Correlation of soil radon and uranium with indoor radon in the Albuquerque,New Mexico area

High indoor radon in approximately 30 percent of private dwellings in the Albuquerque, New Mexico area has been reported previously. The present study explains the areas of high indoor radon as a function of different soil and/or bedrock in the area. Soils were sampled during summer and winter periods using alpha track radon detectors. The values range from 40 to 890 pCi/I air at a depth of 38 cm. The gross mean average is 360 pCi/I for the area for summer readings and 200 pCi/I for winter readings; both values are well over the average U.S. soil radon values of approximately 100 pCi/I. Analyses of soil uranium show a range in values of 1–6 ppm, with a mean of 3.1 ppm. Thorium values range from 3.3 to 28.8 ppm, and Th/U ratios range from 2.9 to 4.6.These values for U, Th, and Th/U suggest that soil U and Th are close to the values reported for the Sandia granite, the source of most of the pediment on which Albuquerque is built. Soil infiltration rates range from ~6 × 10^–4 to 4.5 × 10^–3 cm/sec for the samples, and soil moisture content ranges from 1.4 to 7.2 percent. A fair correlation of summer soil radon with infiltration rate is noted. Correlation of soil radon with moisture content and/or with percent silt, silt + clay, clay size fraction material is not established by this study. Soil radon values do correlate with regions in the Albuquerque area where high indoor radon is common. A better correlation of high indoor radon values with soils developed immediately over bedrock is observed. Furthermore, all values of average soil and indoor radon increase significantly with proximity of the stations to the Sandia Mountains. Soil uranium also shows this trend. The data argue that regions of potentially high radon can thus be identified.     

Uranium in Phosphorites

The uranium concentration in phosphorites on continents and modern seafloor varies from 0.nto n· 10²ppm (average 75 ppm). The average uranium concentration is 4–48 ppm in Precambrian and Cambrian deposits, 20–90 ppm in Paleozoic and Jurassic deposits, 40–130 ppm in Late Cretaceous–Paleogene deposits, 30–130 ppm in Neogene deposits, and 30–110 ppm in Quaternary (including Holocene) deposits. On the whole, the variation range is almost similar for phosphorites of different ages. The U/P₂O₅ratio in phosphorites ranges from less than unity to 24 · 10^–4(average 3.2 · 10^–4). Major phosphorite deposits of the world with ore reserves of approximately 250 Gt (or 58 Gt P₂O₅) contain up to 19 Mt of uranium. Uranium is present in phosphorites in the tetra- and hexavalent, i.e., U(IV) and U(VI) forms, and their ratio is highly variable. At the early diagenetic stage of the formation of marine phosphorites in a reductive environment, U(VI) diffuses from the near-bottom water into sediments. It is consequently reduced and precipitated as submicroscopic segregations of uranium minerals (mainly uraninite) that are probably absorbed by phosphatic material. During the subsequent reaction between phosphorites and aerated water and the weathering in a subaerial environment, uranium is partly oxidized and lost. The uranium depletion also occurs during catagenesis owing to a more complete crystallization of calcium phosphate and replacement of nonphosphatic components.     

Chalcophile elements in western Canadian coals

Concentrations of chalcophile elements (As, Co, Cu, Hg, Mo, Ni, Pb, Sb and Zn) in western Canadian coals were determined using INAA and AAS. The concentrations of these elements in western Canadian coals are within the range for most world coals. However, there are some high values for coals from outcrops and from areas which are not currently being mined.Arsenic content in the majority of western Canadian coals, particularly those currently being mined, is low (0.2–3 ppm). However, there are coals with high arsenic content; for example, lignites from Hat Creek A zone contain between 4.0 and 14.0 ppm As. In some samples from Comox and Suquash, the As concentration is as high as 240 ppm and 1400 ppm, respectively. The enrichment of As in high arsenic coals is related to the geology and nature of country rocks associated with the coal seams. The concentration of other elements for most western Canadian coals, particularly those being mined, are within the range for most world coals. In these coals, the concentration ranges (in ppm) of chalcophile elements are 0.3-3.6 for Sb, 0.8-4.6 for Co, 7–35 for Cu, <0.1 for Hg, 2–6 for Mo, 4–94 for Ni, 6–22 for Pb, 2–7 for Se and 7–110 for Zn.     

