The behavior of some trace elements during solidification of the Skaergaard layered series

Six rocks and twelve mineral separates from the layered series of the Skaergaard intrusion were analyzed by neutron activation for REE, Ag, As, Ba, Co, Cr, Cu, Ga, Mn, Ni, Sb, Sc and Zn. The logarithmic model for trace element partitioning was further developed for use in describing the behavior of the elements during solidification of the layered series. Iterations were made in order to optimize within limits of uncertainty of measured values, such parameters as bulk composition, zone size, relative proportions of cumulus plus adcumulus minerals, zone mineralogy, and distribution coefficients. Values for distribution coefficients for the elements entering the cumulus minerals were obtained and have uncertainties of ~±50 per cent. The relative size of the hidden zone is limited, according to the estimates from the model, to between 20 and 50 per cent of the mass of the layered series.     

尾矿酸浸液制备氢氧化铁过程中施威特曼石的形成与转变

尾矿酸浸液在制备氢氧化铁的过程中,由于逐渐滴加碱液正好形成了pH值为2.8～3.8的高SO2-4、高Fe环境,因而生成了施威特曼石.施威特曼石是一种亚稳定矿物,随着时间的延长和体系状态改变,它可以转变为更稳定的针铁矿(氢氧化铁).考查了pH值、温度及时间对施威特曼石相转变的影响.结果表明,在60℃条件下,在pH值为12的碱溶液中转化36 h,施威特曼石可完全转变为Fe(OH)3.     

Removal of trace elements from landfill leachate by calcite precipitation

Spontaneous precipitation of secondary calcite (CaCO₃) has been observed in 25 samples of landfill leachate-polluted stream waters. During the 6-month precipitation experiment, the formation of calcite acts as a principal trace-element scavenging process. The concentrations of Fe, Sr, Ba and Mn and other trace elements in solution significantly decreased as calcite formed during the experiments. The PHREEQC-2 geochemical code indicated high supersaturation of the initial leachate-polluted waters with respect to calcite. The chemical/mineralogical study (SEM/EDS, XRD, ICP MS) revealed that this newly formed calcite contains considerable amounts of metals and metalloids removed from solution. Such a geochemical process can be considered to be important for spontaneous decontamination in landfill-affected environments (stream sediments, soils) or landfill technical facilities (settling basins). This removal takes place especially during dry periods with low rain precipitation, when the landfill waters exhibit both higher alkalinity and higher trace element concentrations.     

煤矸石中微量元素的地球化学行为

以兖州矿煤矸石中微量元素的淋滤作用及析出含量为例,分析了微量元素在洗选过程和淋滤作用下的分布、迁移规律等地球化学行为。在用不同的pH值酸性溶液作淋滤实验时发现,pH值对微量元素的析出影响很大。研究还发现土壤中微量元素的富集量随着距矸石堆距离的增加呈明显的下降趋势。     

Desorption and coagulation of trace elements during estuarine mixing

Mixing experiments of seawater and the Hudson and Mississippi riverwaters with radiotracer spikes show that Co, Mn, Cs, Cd, Zn and Ba will be desorbed from river suspended particles, while significant fractions of “dissolved” Fe, Sn, Bi, Ce and Hg will be coagulated during estuarine mixing.     

The structure and transformation of the nanomineral schwertmannite: a synthetic analog representative of field samples

The phase transformation of schwertmannite, an iron oxyhydroxide sulfate nanomineral synthesized at room temperature and at 75 °C using H₂O₂ to drive the precipitation of schwertmannite from ferrous sulfate (Regenspurg et al. in Geochim Cosmochim Acta 68:1185–1197, 2004), was studied using high-resolution transmission electron microscopy. The results of this study suggest that schwertmannite synthesized using this method should not be described as a single phase with a repeating unit cell, but as a polyphasic nanomineral with crystalline areas spanning less than a few nanometers in diameter, within a characteristic ‘pin-cushion’-like amorphous matrix. The difference in synthesis temperature affected the density of the needles on the schwertmannite surface. The needles on the higher-temperature schwertmannite displayed a dendritic morphology, whereas the needles on the room-temperature schwertmannite were more closely packed. Visible lattice fringes in the schwertmannite samples are consistent with the powder X-ray diffraction (XRD) pattern taken on the bulk schwertmannite and also matched d-spacings for goethite, indicating a close structural relationship between schwertmannite and goethite. The incomplete transformation from schwertmannite to goethite over 24 h at 75 °C was tracked using XRD and TEM. TEM images suggest that the sample collected after 24 h consists of aggregates of goethite nanocrystals. Comparing the synthetic schwertmannite in this study to a study on schwertmannite produced at 85 °C, which used ferric sulfate, reveals that synthesis conditions can result in significant differences in needle crystal structure. The bulk powder XRD patterns for the schwertmannite produced using these two samples were indistinguishable from one another. Future studies using synthetic schwertmannite should account for these differences when determining schwertmannite’s structure, reactivity, and capacity to take up elements like arsenic. The schwertmannite synthesized by the Regenspurg et al. method produces a mineral that is consistent with the structure and morphology of natural schwertmannite observed in our previous study using XRD and TEM, making this an ideal synthetic method for laboratory-based mineralogical and geochemical studies that intend to be environmentally relevant.     

