to combustion of brown coal with high contents of pyrite and heavy metals. Fly ash produced through high-temperature combustion of fossil fuel is also rich in ferromagnetic minerals. These are also included in emissions, penetrate the soil, and can be identified using rock-magnetic methods. Magnetic susceptibility is directly linked to a concentration of ferromagnetic minerals and is dominated by high values of magnetite. This study reports on a method of monitoring the spatial distribution of pollution due to airborne solid particles based on measurements of magnetic susceptibility of the soil surface near a brown-coal-burning power plant. Areas with high emission levels and their maximum range are determined. A comparison of the spatial distribution of magnetic susceptibility with heavy-metal concentrations in soil samples suggests that magnetic mapping can be beneficially used as a rapid and inexpensive method to determine contamination due to industrial activity.

A range of key biological functions of plant roots such as uptake, respiration and exudation can considerably alter biogeochemical parameters of the soil in the vicinity of the roots, i.e., the rhizosphere: concentrations of nutrients, toxic elements (e.g., aluminium) and pollutants, concentrations of complexing or chelating compounds, pH and redox potential, partial pressures of gases such as O 2 and CO 2 , etc. Such parameters can also be directly influenced by the activities of soil microorganisms that are known to be stimulated by root exudation in the rhizosphere. Changes of biogeochemical parameters of the soil solution occurring in the rhizosphere influence a whole range of reactions at the soil solid/soil solution interface. Higher plants thereby play a key role in (i) the weathering of soil minerals, (ii) soil formation processes (pedogenesis) and (iii) the biogeochemistry of elements that are either beneficial or toxic to themselves and other soil biota. D

Although the term 'geochemical baseline' appears in the international geochemical mapping programmes IGCP 259 and 360. it has never been well defined. Several considerations relevant to such a definition are discussed. A geochemical baseline for an element refers to its natural variations in concentration in the surficial environment. Geochemical baselines were studied in Finland by comparing results from regional geochemical mapping programmes based on samples of till, clay and organic stream sediment. The geochemical background changes regionally with the basic geology and locally with the type and genesis of the overburden. Baseline concentrations depend on sample material collected, grain size and extraction method. In Finland, concentrations of potentially harmful elements tend to be higher in fine-grained marine and lacustrine sediments than in glacial till. Concentrations are also systematically higher in the < 0.06 mm fraction than in the < 2 mm size fraction of till samples. Only small proportions of the total heavy metal concentrations in Finnish marine clays are bioavailable. Geochemical baselines are needed for environmental legislation and political decision-making, especially in the assessment of contaminated soil. In many areas of Finland. natural concentrations of' several heavy metals exceed the guide or limit values designated for contaminated soils. Thus baselines must alway be verified in any assessment of sites for contamination. 0 1997 Elsevier Science B.V. Kr~w~~rrf.\: feochrtnical survey; background level; baseline: chemical analysis: data bar\: grain hize: pollution ' Corresponding author. Tel.: + 358 205.501 I: fax: +35X 20.5. 5012: e-mail: reijo.salminen@gsf.fi 0375.6742/97/$17.00 0 1997 Elsevier Science B.V. All right\ rehelved PII SO375-6713(~7)0002X-9

Kimberlites occur on every continent and the total number of known primary host rock occurrences is generally accepted as 5000, of which 500 are diamondiferous, 50 have been or are being mined and 15 are large active mines. Clifford' s Rule is shown to be valid in that economic kimberlites occur only on Archons, i.e. cratonic regions underlain by Archaean basement, whereas economic lamproites occur on some Protons, i.e. Proterozoic mobile belts adjacent to Archons. These Archons are distributed world wide in twelve potentially diamond producing regions which occur on seven continents. Three of these twelve regions, i.e. North America, Europe and Antarctica do not have any diamond mines, although significant primary diamond deposits have been found on the first two which will probably be mined in the next decade. The South American continent contains several cratons including the Guyana, Guapor6 and S~o Francisco Cratons which each enclose Archons. These are predominantly located in remote, tropical, heavily forested areas which have not yet been fully explored. Most kimberlites discovered so far in South America lie in Protons, i.e. Proterozoic mobile belts encircling the Archons and are not economic. Therefore almost all production from South America is from alluvial deposits. There is no commercial diamond production from the North American continent, although there are many occurrences of diamonds, kimberlites and lamproites. A great staking rush has taken place in Canada in the Northwest Territories, Alberta, Saskatchewan, Ontario and Qurbec and is still continuing. Two, and possibly five, diamond mines may be developed in the next decade. Diamond prospecting is proceeding at a fast pace in Canada and in a more limited way in the United States. The African continent contains three large cratons, the South African, Central African and West African cratons. The South African Craton includes the large Kalahari Archon on which the majority of the world's active major kimberlite diamond mines are located in South Africa, Botswana, Zimbabwe and Swaziland. They comprise 11 kimberlite pipe mines and 3 kimberlite dyke mines. Large alluvial, beach and offshore deposits also produce a large proportion of the world's total. The Central African Craton includes the Lunda-Kasai and the Tanzanian Archons which each contain one active kimberlite pipe mine in Zaire and in Tanzania. Several large kimberlite pipes in Angola may become mines in the next decade. The craton also contains several large alluvial mining areas in Angola (Lunda and Cuango), Zaire (Eastern and Western Kasai) and in the Central African Republic. The West African Craton includes the Man Archon and the Eburuean Proton. Diamondiferous kimberlite pipes and dykes are located on the Man Archon in Sierra Leone, Guinea, Liberia and Mali. Alluvial deposits immediately downstream from kimberlites are mined in Sierra Leone, Guinea and Liberia and occurrences of pipes and alluvials are being evaluated in Mali. Lamproite dykes located on the Eburnean Proton in Ivory Coast were mined in the past and large alluvial deposits, which cannot be traced to their primary host rock, are mined in Ghana and Ivory Coast. The basement of most of Europe is not conducive to the intrusion of diamondiferous kimberlites or lamproites, although there are many vague reports and rumours about diamond finds in several countries. The East European Craton covers most of western Russia and its neighbouring states and extends into Finland and northern Scandinavia. Several diamondiferous kimberlites and lamproites have apparently been found in the Ukraine, Belorus, Russia (Karelia and the Arkhangelsk district) and probably

