Geochemistry and mineralogy of arsenic in (natural) anaerobic groundwaters

Here new data from field bioremediation experiments and geochemical modeling are reported to illustrate the principal geochemical behavior of As in anaerobic groundwaters. In the field bioremediation experiments, groundwater in Holocene alluvial aquifers in Bangladesh was amended with labile water-soluble organic C (molasses) and MgSO₄ to stimulate metabolism of indigenous SO₄-reducing bacteria (SRB). In the USA, the groundwater was contaminated by Zn, Cd and SO₄, and contained <10 μg/L As under oxidized conditions, and a mixture of sucrose and methanol were injected to stimulate SRB metabolism. In Bangladesh, groundwater was under moderately reducing conditions and contained ∼10 mg/L Fe and ∼100 μg/L As. In the USA experiment, groundwater rapidly became anaerobic, and dissolved Fe and As increased dramatically (As > 1000 μg/L) under geochemical conditions consistent with bacterial Fe-reducing conditions. With time, groundwater became more reducing and biogenic SO₄ reduction began, and Cd and Zn were virtually completely removed due to precipitation of sphalerite (ZnS) and other metal sulfide mineral(s). Following precipitation of chalcophile elements Zn and Cd, the concentrations of Fe and As both began to decrease in groundwater, presumably due to formation of As-bearing FeS/FeS₂. By the end of the six-month experiment, dissolved As had returned to below background levels. In the initial Bangladesh experiment, As decreased to virtually zero once biogenic SO₄ reduction commenced but increased to pre-experiment level once SO₄ reduction ended. In the ongoing experiment, both SO₄ and Fe(II) were amended to groundwater to evaluate if FeS/FeS₂ formation causes longer-lived As removal. Because As-bearing pyrite is the common product of SRB metabolism in Holocene alluvial aquifers in both the USA and Southeast Asia, it was endeavored to derive thermodynamic data for arsenian pyrite to better predict geochemical processes in naturally reducing groundwaters. Including the new data for arsenian pyrite into Geochemist’s Workbench, its stability field completely dominates in reducing Eh–pH space and “displaces” other As-sulfides (orpiment, realgar) that have been implied to be important in previous modeling exercises and reported in rare field conditions.     

Occurrence of rare borate minerals: Veatchite-A,tunellite, teruggite and cahnite in the Emet borate deposits,Turkey

The Emet borate deposits were formed in two separate basins, possibly part of an interconnected lacustrine playa lake, in areas of volcanic activity, fed partly by thermal springs and partly by surface streams. The borates are interlayered with tuff, clay and marl. Limestone occurs above and below the borate lenses. Sediments in both basins are similar but borate minerals show different mineralogical and geochemical features in the two basins.The Emet borate deposits are the only deposits known to contain any of the minerals veatchite-A, tunellite, teruggite and cahnite. Principal minerals are colemanite, with minor ulexite, hydroboracite and meyerhofferite.Thermal springs associated with local volcanic activity are thought to be the source of the borates. The initial brines from which the borates crystallized are deduced to have been high in sulphite and sulphate, low in chloride, and hence it is assumed that the initial brines were fed at all times by abundant calcium and boron with minor amounts of arsenic, strontium and sulphur. Realgar, celestite and native sulphur are almost ubiquitous in borates and sediments, and appear to have formed at all stages during deposition and diagenesis.The early colemanite, meyerhofferite, ulexite and teruggite nodules were probably formed directly from brines penecontemporaneously within the unconsolidated sediments below the sediment/water interface, and continued to grow as the sediments were compacted. Later generations of colemanite occur in vugs, veins and as fibrous margins to colemanite nodules. Tunellite appears to have formed during diagenesis with enrichment of Sr in some places. Diagenetic alterations include the partial replacement of colemanite by veatchite-A, cahnite, hydroboracite and calcite.     

