Geochemical mapping in northern Honshu,Japan

Geochemical mapping of northern Honshu in the Northeast Japan Arc was carried out using stream sediments at a sampling density of one sample per 130 km². More than 50 elements were determined in 395 stream sediment samples (<0.18 mm fraction). In geochemical maps, areas with especially low concentrations of large ion lithophile elements (LILE), Be and Li widely overlap with the distribution of Quaternary volcanic rocks along the volcanic front. The areas rich in mafic elements are associated with mafic rocks in many cases. On a regional scale, Ni, Cr and Cu contents are higher in the eastern Paleozoic–Mesozoic basement zone, Pb and Tl tend to be higher on the western zones, and Zn and Cd are high in the western back-arc zone. The areas especially rich in Cu, Zn, Cd, Pb, Bi and Tl coincide with the distribution of large mineral deposits. High concentrations related to Kuroko, hydrothermal-vein, and skarn-type deposits are recognized. High values of As and Sb are related to active geothermal areas near volcanoes and ore deposits. Chemical variations of K, Ce, Th and Sn in the stream sediments are concordant with chemical variations in major rocks. The median and mean concentrations for the stream sediments in northern Honshu, showing arc signatures, are lower in Rb, Cs, Th, Li, K, Be, Ta, LREE, Ni, Hg and Sn, and higher in Sc, Ca and Cd relative to the whole area of Japan, largely because of the contribution of Cenozoic island-arc volcanic rocks that are generally poor in incompatible elements. The averaged chemical compositions of the stream sediments for the geologic zones show systematic variations of many elements. The contrasting variations of LREE and Th contents, which are lower in the zones of Cenozoic rocks relative to the zones of pre-Neogene basements, reflect the regional variations in the main rocks, and also reflect the change of geological settings of the studied area from the continental margin to an island arc during the Cenozoic.     

Natural radioelement concentration in the Troodos Ophiolite Complex of Cyprus

High-resolution γ-ray spectrometry was exploited to determine naturally occurring thorium (Th), uranium (U) and potassium (K) elemental concentrations in the whole area covered by the Troodos Ophiolite Complex of Cyprus. For that purpose, a total of 59 samples from surface soils and 10 from the main rock formations of the region of interest were analysed. Elemental concentrations were determined for Th (range from 2.5×10⁻³ to 2.0 ppm), U (from 8.1×10⁻⁴ to 0.6 ppm), and K (from 1.3×10⁻⁴% to 1.0%). The average values (A.M±S.D.) derived are (0.24±0.34) ppm, (0.10±0.10) ppm and (0.21±0.24)%, for Th, U, and K, respectively, in the soils, and (0.52±0.17) ppm, (0.17±0.11) ppm and (0.49±0.87)% in the rocks. From these values, a radioactivity (radioelement) loss of nearly 50% is estimated in the underlying surface soils due to leaching and eluviation during weathering of the rocks. The measured Th/U ratio exhibits values between 2 and 4, whereas the K/Th ratio is highly variable ranging between 1.5×10³ and 3.0×10⁴.     