Geochemical anomaly separation using the concentration-area (C-A) method at Kahang (Gor Gor) porphyry system in Central Iran is studied in this work. Lithogeochemical data sets were used in this geochemical survey which was conducted for the exploration for Cu mineralization in dioritic and andesitic units at Kahang Cu-Mo porphyry system. Similar surveys were also carried out for Mo and Au exploration in these rock units. The obtained results have been interpreted using rather extensive set of information available for each mineralized area, consists of detailed geological mapping, structural interpretation and alteration data. Anomalous threshold values for the mineralized zone were computed and compared with the statistical methods based on the data obtained from chemical analysis of samples for the lithological units. Several anomalies at a local scale were identified for Cu (224 ppm), Mo (63 ppm), and Au (31 ppb), and the obtained results suggests existence of local Cu anomalies whose magnitude generally is above 1000 ppm. The correlation between these threshold values and ore grades is clearly interpreted in this investigation. Also, the log-log plots show existence of three stages of Cu enrichment, and two enrichment stages for Mo and Au. The third and most important mineralization event is responsible for the presence of Cu at grades above 1995 ppm. The identified anomalies in Kahang porphyry system, and distribution of the rock types, are mainly monzodiorite and andesitic units, do have special correlation with Cu and monzonitic and dioritic rocks, especially monzodioritic type, which is of considerable emphasis. The threshold values obtained for each element are always lower than their mean content in the rocks. The study shows threshold values for Cu is clearly above the mean rock content, being a consequence of the occurrence of anomalous accumulations of phyllic, argillic and propyllitic alterations within the monzonitic and dioritic rocks especially in monzodioritic type. The obtained results were compared with fault distribution patterns which reveal a positive direct correlation between mineralization in anomalous areas and the faults present in the mineralized system.

The combination of revegetation and application of stabilizing soil amendments on heavy metal-contaminated soils is generally considered to be a promising alternative to expensive classical remediation techniques. Here, we simultaneously investigated the effects of six cost-effective amendments (CaCO 3 , iron grit, fly ash, manure, bentonite and bone meal) on Cd, Zn and Pb leaching and phytoavailability (assessed using white lupin, Lupinus albus L.). The Cd and Zn leaching was reduced by all amendments mainly due to alkalinity increase. The Pb leaching was strongly affected by the dissolved organic carbon (DOC) release. Therefore, bone meal and manure treatments, which highly increased DOC concentrations in leachates, increased the flow-weighted mean Pb concentrations by 2.3 and 16 times, respectively. Surprisingly, while iron grit induced strong Cd and Pb leaching reductions, this amendment doubled Cd and Pb concentrations in shoots of white lupin. Conversely, the addition of bone meal reduced Pb concentrations in shoots by 74%, probably because organo-Pb complexes (predicted using Visual MINTEQ) were largely dominant in solution. Overall, the addition of CaCO 3 offered the best compromise as it successfully reduced both the leaching and the phytoavailability of the three considered metals. Our results demonstrate the efficacy of several amendments while stressing the need to measure simultaneously the leaching and the phytoavailability of metals induced by each amendment.

In this paper are discussed the baseline geochemical maps of elements harmful to human health, using concentration values of 2389 stream sediment samples collected over the Campania region (Southern Italy). Each sample was digested in aqua regia and analysed by ICP-MS. For compilation of baseline geochemical maps, a recently developed multifractal inverse distance weighted (lDW) interpolation method and spectral analysis (S-A) was applied, using a new geochemistry dedicated GIS software (GeoDAS). The aim of this study is to discriminate between the geogenic natural content (background) and the anthropogenic contribution in the collected sediments. The definition of background values, in contrast to baseline values, is very important in determining the extent of polluted areas in countries like Italy, where environmental legislation has not yet established intervention limits for stream sediments.

The Hishikari gold deposit: high-grade epithermal veins in Quaternary volcanics of southern Kyushu, Japan EIJI IZAWA 1, YUKITOSHI URASHIMA 2, KENZO IBARAKI 3, RYOICHI SUZUKI 3, TAKE0 YOKOYAMA 3, KIYOSHI KAWASAKI 3, AKITO KOGA 4 and SACHIHIR0 TAGUCHI 5