The impact of hydrological changes on travertine deposits related to thermal springs in the Pamukkale area (SW Turkey)

Pamukkale thermal waters (35 °C), exhibiting calcium-bicarbonate-sulfate composition and high carbon dioxide concentration, are of a predominantly meteoric origin. The meteoric fluid, circulating through faults and fractures, is heated by magmatic intrusions at great depth, and ascends from deep reservoirs to the surface. Mixing with relatively cold groundwater in the near surface zone promotes different saturation conditions with respect to calcium carbonate that later precipitates at depth and/or the surface. Dissolution-deposition processes of calcium carbonate both at surface and depth environments may help to reconstruct past climate direction in the field. During wet climate conditions a high-rate of calcium carbonate accumulation would be expected to occur at the surface because thermal fluid would be under-saturated with respect to calcium carbonate at depth because of a relatively higher mixing ratio with cold groundwater. During dry climate conditions the thermal fluid would be super-saturated at depth because of the highly acidic environment. Hydrometeorological studies reveal that the annual precipitation at the Pamukkale hydrothermal field tends to decrease with time. This climatic change in the area was also detected from geological records. While humid climate conditions prevailed during the late Quaternary, the area has recently been affected by arid/semi-arid climate conditions, followed by some episodic transitions. This study has shown how the system has possibly reacted to different climate conditions since antiquity.     

On elevated fluoride and boron concentrations in groundwaters associated with the Lake Saint-Martin impact structure,Manitoba

Hydrogeological investigations conducted by the Geological Survey of Canada in the Lake Saint-Martin region of Manitoba have confirmed earlier reports of naturally elevated F⁻ and B concentrations in local groundwaters. Fluoride and B concentrations are highly correlated (r² = 0.905) and reach 15.1 mg/L and 8.5 mg/L, respectively. Virtually all groundwaters with F⁻ concentrations greater than the drinking water limit of 1.5 mg/L are from wells within the Lake Saint-Martin impact structure, a 208 Ma complex crater 23 km in diameter underlying a large part of the study area. The high-F⁻ groundwaters can be classified into two groups according to their anionic and isotopic compositions. Group I samples consist of Na-mixed anion groundwaters, with Cl greater than 100 mg/L and highly depleted ¹⁸O compositions indicative of recharge under much cooler climatic conditions than at present. Samples belonging to this group exhibit a striking relationship to crater morphology, and are found in an arcuate belt within the southern rim of the impact structure. Group II high-F⁻ samples consist of Na–HCO₃–SO₄ groundwaters, with little Cl, and less depleted ¹⁸O compositions. Samples belonging to this group are associated with groundwaters recharged locally, on a low ridge within the impact structure. This paper traces the probable source of high-F⁻ groundwaters to phosphatic pellets in shales of the Winnipeg Formation, a regional basal clastic unit which sub-crops at shallow depth beneath the crater rim as a result of more than 200 m of structural uplift associated with the impact event. This extensive aquifer is known elsewhere in southern Manitoba for its naturally-softened groundwaters and locally elevated F⁻ concentrations. Group I groundwaters are interpreted as discharge from the Winnipeg Formation where it abuts against crater-fill deposits. Group II high-F⁻ groundwaters are interpreted as modern recharge from within the impact structure, displacing Group I groundwaters. Thus, elevated F⁻ and B concentrations observed in groundwaters of the Lake Saint-Martin area represent the geochemical signature of upwelling from a deep regional aquifer. The previously unsuspected discharge zone occurs within an isolated sub-crop of the aquifer formed as a result of structural uplift caused by the impact event.     

Heavy metal pollution in the surrounding ore deposits and mining activity: a case study from Koyulhisar (Sivas-Turkey)

The oxidation of sulfide minerals generates acidic waters containing high levels of SO₄ and Fe. The study area has active Pb?CZn?CCu mining. It is thought that the surface/subsurface/underground sulfide minerals in the region generally contribute to the acidification of groundwater. Low pH values are also responsible for dissolved metals (Al, Fe, Mn, SO₄, Pb, Zn) in the groundwater and river. Furthermore, current mining wastes have affected concentrations of trace elements in the water. High Fe and Mn concentrations are generally found in the spring which has acidic and low Eh values, while Al, Fe and Mn concentrations in the acidic waters show notable increases with the maximum values reaching 8,829, 19,084 and 1,708?ppb, respectively. These values exceed the Turkish drinking water standard of 200, 200 and 50?ppb, respectively.     