Geochemical Atlas of the Slovak Republic at a scale of 1:1,000,000

The Geochemical Atlas of Slovak Republic (49,036 km²) at a scale of 1 : 1,000,000 was compiled during 1991–1995 together with maps of associated geochemical and ecological features at a scale of 1 :200,000. Investigations were aimed at the evaluation of concentrations and distributions of Al, As, Ba, Be, Ca, Ce, Co, Cd, Cs, Cr, Cu, Fe, Ga, Hg, K, La, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, Sb, Se, Sn, Sr, Th, U, V, W, Y, Zn, Zr in groundwater (16,359 samples), stream sediments (24,422 samples), rocks (3839 samples), soils (9892 samples from 4946 profiles; A and C horizons of each profile were sampled) and forest biomass (the foliage of the forest tree species from 3063 plots was sampled). In groundwater field measurements of temperature, pH, conductivity, dissolved O₂, acidity, alkalinity were done. The evaluation was oriented to the natural radioactivity of the Slovak territory as follows: rocks (K, U, Th, U_tot and dose rate, 15,573 reference spectrometric points), radon risk and water (U_nat, ²²⁶Ra, ²²²Rn; 5271 samples). The main objective of the Geochemical Atlas was to construct single-component maps showing concentrations of chemical elements, compounds and measured parameters in the researched media of Slovakia at a scale of 1 : 1,000.000 and to create interactive databases of chemical composition and/or measured parameters of groundwater, biomass, rocks, soils, stream sediments and natural radioactivity, for the entire territory of the Slovak Republic. The single-component maps are not constructed in the part ‘Rocks’, where all the main rocks types of Slovakia are presented in the ‘Map of lithogeochemical rock types of Slovakia at a scale of 1: 500,000’. The edition of six atlases has been planned. In 1997 the first three atlases will appear (Groundwater, Biomass, Natural Radioactivity). Publishing of last three atlases (Rocks, Soils, Stream Sediments) is planned for 1998. Since the analytical works on stream sediments were finished during 1997, it was not possible to present here the results of that part of the Geochemical Atlas.     

R-mode factor analysis applied to uranium exploration in the Montrose quadrangle, Colorado

R-mode factor analysis is used to describe the relationships among 18 remotely sensed and geochemical data sets (variables) for the Montrose 1° × 2° quadrangle, Colorado, a region that covers 19 000 km². The data sets contain reconnaissance-scale information and include Landsat imagery, airborne geophysical information (eU, eTh, K40, aeromagnetics), elevation, and hydrogeochemical and stream sediment analyses. The elements U, K, Dy, Hf, V, Th, Ca and Ba in sediments and U in waters were selected.The results of the factor analysis for the entire quadrangle are compared to the results for a 50 km × 50 km test area containing several known uranium occurrences. Four factors account for 70.0% of the total variance in the data. These are interpreted as a felsic factor, Landsat factor, economic or mineralization factor (in terms of uranium mineralization and potential mineralized areas), and a volcanic factor.Graphical representations (maps) of the raw data, factor approximations, residuals for each data set, and the four-factor model greatly aid interpretation of the analytic results. We find that data integration techniques and R-mode factor analysis can be used with some success in uranium resource appraisal.     

Natural radioactivity levels and evaluation of radiological hazards from Beni Haroun dam sediment samples,northeast Algeria

Levels of naturally occurring radioactivity in sediment samples of Beni Haroun dam have been investigated. The activity concentrations of ²³⁸U and ²³²Th decay chains and ⁴⁰K primordial radionuclide have been measured using high-resolution HPGe detector. Activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K radionuclides were found in the ranges 9–66, 14–37, and 177–288 Bq/kg with the mean values 24.67, 25.98, and 208.10 Bq/kg, respectively. Radiological hazard parameters were estimated based on the activity concentrations for ²²⁶Ra, ²³²Th, and ⁴⁰K to find out any radiation hazard associated with the sediments. Correlation studies between pairs of radionuclides were performed and discussed, and the obtained results are compared with international recommended values.     

Natural and artificial radioactivity distribution in soil, rock and water of the Central Ashanti Gold Mine, Ghana

Direct gamma spectrometry study was carried out within and around the operational area of the Central Ashanti Gold of Ghana to ascertain the baseline radioactivity levels of naturally occurring radioactive materials (NORM), prior to processing of gold ore at the mine. The average activity concentrations of ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs in the soil/rock samples were 64.3, 68.4, 1243.9 and 3.5 Bqkg^?1, respectively. For the water samples, the average activity concentrations were 2.5, 2.6, 14.7 and 0.7 BqL^?1 for ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs, respectively. The total annual effective dose to the public was estimated to be 0.141 mSv which is below the ICRP recommended level of 1 mSv for public exposure control. The average radium equivalent activity value was 257.8 Bqkg^?1 in the range of 72.9–402.3 Bqkg^?1. The average values of external and internal indices were 0.7 and 0.8, respectively. The concentrations of U, Th and K were variable in soil and rock samples taken from different locations in the study area with values varying in the range of 0.8–10.9, 2.4–39.4 μg/g and 0.7–6.3 %, respectively. The concentration values of gross-α and gross-β for all the water samples were below the Ghana Standards Board and Who Health Organisation recommended guideline values for drinking water quality. The results obtained in this study shows that radiation levels are within the natural background radiation levels found in literature and compared well with similar studies for other countries.     