This review paper is intended to be a guideline to novices on how to conduct research on silicate melt inclusions in volcanic environments, which analytical techniques are more suitable to gather the desired data and the major pitfalls scientist may encounter. Silicate melt inclusions (SMIs) are small quantities of silicate melt that are trapped in minerals during their growth or crystallization. They contain liquids formed in equilibrium with their host minerals and therefore record the liquid line of descent of magmatic systems. Upon trapping, SMIs become ideally closed to the surrounding environment, and behave as time capsules, giving important information about processes that originated magmas and the nature of their mantle source. A melt inclusions investigation is composed of several steps: (1) a detailed petrographic study to characterize and select representative SMIs, with the aim of identifying Melt Inclusions Assemblages (MIA), the only reliable tool to assess that SMIs obey Roedder's rules and have not re-equilibrated following entrapment; (2) a careful preparation of samples for reheating experiments and microanalysis; (3) high temperature studies in order to homogenize the SMIs and be able to perform chemical analysis; (4) interpretation of SMIs data, which should always be compared with bulk rock composition and relevant experimentally derived liquid compositions. We suggest that the search for good SMI candidates for study will be achieved by good petrographic analysis of SMIs and detailed petrographic information (size, shape, appearance, position relative to the host and other SMI within the same host). If the goal of a SMIs study is to determine volatile concentrations, assessing the relative time of trapping among SMIs is of paramount importance, as it allows understanding if the variation in volatile concentrations is consistent with a certain magmatic physical-chemical process. Researchers that choose to work with SMIs face several challenges. SMIs are not always hosted in all samples or they can be difficult to recognize (mostly due to their small size). Additionally, due several processes, such as post-entrapment crystallization, boundary layer and sampling melt heterogeneity at the micron scale, they may not be representative of the original trapped melt composition.

Volcanic rocks from the Maghnia region of northwest Algeria consist of fresh to altered rhyolitic units that were emplaced during late Miocene time. Petrographic observations and geochemical data indicate that rhyolitic rocks were derived from a hybridized peraluminous magma. Petrogenetic modeling, REE contents and oxygen isotope data of quartz and feldspar and spessartine-rich garnet allows the reconstruction of the fractional crystallization between 680 and 780°C and pressure of less than 0.5 GPa. Rhyolitic units are partially weathered and form an economic deposit of montmorillonite. Spectroscopic data and stable isotopes (O, H) of glass and montmorillonite indicate that the residual glass was partially hydrated by meteoric water at temperatures between 31 and 54°C. The chemical mass balance indicates that rhyolitic rocks were altered to montmorillonite by meteoric water enriched in Ca, Mg and Sr. The combination of the chemical mass balance and the 87 Sr/ 86 Sr initial ratios of rhyolite and montmorillonite indicate that continental water/rock interaction was related to the surrounding Miocene lacustrine limestone.

Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964-79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz-alkali-feldspar-plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation.

We examined the copper isotope ratio of primary high temperature Cu-sulfides, secondary low temperature Cu-sulfides (and Cu-oxides) as well as Fe-oxides in the leach cap, which represent the weathered remains of a spectrum of Cu mineralization, from nine porphyry copper deposits. Copper isotope ratios are reported as δ 65 Cu‰ = (( 65 Cu/ 63 Cu sample / 65 Cu/ 63 Cu NIST 976 standard ) − 1) ⁎ 10 3 . Errors for all the analyses are ± 0.14‰ (determined by multiple analyses of the samples) and mass bias was corrected through standard-samplestandard bracketing. The overall isotopic variability measured in these samples range from − 16.96‰ to 9.98‰. Distinct Cu isotopic reservoirs exist for high temperature hypogene, enrichment, and leach cap minerals. Chalcopyrite from high temperature primary mineralization forms a relatively tight cluster of δ 65 Cu values of 1‰ to − 1‰ whereas secondary minerals formed by low temperature reveal a range of δ 65 Cu values from − 16.96‰ to 9.98‰. Secondary chalcocite is relatively heavy with δ 65 Cu varying from − 0.3‰ to 6.5‰. Leach cap minerals dominated by Fe-oxides (jarosite, hematite and goethite) are relatively light ranging from − 9.9‰ to 0.14‰. Although the dataset is relatively small (n = 50 total minerals analyzed), a combination of these data with values from previously published reports [Zhu, X.K., O'Nions, R.K., Guo, Y., Belshaw, N.S. and Rickard, D., 2000. Determination of natural Cu-isotope variation by plasma-source mass spectrometry; implications for use as geochemical tracers. Chemical Geology, 163(1-4): 139-149.;. Cu isotopic fractionation in the supergene environment with and without bacteria. Geochimica et Cosmochimica Acta, 69(22): 5233-5246.; , show a distinct pattern of heavier isotopic signature in supergene samples and a lighter isotopic signature exists in the leach cap and oxidation zone minerals. The pattern could be used as a tool for exploration geology by providing the following information: 1) Identification of highly fractionated copper isotope ratios in copper sulfide and Fe-oxide samples that indicate supergene processes and the extent of leaching and enrichment copper 2) Identification of highly fractionated copper isotope ratios in surface and/or groundwaters that indicate the active weathering copper sulfides that experienced significant enrichment.

