Bismuth (atomic number 83, atomic mass 209) occupies a position in group Vb of the periodic table, which it shares with As, Sb and P. Crystallochemically it is closely related to As and Sb as well as to Pb (Bi has an identical electronic structure to Pb). Because of its generally low tenor in rocks and the difficulty of determining such low values by commonly used multi-element geochemical methods such as optical emission spectrometry and X-ray fluorescence spectrometry (XRFS), Bi determinations are seldom quoted in rock analyses. However, the rocks of south-west England, especially the granitic rocks, give values of Bi which are substantially above world averages and many values can thus be determined by XRFS, providing an unusual range of data from which reasonable deductions can be drawn about the general geochemistry of Bi.

As, Sb and Bi are enriched in both sedimentary and intrusive igneous rocks of the south-west peninsula, with higher values for argillaceous compared with arenaceous rocks. All elements are particularly enriched close to mineralisation and it is often difficult to determine an effective background level resulting from widespread lowlevel mineralisation. The granites are also enriched in these elements compared to crustal averages, with two orders of magnitude enrichment of Bi and one order for both As and Sb. As is a relatively mobile element and tends to form broad primary haloes near mineral deposits irrespective of the composition and style of the lodes. It is concluded that high As and Bi are ultimately derived from late stage granite derived mineralising fluids. Sb is enriched in association with volcanic basic rocks.

The REE distribution patterns in aureoles surrounding selected small Sri and W specialised granite intrusions are described. In contrast to previous studies of aureoles related to larger plutons no consistent pattern is discernible, This observation also contrasts with the extensive metasomatic haloes for alkalis. Sri and W observed for the same cupolae. It is speculated that the cusps are not sufficiently large to affect the distribution of REE in the aureoles by retaining a temperature gradient long enough for a recognisable pattern to develop.The granites have a lower REE content than the aureoles. Any possible addition of small amounts of REE, with a "granite signature" is not recognisable within the inhomogeneity of the original distribution patterns which are also affected by both enhancement and dilution processes. The variance of the REE increases near to the granites.

A major Ordovician submarine caldera occurs near Snowdon in North Wales. The main lithologies are bimodal basic and acid, intrusive and extrusive igneous rocks with volcaniclastic sediments. Minor volcanogenic base-metal sulphide vein mineralization occurs, dominantly within the caldera. The caldera rocks have undergone extensive hydrothermal alteration, and additional extreme metasomatism is associated with mineral veins. The geochemistry of the alteration is described, rocks within the caldera being compared with those outside as well as with the mineral vein wall-rocks. Major changes in the alkalis, alkaline earth and certain other major and trace elements are observed. The base metals were commonly mobile, their movement being controlled by hydrothermal circulation in the volcanic pile. Some 'immobile' elements have been redistributed by strong alteration close to mineral veins. The alteration is compared in terms of mineralogy and geochemistry with modern geothermal systems, with which similarities are found despite different environments and ages.

Soil-gas radon measurements provide a valuable tool in assessing probable indoor radon levels on a regional basis. However, in Great Britain, seasonal weather changes can cause large changes in soil-gas radon concentration. Although this does not significantly constrain systematic radon potential mapping programmes, it does cause difficulties in responding to ad-hoc requests for site-specific radon investigations. The relationship between soil-gas radon and gamma spectrometry measurements made in the field with radon released from a representative sample of soil in the laboratory has been investigated as part of a program to develop a method of radon potential mapping and site investigation which can be used at any time of the year. Multiple soil and soil-gas samples were collected from sites underlain by bedrocks with widely varying radon potentials. For each geological unit, sites both free of and covered by glacial drift deposits were sampled. Soil and soil-gas samples were taken at the same depth of 60–100 cm. The effectiveness of these radon site investigation procedures has been evaluated by studying the relationship between the soil-gas radon, gamma spectrometry and radon emanation data with an independent estimate of the radon risk. The geologic radon potential (GEORP), which is the proportion of existing dwellings which exceed the UK radon Action Level (200 Bq m−3) for a particular combination of solid and drift geology within a defined geographic area, has been used for this study as the independent estimate of radon risk. Soil-gas radon, radon emanation and eU (equivalent uranium by field γ spectrometry) are all good geochemical indicators of radon risk (GEORP) in Derbyshire but only soil-gas radon correlates significantly with GEORP in Northamptonshire. Radon in soil gas discriminates more effectively between sites with different radon potential in Northamptonshire if soil permeability is also taken into account. In general, measurement of soil-gas radon in the field provides the most universally applicable indicator of radon potential. If soil-gas radon concentrations cannot be determined because of climatic factors, for example when the soil profile is waterlogged, measurement of radon emanation in the laboratory or measurement of eU can be used as radon potential indicators in some geological environments. This applies particularly in areas where the soil composition rather than the composition and permeability of the underlying rock or superficial deposits are the dominant controls of radon potential. It appears, therefore, that it may be necessary to use different radon site investigation methods according to the specific factors controlling radon emanation from the ground. In some cases no method will provide a reliable indicator of radon risk under unfavourable climatic conditions.