Organic geochemical characteristics and depositional environments of the Jurassic coals in the eastern Taurus of Southern Turkey

In this study, organic matter content, type and maturity as well as some petrographic and physical characteristics of the Jurassic coals exposed in the eastern Taurus were investigated and their depositional environments were interpreted.The total organic carbon (TOC) contents of coals in the Feke–Akkaya, Kozan–Gedikli and Kozan–Kizilinc areas are 24.54, 66.78 and 49.15%, respectively. The Feke–Akkaya and Kozan–Kizilinc coals have low Hydrogen Index (HI) values while the Kozan–Gedikli coals show moderate HI values. All coal samples display very low Oxygen Index (OI) values. The Kozan–Gedikli coals contain Type II organic matter (OM), the Feke–Akkaya coals contain a mixture of type II and type III OM; and the Kozan–Kizilinc coals are composed of Type III OM. Sterane distribution was calculated as C₂₇ > C₂₉ > C₂₈ from the m/z 217 mass chromatogram for all coal samples.T_max values for the Feke–Akkaya, Kozan–Gedikli and Kozan–Kizilinc coals are 439, 412 and 427 °C. Vitrinite reflectance values (%R_o) for the Feke–Akkaya and Kozan–Kizilinc coal samples were measured as 0.65 and 0.51 and these values reveal that the Feke–Akkaya and Kozan–Kizilinc coals are at subbituminous A or high volatile C bituminous coal stage. On the basis of biomarker maturity parameters, these coals have a low maturity.The pristane/phytane (Pr/Ph) ratios for the Feke–Akkaya, Kozan–Gedikli and Kozan–Kizilinc coals are 1.53, 1.13 and 1.25, respectively. In addition, all coals show a homohopane distribution which is dominated by low carbon numbers, and C₃₅ homohopane index is very low for all coal samples. All these features may indicate that these coals were deposited in a suboxic environment.The high sterane/hopane ratios with high concentrations of steranes, low Pr/Ph ratios and C₂₅/C₂₆ tricyclic ratios > 1 may indicate that these coals formed in a swamp environment were temporarily influenced by marine conditions.     

Determination of elemental affinities by density fractionation of bulk coal samples from the Chongqing coal district, Southwestern China

The occurrence and distribution of major and trace elements have been investigated in two coal-bearing units in the Chonqing mining district (South China): the Late Permian and Late Triassic coals.The Late Permian coals have higher S contents than the Late Triassic coals due to the fixation of pyrite in marine-influenced coal-forming environments. The occurrence of pyrite accounts for the association of a large number of elements (Fe, S, As, Cd, Co, Cu, Mn, Mo, Ni, Pb, Sb, Se, and Zn) with sulphides, as deduced from the analysis of the density fractions. The marine influence is probably also responsible for the organic association of B. The REEs, Zr, Nb, and Hf, are enriched by a factor of 2–3 with respect to the highest levels fixed for the usual worldwide concentration ranges in coal for these elements. The content of these elements in the Late Permian coal is higher by a factor of 5–10 with respect to the Late Triassic coal. Furthermore, other elements, such as Cu, P, Th, U, V, and Y, are relatively enriched with respect to the common range values, with maximum values higher than the usual range or close to the maximum levels in coal. The content of these elements in the Late Permian coal is higher than the Late Triassic coal. These geochemical enrichments are the consequence of the occurrence, in relatively high levels, of phosphate minerals, such as apatite, xenotime, and monazite, as deduced from the study of the density fractions obtained from the bulk coal.The Late Triassic coal has a low sulphur content with a major organic affinity. The trace element contents are low when compared with worldwide ranges for coal. In this coal, the trace element distribution is governed by clay minerals, carbonate minerals, and to a lesser extent, by organic matter and sulphide minerals.Major differences found between late Permian and Triassic coals are probably related to the source rocks, given that the main source rock of the late Permian epicontinental marine basin is the Emeishan basalt formation, characterised by a high phosphate content.     