The Rock–Eval pyrolysis and LECO analysis for 9 shale and 12 coal samples, as well as, geostatistical analysis have been used to investigate source rock characteristics, correlation between the assessed parameters (QI, BI, S1, S2, S3, HI, S1 + S2, OI, PI, TOC) and the impact of changes in the Tmax on the assessed parameters in the Cretaceous Sokoto, Anambra Basins and Middle Benue Trough of northwestern, southeastern and northcentral Nigeria respectively. The geochemical results point that about 97% of the samples have TOC values greater than the minimum limit value (0.5 wt %) required to induce hydrocarbon generation from source rocks. Meanwhile, the Dukamaje and Taloka shales and Lafia/Obi coal are found to be fair to good source rock for oil generation with slightly higher thermal maturation. The source rocks are generally immature through sub-mature to marginal mature with respect to the oil and gas window, while the potential source rocks from the Anambra Basin are generally sub-mature grading to mature within the oil window. The analyzed data were approached statistically to find some relations such as factors, and clusters concerning the examination of the source rocks. These factors were categorized into type of organic matter and organic richness, thermal maturity and hydrocarbon potency. In addendum, cluster analysis separated the source rocks in the study area into two groups. The source rocks characterized by HI >240 (mg/g), TOC from 58.89 to 66.43 wt %, S1 from 2.01 to 2.54 (mg/g) and S2 from 148.94 to 162.52 (mg/g) indicating good to excellent source rocks with kerogen of type II and type III and are capable of generating oil and gas. Followed by the Source rocks characterized by HI <240 (mg/g), TOC from 0.94 to 36.12 wt%, S1 from 0.14 to 0.72 (mg/g) and S2 from 0.14 to 20.38 (mg/g) indicating poor to good source rocks with kerogen of type III and are capable of generating gas. Howeverr, Pearson’s correlation coefficient and linear regression analysis shows a significant positive correlation between TOC and S1, S2 and HI and no correlation between TOC and Tmax, highly negative correlation between TOC and OI and no correlation between Tmax and HI.
Keywords- Cretaceous, Geochemical, Statistical, Cluster, Factor analyses.

Rainfall events cause both increases and decreases in acid and metals concentrations and their loadings from mine wastes, and unmined mineralized areas, into receiving streams based on data from 3 mines sites in the United States and other sites outside the US. Gradual increases in concentrations occur during long dry spells and sudden large increases are observed during the rising limb of the discharge following dry spells (first flush). By the time the discharge peak has occurred, concentrations are usually decreased, often to levels below those of pre-storm conditions and then they slowly rise again during the next dry spell. These dynamic changes in concentrations and loadings are related to the dissolution of soluble salts and the flushing out of waters that were concentrated by evaporation. The underlying processes, pyrite oxidation and host rock dissolution, do not end until the pyrite is fully weathered, which can take hundreds to thousands of years. These observations can be generalized to predict future conditions caused by droughts related to El Niño and climate change associated with global warming. Already, the time period for dry summers is lengthening in the western US and rainstorms are further apart and more intense when they happen. Consequently, flushing of inactive or active mine sites and mineralized but unmined sites will cause larger sudden increases in concentrations that will be an ever increasing danger to aquatic life with climate change. Higher average concentrations will be observed during longer low-flow periods. Remediation efforts will have to increase the capacity of engineered designs to deal with more extreme conditions, not average conditions of previous years.

Located in semi-arid regions of northwestern China, Datong basin is a Quaternary sedimentary basin, where groundwater is the most important source for water supply. It is very important to study groundwater characteristics and hydrogeochemical processes for better management of the groundwater resource. We have identified five geochemical zones of shallow groundwater (between 5 and 80 m) at Datong: A. Leaching Zone (Zone I); B. Converging Zone (Zone II); C. Enriching Zone (Zone III); D. Reducing Zone (Zone IV); E. Oxidizing Zone (Zone V). In Zones I, II, and V and some parts of Zones III and IV, hydrolysis of albite/K-feldspar/ chalcedony system and/or albite/K-feldspar/quartz system enhanced concentrations of Na + , K + , HCO 3 À and silicate. In Zone I, dissolution of carbonate and hydrolysis of feldspar generally controlled the groundwater chemistry. Infiltration of meteoric water promoted the formation of HCO 3 À in the water. In Zone II, the main geochemical processes influencing the groundwater chemistry were dissolutions of calcite and dolomite, ion exchange and evaporation. In Zones III and IV, in addition to ion exchange, evaporation and precipitation of calcite and dolomite, leaching of NaHCO 3 in saline-alkaline soils dominated the water quality. Zone IV was under anoxic condition, and reduction reactions led to the decrease of SO 4 2À , NO 3 À and occurrence of H 2 S, with the highest arsenic content (mean value of 366 Ag/L), far exceeding Maximum Contaminant Level (MCL). Abnormal arsenic in the groundwater resulted in endemic disease of waterborne arsenic poisoning among local people. Zone V overlapped Zone I was intensively affected by coal mining activities. Sulfide minerals, such as pyrite, would have been oxidized when exposed to air due to coal mining, which directly added sulfate to groundwater and thus increased SO 4 2À concentration. Oxidization of sulfide minerals also decreased pH and promoted dissolutions of calcite and dolomite. D

This study investigates drinking water (surface water and sub-surface water) quality and potential health risk assessment in the mafic and ultramafic terrain of Bucha area, Mohmand agency, northern Pakistan. Heavy metals (HMs) concentrations were analyzed using graphite furnace atomic absorption spectrometer. Statistical analyses like one-way ANOVA, correlation analysis, cluster analysis (CA) and principal component analysis (PCA) were used for contamination sources. Furthermore, HMs health risk assessment showed that average daily dose (ADD) and hazard quotient (HQ) were found in the order of Cr &gt; Fe &gt; Ni &gt; Cu &gt; Mn &gt; Zn &gt; Co &gt; Pb &gt; Cd and Ni &gt; Cd &gt; Cu &gt; Mn &gt; Pb &gt; Zn &gt; Cr, respectively. Water contamination was the main source of diseases like diarrhea, viral hepatitis, headache, hypertension, abdominal pain, liver and kidney problems and fatal cardiac arrest as complained by most of the respondents during field visit and reported in basic he...

