Distribution Of Major Elements Research Articles

Petrographic characterization of Archaean impact spherule layers from Fairview Gold Mine, northern Barberton Greenstone Belt, South Africa

The oldest known evidence of large impacts in Early Earth history are Archaean to Palaeoproterozoic impact spherule layers of the Barberton Greenstone Belt in South Africa and the Pilbara craton in Western Australia. Four drill core sections (BH5901, BH5907, BH5911 and BH5949) containing spherule layers were intersected in exploration drilling at Fairview Gold Mine in the northern Barberton Greenstone Belt. Here, we provide a first detailed mineralogical study of these new spherule layer intersections. The spherule layers are densely packed with sand-sized, spherical to ovoid, i.e., in part strongly deformed, “beads”. They generally have morphological and textural features similar to other 3.4–3.2 Ga old spherule layers of the Barberton Greenstone Belt. The Fairview spherule layers are stratigraphically positioned at the contact between the silicified volcanic tuff of the uppermost unit of the Onverwacht Group and the lowermost siliciclastic rocks of the Fig Tree Group, like the S2 and S4 layers in the southern, and S3 layer in the northern, domain of the greenstone belt. Micro-XRF scanning allowed (i) to distinguish spherule layers from their host rocks by their major element distribution, and (ii) to characterize secondary alteration and micro-deformation features in the SL and host rocks. Ni–Cr spinel, the only primary mineral in evidence in these sections, is not distributed uniformly along a spherule layer intersection, and occurrences can not be stratigraphically correlated between the four layer intersections either. Spinel crystals vary with respect to Ni, Cr, Fe and Zn contents and respective zonation patterns for these elements. Zinc abundances are likely related to post-depositional hydrothermal overprint. The results of this investigation comprising geological, petrographic, semiquantitative micro-X-ray fluorescence spectrometry, and quantitative electron microprobe analysis on spinel support a complex and heterogeneous genetic process that must have taken place during spherule formation in an impact vapor plume and in post-depositional times. The Fairview spherule layers are thought to possibly represent the product of a single impact event. They represent fallout into deep-water conditions, as they lack evidence for reworking or sorting by current or wave action. The heterogeneous Ni–Cr spinel concentrations are similar to what has been reported for spinel occurrences in the S3 layer, but considering the complex tectonic overprint on this lithostratigraphic sequence at the changeover from the Onverwacht to the Fig Tree Group it is not possible to conclude whether or not these spherule layers represent the same impact event.

Geochemical signature of superhigh organic sulphur Raša coals and the mobility of toxic trace elements from combustion products and polluted soils near the Plomin coal-fired power station in Croatia

In the northern Adriatic coast of Croatia, combustion of super-high organic sulphur rich Raša coal was common between 1970 and 2000. These Late Paleocene coals are enriched in a number of trace elements. This work aims to provide a detailed study on the distinctive geochemical patterns of the Raša coal and investigate the environmental effects of the coal and combustion by-products on the area. Several analytical techniques were used to study the mode of occurrence, distribution, levels and solubility of major and trace elements in the Raša coal, fly ash, slag and soils in an area within 10 km from the power station. Due to the sulphur-rich calcareous depositional environment of the Raša coal, the combustion by-products are enriched in S and Ca. Fly ash and slag are enriched in potentially harmful trace elements i.e. Se, Mo, Hg, V and U. Similar enrichment pattern was found for soils suggesting that resuspension and deposition of airborne coal and fly ash particles, transport of gaseous species in the flue gas by dominant winds and/or leaching from ash deposits may have affected the wider environment. Whilst a large number of trace elements were found to be poorly soluble across samples, the leachable concentrations of Se, Cr and Mo in fly ash and slag are noteworthy. Their organic association in coal enhances volatilisation during combustion and then further condensation on ash particles as readily soluble oxyanionic species. Other oxyanionic metalloids such as As or V were insoluble in fly ash and slag, due to precipitation of solubility-limiting Ca-bearing species.

