High Concentrations Of Tl Research Articles

Thallium isotope systematics in volcanic rocks from St. Helena – Constraints on the origin of the HIMU reservoir

It is generally accepted that subduction of the oceanic crust plays an important role in creation of mantle heterogeneity. HIMU (stands for high μ=(238U/204Pb)) is a rare and probably not volumetrically large mantle component, which is sampled at St. Helena in the Atlantic and in the Cook-Austral Islands in the South Pacific. Previous studies that used radiogenic isotopes have specifically invoked subducted hydrothermally altered oceanic crust (AOC) as a significant component in the source of HIMU. However, because radiogenic isotopes are affected by both parent-daughter fractionation and time that cannot be independently determined, it is difficult to unambiguously use these tracers to determine the source material of the HIMU reservoir.Thallium isotopes can be used to identify the involvement of sediments rich in Mn oxides or AOC, because these two components exhibit high Tl concentrations and highly fractionated Tl isotope compositons, whereas the upper mantle is depleted in Tl and homogenous with respect to Tl isotopes. Here we report Tl isotope data for a suite of St. Helena lavas previously characterized to investigate if the HIMU mantle reservoir can be linked to AOC. Samples show large Tl isotopic variation, from ε205Tl=−9.8 to ε205Tl=+3.9 and do not correlate with Sr, Nd, Hf or Pb isotopes. Eight samples have ε205Tl lighter than the mantle value (ε205T=−2), with the lightest values similar to those observed for modern AOC. These features are consistent with the presence of different proportions of recycled oceanic crust in the source of St. Helena mantle source. Our results, therefore, support previous studies that inferred AOC as a significant component in the HIMU mantle reservoir and show that the Tl isotopic system can be used as a powerful tracer to detect contributions of AOC in the creation of mantle heterogeneities.

Mineralogy, geochemistry and genesis of the polymetallic crusts and nodules from the South China Sea

Recent marine mineral investigations in the South China Sea (SCS) have found increasingly significant abundances of Fe–Mn polymetallic crusts and nodules with variable substrates and nuclei. There is, however, no systematic and complete study of the SCS crusts and nodules. The lack of mineralogical and geochemical studies affects our explicit understanding of the mineralization characteristics and genesis of the crusts and nodules. In this study, we analyzed a set of SCS polymetallic crusts and nodules obtained from ten sites to determine their mineralogy, chemistry, and Fe and Os isotopes. The SCS crusts/nodules are composed predominantly of vernadite (δ–MnO2) and amorphous Fe oxides/hydroxides. The nodules also contain minor todorokite. TEM imaging and electron diffractions show that the Fe–Mn minerals are nano–sized minerals with very poor crystallinity. Nitrogen adsorption/desorption analysis indicates an average specific surface area of 257.128 m2/g for the SCS crusts and nodules, and main apertures of 2–10nm for their nanopores in the Fe–Mn minerals. It is noteworthy that the SCS crusts/nodules contain substantial amount of terrigenous detritus, suggesting that marginal sea–type Fe–Mn deposits are strongly influenced by terrigenous sedimentary input. Furthermore, geochemical analysis indicates that the SCS crusts/nodules have relatively lower Co (1482ppm), Cu (556.2ppm), Ni (3132ppm), Mo (276.2ppm), and Zn (598.3ppm) compared to open oceanic crusts/nodules, but relatively high concentrations of REY (1647ppm), PGE (234.0ppb), Ba (1056ppm), Pb (1878ppm), Sr (995.9ppm), Te (28.81ppm), and Tl (67.87ppm). Iron isotopic compositions suggest that the Fe sources of the SCS crusts/nodules may have been Fe dissolved in terrigenous (fluvial) inputs. Osmium isotopes indicate that the main ore–forming elements came directly from the ambient seawater, which was mainly influenced by terrigenous inputs, although there may have been mixing with minor mantle–derived signatures.Evidence from mineralogy, major element geochemistry, shale–normalized rare earth element (REE) patterns, and the Fe and Os isotopes suggest that the SCS crusts/nodules are mainly hydrogenetic, whilst the formation of some nodules may have been contributed by minor pore waters of their surrounding sediments. The SCS crusts/nodules had probably much higher growth rates (mean 19.20mm/Ma) than most hydrogenetic Fe–Mn deposits in other open oceans, which are typical of marginal sea Fe–Mn deposits that contain sufficient supply of ore–forming terrigenous detritus.Grades of some critical metals of economic interest (notably Co, Cu, Ni, Mo, and Zn) are slightly lower in the SCS crusts and nodules than in the crust and nodules from Pacific prime mineralization zones. Concentrations of Mn, REY, Pt, Mo, Co, Te, and Bi, however, show relatively high concentrations relative to the continental crust. The SCS crusts and nodules could thus represent a strategic REE, Co and Pt resource, and will likely catalyse additional investigation of seabed resources in the South China Sea.