General circulation models (GCMs) fitted with stable isotope schemes are widely used to interpret the isotope-climate relationship. However, previous studies have found that the spatiotemporal isotope/ precipitation correlation simulated by GCMs is stronger and more widespread than the observed value. To understand the reason for this failure, we investigated the factors influencing the empirically well-known isotope/precipitation relationship, or precipitation amount effect, in the tropics using newly obtained daily precipitation isotope monitoring data over Asia. As in previous studies, we found an apparent correlation between the long-term monthly mean isotopic content and the corresponding precipitation amount (local precipitation) observed at sub-tropical island stations. Furthermore, on a monthly timescale, the isotopic variability of precipitation for these stations was more clearly related to the regional precipitation amount than to local precipitation. This correlation of isotopic content with the regional precipitation amount was observed at the equatorial (Maritime Continent) stations. For these stations, isotope/local precipitation relationships only appeared over longer timescales, with different regression line slopes at each station. However, at the coastal stations, there was a strong linear relationship between the monthly mean isotopic content and corresponding regional precipitation, and regression line slopes were spatially uniform. For the two sub-tropical terrestrial (Indochina Peninsula) stations, the isotopic minimum appeared without any relationship to rainfall amount but usually occurred at the leeward station during the rainy season. These results suggest that the isotopic variations of precipitation did not depend on the 'local' rain-out history but on the rain-out process in the surrounding region. However, local rainfall events were associated not only with large-scale disturbances but also with regional circulation. Thus, the scale difference of controlling factors between local rainfall amount and isotopic value results in the weakening of the rainfall amount effect at the observation site and in the discrepancy between GCM simulations and observations. This finding suggests that regional precipitation-isotope relationships should be compared with GCM results. Additionally, because the isotope signal reflects the rain-out history at a regional scale, evaluation of the isotopic field using isotopic GCMs will be useful not only to reconstruct paleoclimate conditions but also to examine how GCMs can reproduce real atmospheric circulation over the tropics.

Five hundred years of mercury (Hg) mining activity in Idrija, Slovenia caused widespread Hg contamination. Besides Hg emissions from the ore smelter, tailings have been found to be the major source of river sediment contamination. In the present study, solid phase binding forms and the aqueous mobility of Hg have been investigated in tailings of the Idrija Hg mine by means of a pyrolysis technique and aqueous Hg speciation. Results show that Hg binding forms differ with the age of the tailings due to the processing of different ores with different roasting techniques. In older tailings, the predominant Hg species is cinnabar (HgS), due to incomplete roasting, whereas in tailings of the 20th century the amount of cinnabar in the material decreased due to a higher efficiency of the roasting process and the increasing use of ores bearing native Hg. In younger tailings, metallic Hg (Hg 0 ) sorbed to mineral matrix components such as dolomite and Fe-oxyhydroxides became the predominant Hg binding form in addition to unbound Hg 0 and traces of HgO. Leaching tests show that in younger tailings high amounts of soluble Hg exist in reactive form. In older tailings most of the soluble Hg occurs bound to soluble complexes. It might be assumed that in the long term, matrix-bound Hg 0 could be bound to humic acids derived from soils covering the tailings. This means that, despite the lower total Hg concentrations found in the younger tailings, the long-term risk potential of its mobile matrix-bound Hg 0 is higher than that of older tailings bearing mostly immobile cinnabar.

The Kaviro lead deposit is located in the Lut Block, which is an important metallogenic province in Eastern Iran (lat 34°22'N, long 57°18'E). The deposit includes ore-bearing veins and veinlets emplaced in folds and hosted by middle Jurassic slate units. The ore-forming procedure can be segregated into three stages: pre-mineralization stage quartz-pyrite, main stage quartz-dolomitepyrite-galena, and late stage calcite and pyrite. Hydrothermal alteration minerals are composed of dolomite, quartz, and calcite. Microscopic surveys show that the vein includes galena with minor amounts of pyrite as hypogene minerals. Two types of fluid inclusions are distinguished in quartz and dolomite veins. Microthermometric investigations reveal homogenization temperatures of 180-250 °C and salinities from 5 to 12.5 wt.% NaCl equivalents. The oreforming fluids of the Kaviro deposit are medium-to-low in terms of temperature and salinity. The δ 34 S values for the ore fluid are estimated to be between +0.94‰ and +3.27‰. The isotopic compositions of sulfur suggest that the ore-forming aqueous solutions are derived from a nonmagmatic source, probably from leaching of metamorphic rocks. The 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb ratios of the samples span narrow ranges from 18.514-18.569, 15.668-15.715, and 38.803-38.950, respectively. The 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios plot above the evolution curves and clearly indicate a crustal source. The 207 Pb/ 204 Pb vs. 206 Pb/ 204 Pb data suggest a homogen source for Pb. Most of the galena samples in the CIM Pb-Zn deposits show high 207 Pb/ 204 Pb ratios, indicating that Pb is mainly derived from continental crust or pelagic sediment. The age of the mineralization is after the middle Jurassic. The Kaviro deposit is a metamorphic-related vein deposit, and fluid mixing is the important mechanism for its deposition.

Low-molecular-weight (LMW) organic acids occur widely in soils. Results in pure mineral systems and podzols suggest that LMW organic acids can promote the dissolution of Al from kaolinite, Al oxides and soils, but limited information is available concerning the role of these organic acids on Al mobilization in variable charge soils as yet. This paper deals with the effect of LMW organic acids on Al mobilization and mobilized Al distributed between the solution phase and exchangeable sites in two acidic variable charge soils. The results indicated that LMW organic acids accelerated Al mobilization through proton-and ligand-promoted reactions. The ability of different organic acids to mobilize Al followed the order: citric acid > oxalic acid > malonic acid > malic acid > tartaric acid > salicylic acid > lactic acid > maleic acid. This order was in general agreement with the magnitude of the stability constants of Al-organic acid complexes. The ratio of soluble Al to exchangeable Al also increased as the stability constants increased. These results showed that the organic acids with strong Al-complexation capacity were most effective in Al mobilization, whereas the weak organic acids promoted the retention of mobilized Al by the soil exchangeable sites. Increase in both organic acid concentration and solution pH promoted Al mobilization and also increased the ratio of soluble Al to exchangeable Al due to the increase in the concentration of the effective organic ligands, especially in the strong organic acid systems. These findings may have their practical significance for establishing more effective amelioration procedures for variable charge soils with increased acidity and higher mobility of Al.