Increasing concentrations of arsenic and vanadium in (southern) Swedish streams

The aim of this study was to investigate temporal trends and controlling factors of As and V in running waters throughout Sweden. For this purpose, data on stream water chemistry from 62 streams of varying catchment size and characteristics, included in the Swedish environmental monitoring programmes were evaluated. The geochemical software Visual MINTEQ was used to model the speciation and trend analyses were performed on total concentrations of As and V as well as modelled fractions (dissolved species as well as arsenate and vanadate adsorbed to ferrihydrite). The trend analyses showed increasing total concentrations of As and V in southern Sweden. Concentrations of As and V correlated significantly to Fe concentrations in 59 and 60 of the 62 streams respectively, indicating that Fe is an important determining factor for As and V concentrations in Swedish streams. This was confirmed by the geochemical modelling that indicated that the adsorbed fraction is the dominant form of As and V and that the concentrations of As and V in Swedish streams are thus highly determined by concentrations of colloidal or particulate Fe. It is therefore suggested that the increasing trends of As and V are to a large extent due to increasing concentrations of colloidal Fe, which is stabilised by increasing concentrations of DOC. Further the geochemical modelling indicates that the dissolved fraction of As and V generally is small, with the exception of a few streams with high pH and/or phosphate concentrations.     

滇西锡矿的花岗岩类及其成矿作用

滇西锡矿是三江锡矿域的主体。本文论述了三江锡矿域与东南亚锡矿域各带的对比,指出滇西锡矿受特提斯构造演化的控制。腾冲一梁河地区花岗岩类首次划出3个岩群、8个超单元、28个单元和若干侵入体。对滇西原生锡矿床类型、成矿系列和成矿特征进行了较详细的研究。     

碱性岩相关铜-金(钼)矿床的研究进展

由于超过20%的大型-超大型铜-金(钼)矿床与碱性岩浆有关,因此,该类矿床引起矿床学家的广泛关注。碱性岩有关的铜-金矿床的成矿岩体、物化条件及围岩种类各具特色,成矿成因类型多样,主要的成因类型为斑岩型铜-金(钼)、浅成低温热液脉型金-铜(钼)。总体上,该类矿床的矿化和蚀变具有一定的特征:该类矿床多产出在伸展环境下、均富碲化物矿化、有大量的钾质交代作用、含有氟矿物质和钒云母等,成矿蚀变亦有一定的规律。长英质岩石中经常发生钾长石蚀变,而绢云母、碳酸盐和钾长石的混合蚀变常出现在中基性侵入岩中,水热合成石英和酸性蚀变十分罕见。这种特征矿化可能与碱性岩浆流体演化有关,这种流体富含CO_2,且在高氧逸度、低硫逸度条件下释放。在伸展背景下的碱性-钙碱性省寻找此类矿床具有巨大的勘查潜力,尤其在碱性岩体中心及其外围可能形成勘探的靶区。在中国与碱性岩有关的金矿床亦有广阔的找矿前景,在借鉴国外寻找此类矿床经验的同时,仍需加强对与矿化作用有关的岩浆体活动的研究。     

Lithostratigraphy and depositional environments of the upper cretaceous deposits in the central Taurides (S Turkey)