The distribution of the alkali elements Li, Na, K, Rb and Cs in the aureoles surrounding two buried and four partly exposed granite cupolas are described. Most of the aureole rocks are pelites with subordinate metabasalts (greenstones) and sparse quartzite. Petrographic evidence indicates that metasomatic processes continued after the peak of contact metamorphism. There is a consistent geochemical pattern to both pelites and greenstones, with elevated concentrations of Rb and Cs in the inner aureole (to 500 m from granite) and lower concentrations outside this zone. In some aureoles this general pattern is also reflected in the K and Li distributions. The degree of alkali enrichment depends upon the composition of the core granite. The patterns are consistent with and partly reflect the mineralogical changes observed.

Recently collected data for radon levels in houses in Devon and Cornwall are compared with geological and geochemical information. The region is underlain by granites intruded into folded sedimentary rocks. The highest incidence of affected houses is on granites. The granites are characterised by moderate uranium concentrations, a deep weathering profile and uranium in mineral phase which is easily weathered. However, while the uranium may be removed, radium, the immediate precursor of radon, can remain in situ. Radon is emanated easily from the host rock, and high values of radon in ground and surface waters and soil gases have been detected. The granite areas are also characterised by high values of uranium in stream sediments and waters. In contrast, other zones of high uranium in stream sediment samples do not necessarily exhibit high house radon concentrations, especially when underlain by relatively impermeable rocks. Permeable ground can give rise to high incidences, of affected houses despite having uranium levels close to the crustal abundance. It is concluded that the most efficient method of identifying zones of high radon potential is the soil gas radon survey.

Soil gas radon measurements can provide a rapid means of identifying areas with a high potential for radon to enter buildings. Although variable weather has a strong influence on radon fluxes often the effect of the underlying rocks types is greater. The strong lithological control over the production of Rn-222 and the relatively uniform generation of the gas produced from each rock type means that one can use geological knowledge supplemented by careful soil gas measurements to produce radon distribution maps. Sole reliance upon uranium concentrations and/or gamma spectrometry can be suspect.

A review of the behaviour of radon in the geological environment is presented. The general geochemistry of the element is described and the factors controlling its emanation from minerals and rocks and into the disperse phases itemized. A brief summary of analytical procedures for the analysis of the radon isotopes in waters and soil gases is given. The emanation of radon depends upon the source term uranium concentration, the nature of the host mineralogy, the permeability of the host rock and soil and the characteristics of the transporting medium. Weather can have a profound effect upon the concentration of radon in soil gas but often the variation due to the geological substrate is greater. Radon is not a problem unless it collects in buildings and underground structures. Some guidelines are given for identifying areas of high radon emanation based upon existing data sets.

A detailed study is being carried out at the Needle's Eye locality, on the Solway Firth, into the movement and fixation of U and its daughter isotopes. The site contains pitchblende veins, some of which have acted as a source of soluble uranium flowing into and through estuarine silts laid down in the last 2000 years or so. A section through these has provided samples for detailed analysis by X-ray fluorescence and neutron activation techniques. High resolution gamma spectrometry has contributed information on the distributions and disequilibria between uranium and its daughters. These data have been combined with analyses from groundwaters to produce a geochemical model of the origins of the U radioisotope distributions and transport mechanisms. There are thought to be two main inputs of dissolved U(VI) into this system; the surface flow of groundwater from the exposures of the mineralisation in the cliff, and upward flow from the bedrock below. The fixation of U in the sediments is controlled by the presence of organic matter in the upper humic layers, and by an iron oxy-hydroxide sorption reaction in the deeper silts at about 110cm. This concentration of U in the silt is divorced from the sub U-234 daughters. In contrast. Th is coherently associated with its daughters within detrital resistate phases. This study is a prelude to a more rigorous modelling investigation in collaboration with the Ecole des Mines de Paris.