张家口北部铅锌银多金属矿床区域剥蚀程度分析

张家口北部是河北省重要的铅锌银多金属矿床富集区.区内多金属矿床成矿作用和控矿因素相似,矿化形成均与燕山期酸性小岩体侵入变质结晶基底有关.区域多金属矿床化探异常具可对比性.化探异常图显示区内多金属矿床与化探异常在地表总体呈现无偏性空间分布特征,化探数据因子分析结果表明成矿元素相关性在水系沉积物中未发生改变.据此可将原生晕...     

Geochemical studies in the Indian Pass and Picacho Peak Bureau of Land Management Wilderness study areas, imperial county, Southern California

The U.S. Geological Survey has conducted geochemical studies in the Indian Pass (CDCA-355), 124 km², and Picacho Peak (CDCA-355A), 23 km², Wilderness Study Areas (WSA's) as part of a program to evaluate the mineral resource potential of designated areas in the California Desert Conservation Area. These two WSA's are of particular interest because they lie within a region which has intermittently produced significant quantities of Au since the mid-1800's, and is currently the site of much exploration activity for additional Au resources. Within a 15-km radius of the WSA's, there is one actively producing gold mine, a major deposit which began production in 1986, and one recently announced discovery. In the reconnaissance geochemical surveys of the two WSA's - 177 μm (-80 mesh) stream sediments, heavy-mineral concentrates from stream sediments, and rocks were prepared and analyzed.Four areas of possible exploration interest were identified within the WSA's. The first area is characterized by anomalous W and Bi in nonmagnetic heavy-mineral concentrates, and is underlain primarily by the Mesozoic Orocopia Schist which has been intruded by monzogranite of Oligocene age. Alteration and mineralization appear to be localized near the intrusive contact. The mineralized rock at the surface contains secondary Cu and Fe minerals where the monzogranite intrudes the metabasite horizons of the Orocopia Schist and scheelite where the monzogranite intrudes marble within the Orocopia Schist.The second area is characterized by anomalous As, Sb, Ba, B, and Sr in nonmagnetic heavy-mineral concentrates and by anomalous As in - 177 μm stream sediments. Geologically, this area is underlain by metasedimentary and metavolcanic rocks of Jurassic(?) age; a biotite monzogranite of Jurassic(?) age; and Tertiary volcanic and hypabyssal rocks composed of flows, domes, and tuffs of intermediate to silicic composition. All these rock types are cut by a set of north-south-striking normal faults. The anomalies in the heavy-mineral concentrates are believed to be related to silica-clay alteration observed in the vicinity of some of these faults.     

Radiological risk assessment of naturally occurring radioactive materials in marine sediments and its application in industrialized coastal areas: Bay of Algeciras,Spain

Radioactivity levels in aquatic environments can be assessed through the study of superficial sediments. Anthropogenic activities may alter radioactivity levels leading to the anomalous accumulation of natural radionuclides in coastal areas. In this work, marine sediments from a significant area subjected to severe industrial development were collected in order to measure activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K by gamma spectrometry. Radium equivalent index (Ra_eq), absorbed gamma dose rate in air (D) and annual effective dose equivalent (H) were also calculated and used as risk assessment tools. Results showed low levels of radioactivity in marine sediments from the Bay of Algeciras, discarding any significant radiological risks. Furthermore, the obtained data set could be used as background levels for future research applications and development of environmental regulatory frameworks.     