The study area is located in the Central Taurides (southern Turkey), which is bounded by the K?rkkavak fault to the west and Ecemi? fault to the east. The sequences are studied in detail based on measured sections composed of the rocks deposited during the Cenomanian–Maastrichtian and located within different tectonic units previously described in the Taurides. The study materials include 217 thin section data from seven Cenomanian–Maastrichtian sequences of outcropping in different parts of the Central Taurides. The sediments deposited during the Cenomanian–Maastrichtian period in the Central Taurides are subdivided into eight units based on their lithological, paleontological, and textural properties. The lower boundaries of the upper Santonian and Campanian are unconformable contacts. The Upper Cretaceous sequence starts with the middle Cenomanian and represents a continuation of the Lower Cretaceous tidal flat and shelf lagoon sequence. Upper Turonian–Coniacian sediments are not observed due to the eustatic sea level drop. The second main transgression period of the Upper Cretaceous platform took place in the Santonian. This unit is represented by limestones composed of wackestones/packstones containing benthic foraminifera and rudist fragments, which are deposited in tidal flats and subtidal environments. The late Campanian starts with a transgression, and the environment transformed transitions into slope facies from inner platform facies, as a result of the thrust of ophiolitic rocks. In the following period, slope front and basin plain environments were dominant due to the increasing slope. Slumped pelagic limestones were deposited on the slope. Planktonic foraminiferal pelagic limestones were unconformably deposited on plaque limestone in the slope front environment depending on the increase in slope gradient and local faulting. As a result of decreasing tectonic activity, the sediments were deposited onto a stable basin plain. They were initially fed from the nearby carbonate platform and then by siliciclastic turbidites derived from the thrusted ophiolitic rocks. In this study, the lithostratigraphic properties of the Cenomanian–Maastrichtian units outcropping in various parts of the Central Taurides are described. The sedimentary deposits described here suggest different basinal conditions in the region.     

Intermediate sulfidation epithermal gold-base metal deposits in Tertiary subaerial volcanic rocks,Sahinli/Tespih Dere (Lapseki/Western Turkey)

Gold in the Sahinli and Tespih Dere intermediate sulfidation gold-base metal deposits in Western Turkey occurs in relatively deep epithermal quartz veins along with base metal minerals which have epithermal textures, including plumose quartz, vug infills, comb and cockade textures and matrix-supported milled breccias. The total sulfide content of the veins in the area is variable ranging from < 1% to 60% and is dominated by pyrite, galena, sphalerite and chalcopyrite. Sphalerite is Fe-poor (0.6 to 1.4 mol% FeS). Minor amounts of Ag-rich tetrahedrite are present. Primary hydrothermal alteration minerals include illite/muscovite, mixed-layer illite/smectite (11.6 Å) and clinochlore towards the east and, alunite, dickite/nacrite and pyrophyllite towards the west at Sahinli; major illite/muscovite and dickite occur at Tespih Dere and Sarioluk, respectively.Fluid inclusions in main-stage quartz at Sahinli are only liquid-rich, with homogenization temperatures ranging from 220 to 322 °C and the majority of T_h values between 250 and 300 °C. Salinity ranges from 4.3 to 6.9 wt.% NaCl equiv. First ice-melting temperatures (T_mf) between ?24.5 and ?19.0 °C indicate that the fluids were dominated by NaCl – H₂O during mineralization. The relatively higher average T_h at the Tespih Dere deposit (295 °C) is attributed to a relatively deeper level of exposure.Calculated δ¹⁸O values indicate that ore-forming hydrothermal fluids in the study area had δ¹⁸O_H2O ranging from + 1.1 to + 9.7‰ (average = 3.8‰), strongly ¹⁸O-enriched compared with present-day hydrothermal meteoric water in the area (δ¹⁸O = ?8.5‰). δD values of fluid inclusions in quartz range from ?58 to ?93‰ and δD values of clay minerals and alunite from ?40 to ?119‰. δD values from intermediate argillic alteration (average = ?68‰) in the study area are very similar to δD values of the present-day local geothermal system (average δD = ?54‰) whereas δD values from advanced-argillic alteration (average δD = ?33‰) are very different from the present-day local geothermal system.The δ³⁴S values in samples from the Sahinli and Tespih Dere deposits average ?2.9‰ for pyrite; ?3.3‰ for chalcopyrite; ?5.4‰ for sphalerite and ?7.6‰ for galena. These data are consistent with derivation of the sulfur from either igneous rocks or possibly from local wallrock.     