Sources, Distribution, and Fluxes of Major and Trace Elements in the Yangtze River

Surface water samples were collected from 20 sampling sites in the main stream and its major tributaries of the Yangtze River from April to May 2017. The concentrations of dissolved trace and major elements were analyzed to determine the spatial variation, source identification, and riverine fluxes using various multivariate statistical techniques, including correlation analysis, principal component analysis (PCA), and cluster analysis (CA) with the goal of determining the influence of natural factors and human activities, including the operation of the Three Gorges Dam on the distribution and loading of major and trace elements in the Yangtze River water environment. Spatial distribution results showed that Cu, Zn, Pb, Cd, and As were the major elements affected by human activities in the Yangtze River, and their concentrations downstream were significantly higher than those in the middle and upper reaches (P<0.05). All elements had fairly high concentration values in both channels of the Yangtze River mainstream in Chongqing city and Hanjiang River in Wuhan city, which were mainly related to the enhanced human activities. However, the low concentrations of multi-elements in the reach of the Yangtze River in Yichang were largely caused by the retention effect of Three Gorges Project on element transport, which decreased the riverine loadings of multi-elements. Principal component analysis (PCA) indicated that Na, Mg, K, Ca, Fe, Mn, Co, Ni, Mo, Cr, and V were mainly associated with the weathering and erosion of various rocks and minerals in the river basin. And Cu, Zn, and Pb were mainly affected by enhanced human activities, such as industrial wastewater, metal smelting, and mineral mining, whereas Cd and As were mainly related to agricultural activities. The spatial distribution of trace and major elements showed that concentrations of some elements in the Yangtze River channels were enhanced by human activities. Generally, the heavy metal pollution in the Yangtze River Basin was lower than that in other rivers of the world. However, the annual fluxes of Cu, Zn, Pb, Cd, and As could have far-reaching ecological effects on the Yangtze River estuary and offshore ecological environment.

Geochemical Characteristic of Charnockites in North Margin of North China Craton: Indicating the Significiant of the Neoarchean Tecnotic Event

The Neoarchean charnockites of North margain of North China Craton (NCC) has become a hot topic into understanding the Early Precambrian basement. Although there is a broad consensus that charnockite is usually related to granulite facies metamorphism, whether its petrogenesis and tectonics characteristics remains controversial. Inclusions within hypersthene and garnet in charnockite are used to identify the peak granulite facies mineral assemblage, with the formation of Magnesian–charnockite attributed to anatexis of the protolith associated with this granulite facies metamorphism. The distribution of major and trace elements in charnockite is very uneven, significant depleted in LILEs (eg. Cs, U, Th) and HFSEs (eg. Nb, Ta, P and Ti), riched in Sr. Raising to the coexistence of Eu–enrichment and Eu–depletion type of REE patterns that influenced by the content of plagioclase and the remnants minerals of zircon and apatite. Comparative the petrography, geochemistry and geochronology data of Magnesian–charnockite indicate that the ratios of mafic pellites and basalts involved in anatectic melting are different by the upwelling of mantle magma, also resulting in the Eu anormals characteristics. The formation of the Magnesian–charnockite is closely connected with the subduction of the NCC oceanic crust (About ∼2.5 Ga). However, Ferroan–charnockite may be the formed by the crystallization differentiation of the upwelling of mantle–derived shoshonitic magma (About ∼2.45 Ga), with the lower crust material addition.

Fault-fluid evolution in the Xitian W–Sn ore field (South China): Constraints from scheelite texture and composition