U–Th–Pb–REE systematics of organic-rich shales from the ca. 2.15 Ga Sengoma Argillite Formation, Botswana: Evidence for oxidative continental weathering during the Great Oxidation Event

The redox-sensitive geochemical behavior of uranium permits the use of Th/U ratios as a geochemical proxy for the oxidation state of the atmosphere during deposition. Due to the effects of post-depositional uranium mobility on Th/U ratios during events involving oxygenated fluids, direct measurements of Th/U ratios are often misleading even for drill core samples. Because both of these elements radioactively decay and produce lead isotopes, the Pb isotope composition may reflect the depositional Th/U ratio, although the Th/U ratios induced by changes shortly after deposition may not be distinguished from the true depositional Th/U ratios. In order to effectively evaluate the time-integrated Th/U ratio (κ_a), values for the initial depositional Pb isotope composition must be determined or accepted from the models for the whole Earth.While the timing for the rise of atmospheric oxygen is reasonably well constrained now, its effect on continental weathering and ocean redox state remains poorly constrained and debated. The ca. 2.15 Ga Sengoma Argillite Formation of Botswana contains organic-rich shales deposited during the Great Oxidation Event. The slope of the ²⁰⁷Pb/²⁰⁴Pb–²⁰⁶Pb/²⁰⁴Pb array of shales from the Sengoma Argillite Formation corresponds to a Pb–Pb age that is within analytical error of the depositional age and is, therefore, inferred to be the time by which the time-integrated thorogenic and uranogenic lead growth started. The time-integrated lead growth corresponds to an average κ_a of 2.63 (± 0.62, 1σ) for the organic-rich shales of the Sengoma Argillite Formation. This is lower than Th/U ratios measured in Archean shale suites or estimated for the Archean–Proterozoic average upper continental crust [Taylor, S.R. and McLennan, S.M., 1985. The Continental Crust: Its Composition and Evolution. Blackwell, Oxford, 312 pp.], which indicates that these samples were enriched in uranium with respect to thorium (and perhaps lead) at the time of deposition. In the modern ocean, sediments are enriched in uranium under reducing conditions by reduction of the water-soluble uranyl ion, which is delivered to the ocean by oxidative weathering of continental crust. To evaluate the potential mobility of Th, U, and Pb during post-depositional processes, the concentrations of the rare earth elements (REE) were also determined. Interelement ratios of the largely immobile REE (in this study, La/Nd and Gd/Er) can be used as a proxy for the Th/U ratio, as the geochemical behavior of the lanthanide and actinide elements is similar under a variety of conditions. Furthermore, close similarity in the chondrite-normalized REE patterns and small range in La/Nd and Gd/Er ratios in studied samples indicate that variations in κ_a values are not likely to have been controlled by mixing of one or more REE-, Th-, and U-rich heavy minerals from the multiple detrital sources. Our study of shales from the ca. 2.15 Ga Sengoma Argillite Formation indicates that decoupling of U from Th, most likely related to the oxidative continental weathering, began by 2.15 Ga, at the latest.     

Uranium anomalies in paleo-aquifers near sandstone-type uranium deposits in the devonian catskill formation of Pennsylvania

Background values of U and Th in 371 clastic sedimentary rocks from the Catskill Formation correlate negatively with Si and positively with Al and most other major elements because of the low content of U and Th in quartz and the relative enrichment in clays, Fe oxides, and other fine-grained components. Background U also correlates closely with Th. Similar results are obtained from 100 samples from western Colorado near the Uravan mineral belt. Weak anomalies in U are much more easily recognized by study of residuals or deviations from regressions of U against Al or Th than in the raw data.At Penn Haven Junction near Jim Thorpe, Pa., roll-type uranium deposits similar to those in Wyoming are localized around an iron-stained paleo-aquifer of conglomeratic sandstone. Twenty-four rock samples from this paleo-aquifer contain 1–12 ppm U; eight of the samples contain less than 4 ppm U, the background level for shales of the area. Uranium residuals from regressions against Al or Th are clearly anomalous for all samples. Experiments on another group of samples suggest that readily extractable U (H₂O₂-acetic acid leach) would also show the paleo-aquifer to be anomalous.Anomalies of this type in paleo-aquifers should be useful in evaluation of drill holes, outcrops, and radiometric data in prospective districts, especially when paleo-aquifers are difficult to recognize visually. The anomalies also indicate that U is added to sandstones of the paleo-aquifer rather than leached out to form the ore bodies in reduced rocks at the margins of a geochemical cell.     