Zincian dolomite related to supergene alteration in the Iglesias mining district (SW Sardinia)

One of the main effects of supergene alteration of ore-bearing hydrothermal dolomite in areas surrounding secondary zinc orebodies (Calamine-type nonsulfides) in southwestern Sardinia (Italy) is the formation of a broad halo of Zn dolomite. The characteristics of supergene Zn dolomite have been investigated using scanning electron microscopy and qualitative energy-dispersive X-ray spectroscopy, thermodifferential analysis, and stable isotope geochemistry. The supergene Zn dolomite is characterized by variable amounts of Zn, and low contents of Pb and Cd in the crystal lattice. It is generally depleted in Fe and Mn relative to precursor hydrothermal dolomite (Dolomia Geodica), which occurs in two phases (stoichiometric dolomite followed by Fe-Mn-Zn-rich dolomite), well distinct in geochemistry. Mg-rich smithsonite is commonly associated to Zn dolomite. Characterization of Zn-bearing dolomite using differential thermal analysis shows a drop in temperature of the first endothermic reaction of dolomite decomposition with increasing Zn contents in dolomite. The supergene Zn dolomites have higher δ¹⁸O but lower δ¹³C values than hydrothermal dolomite. In comparison with smithsonite-hydrozincite, the supergene Zn dolomites have higher δ¹⁸O, but comparable δ¹³C values. Formation of Zn dolomite from meteoric waters is indicated by low δ¹³C values, suggesting the influence of soil-gas CO₂ in near-surface environments. The replacement of the dolomite host by supergene Zn dolomite is interpreted as part of a multistep process, starting with a progressive “zincitization” of the dolomite crystals, followed by a patchy dedolomitization s.s. and potentially concluded by the complete replacement of dolomite by smithsonite.     

Volcanic activity related to the formation of the Kuroko-type deposits in the Kosaka district,Japan

In the Miocene Kosaka formation of NE-Japan, submarine volcanic sedimentary deposits of the Kuroko-type occur. This formation consists mainly of volcanics which erupted in a submarine environment. The Kosaka Volcano was built up by nine or more volcanic events of a single eruptive cycle. The mode of eruption during a representative single eruptive cycle changed as follows: The Uwamuki tuff breccia is a contact product between dacitic magma and the sea water. Dacitic magma pushed the Motoyama dacite dome upward, as a result of the decrease in vesicularity and perhaps also in temperature. Next, a steam explosion occurred at a flank of this lava dome. The hydrothermal activity which began in this steam explosion center is responsible for the formation of the Kuroko-type Cu-Zn-Pb-mineral deposits. Similar examples of a single eruptive cycle as at Kosaka are also found in Quaternary terrestrial volcanoes of Japan.

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Zusammenfassung Submarin-vulkanisch-sedimentäre Lagerstätten des Kuroko-Typs kommen in der miozänen Kosaka-Formation vor, wo im letzten Jahrhundert der Name Kuroko zuerst angewandt wurde. Diese Formation besteht hauptsächlich aus submarinen Vulkaniten. Der Kosaka-Vulkan wurde in mindestens neun Ausbruchzyklen aufgebaut. Die Art der Eruption änderte sich während eines typischen Einzelausbruchs folgendermaßen: Die Uwamuki Tuff-Brekzie entstand durch Kontaktwirkung zwischen dazitischem Magma und Seewasser. Eine Abnahme des Gasgehaltes und vielleicht auch der Temperatur führten zur oberflächennahen Intrusion des Motoyama Dazitdoms. An einer Flanke dieses Lavadoms kam es zur Dampfexplosion. Die Hydrothermaltätigkeit, die in diesem Dampfexplosionszentrum begann, ist verantwortlich für die Bildung der Minerallagerstätten vom Kuroko-Typ. Ähnliche Beispiele eines Ausbruchszyklus vom Kosaka-Typ wurden ebenfalls in quartären terrestrischen Vulkanen in Japan gefunden, wobei hier keine Minerallagerstätten des Kuroko-Typs vorkommen.