碳酸盐矿物的阴极发光性与微量元素的关系

碳酸盐矿物的阴极发光特征与其成分有关。笔者用阴极发光与电子探针微区分析法对砂岩中碳酸盐矿物进行测试分析,其结果表明碳酸盐矿物的阴极发光与微量元素含量有如下规律:①碳酸盐矿物在铁含量高于猝灭下限或锰含量低于激活下限时,不具有阴极发光性;②铁的猝灭下限约为0.04 mol,锰的激活下限为小于7×10^-5mol;③铁/锰比值越高,越不利于碳酸盐矿物阴极发光;但是铁/锰比值小于1的碳酸盐一定具有阴极发光;④铁或锰二者之一含量很少时不利于碳酸盐矿物的阴极发光。     

The partitioning of trace elements between clinopyroxene and trachybasaltic melt during rapid cooling and crystal growth

We present the variation in trace element partition coefficients measured at the interface between rapidly cooled clinopyroxene crystals and co-existing melts. Results indicate that, as the cooling rate is increased, clinopyroxene crystals are progressively depleted in Si, Ca and Mg counterbalanced by enrichments in Al (mainly tetrahedral Al^iv), Na and Ti. Partition coefficients (Ds) for rare earth elements (REE), high field strength elements (HFSE) and transition elements (TE) increase with increasing cooling rate, in response to clinopyroxene compositional variations. The entry of REE into the M2 site is facilitated by a coupled substitution where either Na substitutes for Ca on the M2 site or Al^iv substitutes for Si in the tetrahedral site. The latter substitution reflects an increased ease of locally balancing the excess charge at M2 as the number of surrounding Al^iv atoms increases. Due to the lower concentration of Ca in rapidly cooled clinopyroxenes, divalent large ion lithophile elements (LILE) on M2 decrease at the expense of monovalent cations. Conversely, higher concentrations of HFSE and TE on the M1 site are facilitated as the average charge on this site increases with the replacement of divalent-charged cations by Al^vi. Although crystallization kinetics modify clinopyroxene composition, deviations from equilibrium partitioning are insufficient to change the tendency of a trace element to be compatible or incompatible. Consequently, there are regular relationships between ionic radius, valence of the trace element and D. At both equilibrium and cooling rate conditions, Ds for isovalent cations define parabola-like curves when plotted against ionic radius, consistent with the lattice strain model, demonstrating that the partitioning of trace elements is driven by charge balance mechanisms; cation substitution reactions can be treated in terms of the energetics of the various charge-imbalanced configurations.     

The distribution of trace elements in carbonaceous chondrites

12 carbonaceous chondrites, amongst them representatives of nearly all known petrologic types were analyzed for twenty trace elements by spark source mass spectrography combined with the isotope dilution method. Data on different element groups (refractory, moderately volatile and volatile) show that the distribution of the trace elements in the carbonaceous chondrites, with the exception of Renazzo, can be well explained by Anders' two-component model. This is also valid for the highly metamorphosed CV5 chondrite Karoonda.Furthermore, it is observed that the $\text{Zr}\text{Hf}$-ratios in the carbonaceous chondrites increase with increasing petrologic type which is interpreted as the result of mixing two components with different $\text{Zr}\text{Hf}$-ratios     

吉林白山地区原煤微量元素地球化学特征

对吉林白山地区煤矿主采煤层中的As、B、Ba、Cd、Cu、Hg、Pb、Se、Sr等微量元素进行了分析,结果表明:太原组与山西组由于成煤环境不同,微量元素组成及其质量分数存在一定的差异,太原组原煤中As、B、Hg、Pb、Se、Zn的质量分数明显高于山西组,山西组原煤中Ba、Cr、Cu、Mn、V的质量分数明显高于太原组。白山地区原煤中As、B、Hg、Pb、Se的质量分数明显高于地壳元素平均值,呈富集状态;Co、Cd与地壳平均值接近,其他元素均亏损。与全国煤中微量元素的质量分数平均值相比,As、Ba、Co、Cr、Cu、Hg、Ni、Pb、Se、V、Zn的质量分数高于全国平均值。B、Mn、Sr质量分数低于全国平均值。微量元素赋存状态及相关分析表明,Fe与亲硫有害元素As、Cu、Hg、Pb、Se具有显著相关关系,说明煤中黄铁矿及其他硫化物是许多有害微量元素的重要载体。     