Factors Controlling Low Uranium and Thorium Concentrations in the ?ay?rhan Bituminous Shales (?BS) in the Beypazar? (Ankara) Area, Turkey

In this study uranium and thorium contents and depositional characteristics of ay rhan bituminous shales（ BS）, west of Ankara（central Anatolia）, are investigated. Samples used were collected from boreholes opened by Park Holding Ltd. A total of 25 samples were taken from bituminous shale levels in boreholes drilled at 6 different locations in the study area. The H rka formation which hosts bituminous shale deposits is a volcanosedimentary sequence and all lithofacies indicate that a lacustrine environment where the water level was continuously changed. In addition to hydrocarbon generation potential, bituminous shales also accumulate significant amount of radioactive elements such as uranium and thorium. The average uranium and thorium concentrations of BS（1.83/2.62 ppm） are much lower than averages of UC, NASK and PAAS（uranium： 2.70/2.66/3.10 ppm; thorium： 8.50/12.30/14.60 ppm）. Low uranium contents in comparison to those of similar lacustrine environments might be attributed to that waters of depositional environment of BS contain low concentration of dissolved uranium and redox conditions were of oxic and dioxic character. Correlation data indicate that U and Th have a similar source and are associated predominantly with clays and phosphates and dominantly with organic material. Radioactive elements in the basin might be derived from Paleozoic granites and metamorphites（e.g. gneiss, schist） which comprise the basement and volcanism which was active in the region throughout the Miocene period. These elements are probably associated with uraniferous phosphate minerals（e.g. autunite, torbernite） which occur in granite, gneiss and schist. BS with average TOC content of 10.96 % shows very good/perfect source rock potential. Positive correlations between Gamma-Ray values and U, Th and K concentrations imply that radioactivity might be originated from these three elements.     

Anomalous gold contents in brown coals and peat in the south-eastern region of the Western-Siberian platform

One hundred twenty-two samples of Jurassic and Paleogene brown coals and 1254 peat samples from the south-eastern region of the Western-Siberian platform were analyzed for gold by the neutron-activation method. Mean content of Au in Jurassic coals is 30 ± 8 ppb, in Paleogene coals is 10.6 ± 4.8 ppb, and in peat is 6 ± 1.4 ppb. Concentrations of gold as high as 4.4 ppm were found in coal ash and 0.48 ppm in the peat ash. Coal beds with anomalous gold contents were found at Western-Siberian platform for the first time.Negative correlation between gold and ash yield in coals and peat and highest gold concentrations were found in low-ash and ultra-low-ash coals and peat. Primarily this is due to gold's association with organic matter.For the investigation of mode of occurrence of Au in peat the bitumen, water-soluble and high-hydrolyzed substances, humic acids, cellulose and lignin were extracted from it. It was determined that in peat about 95% of gold is combined with organic matter. Forty to sixty percent of Au is contained in humic acids and the same content is in lignin. Bitumens, water-soluble and high-hydrolyzed substances contain no more than 1% of general gold quantity in peat.The conditions of accumulation of high gold concentrations were considered. The authors suggest that Au accumulation in peat and brown coals and the connection between anomalous gold concentrations and organic matter in low-ash coals and peat can explain a biogenic–sorption mechanism of Au accumulation. The sources of formation of Au high concentration were various Au–Sb, Au–Ag Au–As–Sb deposits that are abundant in the Southern and South-Eastern peripheries of the coal basin.     

Distribution, isotopic variation and origin of sulfur in coals in the Wuda coalfield, Inner Mongolia, China

This paper describes coal petrographic characteristics, sulfur abundance, distribution and isotopic signature in coals in the Wuda coalfield, Inner Mongolia, northern China. Petrographic studies suggest that depositional environment influences petrographic composition. The No. 9 and No. 10 coal seams, which are thought to have formed on a tidal delta plain, have high collodetrinite contents (up to 66.1%) indicating enhanced gelification and bacteria activity during coal accumulation, and also have the highest sulfur content (3.46% and 3.42%). Both organic and pyritic sulfur isotope values (−12.3‰ to 5.8‰ and −18.7‰ to 1.1‰, respectively) are variable and generally tend to be more negative in high-sulfur coals than those in low-sulfur coals in the Wuda coalfield. The negative sulfur isotope values indicate that a large portion of sulfur in the high-sulfur coals has a bacterial origin. Sulfur isotopic compositions and variations within the section were used to propose a model to explain the origin of sulfur in these coals. The presence of pyritized rod-like bacteria, cyanophyte's gelatinous sheaths and degraded algae organic matter suggests that bacteria, and perhaps algae, may play an important role in the formation of these high-sulfur coals.     