Factors controlling the groundwater transport of U, Th, Ra, and Rn

A model for the groundwater transport of naturally occurring U, Th, Ra, and Rn nuclides in the²³⁸U and²³²Th decay series is discussed. The model developed here takes into account transport by advection and the physico-chemical processes of weathering, decay, α-recoil, and sorption at the water-rock interface. It describes the evolution along a flowline of the activities of the²³⁸U and²³²Th decay series nuclides in groundwater. Simple sets of relationships governing the activities of the various species in solution are derived, and these can be used both to calculate effective retardation factors and to interpret groundwater data. For the activities of each nuclide, a general solution to the transport equation has been obtained, which shows that the activities reach a constant value after a distance ϰ_i, characteristic of each nuclide. Where ϰ_i is much longer than the aquifer length, (for²³⁸U,²³⁴U, and²³²Th), the activities grow linearly with distance. Where gKⁱ is short compared to the aquifer length, (for²³⁴Th,²³⁰Th,²²⁸Th,²²⁸Ra, and²²⁴Ra), the activities rapidly reach a constant or quasi-constant activity value. For²²⁶Ra and²²²Rn, the limiting activity is reached after 1 km. High δ²³⁴U values (proportional to the ratio^ɛ234Th/^W238U) can be obtained through high recoil fraction and/or low weathering rates. The activity ratios²³⁰Th/²³²Th,²²⁸Ra/²²⁶Ra and²²⁴Ra/²²⁶Ra have been considered in the cases where either weathering or recoil is the predominant process of input from the mineral grain. Typical values for weathering rates and recoil fractions for a sandy aquifer indicate that recoil is the dominant process for Th isotopic ratios in the water. Measured data for Ra isotope activity ratios indicate that recoil is the process generally controlling the Ra isotopic composition in water. Higher isotopic ratios can be explained by different desorption kinetics of Ra. However, the model does not provide an explanation for²²⁸Ra/²²⁶Ra and²²⁴Ra/²²⁶Ra activity ratios less than unity. From the model, the highest²²²Rn emanation equals 2ɛ. This is in agreement with the hypothesis that²²²Rn activity can be used as a first approximation for input by recoil (Krishnaswamiet al 1982). However, high²²²Rn emanation cannot be explained by production from the surface layer as formulated in the model. Other possibilities involve models including surface precipitation, where the surface layer is not in steady-state.     

The recognition of hydrothermal processes in the trace element geochemistry of uranium- and thorium-enriched tuffaceous rocks, Northwest Iran

Radiometrically anomalous tuffaceous rocks occur as conformable lenses in a volcano-sedimentary sequence of Neogene age near the village of Sarkhanlu, northwest Iran. The anomalous rocks have been extensively altered by hydrothermal fluids, and kaolinization and silicification are widespread. 250 samples of the anomalous and background tuffs and other sediments have been analyzed for Fe, Mn and 18 trace elements. Enhanced levels of Ag, As, Mo, Pb, Sn, Sr, Th, U, W and Zr indicate an alkaline volcanic origin of the tuffaceous material, and the elements of this association dominate the statistical analysis of the geochemical data. Maximum U and Th values are among the highest ever recorded in extrusive volcanic rocks. A zone of kaolinization contains increased levels of U, Th, Pb and Sr relative to the unaltered country rock, although nine other elements are depleted in the zone. This association of elements is recognized in the radiometrically anomalous lithologies, particularly in the kaolinized tuffs, and indicates the availability of U in the hydrothermal fluids causing the alteration. Although U mineralization has not yet been found at Sarkhanlu, comparisons with the similar geological environment in central Italy and elsewhere suggest possible exploration criteria for the future. Distinct sedimentary U associations have been defined in tuffs with only background radioactivity and in dark, calcareous shales.     