The Tal y Fan Intrusion is an altered olivine dolerite sheet emplaced into a coeval sequence of subaqueous volcanic rocks of Caradoc (Ordovician) age in NE Snowdonia, Wales. Primary mineral and chemical variations across the 110 m thick sheet suggest that the magma was drawn from a zoned magma chamber, although the intrusion consolidated predominantly as a single cooling unit. An horizon of ferrodolerite resulted from in situ fractionation. Secondary mineral assemblages are indicative of the prehnite-pumpellyite and prehnite-actinolite fades, suggesting metamorphic alteration conditions of approximately 310°C and 1-85 kb. Major elemental variation largely reflects primary mineral variations across the intrusion, although Ca, Al, and Na show limited mobility in the outermost 4-5 m, related to breakdown of plagioclase feldspar during metamorphism. The LIL elements Rb, Sr, K, and Ba were highly mobile, particularly in the marginal zones, whereas Th, in addition to the incompatible elements Zr, Y, Ti, P, Nb, Ta, Hf, and the REE, was immobile even in the marginal zones. Accordingly petrotectonic modelling based on discriminant diagrams using these immobile elements is considered most reliable. The Tal y Fan Intrusion has characteristics transitional between N-type and E-type MORB, similar to tholeiitic within plate basalts. In contrast with other Ordovician volcanic sequences of the Welsh Basin, no subduction component is identified in the Tal y Fan magma, the LIL element enrichment observed being related to alteration

Tungsten ore at Carrock Fell Mine comprises wolframite and scheelite in polyminerallic quartz veins which traverse the Grainsgill Granite cupola and surrounding country rocks. In the veins, a wolframite-scheelite-apatite assemblage pre-dates a scheelite-arsenopyrite-pyrite (plus other sulphides) assemblages. Temperatures of mineralisation declined from a peak near 350°C to 170°C, and the hydrothermal fluid contained about 6 weight% NaCl and 3 wt% NaHCO3. Contemporaneous greisenisation involved loss of Na, Cr, Ca and Ba from granite, but Si and K were retained while B, Be and Al increased slightly. Sn also increased but is always a trace constituent, and F appears to have decreased. Zones of intense alteration contain high concentrations of quartzhosted fluid inclusions resulting from penetration of the granite by fluid chemically similar to that in the vein quartz. The W-rich, Sn-poor nature of the mineralisation may relate to the weakly saline, F-deficient but CO2-rich fluid chemistry. The alteration and mineralisation processes took place during late cooling of the Lower-Devonian Skiddaw Granite. Cross-cutting quartz-ankerite veins and argillitic zones which may be considerably younger than those producing the tungsten ore, have a distinct mineral suite lacking W and As and including major Pb and Zn. Temperatures at this late stage were below 150°C, and the fluid is estimated to have contained approximately 12 wt% NaCl and 15 wt% CaCl2.

The Cae Coch massive pyrite deposit is described and re-interpreted as a sedimentary volcanogenic orebody of about 200 000 tons. It is located at the contact between the Ordovician Dolgarrog Volcanic Formation (basic tuffs and lavas) and the overlying Llanrychwyn Slates (pyritic black mudstone) and close to a major intrusive rhyolite. The minerals are dominantly pyrite and quartz with minor molybdenite and the deposit shows zonal variation in trace Ba, Cu, Zn, Ni, and Co and detectable concentrations of Sn, TI, Hg and Ag. The footwall rocks have been highly altered and the basic rocks show increases in K, Ba, S and carbonate and losses of Cu, V and Co and probably light rare earth elements (LREE). A progressive gain in K, Ba and Pb and a depletion of Ga, Sr, Sn, Zn and REE is observed with increasing alteration of the rhyolite. The deposit is concluded to be the result of accumulation in a brine pool but with a component of debris flow of uncertain provenance. The deposit resembles Kuroko style mineralization and seems to be unique in the immediate district.