Chemical and physical characterization of suspended particles and colloids in waters from the Osamu Utsumi mine and Morro do Ferro analogue study sites, Poços de Caldas, Brazil

Data are presented on suspended particles and colloids in groundwaters from the Osamu Utsumi mine and the Morro do Ferro analogue study sites. Cross-flow ultrafiltration with membranes of different pore sizes (450 nm to 1.5 nm) was used to prepare colloid concentrates and ultrafiltrates for analyses of major and trace elements and U- and Th-isotopic compositions. Additional characterization of colloidal and particulate material was performed by ESCA, SEM and X-ray diffraction. The results indicate the presence of low concentrations of colloids in these waters (typically < 500 μg/l), composed mainly of iron/organic species. Minor portions of uranium and other trace elements, but significant fractions of the total concentrations of Th and REE in prefiltered waters (< 450 nm) were associated with these colloids.Suspended particles (> 450 nm), also composed mainly of hydrous ferric oxides and humic-like compounds, show the same trend as the colloids with respect to U, Th and REE associations, but elemental concentrations were typically higher by a factor of 1,000 or more. In waters of low pH and with high sulphate content, these associations are considerably lower. Due to the low concentrations of suspended particles in groundwaters from the Osamu Utsumi uranium mine (typically <0.5 mg/l), these particles carry only a minor fraction of U and the REE (<10% of the total concentrations in unfiltered groundwaters), but a significant, usually predominant fraction of Th (30–70%). The suspended particle load in groundwaters from the Morro do Ferro environment is typically higher than in those from the mine by a factor of 5 to 10. This suggests that U, Th and the REE could be transported predominantly by particulate matter. However, these particles and colloids seem to have a low capacity for migration.     

Interaction between organic matter and trace metals in a uranium rich bog,Kern County,California, U.S.A.

Surface and groundwaters, plants and organic and inorganic components of sediments from a uranium rich bog in Kern County, California were studied to determine the mechanism of uranium entrapment and concentration.Spring waters which originate along a fault trace and contain elevated uranium concentrations (up to 293 μg/l) and other metals percolate through the waterlogged boggy meadow. Several approaches used to study the speciation of metals in the bog sediments indicate that U, unlike other metals, is predominantly associated with organic matter. In samples with high total organic carbon (>7%), uranium values range up to 1100 ppm. Analyses of organic constituents of the sediments show that humic substances, and not living plant material, are responsible for U entrapment and enrichment. Infra-red studies suggest that the mechanism of entrapment is complexation of the uranyl cation in groundwaters by car☐yl functional groups on the humic and fulvic acid molecules.Published experimental and thermodynamic data are reviewed and a mechanism to explain preferential enrichment of U over other trace metals is proposed for freshwater bog or marsh environments.     

The Northeast Kingdom batholith,Vermont: magmatic evolution and geochemical constraints on the origin of Acadian granitic rocks

Five Devonian plutons (West Charleston, Echo Pond, Nulhegan, Derby, and Willoughby) that constitute the Northeast Kingdom batholith in Vermont show wide ranges in elemental abundances and ratios consistent with major crustal contributions during their evolution. The batholith consists of metaluminous quartz gabbro, diorite and quartz monzodiorite, peraluminous granodiorite and granite, and strongly peraluminous leucogranite. Contents of major elements vary systematically with increasingSiO<₂ (48 to 77 wt.%). The batholith has calc-alkaline features, for example a Peacock index of 57, and values for K<₂O/Na₂O (<1), K/Rb (60–350), Zr/Hf (30–50), Nb/Ta (2–22), Hf/Ta (up to 10), and Rb/Zr (<2) in the range of plutonic rocks found in continental magmatic ares. Wide diversity and high values of minor- and trace-element ratios, including Th/Ta (0.5–22), Th/Yb (0–27), Ba/La (0–80), etc., are attributed to intracrustal contributions. Chondrite-normalized REE patterns of metaluminous and relatively mafic intrusives have slightly negative slopes (La/Yb_cn<10) and negative Eu anomalies are small orabsent. The metaluminous to peraluminous inter-mediate plutons are relatively enriched in the light REE (La/Yb_cn>40) and have small negative Eu anomalies. The strongly peraluminous Willoughby leucogranite has unique trace-element abundances and ratios relative to the rest of the batholith, including low contents of Hf, Zr, Sr, and Ba, low values of K/Rb (80–164), Th/Ta (<9), Rb/Cs (7–40), K/Cs (0.1–0.5), Ce/Pb (0.5–4), high values of Rb/Sr (1–18) low to moderate REE contents and light-REE enriched patterns (with small negative Eu anomalies). Flat REE patterns (with large negative Eu anomalies) are found in a small, hydrothermally-altered area characterized by high abundances of Sn (up to 26 ppm), Rb (up to 670 ppm), Li (up to 310 ppm), Ta (up to 13.1 ppm), and U (up to 10 ppm). There is no single mixing trend, fractional crystallization assemblage, or assimilationscheme that accounts for all trace elementvariations from quartz gabbro to granite in the Northeast Kingdom batholith. The plutons originated by mixing mantle-derived components and crustal melts generated at different levels in the heterogeneous lithosphere in a continental collisional environment. Hybrid rocks in the batholith evolved by fractional crystallization and assimilation of country rocks (<50% by mass), and some of the leucogranitic rocks were subsequently disturbed by a mild hydrothermal event that resulted in the deposition of small amounts of sulfide minerals.     