Thallium isotopes as tracers of recycled materials in subduction zones: Review and new data for lavas from Tonga-Kermadec and Central America

Sediment is actively being subducted in every convergent margin worldwide. Yet, geochemical data for arc lavas from several subduction zones, such as Northern Tonga and Costa Rica have revealed either attenuated or limited evidence for sediment in their mantle source regions. Here we use thallium (Tl) isotopes to trace slab components in lavas from the Tonga-Kermadec and Central American arcs. In general, both arcs display Tl isotope data that are most compatible with addition of sediment to the sub-arc mantle from the subducting slab. This evidence is particular strong in the Tonga-Kermadec arc where pelagic clays dominate the Tl budget along the entire arc. Contributions from altered oceanic crust as well as the Louisville Seamount chain that subducts underneath Northern Tonga are not visible in Tl isotopes, which is likely due to the very high Tl concentrations found in pelagic sediments outboard of the Tonga-Kermadec arc. Lavas from Central America reveal variable and systematic Tl isotope compositions along-strike. In particular, lavas from Nicaragua are dominated by contributions from sediments, whereas Costa Rican samples reveal a significant altered oceanic crust component with little influence from sediments on thallium isotope composition. The absence of a sediment signature in Costa Rica corresponds with the Cocos Ridge and the seamount province subduction, which results in a thinner sediment cover. Furthermore, the subducted sediment is dominated by carbonates with very low Tl concentrations and, therefore, small amounts of carbonate sediment added to the mantle wedge do not contribute significantly to the overall Tl budget.A review of Tl isotope and concentration data from the Aleutians, Marianas, Tonga-Kermadec and Central American arcs demonstrate that pelagic sediments are detectable in most arcs, whereas altered oceanic crust components only become appreciable when sediment Tl concentrations are very low (e.g. carbonate) or if sediments are no longer a significant component of the subducting slab (e.g. slab melting in Western Aleutians). As such, Tl isotopes are a promising tool to trace sediment subduction although this requires at least some pelagic sediment is present in the subducted sediment package.We suggest that thallium partitioning between the slab and mantle wedge is most likely controlled by retention in phengite or by partitioning into fluids. Residual phengite likely produces high Cs/Tl ratios because Tl should be more compatible in phengite than is Cs, however, this conclusion needs experimental verification. The stability of phengite is lower at higher fluid contents, which results in hyperbolic relationships between Cs/Tl and possible indicators of fluids such as Sr/Nd and Ba/Th. Thus, combined Tl isotopic and elemental systematics not only provide detailed information about the specific slab components that contribute to arc lavas, but also potentially shed light on the mineralogy and physical conditions of subducting slabs.

Thallium-rich pyrite ores from the Apuan Alps, Tuscany, Italy:constraints for their origin and environmental concerns

The southern sector of the Apuan Alps (AA) massif, Tuscany, Italy, is characterized by the occurrence of a series of baryte–pyrite–iron oxide orebodies whose Tl-rich nature was recognized only recently. The geochemistry of the pyrite ore was investigated through inductively coupled plasma mass spectrometry. In addition, lead isotope data for selected pyrite ores from AA were collected. Pyrite ores are characterized by a complex geochemistry, with high concentrations of Tl (up to 1100 μg/g) coupled with high As and Sb contents; the Co/Ni ratio is always <1. Geochemical data of pyrite and marcasite ore samples from other mining districts of Tuscany have been collected in order to compare them with those from the AA. These samples usually have very low Tl content (less than 2 μg/g) and high to very high Co/Ni and As/Sb ratios. Only some samples from the Sb–Hg ore deposits showed very high Tl concentrations (up to ~3900 μg/g). Another difference is related to the lead isotope composition, with pyrite ores from AA markedly less radiogenic than those from the other deposits from Tuscany. Geochemical data of pyrite ores from AA give new insights on the genesis of the baryte–pyrite–iron oxide orebodies, relating their formation to low-temperature hydrothermal systems active during early Paleozoic; in addition, these data play a fundamental role in assessing the environmental impact of these deposits.