This paper presents a general discussion on some fundamental issues associated with the current research status in the field of computational hydrodynamics of mineralization. Based on the scientific characteristics of mineral forming systems within the upper crust of the Earth, the fundamental issues under consideration include: (1) simulation of multi-process aspects of a mineral forming system; (2) simulation of multi-scale aspects of a mineral forming system; (3) simulation of fluid convection associated with a mineral forming system; (4) simulation of fluid focusing and mixing associated with a mineral forming system; and (5) simulation of reactive mass transport associated with a mineral forming system. After the current status of each fundamental issue is briefly summarized, the future development in the field of computational hydrodynamics of mineralization is discussed on the basis of further improving the treatments of the fundamental issues considered in this investigation.

The market for mineral water has been growing steadily over the last few years. Germany is the country with the highest number of bottled mineral water brands (908 bottled water samples from 502 wells/brands were analyzed). The per capita consumption of mineral water in Germany in 2003 was 129 L. A wide range of values of one to seven orders of magnitude was determined for 71 elements in the bottled water samples analyzed by ICP-QMS, ICP-AES, IC, titration, photometric, conductometric and potentiometric methods. A comparison of the element concentrations and the legal limits for both bottled and tap water (EU, Germany, US EPA, WHO) shows that only 70% of the 908 mineral water samples fulfill the German and EU drinking water (i.e., tap water) regulations for all parameters (not including pH) for which action levels are defined. Nearly 5% of the bottled water samples not fulfill the German and EU regulations for mineral and table water. Comparison of our results with the current German and European action levels for mineral and table water shows that only 42 of the bottled water samples exceed the limits for one or more of the following elements: arsenic, nitrate, nitrite, manganese, nickel and barium concentrations. Ten of the bottled water samples contain uranium concentrations above the 10 μg/L recommended limit. A selection of existing water quality classification systems was used in order to characterize the different mineral water types. For example, the relationships among selected variables were examined using Durov, Piper and van Wirdum diagrams. Univariate and multivariate (component analysis) statistical methods were used to analyze the data to characterize the bottled water from the different well regions of Germany. Maps of the element distributions are presented. Most of the elements show a clear regional dependency. The bottled water shows conspicuous geochemical influences by the limestone aquifers of the Muschelkalk (Middle Triassic), the sandstone aquifers of the Bunter and Keuper (Lower and Upper Triassic), the gypsum of the Keuper, and the aquifers in gneiss basement rocks.

A volcanic sequence formed by calc-alkaline basalts and basaltic andesites interbedded with pelagic limestones, black shales, radiolarites, and epiclastic rocks that are in tectonic contact with flysch-like strata, is reported in the vicinity of San Miguel de Allende, in Guanajuato state. An upper Aptian age is suggested by paleontological evidence. The sequence is interpreted as the eastern remnant of an allochthonous, lower Cretaceous volcanic stage in central Mexico.

Urban soils may concentrate contaminants in large quantities due to intensive human activities. In the period of centrally dictated industrialization in the 20th century, industrial activity such as mining, coal fired power plants and alumina industry produced huge amount of waste and pollution emission in Hungary. Consequences could be toxic element enrichment in urban public and private areas such as soil of playgrounds and parks. This study focuses on the spatial distribution of potentially toxic element (PTE: As, Pb, Hg, Cd, Ni, Zn and Cu) concentrations of urban soil at playgrounds, parks and other communal areas in Ajka town (western Hungary) in order to find a link between contamination sources and the receiving urban soils. Ajka town has a long-established industrial history with multiple contamination sources of heavy alumina industry and lignite-fired power plants supplied by the nearby bauxite and coal mines. At 8 playgrounds, 11 parks and 25 other open communal areas soil samples have been collected at a depth of 0-10 cm along a 1 × 1 km grid. The whole grid covers an area of 64 km 2 . The laboratory analyses include ICP-OES and CV-AAS method measurements for PTEs of the soil samples. Our results show that Hg is the only PTE having concentrations above the Hungarian environmental pollution limit, at two sampling sites, whereas Ni seems to be the most widely spread PTE in the studied urban topsoil. The spatial and statistical analysis, based on low density sampling with detailed exploratory statistical data analysis, identified the lignite-fired power plant and the lignite mines as the most important point sources; in contrast showed that the alumina industry had no effect on the urban soil samples. According to enrichment factor, correlation and regression analysis, two main PTE groups were distinguished. The first group contains As, Ni, Cu and Zn, whereas Pb, Hg and Cd belong to the second group. Lead, Hg and Cd have a distinct nature in the studied soils due to their non-soluble and non-reactive forms originating from mixed industrial and traffic sources. Risk assessment with the 8 sampled playgrounds shows that sampling sites situated close to the lignite mining area have As, Pb, Ni and Zn concentrations above the Hungarian Regional Geochemical Background (HRGB) value. This geochemical study has revealed the spatial correlation of contamination sources and the contaminated areas with special attention to risk assessment of playgrounds and parks at sensitive human receptors in an industrial urban area.