Understanding fault-fluid evolutionary processes is crucial for understanding the genesis of vein-type deposits. Scheelite and quartz are common hydrothermal minerals in W–Sn ore field faults. In the Xitan ore field (Nanling Range, South China), scheelite textural and compositional features were studied and two types of scheelite were identified: Type I (represented by scheelite in the Xihu fault) is intergrown with quartz, has oscillatory zonation, variable zonation band width and is homogeneous light grey color in cathodoluminescence images; and Type II (represented by scheelite in the Goudalan fault) is intergrown with quartz that shows multi-stage growth, has oscillatory zonation and each zonation band is the same width. Scheelite grains of both types have homogeneous major element distribution (e.g., W and Ca), however trace element contents (e.g., Mg, Nb) are slightly variable, and rare earth element (REE) and Y contents gradually decrease by an order of magnitude from the core to the rim in both types of scheelite. From core to rim, the chondrite-normalized REE patterns of Type I scheelite change from flat curves with no or slightly positive Eu anomalies to intense concave shapes with intense positive Eu anomalies. The middle REEs gradually become depleted, indicating the MREE fractionation associated with early scheelite precipitation in a relatively closed fault-fluid system. In contrast, the chondrite-normalized REE patterns of Type II scheelite grains are similar, all showing weak MREE depletion from the core to rim, implying recurrent fluid pulses in an open fault-fluid system. The REE patterns in the cores of the Type I scheelite are similar to those of the scheelite from Jurassic granites related to the W–Sn mineralization, suggesting that the initial ore-forming fluids were exsolved from the Jurassic magma. The REE patterns in the rims of Type II scheelite are consistent with those of scheelite from the Goudalan W deposit, suggesting that the fault-fluid system experienced a similar evolution to the ore-forming fluid system. Combining the results of this work with previous quartz H-O isotopic and fluid inclusion studies, it can be concluded that fluid mixing occurred in both the fault-fluid system and the ore-forming fluid system, triggering large-scale W precipitation.

Distribution of major and trace elements in bottom sediments of the Taquari River Basin, Caldas municipality (Brazil)

The Taquari River Basin, located in Poços de Caldas Alkaline Complex, in the southern portion of Minas Gerais state, Brazil, is situated in an old volcanic caldera. Due to its chemical and radiological characteristics, it is an area of economic and mineral interest, and is also home to diverse flora and fauna systems. In its surroundings, there are agricultural areas, industries (active and inactive) and urban and rural centers. This work investigated the total and potentially bioavailable concentrations of major and trace elements for the evaluation of geogenic and anthropogenic contamination potentials in the water bodies. The results show that there is an anthropogenic contribution (fertilizers and mining tailings) in some sectors of the Taquari River Basin, generating possible concerns regarding the quantity of elements that may be transferred to the water bodies. Furthermore, there is the striking geogenic contribution from naturally enriched areas, presenting distinct situations that generate an increase in the concentration of chemical elements in the water bodies.

Controlling factors on the geochemistry of Al-Shuaiba and Al-Mejarma coastal lagoons, Red Sea, Saudi Arabia

Abstract Geochemical and mineralogical analyses of bottom sediments collected from Al-Shuaiba (SHL) and Al-Mejarma (MJL) coastal lagoons, Red Sea were carried out. Mineralogically, the sediments consist mainly of carbonate minerals particularly aragonite, high and low Mg-calcite and traces of dolomite admixed with non-carbonate minerals including quartz, k-feldspars, plagioclase and traces of amphiboles, mica and clay minerals. The spatial distribution of major and trace elements at the bottom of the lagoons indicates two groups of elements. The first, less significant, is of terrigenous origin concentrates mainly in the shoreward direction. This group includes the silicates (Al2O3-Fe2O3-SiO2), Feldspars (K2O-Rb-Ba) and heavy minerals (V-Cr-Zr, TiO2-Y-Nb) related elements. The second most dominant group is the carbonate related elements (CaO-Sr) that concentrates in the seaward direction. The two lagoons are not affected by urbanization or anthropogenic impact, and hence the siliciclastic elements are related to the terrigenous influx mainly by aeolian transportation. The carbonate related elements are mainly of biogenic origin related to calcareous skeletal remains. The elemental distribution in the bottom sediments of the MJL is more homogeneous than those in the SHL reflecting the bottom conditions that are mainly controlled by lagoon morphology, hydrodynamic and the water circulation between the lagoon and the sea. Geochemical data show no obvious enrichment of Al-normalized redox-sensitive trace elements V and Cr suggesting that there is no variation in the bottom redox conditions in contrast with other previous studies. The information in this work is an important tool for biogeochemical and biological research projects in the Red Sea coastal lagoons.