Subcellular distribution of trace elements and liver histology of landlocked Arctic char (Salvelinus alpinus) sampled along a mercury contamination gradient

We sampled landlocked Arctic char (Salvelinus alpinus) from four lakes (Small, 9-Mile, North, Amituk) in the Canadian High Arctic that span a gradient of mercury contamination. Metals (Hg, Se, Tl, and Fe) were measured in char tissues to determine their relationships with health indices (relative condition factor and hepatosomatic index), stable nitrogen isotope ratios, and liver histology. A subcellular partitioning procedure was employed to determine how metals were distributed between potentially sensitive and detoxified compartments of Arctic char livers from a low- and high-mercury lake (Small Lake and Amituk Lake, respectively). Differences in health indices and metal concentrations among char populations were likely related to differences in feeding ecology. Concentrations of Hg, Se, and Tl were highest in the livers of Amituk char, whereas concentrations of Fe were highest in Small and 9-Mile char. At the subcellular level we found that although Amituk char had higher concentrations of Tl in whole liver than Small Lake char, they maintained a greater proportion of this metal in detoxified fractions, suggesting an attempt at detoxification. Mercury was found mainly in potentially sensitive fractions of both Small and Amituk Lake char, indicating that Arctic char are not effectively detoxifying this metal. Histological changes in char livers, mainly in the form of melano-macrophage aggregates and hepatic fibrosis, could be linked to the concentrations and subcellular distributions of essential or non-essential metals.

Miocene colored waters: A new significant source of thallium in the environment

Thallium is a toxic non-essential element which is subject to some dispersion in the environment due to industrial activity and natural processes. There is a need for this dispersion to be monitored. Colored Miocene water seems to be a newly discovered significant source of such dispersion.The presence of colored water within the brown coal Miocene formation is related to the formation of organic sediments in that period which changed into layers of brown coal.The aim of this study was to investigate the concentration of Tl in colored waters, both in soluble form and entrapped in suspended solid matter (SS). Tl was determined by flow-injection differential-pulse anodic stripping voltammetry (FI-DP-ASV).It was found that Miocene colored waters from the Wielkopolska region contain very high Tl concentrations, and are thus a newly discovered significant source of Tl pollution in the environment. The concentrations are higher than the results for surface water by 2–3 orders of magnitude, and are a serious cause for concern. The majority of the total Tl in the colored waters is entrapped in suspended solids (more than 95% in the majority of samples). Even a low percentage of soluble Tl, however, creates a high concentration of the element in water (median 0.11μgL−1), which is approximately 10 times higher than in surface water from the River Warta. Tl concentration in SS is very high (median 15μgg−1) and exceeds by one order of magnitude the concentration of the element in crude Zn–Pb ores.

Diversity of algae in a thallium and other heavy metals-polluted environment

Thallium (Tl) compounds are extremely toxic to living organisms, including algae, but there is a dearth of basic information regarding the mechanisms of action of Tl in the environment and its effects on algae in natural conditions. This study examined algal diversity in an environment highly polluted by Tl. Graniczna Woda stream is contaminated by Tl and other heavy metal compounds (Cd, Pb and Zn). There we found 66 algae taxa representing five phyla, among which euglenophytes prevailed. We found that euglenophytes, including Phacus species, can survive and can show high species diversity in the presence of high Tl concentrations. The fact that these small organisms covered only by a pellicle are able to thrive in such inhospitable habitat, shows a great plasticity of these organisms. It is unclear whether the algae of Graniczna Woda stream have a broad tolerance to harmful conditions or rather represent new varieties/clones that evolved in metal-contaminated waters and are adapted to this environment.

