An Upper Carboniferous tonstein of volcanic origin

Previous work on the mineralogy of the volcanic supra-Wyrley Yard tonstein is extended to include the opaque minerals. This has led to a better understanding of the major and trace element geochemistry of the tonstein. The complete mineral assemblage is kaolinite (dominant) with minor quartz, K-mica, zircon, apatite, pyrite, sphalerite, galena, rutile, dolomite, barytes, goethite and organic matter. Information on element location in the tonstein has been obtained by using autoradiography and fission track radiography, the electron probe and by analysing separated fractions with an optical spectrograph. This has enabled the diagenetic history of individual elements to be determined, and the composition of the tonstein to be compared with igneous material. The high concentration of Th, U, Pb, Sn, Bi, Y, Be and B in the tonstein, and the low concentration of Ti, Cr, V, Ni, Cu and Co is indicative of an acidic ash. A source in the Armorican orogenic belt is postulated, based on the contrast with the basaltic Carboniferous volcanism and also the high concentrations of Sn, Pb and Zn.     

滇东黔西晚二叠世煤系中火山灰蚀变粘土岩的元素地球化学特征

对滇东?黔西晚二叠世煤系中同沉积火山灰蚀变粘土岩夹矸?正常沉积粘土岩和煤层共采46件样品,用多种仪器分析方法测定微量元素30余种?研究表明,煤系各层段中赋存的夹矸是由性质不同的火山灰沉积蚀变形成的,各层夹矸的微量元素含量及组合关系各有特点并在较大范围内保持良好的稳定性,可用于判定层位;正常沉积粘土岩与夹矸的原始物质性质不同,其微量元素含量和组合面貌各有自己特定的分布范围,两者易于区别?     

NS935钻孔沉积物不活泼微量元素记录与陆源输入变化探讨

探讨了NS93－5钻孔沉积物的部分高场强元素和大离子亲石元素的含量变化，结果表明，Ti、Rb、Ga、Y、Zr、Nb、Cs、Hf、Ta、Th和稀土元素（REE）相互间含量变化具有很好的相关关系，反映这些元素均基本来自碎屑组分。经Ti和Sc标准化后这些元素含量的变化，以及Zr/Y等特征元素比值和Ge异常指数Ce/Ce、Eu异常指数Eu/Eu的变化，均反映出碎屑输入的通量或者组成的变化，例如火山灰的富集。其中一些变化与气候变化有关，可能反映周边陆壳的风化强度的波动。NS93－5钻孔沉积物的不活泼元素记录，可提供反映输入陆壳物源区的环境演变证据。     

中国几个主要煤产地煤中微量元素特征

采用原煤直接溶样和使用ＩＣＰ－ＭＳ方法对我国平朔,大同,六盘水和唐山几个主要煤产地煤的微是元素进行了检测,报道了这几个主要煤产地煤中５１种微量元素含量,并对基含量特征进行了讨论,研究表明,与海水有关的过渡相沉积环境中的煤的Ｌｉ,Ｂｅ,Ｓｃ,Ｔｉ,Ｖ,Ｚｎ,Ｃｕ,Ｇａ,Ａｓ,Ｓｅ,Ｙ,Ｚｒ,Ｓｎ,Ｐｂ,Ｔｈ,Ｕ和稀土元素含量相对较高,内陆湖泊沉积环境中的煤的微量元素含量相对较低。     

Signatures of Holocene Hydrological Processes from Sedimentary Archives in Southwestern India: Case Studies from Wetlands of Kerala Coast

This study investigates the abundance, modes of occurrence and origin of major and trace elements in the Jurassic Tazareh coal in the northern Iran. A total of 27 samples (coal, coaly shale and siltstones) were collected and analyzed for trace elements by neutron activation analysis (INAA) and for major elements by X-ray fluorescence. The abundance of these elements is discussed in relation to local geological conditions. The correlation between the various elements is demonstrated through scatter diagrams and the possible genetic associations are discussed. Most elements (Al, Si, Na, K, Fe, Mg, Ti, Ba, Cr and REE) are positively correlated with ash yields that are inorganically associated. Bromine displays statistically signiûcant negative correlations with ash yield. The Ca, Zn, Se, As and Co present mixed modes of occurrence in the coal and probably associate with organic fraction.     