Geo-ecological evaluation of mineral, major and trace elemental composition in waste rocks, soils and sediments of a gold mining area and potential associated risks

An investigation has been undertaken on the distribution of mineral, major and trace elements in mine wastes of a gold mining area from geo-ecological perspective and its association with potential human health risks. Mine waste samples consisting of waste rocks, soils and sediments (including borrow pit, waste dump, stockpile and tailings) were collected in the vicinity of Selinsing gold mine in Malaysia. Major elements in terms of their oxide contents such as SiO2, Al2O3, Fe2O3, K2O and MgO were mainly derived from their mineralogical compositions that were dominated by quartz and muscovite (in waste rocks), kaolinite and illite (in soils) and illite and chlorite-serpentine (in mine tailings). Metallic elements (Al, Fe, Mn, Zn, Sr, Cr, Cd, Ni, Cu, Co, and Pb) were found in the range of acceptable values except for metalloid arsenic. Arsenic was found in the range of 1.84–1915 mg/kg (the highest in the waste rocks of stockpile). Geochemical assessment indicated that some locations were classified as extremely contaminated, highly enriched and having high contamination with respect to arsenic according to geo-accumulation index, enrichment factor and contamination factor. In view of ecological perspective, arsenic contamination was noticeable i.e. some samples were classified as having considerable to high potential ecological risk with respect to arsenic, while contamination with regard to all other metals were classified as having low risk. In terms of health aspect, the hazard index as indicated by the lifetime cancer risk for arsenic was found in tolerable range for regulatory purposes. Other metals possess no significant non-carcinogenic or carcinogenic risks both for adults and children. The arsenic concentrations were comparable with other mining-related sites worldwide, e.g. Spain, China, South Korea, Poland and Mongolia among others. Iron, As and Cd in the tailings and discharges from treatment facilities within the mine have been removed by 82.9–94.7%. Overall, this paper has highlighted the geo-ecological importance and implication of mining exploration to avoid ecological damages so as to sustain mining sector without inflicting the environment.

Mineralogical and geochemical characterization of Mo-rich black shales in the Grand Duchy of Luxembourg

“Schistes carton”, Jurassic black shale rocks occurring in the south-western part of the Grand Duchy of Luxembourg, were investigated, based on a combined mineralogical and geochemical approach. The major aim of this study was to understand the lateral and vertical variation in mineralogy, and the distribution of major and trace elements within the different black shale lithologies, as well as in the overlying soils. The mobility of trace metal(loids) in the black shale and in the soil developed upon the black shale was also addressed. The “Schistes carton” bedrock consists mainly of illite and kaolinite, quartz, calcite and pyrite. Framboidal pyrite is found in the clay matrix, while stratiform pyrite lenses are found in calcitic beds or in lag deposits. At a depth of 4.25 m, pyrite is altered to goethite and gypsum. The acidity generated by pyrite oxidation is neutralized by calcite dissolution, resulting in neutral to slightly alkaline pH conditions. The “Shistes Carton” bedrock is characterized by variable concentrations of Ca, S, Cd, Mo and Zn. Compared to the surrounding matrix, the (stratiform) pyrites found in the “Schistes carton” express an enrichment with As, Cd, Pb and Zn, while the lag deposit contained high concentrations of As, Cd, Mn, Zn, and P. Mo concentrations in the bedrock and the soils up to 74 mg/kg were found, which is comparable with Mo concentrations in soils developed on black shales at other locations in the World. Most trace elements are not leached from the shales under the prevailing pH conditions (7–7.5), except Mo, which leaches in concentrations up to 85 μg/l. This study highlights the importance of small and large-scale variations in bedrock composition and its influence on soil geochemistry, which should be taken into account during the development of national and regional guidelines and regulations on soil quality.

Characterisation of Li in the surface film of a corrosion resistant Mg-Li(-Al-Y-Zr) alloy

The surface film formed upon Mg-Li(-Al-Y-Zr) following aqueous immersion and air-exposure was investigated. This alloy (which contains 30.3 at. % Li) possesses a body-centred cubic (bcc) crystal structure and has been reported as being corrosion resistant. It was determined that the principal components of the surface film were Li2CO3 and Mg(OH)2 as characterised by grazing incidence X-ray diffraction (GIXRD). Hexagonal close-packed (hcp) grains near the alloy surface were detected by GIXRD and selected area electron diffraction (SAED). The spatial distribution of Li and Mg in the surface film was characterised by electron energy loss spectroscopy (EELS) and the distribution of other major elements in the alloy was characterised by scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDXS). It was observed that Li was distributed throughout the alloy surface film and with an elevated concentration in the so-called outer layer.