Effects of exposure to high concentrations of waterborne Tl on K and Tl concentrations in Chironomus riparius larvae

Thallium (Tl) is a non-essential metal which is released into the environment primarily as the result of anthropogenic activities such as fossil fuel burning and smelting of ores. The ionic radius of monovalent Tl+ is similar to that of K+ and Tl+ may thus interfere with K+-dependent processes. We determined that the acute (48h) lethal concentration where 50% of the organisms do not survive (LC50) of Tl for 4th instar Chironomus riparius larvae was 723μmolL−1. Accumulation of Tl by the whole animal was saturable, with a maximum accumulation (Jmax) of 4637μmolkg−1 wet mass, and KD of 670μmol Tl l−1. Tl accumulation by the gut appeared saturable at the lowest four Tl concentrations, with a Jmax of 2560μmolkg−1 wet mass and a KD of 54.5μmol Tl l−1. The saturable accumulation at the gut may be indicative of a limited capacity for intracellular detoxification, such as storage in lysosomes or complexation with metal-binding proteins. Tl accumulation by the hemolymph was found to be linear and Tl concentrations in the hemolymph were ~75% of the exposure concentration at Tl exposures >26.9μmolL−1. There was not a significant decrease in whole animal, gut or hemolymph K during exposure to waterborne Tl at any of the concentrations tested (up to 1500μmolL−1). The avoidance of hypokalemia by C. riparius larvae may contribute to survival during acute waterborne exposures to Tl.

Trace metal concentrations measured in blood and urine of adolescents in Flanders, Belgium: Reference population and case studies Genk-Zuid and Menen

In the Flemish human biomonitoring programme FLEHS II (2007-2011) trace metals (Cd, Pb, Cr, Ni, Cu, Mn, Tl, Sb, As and toxic relevant arsenic) were analysed in the blood and urine of adolescents (14-15 years old) in the reference population in Flanders and in areas of important industrial activities: Genk-Zuid and Menen. After adjustment of the results for confounding factors, the adolescents living in Genk-Zuid had higher levels of Cr, Cu and Tl in blood, higher levels of Cd and toxic relevant arsenic (TRA) in urine, but lower levels of Ni in blood and Sb in urine compared to the reference population. In Menen higher levels of Cd and Cu in urine, higher concentrations of Tl in blood but lower concentrations of Pb in blood and lower Ni, Sb and As in urine were found compared to the reference population. For both the reference population and the hot spots the concentrations are within the ranges found in other countries. Compared to the previous biomonitoring programme FLEHS I (2002-2006) a decrease in the concentrations of Cd and especially of Pb in blood was observed. However, it cannot be excluded that differences between the two campaigns are partially due to different sampling strategies.

Air quality comparison between two European ceramic tile clusters

The European ceramic tile industry is mostly concentrated in two clusters, one in Castelló (Spain) and another one in Modena (Italy). Industrial clusters may have problems to accomplish the EU air quality regulations because of the concentration of some specific pollutants and, hence, the feasibility of the industrial clusters can be jeopardised. The present work assesses the air quality in these ceramic clusters in 2008, when the new EU emission regulations where put into force. PM10 samples were collected at two sampling sites in the Modena ceramic cluster and one sampling site in the Castelló ceramic cluster.PM10 annual average concentrations were 12–14 μg m−3 higher in Modena than in Castelló, and were close to or exceeded the European limit. Air quality in Modena was mainly influenced by road traffic and, in a lower degree, the metalmechanical industry, as evidenced by the high concentrations of Mn, Cu, Zn, Sn and Sb registered. The stagnant weather conditions from Modena hindering dispersion of pollutants also contributed to the relatively high pollution levels. In Castelló, the influence of the ceramic industry is evidenced by the high concentrations of Ti, Se, Tl and Pb, whereas this influence is not seen in Modena. The difference in the impact of the ceramic industry on the air quality in the two areas was attributed to: better abatement systems in the spray-drier facilities in Modena, higher coverage of the areas for storage and handling of dusty raw materials in Modena, presence of two open air quarries in the Castelló region, low degree of abatement systems in the ceramic tile kilns in Castelló, and abundance of ceramic frit, glaze and pigment manufacture in Castelló as opposed to scarce manufacture of these products in Modena. The necessity of additional measures to fulfil the EU air quality requirements in the Modena region is evidenced, despite the high degree of environmental measures implemented in the ceramic industry.The Principal Component Analysis (PCA) identified four factors in Modena, attributed to: road traffic + metalmechanical industry, mineral, ceramic, and background; and three factors in Castelló, attributed to: mineral, ceramic (with influence of road traffic) and regional background. The additional measures to improve the air quality should be focused mainly on road traffic in Modena, and on the ceramic industry in Castelló.