Lead and uranium isotopic behavior in diagenetic and epigenetic manganese nodules, Timna Basin, Israel, determined by MC-ICP-MS

Isotope ratios of U and Pb were measured in two types of Mn nodules from the Cambrian Timna Formation, Israel. Type A nodules are mainly composed of pyrolusite and hollandite, with Mn, Ba, Pb and U concentrations of 30–60%, 0.2–2.5%, 0.2–1.0% and 500–3500 ppm, respectively, whereas type B nodules were formed by alteration of the former, and contain mainly coronadite, with Mn, Ba, Pb and U concentrations of 7–48%, 0.2–7%, 0.6–5% and 10–160 ppm, respectively. The isotopic composition of U and Pb was measured by MC-ICP-MS on Mn-rich solutions (up to 100 mg/L) without and with chromatographic separation. The values for the 207/206 and 208/206 ratios have been determined with precisions of up to 50 ppm and those of 206/204, 207/204 and 208/204 – up to 200 ppm. The values for the 234/238 ratios have been determined with precisions of 0.4–1%. The results of the separated and unseparated solutions were shown to be equal within the error. Thus there is no significant matrix effect while measuring U and Pb in Mn rich solution using the MC-ICP-MS.The isotopic composition of Pb and U support the distinction between the two types of Mn nodules. Type A nodules have a wide range of ²⁰⁶Pb/²⁰⁴Pb ratios (18.278–19.776), and an almost constant ratio of ²⁰⁸Pb/²⁰⁴Pb. In contrast, type B nodules have almost constant ²⁰⁶Pb/²⁰⁴Pb ratios and a wide range of ²⁰⁸Pb/²⁰⁴Pb ratios (37.986–38.079). Type A nodules form a linear array on a ²⁰⁷Pb/²⁰⁴Pb vs ²⁰⁶Pb/²⁰⁴Pb diagram, while type B nodules form a tight group characterized by lower Pb isotope ratios that slightly deviate from the type A array. The ²³⁴U/²³⁸U ratio differs between the two types of nodules; type A nodules exhibit a uniform and close to equilibrium ²³⁴U/²³⁸U ratio while type B nodules show a wide range of ²³⁴U/²³⁸U ratios above and below the equilibrium value. The isotopic composition of Pb in type A nodules might reflect Pb contributions from plutonic rock weathering, exposed at the time of deposition or later, to the Cambrian sea. These nodules have remained unaffected by processes that occurred since the Cambrian. The higher ²⁰⁸Pb/²⁰⁴Pb values of type B indicate that these nodules were formed from a Th-enriched solution probably during epigenetic processes which occurred also during the last 1 Ma.Thus the two isotopic systems of U and Pb can record formation, leaching and redeposition of Mn ores.     