Allchar ore deposit, a well-known polymetallic mineralisation, is drained by the Majdanska River characterized by elevated concentrations of heavy metals and metalloids, particularly As, Tl and Sb. The present study was conducted at the spot of the confluence of spring water, heavily loaded with toxic metals, which joins the Majdanska River by a few meters short stream. The spring water is outflow of underground water drained by passage through polymetallic mineralisation. The chemical characteristics of the Majdanska River water and the associated periphyton were used to evaluate and explain the abiotic response to the intrusion of toxicants and its impact on biota. At the site of the stream inflow, thorough mixing of Majdanska River water and incoming spring water resulted in an increase of Eh and pH close to the average river value. This geochemical barrier causes significant changes in the mobility of metal species. Moreover, the output composition of water is further modified by biological processes. The examined biota community was found to consist of algae Audouinella sp. and Spirogyra sp., with coexisting freshwater snails Radix labiata, diatoms and bacteria. While the carbonate bedrock controls the pH of the river water by effective buffering, it seems that bioconcentration and biomineralisation of algae exerted control on toxicants along the entire river flow. The highest bioconcentration factors were obtained for Fe, Mn and Ti which implies the biomineralisation of iron as a product of extracellular deposition on the cell walls on the organic matrices. Bioconcentration of As, Cr, Cs, Cu and Se was more important in Audouinella sp., while Cd, Co, Sr, and Zn preferentially accumulated in Spirogyra sp. High accumulation of Ba (3 mg/g d.w.) in Spirogyra sp. was associated with the intracellular biomineralisation. These findings suggest the potential use of Spirogyra sp. in the remediation of waters polluted by barium or as the biological pathfinder indicator for metal deposits associated with barite.

Analysis of soil and sediment samples, using selective extraction methods to distinguish different phases, is of particular interest in exploration geochemistry to locate deeply buried mineral deposits. There are various mechanisms of binding labile elements in the secondary environment, including physical and chemical sorption, precipitation, chelation and complexation. Phases present in soils and sediments which are likely to scavenge 'free' elements include amorphous Mn and Fe oxides, the humic and fulvic components of humus, and clays. This paper reviews these forms of trace elements and the methods in current use to quantify them. Examples of precision data, both for control and survey samples, are given with respect to trace elements dissolved from the 'soluble organic' component of humus, Mn oxides and amorphous Fe oxides. The high Ž. sensitivity of inductively coupled plasma mass spectrometry ICP-MS is required to measure accurately and precisely a large suite of trace elements, especially where only small fractions of elements are dissolved by such leaches as the Ž. Ž. commercially available Enzyme and MMI Mobile Metal Ion extractions. The relative standard deviations RSD obtained Ž. Ž. for 33 elements e.g. Ag, Cd, In, I in the standard reference sample SRM , TILL-2, are in the range 0.5-8% for the Ž. hydroxylamine hydrochloride NH OH P HCl leach designed to extract hydrous Fe and Mn oxides. The corresponding 2 RSDs for elements in the reactive Mn oxide phase extracted by the Enzyme leach are in the range 3-19% except for some Ž. trace elements at levels close to detection limit e.g. Cd, Bi. The RSDs obtained for field duplicates are inferior to those for Ž. analytical replicates i.e. sample splits , probably a reflection of different concentrations of the host phase. In one soil survey, the Fe extracted by a 0.25 M NH OH P HCl leach ranged conservatively from 0.2 to 1.7% whereas the Mn extracted 2 by the Enzyme leach varied extensively, from 0.3 to) 999 ppm. In contrast, precision, at 1-7% RSD, for field duplicates was found to be comparable with that for both analytical duplicates and the SRM, LKSD-4, for elements associated with the humic and fulvic component of humus samples sieved to-177 mm.

Chromium in groundwater resulting from natural sources has been detected in León Guanajuato Valley, Central-México. The aim of this work was to assess the types of rocks and the geochemical processes responsible for the chromium presence in the water. Superficial and groundwater chemical analyses, X-ray diffraction and EDS determinations in rock samples from the polluted area were performed. Leaching experiments with various types of rocks including SEM/EDS and petrographic observations were used to identify the minerals with higher possibilities to liberate chromium. To the East of León valley the chromium comes from the Sierra de Guanajuato ultramafic units and their alteration products. Recent and past tectonic and hydrothermal events have enhanced the chromium release. Among the studied rocks, the serpentinites showed the highest water pollution potential. Disintegration of exsolution borders appeared to be the main geochemical process for derived chromium. ᭧ (M.A. Armienta). Fig. 4. Thin polished sections of: (a) a chromite showing the accumulation of primary and secondary magnetite in olivine and pyroxene idioblast borders; and (b) a serpentinite showing magnetite interspaced with serpentine fibers.

The research of fluids in the earth's crust is greatly benefiting from methodological (analytical) and experimental advances and the rapid development of increasingly powerful numerical modelling systems. New experimental data continuously refine the accuracy of numerical models aiming to quantitatively reconstruct geological processes. Geological modelling programs have moved on from linear or 2-dimensional approaches to integrating 3 or 4D geology with geothermal aspects, fluids flow and reactive transport processes into complex, quantitative scenarios. These combinations of refinement of the data base and advances in computational capacities are the stepping stones for the development of the predictive quality of mineralising models and hydrocarbon migration and accumulation, access to geothermal energy and the sequestration of CO 2 . This special issue presents a selection of contributions on "Fluids in Geological Processes" following the VIth GEOFLUIDS meeting in Adelaide in 2009, emphasizing on recent developments in the different research trends in this field.

