Hydrogeochemical processes of migration of sulfur and iron sulfides in fuel shales

Local hydrogeochemical regime of the Kashpirian bituminous shales is conducive to a significant mobilization of iron sulfide, e.g. by oxygen or by aggressive carbon dioxide, and to migration of iron in subsurface drainage, “downstream,” as well as to its accumulations a few hundred meters away from its source. Such accumulations may be taken as prospecting indications of the shales, under certain conditions. – IGR Staff.     

Thermal magnetic susceptibility data on natural iron sulfides of northeastern Russia

Dependences of magnetic susceptibility (MS) on the temperature of natural iron sulfide samples (pyrite, marcasite, greigite, chalcopyrite, arsenopyrite, pyrrhotite) from the deposits of northeastern Russia were studied. The thermal MS curves for pyrite and marcasite are the same: On heating, MS increases at 420–450 °C, and unstable magnetite (maghemite) and monoclinic pyrrhotite with a well-defined Hopkinson peak are produced. In oxygen-free media with carbon or nitrogen, magnetite formation is weak, whereas pyrrhotite generation is more significant. The heating curves for chalcopyrite are similar to those for pyrite. They show an increase in MS at the same temperatures (420–450 °C). However, stable magnetite is produced, whereas monoclinic pyrrhotite is absent. In contrast to that in pyrite, marcasite, and chalcopyrite, magnetite formation in arsenopyrite begins at > 500 °C. Arsenopyrite cooling is accompanied by the formation of magnetite (S-rich arsenopyrite) or maghemite (As-rich arsenopyrite) with a dramatic increase in MS. Arsenopyrite with an increased S content is characterized by insignificant pyrrhotite formation. Greigite is marked by a decrease in MS on the heating curves at 360–420 °C with the formation of unstable cation-deficient magnetite.Monoclinic pyrrhotite is characterized by a decrease in MS at ～ 320 °C, and hexagonal pyrrhotite, by a transition to a ferrimagnetic state at 210–260 °C. The addition of organic matter to monoclinic pyrrhotite stimulates the formation of hexagonal pyrrhotite, which transforms back into monoclinic pyrrhotite on repeated heating. The oxidation products of sulfides (greigite, chalcopyrite) show an increase in MS at 240–250 °C owing to lepidocrocite.     

印尼苏拉群岛西部某区铁矿石中锌的赋存状态研究

通过光学显微镜、X射线衍射及微区能谱分析等多种手段对研究区铁矿石中锌的赋存状态进行研究,查明铁矿石中的锌主要以独立矿物(闪锌矿和菱锌矿)及类质同象的形式存在。其中,锌在原生铁矿石中以闪锌矿为主要载体矿物。综合研究发现,原生含硫铁矿石,因锌的主体化学相态为硫化物相,岩矿鉴定表明其矿物相为闪锌矿,故如果锌含量达到综合利用水平,则具有工业利用价值。建议按照铁矿石伴生硫的有关评价指标单独划分块段,选矿时应充分考虑进一步浮选获得闪锌矿精矿产品,注重闪锌矿的回收利用。     

Radon hazards associated with outcrops of Ohio Shale in Ohio

The indoor (basement) radon concentrations and the uranium, organic carbon, and radon contents of samples from the underlying Ohio Shale (Upper Devonian) were investigated in six approximately 100 square kilometer areas of Ashtabula, Cuyahoga, Erie-Huron, Franklin, Pike, and Logan counties. The thickness and lithology of the sediment overburden above the Ohio Shale in these areas also was investigated.Results show that the amount of radon gas emanating from the Ohio Shale is a direct function of the uranium concentration in this geologic unit and that the uranium itself is ultimately controlled by the amount of organic matter. Uranium, organic matter (as measured by total organic carbon), and radon in the Ohio Shale outcrops all increase in a westward direction across Ohio. Similarly, the indoor radon concentration in houses increases from east to west across the state.Where the average thickness of the sediment overburden exceeds 27 m (Franklin and Logan counties), much of the radon in houses may be derived from Ohio Shale clasts in the glacial till. In other areas where the average overburden thickness is 6 m or less (Ashtabula, Cuyahoga, Erie-Huron, and Pike counties), the indoor radon levels appear to be directly controlled by emanations from the underlying Ohio Shale bedrock.     

