Arsenic(V) removal from aqueous solution following addition of either a mixture of synthetic hydroxylapatite and baryte or bone-char is discussed. Arsenic concentrations of 4, 10 and 100 mg/l were investigated and additions of 0.2—10 g/l of solid (hydroxylapatite, baryte or bone-char) were tested, at an initial pH of either 5 or 7. Although the mixture of hydroxylapatite and baryte had a small influence on arsenic concentrations, bone-char was found to be a very effective sorbing agent for arsenic(V). Packed-column studies to investigate the bone-char capacity, followed by leaching tests were carried out. The capacity of bone-char was found to be superior to that of granular activated carbon. The experiments presented here indicate that the mechanism involved is adsorption rather than co-precipitation.

To determine the mechanism of acid-leaching of ilmenite to ultimately forming rutile, we have carried out an experimental study of ilmenite alteration in autoclaves at 150ºC in HCl solutions. The resulting products were studied by X-ray diffraction, scanning electron microscopy, electron microprobe and Raman spectroscopy. In some experiments the solution was initially enriched in 18O and the distribution of the isotope in the alteration products mapped from the frequency shift of cation oxygen stretching bands in the Raman spectra. The alteration begins at the original ilmenite crystal surface and has also taken place along an intricate branching network of fractures in the ilmenite, generated by the reaction. Element-distribution maps and chemical analyses of the reaction product within the fractures show marked depletion in Fe and Mn and a relative enrichment of Ti. Chemical analyses however, do not correspond to any stoichiometric composition, and may represent mixtures of TiO2 and Fe2O3. The fracturing is possibly driven by volume changes associated with dissolution of ilmenite and simultaneous reprecipitation of the product phases (including rutile) from an interfacial solution along an inward moving dissolution-reprecipitation front. Raman spectroscopy shows that the 18O is incorporated in the rutile structure during the recrystallization. Throughout the alteration process, the original morphology of the ilmenite is preserved although the product is highly porous. The rutile inherits crystallographic information from the parent ilmenite, resulting in a triply-twinned rutile microstructure. The results indicate that the ilmenite is replaced directly by rutile without the formation of any intermediate reaction products. The reaction is described in terms of an interface-coupled dissolution-precipitation mechanism.

Synchrotron-based XANES characterization of sulphated sulphur combined with atomic force microscopy and transmission electron microscopy (imaging and diffraction) allow insights into the crystallization of the calcareous units produced by invertebrates. As a result of a series of converging data, reticulate crystallization of the amorphous Ca-carbonate molecules conveyed to the micron-thick growth layer by the sumicrometric organo-mineral units seems a reasonable hypothesis, providing us with a method of explaining the multiple and taxonomy-linked ‘vital effects’ which have long been recognized among the calcareous biocrystals.

Late Tertiary-Quaternary volcanism around Calatrava, within the Hercynian massif of central Spain, is alkaline mafic-ultramafic, with ∼250 centres, mainly monogenetic cones and vents, with melilitite the most abundant eruptive. Carbonatite may be expected in association with melilitite and a clear example of magmatic carbonate emerged from a brief field reconnaissance. It is a vent filled with a mixed eruption of glassy melilitite lapilli in a carbonate matrix. Levels and profiles of trace elements are inseparable from recognized carbonatite, and totally unlike those in local sedimentary limestone and caliche. C and O isotopes are the same as those reported for carbonatite ashes in other provinces. Carbonate is present as globules in the melilitite glass, and as inclusions within large clinopyroxene and olivine grains, which are largely xenocrystic. Euhedral spinels in melilitite and carbonate matrix are chromite mantled with titano-magnetite, reported previously only from high-temperature kimberlite. Wehrlite fragments indicate direct eruption from the mantle. Phlogopite and chromian spinel are found only as inclusions in the olivine, pointing to a phlogopite-carbonate mantle source region of the type favoured for carbonatite and melilitite melt generation. Calatrava represents the most southerly and westerly expression in mainland Europe of intra-continental carbonatite-melilitite volcanism. Follow-up field visits have shown that carbonate volcanism is extensive and voluminous throughout the province, requiring a long-term research programme.