Distribution of 238U, 232Th and 40K in plutonic rocks of Greece

One hundred and twenty one samples from every major plutonic body (mainly granitic) of Greece have been analyzed by γ-ray spectrometry to determine the specific activities of ²³⁸U, ²³²Th and ⁴⁰K (Bq/kg). The range of the activity concentrations of these radionuclides was 2.3–266.4, 1.8–375.5 and 55.0–1632.0 Bq/kg and their average values were 79.2, 85.3 and 881.4 Bq/kg respectively. Any possible connection between the specific activities of ²³⁸U, ²³²Th and ⁴⁰K and some characteristics of the studied samples (age, rock-type, colour, grain-size, occurrence and chemical composition) is investigated. Samples of particular colour, rock-type, occurrence and chemical composition have been identified for their distinctive levels of natural radioactivity, while age and grain-size do not affect the concentrations of ²³⁸U, ²³²Th and ⁴⁰K. The range of the Th/U ratio was 0.7–12.69. This great variation in the Th/U ratios, especially when it is found among the samples of the same pluton, is also discussed and explained by alteration and tectonic–metamorphic processes.     

Investigation of natural background radiation of sediments in Rameswaram Island,Tamil Nadu,India

The aim of the study is to assess the natural background radiation in and around Rameswaram Island. In this context, samples were collected to measure the gamma radiations of ²³⁸U, ²³²Th, and ⁴⁰K using NaI(Tl) detector-based gamma ray spectrometer. The average activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K are noted to be well below the world average values. The calculated absorbed dose rate, radium equivalent activity, and hazard index values were below the prescribed limit. The grain size of the sediment was analyzed following Trefethen’s nomenclature, and its correlation with the natural background radioactivity was studied. The sample that contained clay show elevated activity of ⁴⁰K. The percentage of heavy minerals shows concomitant variation in natural radioactivity, especially in the activity of ²³⁸U and ²³²Th.     

Natural radioactivity measurements in beach sand along southern coast of Orissa,eastern India

The beach placer deposits in the southern coastal Orissa, India may have significant levels of radiation due to the presence of Th and U bearing minerals such as monazite and zircon. In this study, Gopalpur and Rushikulya beach regions were selected to study the ambient radiation environment. The average activity concentrations of radioactive elements such as ²³²Th, ²³⁸U and ⁴⁰K of beach sand samples were measured by γ-ray spectrometry using a HPGe detector, and found to be much higher than the internationally accepted values. The cross plots of eTh/eU and eTh/K inferred that the sand samples of Gopalpur and Rushikulya beach placer deposit were deposited in leached uranium and an oxidising environment. The absorbed γ dose rate levels of the study areas are similar to other monazite sand-bearing HBRAs of southern and southwestern coastal regions of India and of world. Different radiation hazard indices were estimated for the present study area and were found to be much higher than the internationally accepted values. Hence, Gopalpur and Rushikulya beach placer region can be considered as a high background radiation area and a potential zone for radiogenic heavy mineral exploration.     

渤海沉积物中放射性核素分布及其对沉积环境变化的响应

为了探讨近百年来,人类活动背景下近海沉积物中放射性核素的沉积记录及其对物质输入与埋藏等沉积环境变化的响应,利用γ能谱法对渤海表层和柱状沉积物中的放射性核素238U、226Ra、232Th、210Pb、40K和137Cs进行分析.结果显示,渤海沉积物中放射性核素水平和垂直分布特征明显,铀衰变系核素238U、226Ra和210Pb不平衡,232Th和210Pb受沉积物粒度和有机碳影响显著,238U与226Ra、232Th、40K存在显著相关性.226Ra/238U、232Th/238U和40K/238U比值时空差异显著,渤海沉积物陆源输入影响由西南向东北方向延伸,受河流影响,渤海北部和南部的沉积物输入不稳定,近几十年波动显著.利用210Pb_ex和137Cs法的测年结果计算获得的渤海近百年来沉积速率在中国近海沉积速率研究背景值范围内;空间上,渤海北部、中部和南部沉积速率处于同一水平,其中北部偏高;时间上,近百年来渤海沉积速率随时间波动,整体上呈现增加趋势,尤其是1980年之后,人类活动影响下渤海沉积速率增加幅度显著,与沉积物输入的波动变化相对应.      