Soil elemental concentrations, geoaccumulation index, non-carcinogenic and carcinogenic risks in functional areas of an informal e-waste recycling area in Accra, Ghana

This study assesses the distribution, contamination and human health risks of major, minor and trace elements in the topsoil and subsoil of two informal e-waste recycling sites in Accra, Ghana. Metal concentrations in Agbogbloshie exceeded the Dutch Soil intervention values with exceedances of 72%, 57%, 57%, 38%, 16%, 2% for Cu, Zn, Pb, Ba, Cd and As respectively. Metal concentrations in Ashaiman exceeded the Dutch Soil intervention values with exceedances of 62%, 57% and 46% for Cu, Zn and Pb respectively. Geoaccumulation indices indicated that the topsoils of the burn area and dismantling areas of Agbogbloshie e-waste recycling site were strongly contaminated by Pb and uncontaminated by Cr, Fe, As and Ba. Lead (Pb) contributed greatly to non-carcinogenic ingestion hazard quotient for residents living near Agbogbloshie and Ashaiman e-waste recycling sites while arsenic (As) presented carcinogenic risks to children from the dismantling area topsoils. Non-carcinogenic risks from ingestion were significant with children being more susceptible to non-carcinogenic ingestion risks than adults. Non-carcinogenic risks from dermal exposure were negligible. Hazard quotients of Pb for children in burn area topsoils and dismantling area topsoils were 7.4–7.6-fold greater than that for adults. The mean geoaccumulation indices values of Pb and Cu indicated extreme contamination of topsoils with these elements. A “novel environmental assessment tool” based on the Agency for Toxic Substances and Disease Registry (ASTDR) total impact points confirmed Pb and Cu as the most toxic elements.

Distribution of trace and major elements in subarctic ecosystem soils: Sources and influence of vegetation

Artic and subarctic environments are particularly sensitive to climate change with a faster warming compared to other latitudes. Vegetation is changing but its role on the biogeochemical cycling is poorly understood. In this study, we evaluated the distribution of trace elements in subarctic soils from different land covers at Abisko, northern Sweden: grassland, moor, broad-leaved forest, and peat bog. Using various multivariate analysis approaches, results indicated a spatial heterogeneity with a strong influence of soil horizon classes considered: lithogenic elements (e.g., Al, Cr, Ti) were accumulated in mineral horizon classes and surface process-influenced elements (e.g., Cd, Cu, Se) in organic horizon classes. Atmospheric influences included contamination by both local mines (e.g., Cu, Fe, Ni) and regional or long-range atmospheric transport (e.g., Cd, Pb, Zn). A non-negative matrix factorization was used to estimate, for each element, the contribution of various sources identified. For the first time, a comparison between geochemical and ecological data was performed to evaluate the influence of vegetation on element distribution. Apart from soil pH that could control dynamics of As, Cu, and Se, two vegetation classes were reported to be correlated to geochemical factors: forbs and shrubs/dwarf shrubs probably due to their annual vs. perennial activities, respectively. Since these are considered as the main vegetation classes that quickly evolve with climate change, we expect to see modifications in trace element biogeochemical cycling in the future.

Geochemistry of Carbonate Rocks in the Early Precambrian and Phanerozoic Metamorphic Complexes of East Siberia, North-West Russia, and Pamirs