A brief review is given of the ways in which the local structure in glass can influence the microstructure that supports ionic transport. This in turn contributes to the co-operative nature of ion dynamics and ways in which this underpins the ‘mixed alkali effect’ are discussed. Glass microstructure too is expected to affect glass fracture as well as the chemistry of glass surfaces. In melts, though, these restrictions appear to vanish as the rigidity of intermediate range order is lost.

The uraninite-albite veins of the Mistamisk area occur in the argillite member of the Dunphy Formation, which is near the base of the slightly meta-morphosed Lower Proterozoic sequence of the central Labrador Trough. The vein minerals are albite, uraninite, dolomite, and chlorite, and minor quantities of quartz, tellurides, sulphides, gold, and organic material. Pitchblende and calcite are related to late remobilization.

The veins were deposited in fractures by hydrothermal solutions, and metasomatism caused albitization of wall rocks. Fluid inclusions have an unusual composition, described here for the first time in connection with soda-metasomatism; the aqueous solution of the inclusions is oversaturated in NaCl and contains Ca2+ and Mg2+, and the gas phase mostly consists of N2, CO and CO2. The presence of hematite and absence of hydrocarbons indicates that the vein-forming solution was oxidizing.

The temperature and pressure of vein formation, estimated from fluid inclusion data, was 300°–350° and 2.5 kbar respectively consistent with the composition of the phengite which is a common metamorphic mineral of the host rock. Vein emplacement occurred in the waning stages of the Hudsonian Orogeny, the hydrothermal solution possibly originating by metamorphism of sodic schists of the Mistamisk area, which are possibly of evaporitic origin.

The basis for an ecological risk assessment based on meeting the needs of recent UK and EU legislation is described. The background to the framework and the legislative driver and relevant definitions of harm are provided, prior to an overview of the proposed ecological risk assessment process, which has been broken down into a Tiered approach. Tier 0 requires the establishment of a conceptual site model, where potential contaminant-pathway-receptor linkages are sought and, assuming they are identified, lead on to higher Tier assessments. Tier 1 relies largely on chemical analysis of soil contaminant levels and comparison with soil quality guideline values to assess the likelihood of harm. In some cases biological screening assays may also be undertaken within this Tier. Based on a weight of evidence approach, should data from Tier 1 indicate harm or leave uncertainty, then Tier 2 biological testing is undertaken using assays relevant to the site of interest. In situations where harm is identified under Tier 2 then Tier 3 is reserved for establishing the extent of harm within the ecosystem. Finally the use of the 'weight-of-evidence' approach to generate scientifically robust conclusions regarding the harm (or potential for harm) within the ecosystem is briefly outlined. The framework discussed is currently being adopted by the UK Environment Agency, with implementation expected in 2005. The UK scheme compares favourably with comparative schemes operating in other countries possessing the merits of being iterative, tiered, flexible with agreed exit points subject to satisfying defined criteria and so speeding the decision-making process.

The phenocrysts of four porphyritic obsidians from Pantelleria have been analysed chemically, together with the residual glasses (liquids). Three new analyses of anorthoclase (one partial analysis), two of sodic ferrohedenbergite, one of fayalitic olivine, and two of cossyrite are presented together with their optical properties, and the relationship of these phenocrysts to their liquids is considered.

The experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O show that for synthetic liquids of similar composition to the normative salic constituents of the pantelleritic liquids, a potassic alkali feldspar crystallizes, whereas in the pantelleritic liquids phenocrysts of anorthoclase (Ab67–Ab61) occur. It is suggested that sodium metasilicate, which appears in the norms of all the pantelleritic liquids, may be responsible for the divergence in trend between the synthetic feldspar-liquid tie-lines and the pantelleritic feldspar-liquid tie-lines.

A hypothesis for the mechanism of oxidation in titanomagnetites is first put forward on the basis of new oxidation data for pure magnetite and the new model for cation distribution in titanomagnetites. Contrary to previous claims by other workers, it is shown that single-phase spinel oxidation products of titanomagnetites can only be produced under very exacting circumstances. Lowtemperature magnetic measurements on such synthetic, oxidized materials were made to show the formation of magnetite by the decomposition of the metastable oxidation products of titanomagnetites on prolonged heating at moderate (∼ 390° C) temperatures. This magnetic method of detection is more sensitive than that of normal X-ray diffraction. It is concluded that previous claims of an increase in magnetization due to the formation of synthetic single-phase, highly oxidized titanomagnetites must be due to the formation of undetected magnetite.