     

Heavy metal concentrations in sultana-cultivation soils and sultana raisins from Manisa (Turkey)

This paper describes the concentrations of heavy metals in soils and in raisins (sultanas) cultivated upon the Gediz Plain (Manisa), western Turkey, which is cut by major roads from ?zmir to ?stanbul and ?zmir to Ankara. A total of 212 samples of surface soil and 82 raisin samples were analysed. Soil samples have nearly same mineralogy, quartz, calcite, magnetite, pseudo-rutile and clay minerals. Dolomite is seen especially in areas close to Neogene sediments. Clay minerals are mainly mica (illite?Cmuscovite), chlorite/kaolinite, smectite and mixed layers (Sm-Il). The concentrations of 21 elements (Ba, Ni, Mo, Cu, Pb, Zn, Co, Mn, As, U, Sr, Cd, Sb, Bi, Cr, B, W, Hg, Sn, Li and organic C) were determined in the surface soils. The degree of element enrichment in soil can be measured in many ways, the most common of which are the geoaccumulation index (Igeo), enrichment factor and the pollution index. Arsenic and Sb showed the highest Igeo values, corresponding to Igeo classes 3?C4. Hence, the area is characterised as ??being heavily contaminated to polluted?? by As and Sb. Arsenic contamination has been reported from all over world. Arsenic-related pollutants enter the groundwater system by gradually moving with the flow of groundwater from rains and irrigation. Gediz Plain forms the main groundwater supply of ?zmir city. The enrichment factor (EF_arsenic) of the analysed soil samples is around 76, which corresponds to ??extremely high enrichment??. The concentrations of 33 elements (Al, Sb, As, Ba, Be, Bi, B, Cd, Ca, Cr, Co, Cu, Fe, Pb, Li, Mg, Mn, Hg, Mo, Ni, K, Se, Ag, Na, Sr, Ta, Th, Sn, Ti, U, V, Zn and Zr) were determined in the raisin samples. The Pb and Cd contents of raisins are of great concern due to their toxicity. Pb contents ranged between 0.05 and 0.46?mg?kg^?1, and average Cd content was 0.04?mg?kg^?1. Only one sample contained high level of Cd, 0.23?mg?kg^?1. After cleaning the raisins, the heavy metal concentrations were low as in the European Community (EC) regulation No: 466/2001 for allowable levels of Pb (0.2?mg?kg^?1) and Cd (0.05?mg?kg^?1).     

Mid-Jurassic events in the Western High Atlas (Morocco)

Angular unconformities, time gaps, and progressive increase of thickness in the Mesozoic sedimentary pile of the Western High Atlas, Morocco, point to mid-Jurassic tectonic pulses in this area. Red beds, Middle Jurassic in age, were deposited in the nearshore Agadir-Essaouira basin in contrast to transgressive tendencies of the eustatic curve. These phenomena are easily explained by uplift and erosion in the central part of the mountain belt even in the Middle Jurassic. Thus, a rift stage (Permian to Early Jurassic) in the tectonic history of the Western High Atlas was followed by a gulf stage (Late Jurassic to Middle Cretaceous) until later the high mountain range generated by inversion in Late Cretaceous and Neogene to recent times. Tensional forces that created the mobile rift belt were superimposed by vertical uplift during the Middle Jurassic that gave rise to a NNE-SSW stretching high. Even in the present-day high mountain range this area, called the »ancient massif«, is strongly elevated. Thus, the evaluation of the geological history of the Western High Atlas seems much complicated.