陕西商州地区丹凤变质火山岩的地球化学特征

陕西商州地区丹凤变质火山岩具有洋内岛弧火山岩地球化学特征,它们是分别来自不同源区的拉斑玄武和钙碱性2个系列共存的一套变质火山岩。其Th/Ta比值高及Ni、Ta、Ti、Y和Yb含量低,表明岩石受到消减带组分的影响。种种证据表明,丹凤变质火山岩是早古生代华北地块南缘消减带之上洋内岛弧环境的产物。     

Trace element geochemistry of altered volcanic ash layers (tonsteins) in Late Permian coal-bearing formations of eastern Yunnan and western Guizhou Provinces, China

Trace element compositions were determined (by instrumental neutron activation analysis; INAA) in 30 samples of synsedimentary volcanic ash-derived tonsteins and detrital claystones from coal seams within the late Permian coal-bearing formation of eastern Yunnan and western Guizhou Provinces, China. The characteristics of trace-element geochemistry in the tonsteins can be distinguished from those of detrital claystones because of the former's unique volcanic-ash origin. The detrital claystones are characterized by their relatively high content of V, Ti, Sc, Cr, Co and Ni, relatively low content of Th and U, Th/U ratio, and small negative Eu anomaly (Eu/Eu* 0.63–0.93). Overall, these trace element characteristics are consistent with a mafic source similar to the composition of basalt rocks in the erosional region on the western edge of the study area. In contrast, the tonsteins are low in V, Ti, Sc, Cr, Co and Ni contents and have a high Th/U ratio with a distinct negative Eu anomaly (Eu/Eu* normally in the range of 0.2–0.4), consistent with a silicic magmatic source.Within the group of tonsteins, those from the lower section (P_2.1) of the coal-bearing formation are relatively high in Ti, Zr, Hf, Nb, Ta and rare earth elements (REE), as compared to those from the middle and upper sections (P_2.2+3). In trace-element discrimination diagrams (scatter plots) of Hf–Ta, Ti–Ta, Ti–V, Hf–Sc, Lu–Hf and Lu–Th, tonsteins from the P_2.1 horizon always fall in isolated distribution areas, separate from the tonsteins of the P_2.2+3 horizon. These results suggest that the source materials of tonsteins from the two separate horizons were probably derived from volcanic ash falls of two distinctly different natures. Based on a comparison of the concentrations and assemblages of trace elements between various magmatic rocks, the source materials of tonsteins from P_2.1 horizon were mostly composed of calc-alkalic, silica-poor volcanic ash (similar to rhyodacitic magma), whereas those from P_2.2+3 were apparently more siliceous and K-rich (rhyolitic magma). Thus, tonsteins from the two different horizons are characterized by unique geochemical properties, which remain constant over a wide lateral extent. Integration of trace-elemental compositions with mineralogical and textural observations makes possible the establishment of tonstein stratigraphy, thus, facilitating more precise and reliable coal-seam correlations.     

Mineralogical and geochemical evolution of the Bidgol bauxite deposit,Zagros Mountain Belt,Iran: Implications for ore genesis,rare earth elements fractionation and parental affinity