Cement and concrete will be used as fracture grouts, shotcrete, tunnel and borehole seals, and as matrices for waste encapsulation inter alia in geological repositories for radioactive wastes. Alteration of the host rock and/or swelling clay in waste package buffers and tunnel backfills by hyperalkaline solutions from cement/concrete may be deleterious to system performance through changes in the physicochemical properties of these barrier materials.

Analogue systems (and timescales) relevant to the understanding of the alkaline disturbed zone include: industrial analogues, such as alkaline flooding of hydrocarbon reservoirs (up to 30 y), cement-aggregate reactions (up to 100 y) and the Tournemire tunnel (up to 125 y); and natural analogues, including the hyperalkaline springs at Maqarin, Jordan (more than 100,000 y), saline, alkaline lakes (more than 1,000,000 y) and certain fracture fillings in granites (more than 1,000,000 y).

These systems show that alkaline alteration can be observed for thousands of years over distance scales of hundreds of metres under extreme conditions of hydraulic gradients in fractured rocks (Maqarin), but may be limited to a few centimetres over tens to a hundred years in mudstone (Tournemire). Important reaction mechanisms for retardation of alkaline fluids include: fluid mixing (alkaline oil floods, Maqarin), ion exchange (alkaline oil floods, Tournemire) and kinetic mineral dissolution-precipitation reactions (all systems studied). Qualitative and quantitative kinetic data for mineral reactions are available from cement aggregate reactions and the Searles Lake analogue, respectively. Short-term alteration observed in cement-aggregates is characterized by calcium silicate hydrate (C-S-H) minerals and incipient zeolite formation, whereas evidence from the Tournemire tunnel shows the growth of K-feldspar after relatively short time intervals (tens to a hundred years). There is a tendency for alkaline alteration to result in porosity decreases, but locally, porosity may be enhanced (e.g. near-injection well interactions in alkaline oil floods, or at fracture margins at Maqarin, Jordan). Data from industrial and natural analogues may thus supply some key data for bridging time and space scales between laboratory and in situ experiments on one hand and the requirements for safety assessment on the other.

Low-salinity fluids (T > 200°C reduced S, modest CO2) and high geothermal gradients are common to many gold deposits and provinces. In contrast, host rocks, hosting structures, depth of formation (in the crust during deposition), subsequent metamorphic overprint, alteration mineralogy and isotopic signatures can vary dramatically within single deposits or provinces. Gold deposits with co-product base metals are an exception to the above comments, and probably relate to saline fluids.

The low salinity fluids inferred for major gold-only deposits are not easily explained by seawater, basinal brines, meteoric fluid or common magmatic processes. In contrast, metamorphic devolatilisation of mafic/greywacke rocks is one effective way to produce low-salinity metamorphic fluids with characteristics matching the gold fluids. Such an origin also explains the link to geothermal gradients.

The transition from chlorite—albite—carbonate assemblages to amphibole-plagioclase assemblages (commonly greenschist—amphibolite facies boundary) involves considerable loss of metamorphic fluid whose composition is buffered by the mineral assemblage, and is a function of P and T. This low salinity, H2O-CO2 fluid is evolved at T > 400°C commonly carries reduced sulphur, and may contain Au complexed with this sulphur. This auriferous fluid is likely to mix with other fluid types during times of elevated temperature, especially magmatic fluids at depth, and upper crustal fluids at higher levels.

Gold deposits in Archaean greenstone belts exhibit good evidence of low salinity, H2O-CO2 fluids of T > 300°C these include examples from Canada, Australia, Brazil, Zimbabwe, India, and South Africa. Turbidite-hosted (slate-belt) deposits exhibit similar evidence for such fluids but commonly with appreciable CH4; the Victoria and Juneau (Alaska) goldfields are examples. The Witwatersrand goldfields also show evidence of low salinity, H2O-CO2 fluids carrying reduced sulphur and gold, but their distribution and timing are not well established. Epithermal (sensu lato) gold deposits have evidence for low salinity fluids carrying Au and S, but are much more diverse in character than those from the previously mentioned gold provinces: this probably arises from mixing of several fluid types at high crustal levels. Together these four types of gold provinces account for over 80% of the primary gold mined to date.