Abstract—The geochemical study of carbonate rocks of Early-Precambrian and Phanerozoic metamorphic complexes was carried out and their differences were revealed. The Precambrian marbles and calciphyres were studied in the Оnot Greenstone Belt, Kitoy and Sharyzhalgay granulite complexes of the Prisayan inlier and the Yenisei Group of the Angara–Kan inlier of the Siberian craton, the Belomorian and Lapland Complexes, the North Pechenga Structure, the Sortavala Formation of the Fennoscandian Shield, and the Wakhan Complex of the Badakhshan massif. Phanerozoic marbles and calciphyres were analyzed in the Olkhon, Slyudyanka, and Svyatoi Nos complexes of the Baikal region, Bokson Group and Irkut Formation of the East Sayan, Derbin Complex and Alkhadyr Formation of the Sayan region, Yudin Formation and Panimba–Rybinsk Zone of the Yenisei Ridge, Muzkol Complex of the East Pamirs. As compared to the Phanerozoic rocks, the Precambrian carbonate rocks are enriched in Fe, Mn and depleted in Sr, Ba at a close low level of REE content. The enrichment of Archean protoliths of marbles and calciphyres in Fe and Mn is caused by the predominance of basic and ultrabasic rocks in source areas. As compared to the Phanerozoic carbonates, the Paleoproterozoic carbonate rocks demonstrated a decrease of Fe and Mn and increase of Al, K, Ba, and Sr owing to the contribution of granite-metamorphic layer in the formation of their protoliths. The distribution of major and trace elements in marbles and calciphyres is determined by their modes of occurrence: 1) admixture of Fe, Mn, Ba, Sr, and REE in the isomorphic series of Ca–Mg carbonates; 2) the presence of Na, K, Ba, Sr minerals in marbles; 3) the presence of fine (in marbles) and coarse (calciphyres) fractions of minerals with Fe, Mn Al, Ti, Zr, Cr, V, Ni, S. The paleoreconstruction based on REE behavior in the carbonate rocks revealed the predominant development of intracratonic shallow sea in the Archean and Early-Paleoproterozoic. Open oceans appeared at the turn of 2–1.9 billion years, but the widespread development of carbonate rocks occurred in the Meso-Neoproterozoic and Phanerozoic. The revealed features serve as the basis for age paleoreconstructions of protoliths using petrogeochemical characteristics of carbonate rocks of Precambrian and Phanerozoic metamorphic complexes.

Petrogenesis and geological significance of charnockite in the Yinshan Block of North China Craton

ABSTRACTA comparative study was performed on the petrography, geochemistry and geochronology of charnockite and granulite in the Xiwulanbulang (XWLBL) area, northern margin of the North China Craton, NW China. Inclusions within garnet in the charnockite are used to identify the mineral assemblage in the granulite during peak metamorphism. The formation of charnockite is attributed to the anatectic of the protolith, as a result of granulite-facies metamorphism during the same tectono-thermal event. Anatexis occurred mainly during the post-peak isothermal depressurization stage (granulite and charnockite yield peak P–T conditions of 800–850°C and 1.0–1.2 GPa, and 750°C and 0.9–1.0 GPa, respectively), as inferred from the metamorphic evolution and P–T conditions derived from analyses of metamorphic minerals by electron microprobe (EMP). The garnets in the charnockite were a residual or peritectic mineral facies during anatexis, and the charnockite was the product of crystallization from melt with abundant residual minerals. Charnockite has similar geochemical characteristics to felsic granulite, although it differs in having 1) an uneven distribution of major and trace elements; 2) strong depletions in the large-ion lithophile element Cs, the heat-producing elements U and Th, and the high-field-strength elements Nb, Ta, P and Ti; and 3) both Eu-enriched and Eu-depleted patterns that are characteristic of granite formed by largely in situ anatectic. The geochemical data indicate that the XWLBL charnockite formed in a subduction-related volcanic arc setting. On the basis of our results, combined with geological data on the Neoarchean structural evolution of the Yinshan Block and εHf(t) values of 1.60–7.81, we propose that the anatectic of charnockite was related to slab break-off during mid-ocean-ridge subduction, which resulted in the ascent of mantle magma through the slab window.