Ion activity products of iron sulfides in groundwaters: Implications from the Choshui fan-delta, Western Taiwan

Precipitation of iron sulfides is an important process in groundwater geochemistry because it reduces iron mobility in anaerobic aquifers. Iron sulfides occur in various allotropic forms such as amorphous FeS and pyrite, and their solubility products differ up to 13 orders of magnitude. However, few data for ion activity products (IAP) of iron sulfides defined by the equation: H⁺ + FeS_(S) = Fe²⁺ + HS^- in groundwater have been reported in the literature. We computed IAP values of iron sulfides for 46 groundwater samples from the Choshui fan-delta of Taiwan and 65 samples from other areas of the world. The mean of -log(IAP) values obtained for the 46 samples is 3.07 ± 0.34 (1σ), which is consistent with the solubility constant 3.00 ± 0.12 (Davison et al., 1999) of amorphous FeS, implying that the anaerobic aquifers in the Choshui fan-delta are still undergoing active sulfate-reduction processes and keeping the groundwater saturated with amorphous FeS.We suggest that the −logKsp value 3.91 of amorphous FeS adopted in the databases for WATEQF and PHREEQC computer programs ought to be revised to 3.00. Otherwise, the saturation indices (SI) calculated by the two computer programs will be an order of magnitude too high.     

Ruby Occurrences in Turkey: Principle Characteristics

The G ksun Ophiolites in Do an ehir area (Malatya-Southern Turkey) contain corundum mineralizations with significant gem-quality (ruby). Modal mineralogical composition of ruby-bearing rocks consists of hornblende (65%-70 %), plagioclase (20%-25%), green garnet (4%-5 %), ruby (2%-3%), and opaque minerals (<1%). Although ruby shows varying colors in the groundmass, it is generally colorless and rarely very pale pink and has high relief. It has no cleavage but rotund fractures. It has highest interference colors and twinning in some poly-prismatic crystals under the microscope. Crystal sizes range from 2x10 mm up to 30x50 mm. The most remarkable properties are red to pink in color, low to medium transparency, medium to big crystal sizes, lamellar and deformation twinning, secondary liquid feathers, hollow tubes, mineral inclusions, asterism, high birefringence and refractive indices and specific gravity. Rubies show crimson red cathodoluminescence colors activated by Cr3+ in the crystal structure, which is confirmed by the Electron Probe Microanalyses (EPMA). Tectonic setting, geological environment, petrographical, mineralogical, geochemical and gemological characteristics of rubies suggest that the Do an ehir ruby mineralization can be classified into the amphibolite-hosted type of corundum deposits of Tanzania.     

Mercury-binding forms in coals and their geological provenances in coals of different types

Mercury (Hg) is an element of environmental and geological significance. Quantification of different Hg-binding forms is crucial to understand geological Hg provenances and associated geochemical processes during coal formation. In this study, seven coal samples were selected, according to coal rank (i.e., middle volatile bituminous, C-3; low volatile bituminous, C-2; anthracite, C-1), chemical anomalies (high S coal, IBC-105; high Cl coal, C22650) and sampling environment (fresh coal, LH; weathered coal LHW), to determine their Hg-binding forms using well-established sequential extraction procedures coupled with sink–float experiment. In the thermally metamorphosed samples C-1 and C-2, a comparative enrichment of total Hg relative to C-3 is observed. Silicate- and organic-bound Hg are the dominant Hg-binding forms in C-1, suggesting possible Hg sources from magma silicate and secondary Hg enrichment by adsorption. Sulfide- and organic-bound Hg are the most abundant Hg-binding forms in IBC-105, whereas only organic-bound Hg dominates in CC22650. Weathering processes are suggested to transform the abundant sulfide-bound Hg in LH to silicate- and organic-bound Hg in its weathering product LHW.     