Total concentrations of chemical elements in soils may not be enough to understand the mobility and bioavailability of the elements. It is important to characterise the degree of association of chemical elements in different physical and chemical phases of soil. Another geochemical characterisation methodology is to apply sequential selective chemical extraction techniques. A seven-step sequential extraction procedure was used to investigate the mobility and retention behaviour of Al, Fe, Mn, Cu, Zn, Pb, Cr, Co, Ni, Mo, Cd, Bi, Sn, W, Ag, As and U in specific physical-chemical and mineral phases in mine tailings and soils in the surroundings of the abandoned Ervedosa mine. The soil geochemical data show anomalies associated with mineralised veins or influenced by mining. Beyond the tailings, the highest recorded concentrations for most elements are in soils situated in mineralised areas or under the influence of tailings. The application of principal components analysis allowed recognition of (a) element associations according to their geochemical behaviour and (b) distinction between samples representing local geochemical background and samples representing contamination. Some metal cations (Mn, Cd, Cu, Zn, Co, Cr, Ni) showed important enrichment in the most mobilisable and bioavailable (i.e., water-soluble and exchangeable) fractions due likely to the acidic conditions in the area. In contrast, oxy-anions such as Mo and As showed lower mobility because of adsorption to Fe oxy-hydroxides. The residual fraction comprised largest proportions of Sn and Al and to a lesser extent Zn, Pb, Ni, Cr, Bi, W, and Ag, which are also present at low concentrations in the bioavailable fractions. The elements in secondary mineral phases (mainly Fe, Mn, Cu, Zn, Cd, Pb, W, Bi, Mo, Cr, Ni, Co, As and U) as well as in organic matter and sulphides are temporarily withheld, suggesting that they may be released to the environment by changes in physico-chemical conditions.

A collection of 235 samples were taken from 115 sites (representing a density of 1 sampling site ca. 130 km 2) on rural soils derived from the major rock types in the southern Iberian Massif. The geochemical baselines of selected trace elements (As, Co, Cr, Cu, Ni, Pb and Zn) were determined on the b 2 mm soil fraction. The sampling sites were not directly influenced by external pollution. Soil geochemical baseline and threshold values were calculated for each element in two geologically different zones: the Ossa-Morena Zone (OMZ) and the South-Portuguese Zone (SPZ). All the trace elements showed significantly high median concentrations when compared to reference values for soils of Andalusia, the European Union and the world indicative of regional scale enrichment of topsoils, particularly with respect to As (24.7 mg kg − 1), Cu (32 mg kg − 1) and Pb (37.9 mg kg − 1) in the SPZ, and Zn (78.5 mg kg − 1) in the OMZ. The distribution patterns of element concentrations are primarily influenced by the lithology and geochemistry nature of bedrock and the occurrence of metallogenic belts in the survey area, notably the Iberian Pyrite Belt. In the SPZ the highest median values of As (34.4 mg kg − 1), Pb (56 mg kg − 1) and Cu (57.4 mg kg − 1) were found in soils derived from acid igneous rocks of the Iberian Pyrite Belt. By contrast, the soils developed on carbonate rocks of the OMZ recorded the largest median values for As (27.8 mg kg − 1), Pb (44 mg kg − 1) and Zn (83.1 mg kg − 1), probably regarded to base-metal (SEDEX) deposits. These results indicate that regional geology is an important determinant of soil geochemical baselines for soil pollution assessment.

This paper traces the history of mineral exploration in Indonesia between 1967 and 1992, and discusses various technical aspects, such as area selection, exploration and discovery methods, and significant geologic features of the more important new discoveries. Exploration activity over the past 25 years can be divided into four main phases. Phase I (1967-1976) mostly involved investigations of mineral prospects and districts previously identified by the Dutch. These investigations resulted in many discoveries, including: a major copper-gold district (skarn-porphyry copper) in Irian Jaya, where exploration is still in progress (resources identified to date: 28 Mt Cu and 2,700 t Au); large nickel resources in Eastern Indonesia (13 Mt Ni); significant onshore and offshore tin resources in the Sumateran tin belt (0.13 Mt Sn); and large but low grade bauxite deposits in West Kalimantan (300 Mt A1203). Of the eight Contracts of Work signed between 1967 and 1972, six reached the mining stage. Phase 2 (1970-1975) consisted of an extensive porphyry copper search in the Sunda arc, the western arc of Sulawesi and the central belt of Irian Jaya. Best results were obtained from northern Sulawesi, where follow-up between 1976 and 1982 identified three potentially economic copper-gold deposits (1.7 Mt Cu and 140 t Au) and one subeconomic molybdenum porphyry system (0.8 Mt Mo). During Phase 3 (1981-1988) extensive coal exploration in South and East Kalimantan delineated over 5,000 Mt of coal of varying rank and quality, including 1,500 Mt as measured reserves in 17 deposits, eight of which have been developed to date. Phase 4 (1984-1990) involved a major gold rush, focused primarily on the Cenozoic magmatic belts of Kalimantan, Sulawesi, Moluccas and the Sunda arc. Over 80 primary and alluvial gold prospects were drill tested. Five of these were brought into production (two alluvial deposits, two new hard rock discoveries and one Dutch mine), containing approximately 135 tonnes of mineable gold, and several other projects are under development or undergoing feasibility studies. Total geological resources identified to date are estimated to contain about 700 tonnes of gold. Exploration during phase 4 also resulted in several gold-rich porphyry copper discoveries, including a major deposit in Sumbawa (2.7 Mt Cu and 250 t Au). Intermittent exploration for uranium, diamonds and lead/zinc since 1969 has been largely unsuccessful.