The present study focuses on the Late Cretaceous Bidgol bauxite deposit in the Zagros Simply Fold Belt, SW Iran. The orebody is located in the eroded major NW–SE trending Koh-e-Hosseyn anticline and hosted as discontinuous stratified layers and lenses within the upper member of the Cenomanian–Turonian Sarvak Formation. Detailed mineralogical analysis reveals that diaspore, hematite, goethite, anatase, clinochlore, chamosite, and calcite are the major mineral components accompanied by minor amounts of detrital and REE-bearing minerals such as rutile, zircon and parisite. The ore texture suggest that the bauxite material has an authigenic origin but in some parts it has been transported short distances from a primary in situ environment and redeposited in karstic depressions. The spheroidal pisolites of the Bidgol bauxite formed under conditions of low water activity, favouring the formation of large diaspore cores and a single dry-to-wet climatic fluctuation. The mass change calculations relative to the immobile element Ti show that elements such as Si, Fe, Mg, K, Na and Sr are leached out of the weathered system; Al, Ni, Zr, Ga, Cr and Ba are concentrated in the residual system; and Hf, Ta, Co, Rb, Cs, Be, and U are relatively immobile during the bauxitisation processes. The Nb, Th, Y, V, Sc, Sn and ΣREE are relatively immobile in the initial stage of bauxitisation processes in the bauxite ores, but were slightly mobile at the later stage of bauxitisation. Geochemical data reveal progressive enrichment of the REE and intense LREE/HREE fractionation toward the lower parts of the bauxite profile. Cerium behaves differently from the other REEs (especially LREE) and show positive anomalies in the upper horizons that gradually become negative in the deeper parts of the profile. The distribution and fractionation of trace elements and REEs during the bauxitisation process in the Bidgol deposit are mainly controlled by the presence of REE-bearing minerals, fluctuations in soil solution pH, REE ionization potential and the presence of bicarbonates or organic matter. Geochemical analyses confirm a protolith contribution from the bedrock argillaceous limestone and suggest that the source material for the Bidgol bauxite was provided from a siliciclastic material derived from a continental margin. The mid-Turonian uplift led to the formation of karstic topography, rubbly breccia and a layer of ferruginous–argillaceous debris that was affected by lateritic weathering under humid tropical climate. Subsequently, mobile elements are removed from the profiles, while Al, Fe and Ti are enriched, resulting in the formation of the pristine bauxite materials. When the platform subsided into the water again, the pristine bauxitic materials were partly converted to bauxite. During the exposure of bauxite orebodies on the limbs and crests of anticlines and subsequent eroding and accumulation in the karstic depressions during folding and faulting in Oligocene–Miocene, important factors such as intensity of the weathering, drainage and floating flow may have improved the qualities of the bauxite ores.     

火山岩风化过程中难熔元素的活动性研究——以广西凭祥英安岩风化剖面为例

对广西凭祥叫弄英安岩风化剖面中6个难熔元素的活动性进行了研究。结果表明，Ti,Nb和Ta 3种元素在整个风化成土过程中基本上保持了它们的不活动性。Zr,Hf和Th在风化的初期阶段基本上保持不活动，而在风化中期表现出一定的富集，风化高级阶段则有明显的富集。Th的富集可能与风化壳表层（已剥蚀）淋溶出来的Th向下迁移过程中被氧化铁吸附和形成磷酸盐矿物有关，而Zr的富集则可能与淋溶出来的Zr与SiO2或磷酸盐结合形成某种硅酸盐矿物和磷酸盐矿物有关，具体富集原因还需作进一步的研究。     

新汶 肥城太原组火山灰蚀变高岭石夹矸化学成分研究

在前人研究成果的基础上,从化学成分特征这一角度,对山东新汶、肥城煤田太原组高岭石粘土岩夹矸进行了主常量元素、微量元素及稀土元素分析。结果不仅进一步证明了,研究区高岭石粘土岩夹矸确由火山灰降落于泥炭沼泽或泥炭坪环境后经蚀变而成,而且通过对微量及稀土元素分析结果的研究,提出该层夹矸的形成可能受到不同期次及不同性质的火山物质影响的新见解,为含煤岩系中火山事件沉积的研究提供了新思路。      

Iron colloids/organic matter associated transport of major and trace elements in small boreal rivers and their estuaries (NW Russia)