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Zusammenfassung Bei Kartierarbeiten und Profilaufnahmen im Westlichen Hohen Atlas in Marokko beobachtete Winkeldiskordanzen, Schichtlücken und progressive Mächtigkeitsentwicklungen deuten auf mitteljurassische tektonische Aktivitäten hin. Unterstützung erhält diese Hypothese durch Rotsedimente des Dogger im Küstenbecken von Agadir-Essaouira, die hier im Gegensatz zur allgemeinen Meeresspiegelentwicklung zum Absatz kamen.In der tektonischen Entwicklung ergibt sich ein Rift-Stadium von Perm bis Unterjura, das von einem Golf-Stadium von Oberjura bis Mittelkreide abgelöst wird, bevor sich durch Inversion in der Oberkreide und seit dem Jungtertiär das heutige Hochgebirge bildete. Im Mesozoikum wird Zerrungstektonik überlagert durch vom Atlantik ausgehende Vertikaltektonik. Sie führte bereits im Mittleren Jura zu einem NNE-SSW verlaufenden Hochgebiet, das auch im heutigen »massif ancien« des Westlichen Hohen Atlas gipfelt und die Aufklärung der sedimentären Vorgeschichte des Gebirges erheblich erschwert.

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Résumé Dans les couches mésozoïques du Haut Atlas occidental (Maroc), des discordances angulaires, des lacunes stratigraphiques ainsi que des variations progressives d'épaisseur, témoignent d'activités tectoniques au Jurassique moyen. C'est ainsi qu'au Dogger, des couches rouges se sont déposées dans le bassin côtier d'Agadir-Essaouira en opposition avec les tendances transgressives générales de la courbe eustatique. Ces phénomènes s'expliquent facilement par des processus de soulèvement et d'érosion dans la partie centrale de la zone mobile atlasique au Jurassique moyen.L'histoire tectonique a comporté une période de rifting (du Permien au Jurassique inférieur) suivie par une période où le golfe marin atlasique s'est constitué (du Jurassique supérieur au Crétacé moyen) et enfin par un processus d'inversion qui, au Crétacé supérieur et depuis le Néogène, a produit le relief moderne du Haut Atlas.Les forces d'extension, responsables de la naissance de la zone mobile du rift atlasique, ont été suivies au Jurassique moyen par un soulèvement vertical en relation avec l'expansion de l'Océan atlantique. Il en est résulté un bombement NNE - SSW, appelé la »Terre des Almohades« par les auteurs français. Le »massif ancien« dans la zone centrale de la haute montagne actuelle est une partie de ce vieux bombement, où on ne trouve guère de séries mésozoïques. C'est de ce fait que la reconstitution de l'histoire du Haut Atlas occidental est particulièrement difficile.

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Engelmann Spruce (Picea engelmannii) as a biological monitor of changes in soil metal loading related to past mining activity

Engelmann spruce (Picea engelmannii) is the dominant tree species in many abandoned mine areas of the Rocky Mountains. It is long-lived, and therefore, may act as a long term biological monitor of changes in soil chemistry caused by past mining activity. In this study, laser ablation inductively coupled mass spectrometry (LA-ICPMS) was used to analyze individual tree rings of Engelmann spruce for Fe, Zn, Cu, Cd, Mn, Pb and Sr concentrations. Cores were obtained from trees growing in tailings-impacted and control (non-tailings impacted) sites near the Waldorf mine (Waldorf, CO, USA). Zinc, Cu, Fe, Cd, Pb and Sr concentrations remained low and consistent over time in the control tree rings. However, in the tailings impacted cores, concentrations of Zn, Cu, Fe and Cd increase significantly in post-mining rings. In addition, Zn, Cu, Fe, and Cd concentrations in pre-mining rings of both the control and tailings impacted cores are similar, indicating that present day soil concentrations of these elements in the control area are a reasonable estimation of background for this area. Lead and Sr concentrations in control and tailings-impacted rings remained similar and relatively constant through time and are not useful in determining changes in soil chemistry due to past mining activity.     