The Rocky Beach Metamorphic Melange contains metre-scale phacoids of high-P low-T metamorphic rocks embedded in chlorite-actinolite schist. The phacoids include eclogite, glaucophane schist and omphacitite and provide evidence for four episodes of metamorphism with mineral assemblages: M1 = actinolite-glaucophane-titanite-apaite, M2 = almandine-omphacite-lawsonite ±quartz, M3 = phengite- glaucophane-K-feldspar-quartz, and M4 = chlorite-actinolite-calcite-quartz-titanite-white mica ± albite ± talc. M1-M3 occurred at a Neoproterozoic-Early Palaeozoic convergent plate boundary close to the eastern margin of Gondwana. Peak metamorphic conditions were attained during the static phase M2, with temperatures of ~560°C and pressures in excess of 1.8 GPa, equivalent to a depth of burial of at least 54 km.

A full-matrix, three-dimensional refinement of kalsilite, KAlSi04 (hexagonal, a 5·16, c 8.69 Å, P6a), shows that the silicon and aluminium atoms are ordered. The respective tetrahedral distances of 1·61 and 1·74 Å agree with values of 1·61 and 1·75 Å taken to be typical of framework structures. As in nepheline, an oxygen atom is statistically distributed over three sites displaced 0·25 Å from the ideal position on a triad axis. This decreases the bond angle from 180° to 163° in conformity with observations on some other crystal structures. The potassiumoxygen distances of 2·77, 2·93, and 2·99 Å are consistent with the wide range normally found for this weakly bonded atom.

The Mineralogical Society of Great Britain & Ireland has published two full-colour posters describing the feldspar minerals, designed primarily for student use. They may be downloaded free of charge by all from http://www.minersoc.org/pages/education/edu.html and are designed to be printed at A3 size, although they are legible at A4 and in greyscale. Sheet 1 deals with nomenclature, crystal structure and phase relationships, while Sheet 2 covers phase behaviour. For brevity no sources are given on the posters, and these are provided in the present article, together with supporting notes and suggested reading on the more complex topics.

A nomenclature is proposed for the alluaudite and wyllieite complex series which is based on sequentially distributing the cations in the cell according to increasing polyhedral size, matching that size with increasing ionic radii of the cations. For oxidized members, the largest site may be partly occupied to empty after all the cations have been distributed. This is supported by structural study.

For alluaudites, the cell formula is X(2)4X(I)4 M(I)4M(2)8(PO4)12 and is written according to decreasing size of the discrete sites. The X(I) and X(2) sites are appended as suffixes in the trivial nomenclature, that is specific name—X(I)X(2).

For wyllieites, the cell formula is X(2)4X (1a)2X(1b)2M(I)4M(2a)4A14(PO4)12. The X(1a), X(1b), and X(2) sites are appended as suffixes in the trivial nomenclature, that is specific name--X(la) X(Ib)X(2).

The nomenclature proposed is:

Seventeen analyses are discussed (of which five are new) for alluaudite and four analyses (of which three are new) for wyllieites. Their distribution is given parenthetically above. One analysis revealed predominant Mg2+ in M(2). It is named maghagen-dortite.

Six new analyses are presented for the arrojadite family of minerals including re-examination of dickinsonite from Branchville, Connecticut. Al3+ is always present. We propose X1 Al (OH,F)(PO4)12, Z = 4, where X = large cations (K+, Ba2+, Pb2+, etc.), Y = Na1+, Ca2+, and M = Fe2+ Mn2+, Mg2+. A range of cations X, Y, M, and Al between 76.8 and 85.9 in the cell (84 for proposed formula) suggests the likelihood of some vacancies in the structure.

Clasts of metamorphosed Cadomian granites from the ∼50—60 Ma Carpathian flysch in Gródek near the Rożnowskie Lake (Silesian Unit, SE Poland) are studied. They are considered to represent the Silesian Ridge, one of the hypothetical, currently unexposed source areas that supplied Carpathian sedimentary basins with clastic material. The gneisses preserve several examples of corona textures that include cores of primary monazite surrounded by polygonal grains of secondary apatite with thorianite inclusions, with intermediate zones of lamellar grains of secondary monazite and outermost rims of clay minerals, or various combinations thereof. Preservation of the complete textures is rare with polygonal apatite with thorianite inclusions, lamellar grains of monazite and clay minerals being particularly prevalent. Locally, polygonal apatite with thorianite inclusions surrounded by allanite and REE-epidote corona with a bastnasite-synchysite phase occurs also. The textures observed developed during primary monazite breakdown and replacement by secondary minerals. The variation in reaction products indicates that alteration was strictly dependent on the local chemical system.