The chemical status of major and trace elements (TE) in various boreal small rivers and watershed has been investigated along a 1500-km transect of NW Russia. Samples were filtered in the field through a progressively decreasing pore size (5, 0.8 and 0.22 μm; 100, 10, and 1 kD) using a frontal filtration technique. All major and trace elements and organic carbon (OC) were measured in filtrates and ultrafiltrates. Most rivers exhibit high concentration of dissolved iron (0.2–4 mg/l), OC (10–30 mg/l) and significant amounts of trace elements usually considered as immobile in weathering processes (Ti, Zr, Th, Al, Ga, Y, REE, V, Pb). In (ultra)filtrates, Fe and OC are poorly correlated: iron concentration gradually decreases upon filtration from 5 μm to 1 kD whereas the major part of OC is concentrated in the <1–10 kD fraction. This reveals the presence of two pools of colloids composed of organic-rich and Fe-rich particles. According to their behavior during filtration and association with these two types of colloids, three groups of elements can be distinguished: (i) species that are not affected by ultrafiltration and are present in the form of true dissolved inorganic species (Ca, Mg, Li, Na, K, Sr, Ba, Rb, Cs, Si, B, As, Sb, Mo) or weak organic complexes (Ca, Mg, Sr, Ba), (ii) elements present in the fraction smaller than 1–10 kD prone to form inorganic or organic complexes (Mn, Co, Ni, Zn, Cu, Cd, and, for some rivers, Pb, Cr, Y, HREE, U), and (iii) elements strongly associated with colloidal iron in all ultrafiltrates (P, Al, Ga, REE, Pb, V, Cr, W, Ti, Ge, Zr, Th, U). Based on size fractionation results and taking into account the nominal pore size for membranes, an estimation of the effective surface area of Fe colloids was performed. Although the total amount of available surface sites on iron colloids (i.e., 1–10 μM) is enough to accommodate the nanomolar concentrations of dissolved trace elements, very poor correlation between TE and surface sites concentrations was observed in filtrates and ultrafiltrates. This strongly suggests a preferential transport of TE as coprecipitates with iron oxy(hydr)oxides. These colloids can be formed on redox boundaries by precipitation of Fe(III) from inflowing Fe(II)/TE-rich anoxic ground waters when they meet well-oxygenated surface waters. Dissolved organic matter stabilizes these colloids and prevents their aggregation and coagulation. Estuarine behavior of several trace elements was studied for two small iron- and organic-rich rivers. While Si, Sr, Ba, Rb, and Cs show a clear conservative behavior during mixing of freshwaters with the White sea, Al, Pb and REE are scavenged with iron during coagulation of Fe hydroxide colloids.     

Occurrence modes and cleaning potential of sulfur and some trace elements in a high-sulfur coal from Pu’an coalfield,SW Guizhou,China

In this research, a float-sink test was applied to a Late Permian high-sulfur coal collected from Pu’an coalfield, Southwest in Guizhou, China. To investigate the occurrence modes and the mobility of various trace elements, as well as the cleaning potential of some harmful elements in density separation, coal quality parameters and concentrations of 46 elements of 7 density fractionated samples were determined and statistically analyzed. Results show that larger size and higher density fractions have higher total sulfur content and ash yield than the smaller and lower ones. In fact, most (74.39 %) of the total sulfur occurs in the inorganic matter. Affinity and correlation analysis show that Mo and Ni have apparently strong organic affinity, whereas Rh, Cs, Sr, Co, Nb, Zr, V, Ga, Sc, Be, Ge, Hf, Th, U, Ag, As, In, Cu, Cd, Ta, Li, TI, and Ba are mostly in the heavy fractions. Rare earth element (REE) patterns for the seven density fractions present good uniformity and show that they are of right-inclined pattern type characterized by Light REE (LREE, La ~ Eu) enrichment relative to Heavy REE (HREE, Gd ~ Lu) and pronounced negative δ _Eu anomalies. This suggests that REE was mainly derived from basalt-weathered materials. LRREE/HREE ratio variations reveal that LREE has stronger affinity with the organic matter relative to the HREE, while high LRREE/HREE in heavy fractions may be related to pyrite. Supposing the maximum sulfur content of the cleaned coal is 1.00 %, the theoretical removal ratios of Co, TI, and Ba are as high as 90.94, 93.73, and 92.29 %, respectively, while those of As, Ni and Mo are only 56.33, 48.85, and 45.05 %, respectively. As these figures change with different maximum sulfur contents required for the cleaned coal, not only the decrease of sulfur and ash in coal washing, but also the mobility of some harmful trace elements should be taken into consideration.     