辽东宽甸地区硼酸盐矿床成矿时代的限定：来自SHRIMP锆石U Pb年代学和硼同位素地球化学的制约

辽宁宽甸地区砖庙硼矿区的硼矿体呈层状或透镜状赋存于古元古代辽河群里尔峪组火山—沉积建造下部的蛇纹石化大理岩之中。本研究对矿区内外的伟晶岩和变粒岩中的电气石进行了LA-MC-ICP-MS硼同位素微区原位测试,分析了矿床成因;同时对栾家沟矿段矿体上盘含电气石变粒岩和斜长角闪岩进行了SHRIMP锆石U-Pb定年,探讨了成矿时代。得到以下数据和认识:1矿区伟晶岩中电气石的δ11 B为10.9‰~12.7‰,变粒岩中电气石的δ11B为5.7‰~7.6‰,矿区外伟晶岩中电气石的δ11B为-9.9‰~-9.2‰,变粒岩中电气石的δ11 B为-8.3‰~-5.9‰。硼同位素组成往外降低的现象说明,围岩及侵位其中的伟晶岩的B同位素组成均受硼矿床影响,硼矿可能是海相蒸发沉积成因;2含电气石变粒岩核部岩浆锆石的207 Pb/206 Pb加权平均年龄为2174±10Ma,代表了辽吉裂谷早期的火山喷发时代,亦大致代表了初始的含硼蒸发岩的沉积时代上限,根据硼同位素研究结果,可将宽甸地区硼矿的初始沉积成矿时代限定在2.17Ga;3斜长角闪岩重结晶锆石207 Pb/206 Pb加权平均年龄为1869±28Ma,代表了吕梁运动所引起的区域构造热事件和混合岩化作用的时间。     

Assessment of naturally occurring arsenic contamination in the groundwater of Sarkisla Plain (Sivas/Turkey)

High arsenic levels in groundwater of the aquifers, belonging to the Pliocene terrestrial layers and Quaternary alluvial sediments, have become a significant problem for the inhabitants living in Sarkisla (Turkey). The main objective of this study was to determine the origin and arsenic contamination mechanisms of the Sarkisla drinking water aquifer systems. The highest arsenic concentrations were found in Pliocene layers and alluvial sediments with concentrations ranging from 2.1 to 155 mg/kg. These rocks are the main aquifers in the study area, and most of the drinking groundwater demand is met by these aquifers. Groundwater from the Pliocene aquifer is mainly Ca-HCO₃ and Ca-SO₄ water type with high EC values reaching up to 3,270 μS/cm, which is due to the sulfate dissolution in some parts of the alluvial aquifer. Stable isotope values showed that the groundwater was of meteoric origin. Tritium values for the groundwater were between 8.31 and 14.06 TU, representing a fast circulation in the aquifer. Arsenic concentrations in the aquifers were between 0.5 and 345 μg/L. The highest arsenic concentrations detected in the Pliocene aquifer system reached up to 345 μg/L with an average value of 60.38 μg/L. The arsenic concentrations of the wells were high, while the springs had lower arsenic concentrations. These springs are located in the upper parts of the study area where the rocks are less weathered. The hydrogeochemical properties demonstrated that the water–rock interaction processes in sulfide-bearing rocks were responsible for the remarkably high groundwater arsenic contamination in the study area. In the study area, the arsenic levels determined in groundwater exceeded the levels recommended by the WHO. Therefore, it is suggested that this water should not be used for drinking purposes and new water sources should be investigated.     

Palynology, geochemistry, and thermal history of the shales associated with the Küre massive sulfide deposits (northern Turkey)

The relationship between the palynology and geochemistry of the shales associated with the Küre massive sulfide deposits in the Kastamonu Province, northern Turkey, has been studied. SEM seems to be the most effective method to study the palynology of fusinitic particulate organic matter in these thermally-altered sedimentary rocks. Major thermal maturation indicators obtained from the organic and inorganic fractions of the shales and mineral geothermometers of the orebodies suggest that the shales indicate much lower temperatures that the ore and therefore were deposited after the formation of the massive sulfide ores in the area of study.