Environmental Assessment of the Caveira Abandoned Mine (Southern Portugal): Part 1: Characterization of Metal Contaminated Soil

Mine activity in Portugal had a huge impact on the growth of the regions where it took place, like in the Iberian Pyrite Belt. Nowadays, most of these mines are abandoned, as is the case for the Caveira mine. Soil geochemistry indicates that high contents of Cu, Pb, Zn, As, Cd, and Hg occur in the soils collected near the tailings. Multiple Correspondence Analysis identifies two areas with high concentrations of Pb, As, Hg, Sb, Mo, and Tl. However, the results suggest a different geochemistry for each of the areas. The non-site-specific methods (Hazard Index and GLC guidelines) classify all the areas as contaminated. Metal fractionation in the soil phases is different for the several elements studied. The articulation of the metal fractionation results with the GLC guidelines reduces the area of soil contaminated by Pb, but not by As.

Response of Holm oak ( Quercus ilex subsp. ballota) and mastic shrub ( Pistacia lentiscus L.) seedlings to high concentrations of Cd and Tl in the rhizosphere

The impairment of root growth and photosynthetical functioning are the main impacts of trace elements on woody plant seedlings. In this work, we assessed the response of Holm oak ( Quercus ilex subsp. ballota) and mastic shrub ( Pistacia lentiscus) seedlings to high concentrations of Cd and Tl in the rhizosphere. These are non-essential trace elements, with a potential high mobility in the soil–plant system. Seedlings of these species are frequently used in the afforestation of degraded soils in mining areas. Plants were exposed to different levels of Cd (20, 80 and 200 mg L −1) and Tl (2, 10 and 20 mg L −1) in a sand culture. Biomass allocation, growth rates, chlorophyll fluorescence and gas exchange were studied. Both metals affected root biomass. Cadmium produced an increase in the root mass ratio and a decrease in the specific leaf area of the plants in oak seedlings, while Tl did not provoke such response. Mastic plants were more sensitive to Tl and Cd than oak plants. Between elements, Tl provoked more severe toxic effects in the plants, affecting the antennae complexes and reaction centers of the photosystem II. Both elements decreased net assimilation rates (down to a 20% of the control plants) and stomatal conductance (5–10% of the values for the control plants). Cadmium was highly retained in the roots of both species, while Tl was highly translocated into the leaves. In general, Holm oak showed a higher tolerance for Cd than for Tl, and a higher resistance to both metals than mastic shrub, due to a high capacity for Cd retention at the root level. However, such accumulation in roots may induce water stress in the seedling exposed to Cd.

Fluid elemental and stable isotope composition of the Nibelungen hydrothermal field (8°18′S, Mid-Atlantic Ridge): Constraints on fluid–rock interaction in heterogeneous lithosphere