Kinetically induced compositional zoning in titanite: implications for accessory-phase/melt partitioning of trace elements

Usually it is assumed that the partitioning of trace elements into titanite in metaluminous granitoid plutonic environments takes place under equilibrium conditions and that compositional zoning is due solely to progressive changes in melt chemistry and/or mineral/melt partition coefficients. Examination of titanites from a variety of Caledonian metaluminous granitoids and related rocks has revealed that sector zoning is present, indicating disequilibrium partitioning. The sector zoning in titanites is defined principally by the distribution of the rare earth elements (REE), Y, Nb, Al and Fe. The REE, Y and Nb preferentially occur within the minor (100) sectors relative to the morphologically important (111) sectors. The reverse is true of Al and Fe which preferentially occur within the (111) sectors relative to the (100) sectors. The patterns of sector zoning are complicated by the fact that the relative growth rates of the various crystal faces fluctuated during growth. Sector zoning indicates that crystal-interface kinetics are responsible for the observed patterns of element partitioning. It is concluded that differences in the lateral-layerspreading rates of crystal faces bring about the sector zoning. The results have implications for the use of trace element partition coefficients in the modelling of fractionation processes.     

Trace element degassing and enrichment in the eruptive plume of the 2000 eruption of Hekla volcano, Iceland

During its last eruption in February 2000, Hekla volcano (Iceland) emitted a sub-Plinian plume that was condensed and scavenged down to the ground by heavy snowstorms, offering the unique opportunity to study the chemistry of the gaseous plume released during highly explosive eruptions. In this paper, we present results on trace element and minor volatile species (sulfates, chlorides, and fluorides) concentrations in snow samples collected shortly after the beginning of the eruption. The goal of this study is to better constrain the degassing and mobility of trace elements in gaseous emissions. Trace element volatility at Hekla is quantified by means of enrichment factors (EF) relative to Be. Well-known volatile trace elements (e.g., transition metals, heavy metals, and metalloids) are considerably enriched in the volcanic plume of Hekla. Their abundances are governed by the primary magmatic degassing of sulfate and/or halide compounds, which are gaseous at magmatic temperature. Their volatility is, however, slightly lower than in basaltic systems, most likely because of the lower magma temperature and higher magma viscosity at Hekla. More surprisingly, refractory elements (e.g., REE, Th, Ba, and Y) are also significantly enriched in the eruptive plume of Hekla where their apparent volatility is two orders of magnitude higher than in mafic systems. In addition, REE patterns normalized to the Hekla 2000 lava composition show a significant enrichment of HREE over LREE, suggesting the presence of REE fluorides in the volcanic plume. Such enrichments in the most refractory elements and REE fractionation are difficult to reconcile with primary degassing processes, since REE fluorides are not gaseous at magma temperature. REE enrichments at Hekla could be attributed to incongruent dissolution of tephra grains at low temperature by F-rich volcanic gases and aerosols within the eruptive plume. This view is supported by both leaching experiments performed on Hekla tephra and thermodynamic considerations on REE mobility in hydrothermal fluids and modeling of glass dissolution in F-rich aqueous solutions. Tephra dissolution may also explain the observed enrichments in other refractory elements (e.g., Th, Y, and Ba) and could contribute to the degassing mass balance of some volatile trace elements, provided they are mobile in F-rich fluids. It thus appears that both primary magmatic degassing and secondary tephra dissolution processes govern the chemistry of eruptive plumes released during explosive eruptions.     