Nitrogen in Chinese coals

Three hundred and six coal samples were taken from the main coal mines of twenty-six provinces, autonomous regions, and municipalities of China. The method of Kjeldahl-Gunning Analysis was used to measure the nitrogen contents in the samples. Nitrogen in coals is principally of organic nature. A weak positive correlation between coal rank and nitrogen content is inferred in the study. The distribution of nitrogen in each geological age, coal-cumulating area and province＇s coals was studied. The contents of nitrogen in Chinese coals show approximately a normal distribution, and 90% of the values range from 0.52% to 1.41%, the average nitrogen content in Chinese coals is designated as the arithmetic mean, 0.98%.     

Nitrogen in Chinese coals

Three hundred and six coal samples were taken from main coal mines of twenty-six provinces,autonomous regions,and municipalities in China,according to the resource distribution and coal-forming periods as well as the coal ranks and coal yields.Nitrogen was determined by using the Kjeldahl method at U.S.Geological Survey(USGS),which exhibit a normal frequency distribution.The nitrogen contents of over 90% Chinese coal vary from 0.52% to 1.41% and the average nitrogen content is recommended to be 0.98%.Nitrogen in coal exists primarily in organic form.There is a slight positive relationship between nitrogen content and coal ranking.     

Occurrences of major earthquakes by groups in North China

The earthquakes with magnitude M 6 which occurred in North China (30°–42°N, 105°–124°E) from 780 B.C. to 1978 A.D. have been analysed. Most of them appear in groups, each of which is confined to a definite region and period of time, called respectively the active region and active period. From 780 B.C. to 1000 A.D., groupings of earthquakes were not apparent, due to scanty data. Since 1000 A.D., 16 groups of earthquakes can be recognized. Statistics show that about 73% of the earthquakes occurred in groups. This implies that grouping of earthquakes of M 6 is a characteristic feature of seismic activity in North China. On this basis, a concept of a unified seismogenic process of major earthquakes has been proposed with the support of the geodetic data. Finally, the significance of this concept with regards to earthquake prediction has been discussed.     

Microporosity in Alberta Plains coals

The nature of porosity in 11 Alberta Plains coals is scanned using different characterization techniques, namely, gas adsorption, helium and mercury displacement, and mercury porosimetry. Surface areas calculated from carbon dioxide adsorption at 25°C (varying between 75 and 506 m²/g) are consistently higher than those calculated from nitrogen at −196°C (varying between 1 and 9 m²/g). The samples from Paskapoo deposits have slightly higher surface areas as compared to samples from Horseshoe Canyon deposits. The carbon content in the tested coals (73.4 to 76.8%) is too narrow of range to determine the influence of this parameter on surface area and porosity.Total pore volumes are measured in the range 1.2 to 3000 nm and then divided into macropores (30 to 3000 nm), transitional pores (1.2 to 30 nm) and micropores (less than 1.2 nm). Almost all the surface area in coals is located in the micropores. Coals vary widely in their total pore volumes and porosities range between 9.5 and 22.3%. Percent pore volume contained in micropores varies between 29.5 and 75.9, in transitional pores between 1.1 and 20.5 and in macropores between 18.5 and 50.0.     

Geochemistry of beryllium in Bulgarian coals

The beryllium content of about 3000 samples (coal, coaly shales, partings, coal lithotypes, and isolated coalified woods) from 16 Bulgarian coal deposits was determined by atomic emission spectrography. Mean Be concentrations in coal show great variability: from 0.9 to 35 ppm for the deposits studied. There was no clear-cut relationship between Be content and rank. The following mean and confidence interval Be values were measured: lignites, 2.6 ± 0.8 ppm; sub-bituminous coals, 8.2 ± 3.3 ppm; bituminous coals, 3.0 ± 1.2 ppm; and anthracites, 19 ± 9.0 ppm. The Be contents in coal and coaly shales for all deposits correlated positively suggesting a common source of the element. Many samples of the coal lithotypes vitrain and xylain proved to be richer in Be than the hosting whole coal samples as compared on ash basis. Up to tenfold increase in Be levels was routinely recorded in fusain. The ash of all isolated coalified woods was found to contain 1.1 to 50 times higher Be content relative to its global median value for coal inclusions.Indirect evidence shows that Be occurs in both organic and inorganic forms. Beryllium is predominantly organically bound in deposits with enhanced Be content, whereas the inorganic form prevails in deposits whose Be concentration approximates Clarke values.The enrichment in Be exceeding the coal Clarke value 2.4 to 14.5 times in some of the Bulgarian deposits is attributed to subsynchronous at the time of coal deposition hydrothermal and volcanic activity.     