The spatial distribution of major and trace elements of surface sediments in the northeastern Beibu Gulf of the South China Sea

A multi-index analysis including grain size, major and trace elements is performed on the surface sediments from the northeastern Beibu Gulf to trace the sources of the sediments and to understand the controlling factors for elements distribution. The mean grain size exhibits a wide variation ranging from 0.09Φ to 8.05Φ with an average value of 5.33Φ. The average contents of major elements descend in an order of c(SiO2)>c(Al2O3)>c(Fe2O3)>c(CaO)>c(MgO)>c(K2O)>c(Na2O)>c(TiO2)>c(P2O5)>c(MnO), while those of trace elements exhibit a descending order of c(Sr)>c(Rb)>c(V)>c(Zn)>c(Cr)>c(Pb)>c(Ni)>c(Cu)>c(As). On the basis of elementary distribution characteristics and statistical analyses, the study area is divided into the four zones: Zone I is located in the northeastern coastal area of the gulf, which receives large amount of fluvial materials from local rivers in Guangxi and Guangdong, China, and the Qiongzhou Strait; Zone II is located in the center of the study area, where surface sediments exhibits a multiple source; Zone III is located in the Qiongzhou Strait, where surface sediments are dominated by materials from the Zhujiang River and Hainan; Zone IV is located in the southwest of the study area, where surface sediments are mainly originated from the Red River and Hainan. The statistical analyses of sediment geochemical characteristics reveal that the grain size, which is mainly influenced by hydrodynamics and mineral composition of terrigenous materials, is the leading factor controlling the elementary distribution. Meanwhile, impacts from anthropogenic activities and marine biogenic process will also be taken into consideration.

Distribution of major and trace elements in the Kovin lignite (Serbia)

A geochemical and mineralogical study was performed on lignite samples from the Upper Miocene Kovin deposit, hosting three coal seams. The Kovin lignite is characterized by high moisture content, medium to high ash yield, medium to high sulphur content and a relatively low gross and net calorific value. The mineralogical composition, and major and trace element contents were determined by X-ray diffraction, scanning electron microscopy with energy dispersive Xray spectroscopy (SEM-EDS) analyses, and inductively coupled plasma optical emission spectrometry (ICP-OES). The most abundant minerals in all lignite samples from the three coal seams are clays (illite/smectite), silicates (quartz, plagioclase), sulphates (gypsum/anhydrite) and carbonate (calcite). The other iron-rich minerals are sulphides, oxides and hydroxides (pyrite, magnetite, haematite, and limonite). In general, mineral matter in the matrix coal consists of illite/ smectite and quartz, while xylite-rich coals, apart from illite/smectite, have a higher content of sulphates and Fe-oxide/hydroxide minerals. The lignite from the Kovin deposit is enriched in As, Cd, Co, Cr, Cu, Ga, Li, Mn, Mo, Ni, Pb, V, Zn, Gd, Tb, Er and Lu in comparison with the Clarke values for brown coals. The statistical analysis of bulk compositional data shows inorganic affinity for the majority of the major and trace elements and possible association with pyrite, illite/ smectite and calcite.

Environmental Research and Geochemical Evaluation of Recent Bottom Sea Sediments North and North –East of Lesvos Island, Greece

An environmental and geochemical investigation of 33 surficial sediments of the continental shelf north and north east of Lesvos Island Greece was undertaken to study the mineralogy and geochemistry of the sediments and understand the distribution and sources of various major and trace elements. Texturally all the sediments contain high amounts of mud and clay indicating a uniform facies at depths between 30m - 300m. The sediments are a mixture of terrigenous components (albite, K-feldspar, muscovite, quartz, illite, amphibole and biogenic components (calcite, Mgcalcite, aragonite). Pyrite and glauconite are ascribed to diagenesis. There are four distinctive groups of elements each of which includes related elements, derived from different natural sources on land or in the marine basin. The first group (Ca, Sr) reflects the biogenous carbonate fraction and is negatively correlated against every other element determined. A second (Si, Al, Fe, Na, K, Ti, Ba and Zr) group reflects the aluminosilicate minerals derived from the alteration of volcanic rocks, and a third group (Mg, Ni, Cr, C and Zn) reflects the aluminosilicate minerals derived from the alteration of ultrabasic rocks (peridotites) and the organic carbon. The group of Fe, Mn, Zn and Y is a diagenetic association reflecting the distribution of these elements with pyrite. The association of Cu with Zn reflects a mineralization control in the sediment area. Finally, La and Ce are associated with the K-bearing minerals, while P is related to K and Fe-finegrained minerals. The concentrations of heavy metals in the sediments are normal comparing to the contents of other AEGEAN SEA sediments and are due to natural lithogenic sources.