Trace elements in the Goze Delchev coal deposit, Bulgaria

The geochemistry of trace elements in the underground and open-pit mine of the Goze Delchev subbituminous coal deposit have been studied. The coals in both mines are highly enriched in W, Ge and Be, and at less extent in As, Mn and Y as compared with the world-wide Clarkes for subbituminous coals. Ni and Ti are also enhanced in the underground coals, and Zr, Cr and Mo in the open-pit mine coals.Characteristic for the trace element contents in the deposit is a regular variation with depth. The following patterns were distinguished for profile I: a — the element content decreases from the bottom to the top of the bed paralleling ash distribution (Fe, Co, As, Sb, V, Y, Mo, Cs, REE, Hf, Ta, Th, P and Au); b — Ge and W are enriched in the near-bottom and near-top coals; c — in the middle part of the bed the content of K and Rb is maximal, while that of U is slightly enriched; d — Ba content decreases from the top to the bottom of the bed. In profile II, W and Be contents decrease from the bottom to the top. The near-bottom, and especially the near-roof samples of profile IV are highly enriched in Ge, while for W the highest is the content of the near-bottom sample.Ge, Be, As, Mn, Cl and Br are mainly organically associated. The organic affiliation is still strong for Co, B, Sr, Ba, Sb, U, Th, Mo, La, Ce, Sm, Tb and Yb in the underground coals, and Fe, Co, Na, W, Sr, Y and Ag in the coals from the open-pit mine. K, Rb, Ti, Zr, Hf and Ta are of dominant inorganic affinity. The chalcophile and siderophile elements correlate positively with Fe and each other and may be bound partly with pyrite or other sulphides and iron containing minerals.Compared statistically by the t-criteria, the elements Na, Li, Cu, Zn, Pb, Cr, Ni, Co, Mo, Fe and Be are of higher content in the open-pit mine. Tungsten is the only element of higher concentration in the underground mine. The contents of Ge, As, Sr, V, Mn, Y, Zr and P are not statistically different in both mines.It was supposed that there were multiple sources of the trace elements in the deposit. The source of the highly enriched elements (W, Ge, Be, and As) most probably were the thermal waters in the source area. The contemporary mineral springs are of high content of these elements. Another source were the hosting Mesta volcanic rocks, which are enriched in Sb, Mo, Hf, U, Th, As, Li and Rb. Some of the volcanics were hydrothermally altered and enriched or depleted of many elements. Thus, the hydrothermal solutions were also suppliers of elements for the coals. It is obvious that the contents, distribution and paragenesis, of the trace elements in both Goze Delchev coals reflect the geochemical specialization of the source area, including rocks, paleo- and contemporary thermal waters.     

辽宁北票地区煤中微量元素研究

对辽宁北票地区煤中微量元素进行了研究 ,将研究区煤中微量元素的平均质量分数与世界范围煤的微量元素的平均质量分数进行比较 ,发现北票煤中的Cr、Co、Ni、As、Sr、Y、Zr、Ba、Ta、Sc具有较高的富集 ,而Sn、U具有较低的富集 ,这种差异可能主要与聚煤区域的地球化学背景有关。计算了微量元素之间的相关系数 ,得出北票地区煤中稀土元素总量较世界范围稀土元素总量的平均值偏高 ,且煤中稀土元素分布模式十分相似 ,表明在成煤期间陆源物质供应相对稳定。煤中矿物主要为高岭石、石英及方解石及少量的伊利石 ,并对其中的地质成因进行了初步解释。     

A geochemical and mineralogical investigation of some British and other European tonsteins

The volcanic origin of a number of major tonstein horizons has been established from mineralogical compositions and from trace elements that are quantitatively retained during diagenesis. Discriminant function analysis using the variables Ti/Al, Cr/Al, Zr/Al and Ni/Al allows the tonsteins to be classified according to original composition. Two main groups are recognized amongst the British tonsteins. Those formed from acid volcanic ash are comparable in composition with French and German tonsteins and a common source is postulated, whereas tonsteins formed from basic volcanic ash contain variable amounts of detrital sediment and are thought to originate from local eruptions. Possible lateral equivalents between tonstein horizons in Britain and elsewhere in Europe are suggested.     

Characteristics of Coal Ashes in Yanzhou Mining District and Distribution of Trace Elements in Them

In the process of combustion of coal organic and inorganic materials in it will undergo a complex variation.Part of thew will become volatiles and,together with coal smoke,enter into atmosphere,some will remain in micro-particulates such as ash and dust and find their way into atmosphere in the form of solid particles,and the rest will be retained in ash and slag.Coal ashes are the residues of organic and inorganic substances in coal left after coal combustion and the compostition of coal ashes in dependent on that of minerals and organic matter in coal.This paper deals with the chemical composition of coal ashes,the distribution of trace elements in them and their petrological characteristics,and also studies the relationship between the yield of coal ashes and the distribution of trace elements.In addition,a preliminary study in also undertaken on the factors that affect the chemical composition of coal ashes.As viewed from the analyses of coal ash samples collected from the Yanzhou mining district,it can be seen clearly that coal ashes from the region studied are composed chiefly of crystalline materials,glassy materials and uncombusted organic matter and the major chemical compositions are SiO2,Al2O3,Fe2O3,and CaO,as well as minor amounts of SO3,PWO5,Na2O,K2O and TiO2.During the combustion of coal,its trace elements will be redistributed and most of them are enriched in coal ashes.At the same time,the concentrations of the trace elements in flying ash are much higher than those of bottom ash,i.e.,with decreasing particle-size of coal ashes their concentrations will become higher and higher.So the contents of trace elements are negatively proportional to the particle-size of coal ashes.There has been found a positive correlation between the trace elements Th.V.Zn,Cu and Pb and the yield of coal ashes while a negative correlation between Cl and the yield of coal ashes.     