Depending on the geological setting, the interaction of submarine hydrothermal fluids with the host rock leads to distinct energy and mass transfers between the lithosphere and the hydrosphere. The Nibelungen hydrothermal field is located at 8°18′S, about 9 km off-axis of the Mid-Atlantic Ridge (MAR). At 3000 m water depth, 372 °C hot, acidic fluids emanate directly from the bottom, without visible sulfide chimney formation. Hydrothermal fluids obtained in 2009 are characterized by low H 2S concentrations (1.1 mM), a depletion of B (192 μM) relative to seawater, lower Si (13.7 mM) and Li (391 μM) concentrations relative to basaltic-hosted hydrothermal systems and a large positive Eu anomaly, and display a distinct stable isotope signature of hydrogen (∆ 2H H2O = 7.6–8.7‰) and of oxygen (∆ 18O H2O = 2.2–2.4‰). The heavy hydrogen isotopic signature of the Nibelungen fluids is a specific feature of ultramafic-hosted hydrothermal systems and is mainly controlled by the formation of OH-bearing alteration minerals like serpentine, brucite, and tremolite during pervasive serpentinization. New isotopic data obtained for the ultramafic-hosted Logatchev I field at 14°45′N, MAR (∆ 2H H2O = 3.8–4.2‰) display a similar trend, being clearly distinguished from other, mafic-hosted hydrothermal systems at the MAR. The fluid geochemistry at Nibelungen kept stable since the first sampling campaign in 2006 and is evident for a hybrid alteration of mafic and ultramafic rocks in the subseafloor. Whereas the ultramafic-fingerprint parameters Si, Li, B, Eu anomaly and ∆ 2H H2O distinguish the Nibelungen field from other hydrothermal systems venting in basaltic settings at similar physico-chemical conditions and are related to the interaction with mantle rocks, the relatively high concentrations of trace alkali elements, Pb, and Tl can only be attributed to the alteration of melt-derived gabbroic rocks. The elemental and isotopic composition of the fluid suggest a multi-step alteration sequence: (1) low- to medium-temperature alteration of gabbroic rocks, (2) pervasive serpentinization at moderate to high temperatures, and (3) limited high-temperature interaction with basaltic rocks during final ascent of the fluid. The integrated water/rock ratio for the Nibelungen hydrothermal system is about 0.5. The fluid compositional fingerprint at Nibelungen is similar to the ultramafic-hosted Logatchev I fluids with respect to key parameters. Some compositional differences can be ascribed to different alteration temperatures and other fluid pathways involving a variety of source rocks, higher water/rock ratios, and sulfide precipitation in the sub-seafloor at Logatchev I.

Characterisation of Two New Reference Materials: STL‐1, the Stewart Lepidolite and ZA‐1, the Zapot Amazonite

The analysis of granitic pegmatites still remains a challenge because suitable natural reference materials are scarce or not available. Two new reference materials were prepared at the Smithsonian Institution, to provide an avenue to pursue the geochemical analysis of micas and feldspars in granitic pegmatites: STL‐1, the Stewart lepidolite (NMNH 174041) and ZA‐1, the Zapot amazonite (NMNH 174042). STL‐1 was prepared from lepidolite collected from the lithium‐rich Stewart pegmatite, San Diego County, California (33°22′52′’N, 117°03′41′’W). ZA‐1 was prepared from an amazonite from the topaz‐bearing Zapot pegmatite, Mineral County, Nevada, (38° 41’N, 118 °33’W). The results of this study indicated that STL‐1 and ZA‐1 are homogeneous and could be used as reference materials that would allow the expansion of calibration curves in XRF analysis up to 16000 μg g−1 for Rb, 2000 μg g−1 for Cs and 100 μg g−1 for Tl. STL‐1 and ZA‐1 also contain unusually high concentrations of Ga and Tl, and STL‐1 of Nb.

Trace elements in Zn–Pb–Ag deposits and related stream sediments, Brooks Range Alaska, with implications for Tl as a pathfinder element

ABSTRACT The Zn–Pb–Ag metallogenic province of the western and central Brooks Range, Alaska, contains two distinct but mineralogically similar deposit types: shale-hosted massive sulphide (SHMS) and smaller vein-breccia occurrences. Recent investigations of the Red Dog and Anarraaq SHMS deposits demonstrated that these deposits are characterized by high trace-element concentrations of As, Ge, Sb and Tl. This paper examines geochemistry of additional SHMS deposits (Drenchwater and Su-Lik) to determine which trace elements are ubiquitously elevated in all SHMS deposits. Data from several vein-breccia occurrences are also presented to see if trace-element concentrations can distinguish SHMS deposits from vein-breccia occurrences. Whole-rock geochemical data indicate that Tl is the most consistently and highly concentrated characteristic trace element in SHMS deposits relative to regional unmineralized rock samples. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of pyrite and sphalerite indicate that Tl is concentrated in pyrite in SHMS. Stream sediment data from the Drenchwater and Su-Lik SHMS show that high Tl concentrations are more broadly distributed proximal to known or suspected mineralization than As, Sb, Zn and Pb anomalies. This broader distribution of Tl in whole-rock and particularly stream sediment samples increases the footprint of exposed and shallowly buried SHMS mineralization. High Tl concentrations also distinguish SHMS mineralization from the vein-breccia deposits, as the latter lack high concentrations of Tl but can otherwise have similar trace-element signatures to SHMS deposits.