A comparison of the dissolution behavior of troilite with other iron(II) sulfides; implications of structure

Further knowledge as to the nature of the structure of a terrestrial sample of troilite, FeS [stoichiometric iron(II) sulfide] is revealed by a combination of XPS studies and dissolution studies in acid. The XPS analysis of a pristine troilite surface (the sample being cleaved under high vacuum) is compared to that of a surface polished in an inert atmosphere and a surface after reaction in deoxygenated acid. Further comparison is made with polished and acid-reacted surfaces of pyrrhotite (Fe_1-xS) and pyrite (FeS₂). The pristine troilite S2p spectrum comprises mainly monosulfide 161.1 eV, within the reported range of monosulfide, together with evidence of an unsatisfied monosulfide surface state arising from S-Fe bond rupture. Small, higher oxidation state sulfur contributions, including a disulfide-like state are also present, which suggest the presence of defects due to some nonstoichiometry. The dissolution studies showed that the troilite, in addition to dissolving in acid as an ionic solid to produce H₂S, also exhibits some oxidation of sulfur in the surface layers. In addition, a study of the dissolution behavior of troilite under the influence of cathodic applied potential supported the existence of a proportion of the sulfur within troilite needing reduction before dissolution forming HS⁻ or H₂S can occur. A significant increase in the dissolution rate was observed with application of −105 mV (SHE), but further stepped decreases in potential to −405 mV and −705 mV resulted in a decreased rate of dissolution, a response typical of an ionic solid. The results of the studies emphasise the viewing of iron(II) sulfides as a continuum. Pyrrhotite has been reported previously to dissolve in acid both oxidatively (like pyrite) and nonoxidatively (like troilite) on the same surface. Dissolution studies using troilite, in Ar-purged acid, indicate that dissolution of this material may not be uniformly nonoxidative. XPS evidence of restructuring of the surface of troilite to pyrrhotite and the surface of pyrrhotite towards a FeS₂ type structure, after exposure to Ar-purged acid, is presented.     

超高压变质岩中柯石英的产出和保存机制

了解柯石英的产出并制约其保存机制对于深入认识超高压变质岩的形成和演化具有重要的启示意义.早期的研究发现超高压变质岩中的柯石英主要以包裹体的形式产在刚性寄主矿物中,而粒间柯石英之前仅在苏鲁仰口的超高压双矿物榴辉岩中有过发现.目前提出的柯石英保存机制主要包括以下两种:涉及"构造超压"的"高压釜"模型和较干的变质演化环境.新近报道的大别山甘家岭超高压变沉积岩中的粒间柯石英和白云石中的大量柯石英包裹体肯定了较干的变质演化环境而削弱了传统的"高压釜"模型在保存柯石英方面所起的作用.      

金川富铜矿体金银赋存特征

１　地质概况及矿体特征金川铜镍硫化物矿床产于金川岩体中。金川岩体为一超基性岩体,侵入于下元古界白家嘴子组,直接与片麻岩、蛇纹大理岩、条带均质混合岩接触,呈不规则岩墙状产出,长约６５００ｍ,宽约２０～５２７ｍ,垂直延深达１１００ｍ,出露面积为１－３４ｋｍ２。与成矿关系密切的岩石主要有二辉橄榄岩、橄榄二辉岩、含辉橄榄岩、纯橄岩等,一般基性程度越高,含矿性越好。该岩体被北东东向断裂分割为四段,每一段都有矿体产出,与围岩之间有接触交代作用。本文所研究的富铜矿体产在金川龙首矿区东采区,位于１１６０～１４…     

New data on equilibrium iron isotope fractionation among sulfides: Constraints on mechanisms of sulfide formation in hydrothermal and igneous systems