Concentration and association of minor and trace elements in Mukah coal from Sarawak, Malaysia, with emphasis on the potentially hazardous trace elements

The ash yield and concentrations of twenty-four minor and trace elements, including twelve potentially hazardous trace elements were determined in Mukah coal from Sarawak, Malaysia. Comparisons made to the Clarke values show that Mukah coal is depleted in Ag, Ba, Be, Cd, Co, Mn, Ni, Se, U, and V. On the other hand, it is enriched in As, Cr, Cu, Pb, Sb, Th, and Zn. Among the trace elements studied, V and Ba are associated predominantly with the clay minerals. Manganese, Cr, Cu, Th, and Ni are mostly bound within the aluminosilicate, sulphide and/or carbonate minerals in varying proportions, though a portion of these elements are also organically bound. Arsenic, Pb and Sb are mostly organically bound, though some of these elements are also associated with the sulphide minerals. Zinc is associated with both the organic and inorganic contents of the coal. Among the potentially hazardous trace elements, Be, Cd, Co, Mn, Ni, Se, and U may be of little or no health and environmental concerns, whereas As, Cr, Pb, Sb and Th require further examination for their potential health and environmental concerns. Of particular concern are the elements As, Pb and Sb, which are mostly organically bound and hence cannot be removed by physical cleaning technologies. They escape during coal combustion, either released as vapours to the atmosphere or are adsorbed onto the fine fly ash particles.     

Rare earth element sources and modification in the Lower Kittanning coal bed, Pennsylvania: implications for the origin of coal mineral matter and rare earth element exposure in underground mines

In this study, we examine the variations in rare earth elements (REE) from the Lower Kittanning coal bed of eastern Ohio and western Pennsylvania, USA, in an attempt to understand the factors that control mineral matter deposition and modification in coal, and to evaluate possible REE mixed exposure hazards facing underground mine workers. The results of this study suggest that the Lower Kittanning coal mineral matter is derived primarily from a clastic source similar to that of the shale overburden. While highly charged cations like silicon, aluminum, and titanium remained relatively immobile within the coal mineral matter, iron (primarily as pyrite) was added from nonclastic sources, either during deposition of the coal mire vegetation or subsequent to burial. Other mobile cations (e.g., alkali and alkaline earth elements) appear to have been added to and/or leached from the originally deposited clastic mineral matter. Most of the sulfur in the Lower Kittanning coal bed is bound as FeS₂ in the mineral matter, but a majority of samples contain a small excess of S that is most likely organically bound.In general, the total rare earth element content (TREE) in coal ash is greater than that in the shale overburden. If the primary source of mineral matter is the same as that for the overlying shale, then REE must have been enriched in the coal mineral matter subsequent to deposition. The total rare earth element content of Lower Kittanning coals correlates strongly with Si concentration ([TREE]≈0.0024 [Si]), which provides a threshold for evaluating possible mixed exposure health effects. Chondrite-normalized REE patterns reveal a shale-like light rare earth element (LREE) enrichment for the coal, similar to that of the shale overburden, again suggesting a primarily clastic REE source. However, when normalized to the shale overburden, most of the coal ash samples display a small but distinct heavy rare earth element (HREE) enrichment. We surmise that the HREE were added and/or preferentially retained during epigenesis, possibly associated with groundwater flow through the coal unit, but not necessarily in close association with the addition of iron. At least some of the “excess” HREE could be organically bound within the Lower Kittanning coal.