Geochemical background and baseline values of toxic elements in stream sediments of Campania region (Italy)

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.     

Contaminant dispersion at the rehabilitated Mary Kathleen uranium mine, Australia

This study reports on the transfer of contaminants from waste rock dumps and mineralised ground into soils, sediments, waters and plants at the rehabilitated Mary Kathleen uranium mine in semi-arid northwest Queensland. Numerous waste rock dumps were partly covered with benign soil and the open pit mine was allowed to flood. The mineralised and waste calc-silicate rock in the open pit and dumps has major (>1 wt%) Ca, Fe and Mg, minor (>1,000 ppm) Ce, La, Mn, P and S, subminor (>100 ppm) Ba, Cu, Th and U, and trace (<100 ppm) As, Ni, Pb, Y and Zn values. Consequently, chemical and physical weathering processes have acted on waste rock and on rock faces within the open pit, mobilising many elements and leading to their dispersion into soils, stream sediments, pit water and several plant species. Chemical dispersion is initiated by sulfide mineral breakdown, generation of sulfuric acid and formation of several soluble, transient sulfate minerals as evaporative efflorescent precipitates. Radiation doses associated with the open pit average 5.65 mSv year⁻¹; waste dumps commonly have lower values, especially where soil-covered. Surface pit water is slightly acid, with high sulfate values accompanied by levels of U, Cu and Ni close to or above Australian water guideline values for livestock. Dispersion of U and related elements into soils and stream sediments occurs by physical (erosional) processes and from chemical precipitation. Plants growing in the mine void, on waste dumps and contaminated soil display evidence of biological uptake of U, LREE, Cu and Th and to a lesser degree of As, Ni, Pb, Y and Zn, with values being up to 1–2 orders of magnitude above background sites for the same species. Although rehabilitation procedures have been partly successful in reducing dispersion of U and related elements into the surrounding environment, it is apparent that 20 years after rehabilitation, there is significant physical and chemical mobility, including transfer into plants.     

Geostatistical techniques application to dissolved radon hazard mapping: An example from the western sector of the Sabatini Volcanic District and the Tolfa Mountains (central Italy)

Dissolved Rn was determined in 192 samples collected from cold shallow volcanic and sedimentary aquifers, deep thermal aquifers and from waters associated with bubbling gases in the western sector of the Sabatini Volcanic District and the Tolfa Mountains (central Italy). Shallow aquifers hosted in the Quaternary volcanic complexes show values ranging from 1.0 to 352 Bq/L (median value 55 and inter-quartile distance 62 Bq/L), while waters circulating within the permeable horizons of the sandy-to-clayey sediments of the Tolfa flysch have values from 1.0 to 44 Bq/L (median value 6.9 and inter-quartile distance 8.1 Bq/L). Thermal waters are hosted in the Mesozoic carbonate formations and move towards the surface along faults. Here, dissolved Rn values range from 0 to 37 Bq/L (median value 3.0 and inter-quartile distance 9.5 Bq/L). Waters associated with bubbling gases show dissolved Rn contents ranging from 2.0 to 48 Bq/L (median value 6.2 and inter-quartile distance 23 Bq/L). Those results suggest that lithology is the main factor affecting the Rn contents in shallow aquifers, due to the high levels of Rn progenitors U and Ra in the volcanic rocks relative to sedimentary units. The influence of other factors such as the presence of a fracture network, seasonal flow variations, type of discharge (from well or spring) was also investigated. Radon contents of thermal waters result from mixing with shallow waters (from both volcanic and sedimentary rock aquifers) and decrease of Rn solubility with temperature, while for bubbling pools the effects of strong degassing were also considered.In terms of health hazard from direct ingestion of Rn-rich waters, 20.8% of those circulating within the volcanic aquifer show values higher than the recommended value of 100 Bq/L, while none of those circulating within the sedimentary aquifers exceed the threshold value. Geostatistical techniques were used for the elaboration of contour maps by using variogram models and kriging estimation aimed at defining the areas where a potential health hazard due to the direct ingestion of Rn-rich waters and to inhalation of air following degassing of Rn from waters may be expected.     