Fe, S, and Cu reduced partition function ratios (β-factors) allow calculation of equilibrium isotope fractionation factors. β-Factors for chalcopyrite are calculated from experimental and theoretical partial phonon densities of state states (Kobayashi et al., 2007). The Fe β-factors for mackinawite are calculated from Mössbauer spectroscopy data (Bertaut et al., 1965). Excellent agreement exists between Fe β-factors for chalcopyrite calculated from the experimental and theoretical ⁵⁷Fe phonon densities of states, supporting the reliability of the Fe β-factors for chalcopyrite. The ³⁴S β-factor for chalcopyrite is consistent with experimental data on equilibrium sulfur isotope fractionation factors among sulfides and theoretical ³⁴S β-factors, except those recently calculated by a DFT approach.Up-to-date experimental isotope-exchange data on equilibrium Fe isotope fractionation factors between minerals and aqueous Fe were critically reevaluated in conjunction with Fe β-factors for minerals, and the following expressions for β-factors for aqueous Fe²⁺ and Fe³⁺ were obtained:

     

Volatile displacement of Meghalaya coals — A pointer to explore low sulphur coals

Volatile displacement, which measures the difference between calculated and experimental volatile matter, is indicative of abnormality in coals which may be related to petrological or chemical parameters. The volatile displacement (δυ) values of Meghalaya coals were calculated from their chemical analyses. Correlations of volatile displacement (δυ) with parameters such as carbon, hydrogen, moisture, oxygen, oxygen plus sulphate sulphur, oxygen plus pyritic sulphur, oxygen plus organic sulphur and total sulphur were studied. An approximately linear relationship exists only between δυ and moisture, and δυ and total sulphur, and not between other parameters. Plots on Seyler’s chart indicate the coals as perhydrous to orthohydrous. The linear relationship with total sulphur indicates that the coals may have become abnormal mainly due to the marine environment of deposition and weathering.     

原油族组分在煤中留存能力的研究

研究了煤及其干酪根对不同组分油气的留烃能力.将原油分成5个组分,引入溶胀理论,对低、中、高成熟度的煤及其干酪根在不同溶解度参数的溶剂中进行了溶胀实验,获得不同成熟度的煤及其干酪根的溶胀特征,进而得到不同成熟度的煤及其干酪根对5个组分的留烃能力.R°在0.4%～1.25%范围内的煤及其干酪根,其溶胀比随着煤的成熟度增加而降低;而R°大于1.25%的干酪根,其溶胀度则随着Ⅲ型干酪根的成熟度的增加而升高.在"油窗"范围内,随着成熟度的变化,煤和Ⅲ型干酪根的溶胀比降低,表明其留烃能力在下降.对于具有中等溶解度参数的组分,其留烃能力下降约20%.     

Chalcophile elements in western Canadian coals

Concentrations of chalcophile elements (As, Co, Cu, Hg, Mo, Ni, Pb, Sb and Zn) in western Canadian coals were determined using INAA and AAS. The concentrations of these elements in western Canadian coals are within the range for most world coals. However, there are some high values for coals from outcrops and from areas which are not currently being mined.Arsenic content in the majority of western Canadian coals, particularly those currently being mined, is low (0.2–3 ppm). However, there are coals with high arsenic content; for example, lignites from Hat Creek A zone contain between 4.0 and 14.0 ppm As. In some samples from Comox and Suquash, the As concentration is as high as 240 ppm and 1400 ppm, respectively. The enrichment of As in high arsenic coals is related to the geology and nature of country rocks associated with the coal seams. The concentration of other elements for most western Canadian coals, particularly those being mined, are within the range for most world coals. In these coals, the concentration ranges (in ppm) of chalcophile elements are 0.3-3.6 for Sb, 0.8-4.6 for Co, 7–35 for Cu, <0.1 for Hg, 2–6 for Mo, 4–94 for Ni, 6–22 for Pb, 2–7 for Se and 7–110 for Zn.     

Strenes and triterpenes in brown coals

The method of gas chromatography-mass spectrometry was used to identify rearranged 24-methylcholestenes, 24-ethylcholestenes and isohopene in brown coals. Possible routes and sources of formation of these hydrocarbons in nature are discussed. Mass spectra both of original hydrocarbons and of their saturated analogues are given.