Uranium districts defined by reconnaissance geochemistry in South Greenland

A reconnaissance exploration survey over 14 000 km² of Precambrian terrain in South Greenland using stream-sediment and stream-water samples delineated a central uranium district of 2000 km² with enhanced uranium levels and smaller anomalous zones in the south of the field area.The area is underlain by Archean and Proterozoic gneisses, granites and metasediments all of which have been intruded by late Proterozoic alkaline intrusions (Gardar Province). The terrain is mountainous and the streams are either steep torrents or impeded drainages typical of glaciated terrains with boggy organic rich sediments.The central uranium district was defined by a high uranium background in both stream sediments (5–20 ppm) and stream waters (0.5–1.0 ppb) and a markedly higher frequency of very anomalous values in the order of 50–100's ppm in the stream sediments and 1–10 ppb in the stream waters. An areal correlation of uranium, in this district, with high pH and conductivity in the stream water in addition to a higher organic content noted in the stream sediment raised the question of a possible enhancement of uranium values due to secondary environmental effects. On the other hand, an areal correlation of uranium with niobium and other trace elements characteristically associated with alkaline rocks, and the geographic proximity of this uraniferous district to the alkaline intrusions suggested a genetic relationship between uranium mineralization and the alkaline igneous activity.Limited follow-up work located 8 pitchblende occurrences in this extensive district. The pitchblende is in veins which contain quartz, calcite, iron oxide, fluorite and minor sulphides. The isotopic (U-Pb) age of the pitchblende, which ranges from 1180-1090 Ma, corresponds to the late stages of Gardar alkaline igneous activity. It is concluded, therefore, that the reconnaissance geochemistry reflects a district-wide hydrothermal event related to the late volatile differentiates derived from the highly fractionated alkaline magma. A combination of primary and secondary features have complemented each other in enhancing the geochemical reconnaissance data and emphasized its importance but has not materially altered the interpretation.The south of the field area also has a relatively high uranium background in both the sample media with some discrete anomalous zones, usually with a slightly lower order of magnitude than the central area, but still with a distinct contrast of 5–10 times. Fine-grained uraninite has been found in the area occurring as disseminated grains in pegmatitic elements as in the central district. Isotopic ratios (U-Pb) suggest an age of 1728 ± 30 Ma which probably reflects the long cooling of the granite.It is concluded that the geochemical reconnaissance data delineated two uranium metallogenic districts characterized by distinctly different types of uranium mineralization. It is suggested that South Greenland may be part of a much wider uranium geochemical province which includes parts of Labrador. To the present plate-tectonic models, which suggest such a connection (Le Pichon et al., 1977), must be added the comparable reconnaissance geochemical results (G.S.C. Open Files nos. 748 and 749), and the similar 1730 Ma age of the Kitts uranium mineral occurrence in Labrador (Gandhi, S.S , 1978) to that of the uraninite found in the south of the field area in Greenland.     

Iodine in Chinese coals and its geochemistry during coalification

To determine the I distribution in Chinese coals, a nationwide survey was undertaken based on the distribution, periods of formation, rank and production yields of various coal deposits. A total of 305 coal samples were collected and their I contents were determined by catalytic spectrophotometry with pyrohydrolysis. The geochemistry of I during coalification (including both peat diagenesis and coal metamorphism) was assessed. It was found that the I contents of Chinese coals range from 0.04 mg kg^–1 to 39.5 mg kg^–1 and exhibit a lognormal distribution, with a geometric mean of 1.27 mg kg^–1. Statistical correlation analysis and the observation that I contents increase with coal rank indicate that coal I is chalcophile in nature, and not generally organically bound. When peat developed into lignite through diagenesis, 95–99.9% of the original I was lost. The composition and structure of clay minerals present in the coal were controlled by the original depositional environment. The higher the I content of coals, the more likely the original sediments were affected by a marine environment. Iodine contents increased from lignite through sub-bituminous and bituminous coals to anthracite. This indicates that coal absorbed excess I from hydrothermal fluids during metamorphism (including geothermal metamorphism and telemagmatic metamorphism). The telemagmatic metamorphism was caused by magmatic activities that depended on the specific geological structure of the region. In China, most high-rank coals were formed by telemagmatic metamorphism.     

Interpretation of lead isotope data from the uraniferous Cu-Fe-sulfide mineralizations in the Proterozoic greenstone belt at Kopparåsen,northern Sweden

The polymetamorphic Early Proterozoic basic metavolcanites of the Kopparåsen greenstone belt, northern Sweden, contain U mineralizations which are confined to Cu-Fe-sulfide mineralizations in mylonitized zones within basic metatuffs and graphite-bearing mica schists. Trace-lead isotope data from sulfides indicate contamination of the sulfide lead with two different lead components at ca. 430 Ma. One lead component was leached from rocks with a ²³²Th/²³⁸U ratio of 3.0–3.2, while the other lead component had evolved in a environment with a lower ²³²Th/²³⁸U ratio (0.0–0.05). The source for this latter lead component underwent a U-Th separation, probably in relation to the formation of the U mineralizations. If this lead component was leached from the U mineralizations, these mineralizations have a ²⁰⁷Pb/²⁰⁶Pb model age of ca. 1,780 Ma, which is less than the least radiogenic lead model age of the supracrustal belt (ca. 2,050 Ma). A possible genetic model for the uranium mineralizations includes the transport of U with an oxidized metamorphic fluid, which was channelled into the permeable zones, and the local reduction of the fluid by sulfides, which caused the precipitation of U.     