Trace elements distribution in stream sediments of an abandoned U mining site in the Eastern Carpathians,Romania, with particular focus on REEs

Trace elements distribution, including rare earth elements (REEs), in stream sediments of an abandoned U mining site in the Eastern Carpathians, Romania, were of high concern of interest in the present work. A total number of 40 riverbed sediments samples collected from the Bistricioara River and local tributaries (Primatar, Bradul, Prisacani, Barasau, Grintiesul Mare and Valea Seaca) were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and energy dispersive X-ray fluorescence spectrometry (XRF). All REEs including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu were identified and quantified in the present work using ICP-MS technique. For other 24 elements (Ti, V, Cr, Co, Zn, Li, Be, Rb, Sr, Y, Sc, Zr, Nb, Sb, Ba, Ta, W, Pb, U, Ni, Cu, Mo, As, Th) similar information was obtained either by ICP-MS or XRF techniques. The impact and the relevance of the obtained data base might be significant at a local scale of about 50 km².Enrichments of some trace elements of interest in comparison to the upper continental crust allowed discrimination between various mineralization processes specific for the investigated areas. Uranium mineralization and Paltin-type (Pb, Zn) mineralization seems to be specific for the NW area of the investigated region. Negative anomaly characteristic for the upper crustal rocks was identified for Eu and Ce elements. Evidences were obtained also for the existence of ultramafic rocks (Ni, Cr, Co and V) in the investigated riverbed sediments. The observation was also confirmed by the binary plots analysis of Th/Cr vs. Th/Co and Cr/V vs. Y/Ni pairs. From the investigated tributaries to Bistricioara River, Barasau seems to exert the highest influence on the abundances of REEss in the entire area. Most probably some chemical parameters such as the pH of the water streams influence leaching and depletions of some chemical constituents in various minerals specific for the region.The existence of magnetite, garnets, pyrite and sillimanite minerals was confirmed by SEM-EDAX and XRF analysis, as well by optical microscopy. Principal Component Analysis runs confirmed the association of some chemical elements in the riverbed sediments in close connection with the minerals from which they originate.The present work reports for the first time upon the authors knowledge clear scientific evidence and chemical information concerning the geology and geochemistry, i.e. transition metals, high field strength elements, alkali and alkaline earth elements, rare earth elements (REEs) and others, in stream sediments crossing the Tulghes-Grinties mining area (Eastern Carpathians, Romania). For the analysed REEs this is the first study reporting consistent information on the concentrations of the entire array of both light REEs (six elements) and heavy REEs (ten elements) in Bistricioara Basin stream sediments. Relevant scientific data related to geochemical characteristics of ultramafic rocks existent in the investigated area were also generated. Moreover, data reported in the present work might be considered as a reference geochemical database relevant for the investigated area, which can be used as a trustworthy input for a systematic national geochemical atlas.     

Radiometric survey for exploration of hydrothermal alteration in a volcanic area

A radiometric survey on a sector of the Lipari volcanic island particularly affected by argillification due to hydrothermal processes was carried out. Preliminarily, on the basis of a wide set of field measurements over unaltered outcrops U and K distribution maps were obtained. The concentration of these radioelements increases with the degree of magma differentiation; the U and K content shows maxima (13.4 ppm and 3.7% on average, respectively) in the felsic materials, belonging to the youngest volcanic cycles, and minima (2.7 ppm and 2.0%) in the mafic rocks of the oldest cycles. The Th/U ratio insignificantly varies with magma differentiation and it equals 3.2. Laboratory measurements on volcanic products from altered zones were then used to identify radiometric anomalies related to hydrothermal processes. On the average, argillized rocks have radioactivity approximately five times lower than that measured in the unaltered volcanics. The Th/U ratio against U is rather uniform, whereas Th/K ratio is of the order of 3.6 in less altered rocks K > 0.2%) and it ranges from 7 to 11 in kaolin deposits having the largest depletion in potassium.