Potential health risk in areas of high natural concentrations of thallium and importance of urine screening

There is a lack of information in the literature regarding Tl exposure from naturally occurring Tl enrichment. This paper draws attention to the potential health risk posed by high concentrations of naturally occurring Tl in the environment. The inhabitants of a rural area in SW Guizhou Province, China, reside within a natural Tl accumulated environment resulting from Tl-rich sulfide mineralization, and they face ongoing severe Tl exposure. High Tl concentrations were detected in urine of the local residents. Urinary Tl concentrations are as high as 2668 μg/L, with most subjects surpassing the accepted world urinary Tl concentration at <1 μg/L for “non-exposed” humans. The urinary Tl concentrations show significant differences among three communities ( n = 21, p = 0.001), but no significant difference in either sex or age groups ( n = 21, p = 0.7806). However, there is a positive statistical relationship between the extent of Tl exposure from Tl concentrations in soil and crops in the immediate environment and the concentrations of Tl detected in urine. A majority of the volunteer subjects from the communities have urinary Tl concentrations above 4.5–6 μg/L, implying early adverse health effects, and some of them have over 500 μg/L urinary Tl, considered to be at/about the level of clinical intoxication. This study has been able to identify that the elevated urinary Tl concentrations are mainly attributable to Tl accumulation in locally grown vegetables, which acquire Tl from the soil. This study also shows that Tl in urine of the local population represents a steady-state condition with long-term exposure, and that urinary Tl concentrations can be taken as a bio-marker of total dose based upon total daily dietary intake. This study demonstrates that natural sources of elevated Tl pose a potential health risk to the population, and that monitoring the urinary Tl concentration is a reliable and accurate way of bio-marking Tl exposure.

New insights through LA-ICP-MS and sulphur isotope investigations into the occurrence of gold in the Sepon gold deposits, Laos

The Sepon sedimentary-rock hosted gold deposits (SHGD) in Laos contain micro-disseminated gold associated with sulphide minerals. New insights into the nature of gold occurrence in the Sepon SHGD through Laser Ablation Inductively Couple Plasma Mass Spectrometer (LA-ICP-MS) investigations have detected gold mostly occurring in overgrowth rims on disseminated pyrite (main-gold stage) containing: (1) high gold grades along the pyrite rims, ranging from >2 to 187 ppm Au with associated high concentrations of Ag, As, Cu, Sb, Tl, Zn, and; (2) and gold poor cores with inclusions of Co, Ni and Pb and very low levels of As, Cu, Sb and Tl. Sulphur isotope values from the Sepon SHGD main-gold stage pyrite are similar to the light d34S values reported for the late gold-ore stage pyrite occurring in the Nevada Carlin-like gold deposits.

Metalliferous Constituents of Rhizosphere Soils Contaminated by Zn–Pb Mining in Southern Poland

Industrial soils near Zn–Pb mines and metallurgical plants in the vicinity of Olkusz (southern Poland) are exposed to high environmental stress related to heavy metal pollution (Zn, Pb, Cd, Mn, Fe, Tl and As) from waste disposal sites and primary ores. X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectrometry analyses (EDS) and Atomic Absorption Spectroscopy (AAS) were used to analyse rhizosphere soil samples from the area. The mineral composition of the rhizosphere soils was determined. Carbonates of lead, cadmium and zinc, arsenic–lead sulphosalts and other minerals occurring on the root epiderm are described. Mineral aggregates of secondary origin include polymineralic spherules containing high concentrations of Zn (up to 2.3%), Pb (up to 0.7%), Fe (up to 23%), Cd (up to 427 mg kg−1) and Tl (up to 139 mg kg−1). Processes on the rhizoplane, and in the zone where plant-root exudation solutions are active, promote the crystallization of metalliferous minerals. ESEM is recommended as an efficient method for examining alteration occurring in the rhizosphere environment.