Hydrothermal alteration of sediments in the high-temperature reaction zone at Central Hill of Escanaba Trough, Gorda Ridge

In sediments from Holes ODP 1038A and 1038H, drilled near the hot springs at Central Hill, Escanaba Trough (Gorda Ridge), redistribution of major elements occurs during the water-rock interaction. Contents of Si, Fe, Mg, Ca, Na and K have changed in altered sediments. In this process, an increase/decrease in contents of major elements in altered sediments shows a decrease/increase in their contents in fluids. The irregular distribution of major elements in altered sediments resembles a layer pie, which reflects the existence of lateral flows of hydrothermal fluids.

Environmental significance and geochemical speciation of trace elements in Lower Baram River sediments

The geochemistry and distribution of major, trace and rare earth elements (REE's) was studied in the surface sediments of the Lower Baram River during two seasons: the Monsoon (MON) and Post – monsoon (POM). The major geochemical processes controlling the distribution and mobility of major, trace and REE's in the Lower Baram River surface sediments was revealed through factor analysis. The risk assessment of major and trace element levels was studied at three specific levels; i.e. the enrichment level [Contamination Factor (Cf), with the geo-accumulation index (Igeo)], the availability level [metals bound to different fractions, risk assessment code (RAC)], and the biological toxicity level [effect range low (ERL) and effect range medium (ERM)]. The results of all the indices indicate that Cu is the element of concern in the Lower Baram River sediments. The geochemical fractionation of major and trace elements were studied through sequential extraction and the results indicated a higher concentration of Mn in the exchangeable fraction. The element of concern, Cu, was found to be highly associated in the organic bound (F4) fraction during both seasons and a change in the redox, possibly due to storms or dredging activities may stimulate the release of Cu into the overlying waters of the Lower Baram River.

Geochemistry and isotopic study of southern Bay of Bengal sediments: Implications for provenance and paleoenvironment during the middle Miocene

The Bay of Bengal (BoB), the largest bay in the world, is known to receive large amounts of fresh water and suspended particulate matter from different sources. The sediments deposited in the bay serve as a repository for paleoenviromental reconstruction studies. The Miocene Epoch is an important interval in geologic time as it is marked by major climatic events that controlled ocean productivity, redox conditions and provenance of sediments. However, limited work has been carried out to establish paleoenviromental changes and provenance of sediments during the Miocene. Here we present detailed geochemical and radiogenic (Sr, Nd) isotopic results from predominantly middle Miocene sediments of Ocean Drilling Program (ODP) Site 758A, located in the southern BoB (Lat. 5 °23′N, Long. 90°21′E; water depth 2925 m), to understand paleoredox conditions, paleoproductivity and provenance. The results suggest that these sediments are strongly linked to climatically modulated surface processes that affected the region.The distribution of redox-sensitive element proxies (U, V, Cr) at interval ~17–8 Ma points to an oxic depositional environment. The major, trace and rare earth elements distribution supports prevalence of the Indian summer monsoon (ISM) at ~12–10 Ma. Productivity proxies (Babio, Porg) show a decreasing trend during colder events (East Antarctic Ice Sheet expansion – EAIS and advent of late Miocene cooling – LMC events). The trace and rare earth element concentrations are generally low, except at intervals where glass shards were found. The 87Sr/86Sr and εNd(0) values indicate that the sediments belong to the High Himalayan sedimentary series (HHSS) throughout the middle Miocene. However, prior to initiation of the ISM, these sediments underwent meteoric alteration in the lowlands before deposition in the BoB. Our records suggest that sediments at ODP Site 758A may have been introduced into the BoB through the Irrawaddy-Yarlung-Tsangpo drainage system during the entire period of this study. The Irrawaddy-Yarlung-Tsangpo system drained the Indus-Tsangpo Suture zone, southern Tibet, the eastern Himalayas and the Arakan coast before debouching in the BoB.