Europium LIII-edge X-ray absorption near-edge structure (XANES) was employed to determine the Eu(II)/Eu(III) ratios in minerals. This ratio can be determined based on the peak-area ratio of white lines, the resonance peak, in normalized XANES spectra for Eu(II) and Eu(III) species. For precise determination of the Eu(II)/Eu(III) ratios, however, it was revealed that the transition probabilities for each individual Eu(II) and Eu(III) species in the system must be quantified, because we found that the peak area in normalized XANES spectra is different in each Eu(II) and Eu(III) species. Despite this ambiguity, the method was applied to Eu in natural hydrothermal apatites (Eu = 39 and 64 ppm) and fluocerite (Eu = 282 ppm). The relationship between the Eu(II)/Eu(III) ratio in these hydrothermal minerals, and the distribution coefficients of Eu(II) and Eu(III) were discussed, taking into account Eu anomalies in their REE patterns. It is considered that by combining the Eu(II)/Eu(III) ratios determined by XANES and the degree of Eu anomaly in REE patterns, we can provide new information on the distribution of Eu(II) and Eu(III) in various geochemical studies.

Non-hydrocarbon gas species (CO2, N2, H2) are locally important in exploration for gas, and there is a growing body of evidence that acid water originating in shales materially affects the diagenesis of nearby sandstones. These gases have been studied by analysing the products of closed-vessel hydrous pyrolysis of known petroleum source rocks, and comparing the results with field observations. Alteration of petroleum source rocks at temperatures >250°C yields a significant amount of non-hydrocarbon components. Ethanoate and higher acid anions are liberated in substantial quantities; the yield appears to be related to the oxygen content of the sedimentary organic matter present.

The non-hydrocarbon gases CO2, H2 and N2 are frequently the dominant gaseous products from hydrous pyrolysis: in the natural environment the same rock sequences at a higher maturity preferentially generate hydrocarbon gases—mainly methane. This discrepancy may be attributed to reaction and phase thermodynamic effects between laboratory and natural systems, behaviour that has important implications in the prediction of gas generation and composition in nature by source rock pyrolysis in the laboratory.

The composition of magmas proposed as parental to the layered suite of the Bushveld Complex, and some models for the manner of their emplacement, are reviewed briefly. Included are some contributions published in South Africa, with which overseas readers might be less familiar. Emphasis is given to the broader features of the cumulates, and the contradictions raised by whole-rock compositional, Sr-isotopic, and trace-element data that cloud their correlation with proposed parental magmas. It is concluded that the Lower, Critical and Main Zones are the derivatives of only two primary magmatic lineages, while a third was added to residual liquids from which the layered rocks above the Pyroxenite Marker were formed. Excessive amounts of olivine and chromium in the cumulates of the Lower and Lower Critical Zones in the northern sector of the Western Limb can seemingly not be accounted for by the composition and volume of the putative magmas. This is attributed to (1) this sector being a proximal facies located close to the original feeder, and/or (2) crystal-charged magma batches, expelled from a lower magma chamber, being periodically injected into and dispersed within the liquids already in place in the Bushveld chamber. Thus, ongoing changes in the bulk composition of the liquids within the chamber would not be reflected in the rinds of earlier, chilled-facies rocks. The expulsion of significant volumes of liquid residua from the chamber during cumulate deposition is not ruled out.

The affinity between certain organic compounds and clays has been known for many years. Lloyd reported the adsorptive capacity of fuller's earth for alkaloids in 1916 without theorizing extensively about the mechanism. Smith reacted organic bases and their salts with bentonite and presented evidence that the reaction was one of base-exchange or metathesis, while Hauser has discovered that certain organic compounds of bentonite have the property of swelling and dispersing in organic liquids. This paper reports observations on the rather striking conversion of bentonite from the hydrophilic to the organophilic condition and proposes a mechanism to explain the observed phenomena.