High thallium content in rocks associated with Au–As–Hg–Tl and coal mineralization and its adverse environmental potential in SW Guizhou, China

Very few investigations have dealt with the environmental impact of the highly toxic metal thallium (Tl), and its subsequent dispersion through natural processes and human activities such as mining and farming. This study is focused on high concentrations of Tl in rocks in SW Guizhou, China, that are related to several widely scattered disseminated gold–mercury–arsenic and coal deposits, and a primary Tl deposit within an Au–As–Hg–Tl metallogenic belt of the Huijiabao anticline. The Tl, Hg and As in the Lanmuchang Hg–Tl deposit area are associated with the abundant occurrence of sulfide minerals such as lorandite, realgar, orpiment and cinnabar. Concentrations of Tl range from 100 to 35 000 ppm in sulfide ores, and 39–490 ppm in host rocks. The enrichment of Au, Tl, Hg, As, and Sb in the Yanshang gold mineralized area reflects the occurrence of Au mineralization and its mineral assemblage of Tl–Hg–As–Sb sulfides. Thallium ranges from 0.22 to 16 ppm in Au ores and host rocks. Thallium in coals is enriched up to 46 ppm within the Au–As–Hg–Tl metallogenic belt, and is derived from the regional Au–As–Hg–Tl mineralization. Mercury and As show a similar distribution to Tl with high concentrations in sulfide ores, coals and host rocks. Human populations living near and downstream of Tl deposits and Tl-bearing ore deposits are susceptible to Tl contamination because of its high toxicity and high uptake rate by crops. The dispersion of Tl, Hg and As associated with the primary mineralization of Au–As–Hg–Tl can be traced through physical erosion and chemical weathering, producing secondary dispersion into soils, groundwater and surface water and crops. Mining activities compound the natural processes, readily dispersing Tl into the surface environment. The Lanmuchang area illustrates Tl contamination related to a Tl-rich deposit due to both natural processes and the impact of mining. The Yanshang area demonstrates Tl contamination related toa Tl-bearing gold deposit, caused by natural processes in the absence of mining activity.

Geochemistry of glacial sediments in the area of the Bend massive sulfide deposit, north-central Wisconsin

Geochemical exploration in northern Wisconsin has been problematic because of thick glacial overburden and complex stratigraphic record of glacial history. To assess till geochemical exploration in an area of thick glacial cover and complex stratigraphy samples of glacial materials were collected from cores from five rotasonic boreholes near a known massive sulfide deposit, the Bend deposit in north-central Wisconsin. Diamond drilling in the Bend area has defined a long, thin zone of mineralization at least partly intersected at the bedrock surface beneath 30–40 m of unconsolidated glacial sediments. The bedrock surface has remnant regolith and saprolite resulting from pre-Pleistocene weathering. Massive sulfide and mineralized rock collected from diamond drill core from the deposit contain high (10s to 10,000s ppm) concentrations of Ag, As, Au, Bi, Cu, Hg, Se, Te, and Tl. Geochemical properties of the glacial stratigraphic units helped clarify the sequence and source areas of several glacial ice advances preserved in the section. At least two till sheets are recognized. Over the zone of mineralization, saprolite and preglacial alluvial and lacustrine samples are preserved on the bedrock surface in a paleoriver valley. The overlying till sheet is a gray, silty carbonate till with a source hundreds of kilometers to the northwest of the study area. This gray till is overlain by red, sandy till with a source to the north in Proterozoic rocks of the Lake Superior area. The complex glacial stratigraphy confounds down-ice geochemical till exploration. The presence of remnant saprolite, preglacial sediment, and far-traveled carbonate till minimized glacial erosion of mineralized material. As a result, little evidence of down-ice glacial dispersion of lithologic or mineralogic indicators of Bend massive sulfide mineralization was found in the samples from the rotasonic cores. This study points out the importance of determining glacial stratigraphy and history, and identifying favorable lithologies required for geochemical exploration. Drift prospecting in Wisconsin and other areas near the outer limits of the Pleistocene ice sheets may not be unsuccessful, in part, because of complex stratigraphic sequences of multiple glaciations where deposition dominates over erosion.