Anomalous Concentrations of Trace Elements in the Spetsugli Germanium Deposit (Pavlovka Brown Coal Deposit,Southern Primorye): Communication 2. Rubidium and Cesium

Data on Rb and Cs concentrations in typical (in terms of Ge content) and Ge-bearing coals, as well as host sedimentary rocks and underlying granites, are reported. It is shown that all Miocene deposits within ore zone are strongly enriched in these elements relative to Ge-barren areas of the deposit. The relative Cs accumulation is several times higher relative to Rb, because Ge-bearing sediments are characterized by anomalously low Rb/Cs ratio (up to 0.9). The average Cs concentration in coals (30.3 ppm) is more than one order of magnitude higher than the typical content in such rocks, while the maximal contents (57.2 ppm) exceed all known highest Cs contents found in solid fuel. Differences in Rb and Cs accumulation were found in the following sequence: coals (A^d < 50%)–coaly siltsones (50% < A^d < 75%)–coal-free and low-coaly silty sandstones and mudstones (A^d > 75%). The Rb content in this sequence increases, while the Cs content reaches maximum (up to 118.1 ppm) in the coaly siltstones. The anomalous Rb and Cs accumulation in Ge-bearing sediments is related to the circulation of volcanogenic thermal solutions, which are enriched in Ge, Rb, and Cs. It is suggested that Rb is mainly sorbed by clayey particles, whereas Cs is concentrated in the organic matter as well. This work presents the first data on high contents and distribution of Rb and Cs in Ge-bearing coals of the Pavlovka deposit. The data obtained make its possible to consider Rb and Cs as new associated elements of Ge mineralization, although their occurrence mode differs from that of Ge.     

Chemical composition of low temperature (<20–40 °C) thermal waters in Slovenia

Low-temperature thermal waters (<20–40 °C) from Mesozoic carbonate formations of Outer and Inner Dinarides which outcrop along the margins of small Tertiary basins, are characterised by low content (commonly <500 mg/l) of total dissolved solids and the dominance of calcium-(magnesium) bicarbonate hydrogeochemical facies. Trace elements occur in the ppb to ppt range, and can be substantially enriched in carbon dioxide-rich thermomineral waters. Contacts of thermal waters with clastic sediments affect the abundance of many trace elements, like B, Ni, Mn, Fe, Se, Sr, Ba, REE and Th. The U/Th ratios are commonly very high for the waters from carbonate aquifers, although the U abundance is in the range of some ppb. The influence of clastic sediments is reflected in an increased abundance of Th, and therefore much lower U/Th ratio. Some waters are rich in strontium (over 1 ppm), which probably originates from aragonite in Cretaceous carbonate rocks.     

The biogeochemical expression of deeply buried uranium mineralization in Saskatchewan, Canada

Ten kilometres from the eastern edge of the Athabasca Sandstone, near McClean Lake, uranium mineralization (locally up to 27% U₃O₈) lies 150 m beneath the surface at the unconformity between the Athabasca and crystalline basement.A biogeochemical survey of the area sampled A_H and B_F soil horizons, peat moss, and plant organs from the dominant species, viz. black spruce (Picea mariana), jack pine (Pinus banksiana), labrador tea (Ledum groenlandicum), and leather leaf (Chamaedaphne calyculata). Uranium concentrations in the ash of various media are surprisingly high: spruce twigs up to 154 ppm U; labrador tea and leather leaf stems around 100 ppm U. Conversely, labrador tea roots yield < 5 ppm U and spruce trunk wood usually < 1 ppm U. Soils give values of 1–3 ppm U. Contoured U values reveal that highest concentrations occur in plants growing above, but laterally displaced from the mineralization. Track-Etch data show a similar pattern. Upward migration of ions along steeply inclined fractures is invoked to explain the phenomenon. Other elements are present in varying concentrations, depending upon the plant species and the plant organ. High concentrations of several elements are recorded, most notably Cd and Ag in the conifers.