长江三峡地区成冰纪-埃迪卡拉纪转换时期微量元素和稀土元素地球化学特征

通过微量元素和稀土元素地球化学分析,对长江三峡地区陡山沱组层型剖面--田家园子剖面成冰系南沱组顶部和埃迪卡拉系陡山沱组下部102个岩石样品进行了地球化学研究。重点分析了氧化还原敏感元素(Zn,Co,U,Mo,Ni,V)的富集特征,并探讨其可能成因机制以及三峡地区成冰纪-埃迪卡拉纪转换时期的水体特征。结果表明:在南沱组顶部仅Zn和Co富集;在盖帽白云岩下部,氧化还原敏感元素均富集,而在盖帽白云岩上部,除Zn和V外,其他氧化还原敏感元素均亏损;在陡山沱组Ⅱ段下部,氧化还原敏感元素由最初的亏损,逐渐变为较稳定的富集。在陡山沱组下部,出现2次明显的富集峰值,分别出现在剖面的0.4m处(盖帽白云岩中间)和6.5m处(陡山沱组Ⅱ段下部)。整个剖面大部分样品具有Eu的轻微正异常(Eu/Eu^*＜1.6), 而在剖面0.4m和6.5m处,Eu具有明显的正异常,结合稀土配分类型、Y/Ho值、La异常、Ce异常等指标,推测这2次异常均可能受到深海热液流的影响,而缺氧海水的上涌造成水体缺氧,导致这些元素出现富集峰值。U/Th、V/(V+Ni)以及稀土元素指标综合指示,三峡地区南沱组顶部冰碛岩应为氧化环境下的沉积物;随着冰川消融,冰融淡水注入古海洋,陡山沱组盖帽碳酸盐的沉积受冰融淡水的影响,深部缺氧海水的上涌使沉积水体经历氧化-缺氧-氧化的转变,海水的分层性较强;而陡山沱组Ⅱ段下部沉积环境以分层性较弱的弱氧化环境为主。     

The behavior of actinides,phosphorus, and rare earth elements during chondrite metamorphism

New data on the U, Pu, and P distributions in less metamorphosed H-chondrites (type 3–5), coupled with literature results, permit a provisional picture to be assembled of the chemistry of these elements and for the rare earth elements in ordinary chondrites and the changes brought about by chondritic metamorphism. Preferential associations of phosphates with metals and/or sulndes in all chondrites strongly indicate an “initially” siderophile or conceivably chalcophile character for P in ordinary chondrite precursor materials with phosphate subsequently formed by oxidation. This oxidation occurred prior to or during chondritic metal-silicate fractionation. Uranium is initially concentrated in chondrule glass at ~ 100 ppb levels with phosphates (primarily merrillite) in H-3 chondrites being essentially U-free (<20 ppb). As chondrule glass devitrified during metamorphism, U migrated into phosphates reaching ~ 50 ppb in Nadiabondi (H-5) merrillite and 200–300 ppb in merrillite from equilibrated chondrites but “froze out” before total concentration in phosphates occurred. Relative ²⁴⁴Pu fission track densities in the outer 5 μm of olivine and pyroxene grains in contact with merrillite and with chondrule mesostasis in Bremervörde (H-3) give Pu(mesostasis)/Pu(merrillite) <0.01, implying total concentration of Pu in phosphates. Similarly, no detectable Pu (<0.1 ppb) was found in chondrule mesostasis in Tieschitz and Sharps; whereas, direct measurements of tracks in phosphates in H-3 chondrites are consistent with high (?10 ppb) Pu concentrations. Thus, a strong Pu-P correlation is indicated for ordinary chondrites. There is variable Pu/U fractionation in all chondritic phosphates reaching an extreme degree in the unequilibrated chondrites; therefore, the Pu/U ratio in phosphates appears relatively useless for relative meteorite chronology. Literature data indicate that the REE are located in chondrules in unequilibrated chondrites, most likely in glass; thus there may also be strong Pu/Nd fractionation within these meteorites. Like U, the REE migrate into phosphates during metamorphism but, unlike U, appear to be quantitatively concentrated in phosphates in equilibrated chondrites. Thus relative ages, based on Pu/Nd, may be possible for equilibrated chondrites, but the same chronological conclusions are probably obtainable from Pu concentrations in phosphates, i.e., on the Pu/P ratio. However, Pu/P chronology is possible only for ordinary chondrites; so there appears to be no universal reference element to cancel the effects of Pu chemical fractionation in all meteorites. Available data are consistent with — but certainly do not prove-that variations in Pu/P represent age differences, but if these age differences do not exist, then it is conceivable that the solar system ${}^{244}\text{Pu}{}^{238}\text{U}$ ratio, important for cosmochronology, is still lower than the presently accepted value of 0.007.     

The sorption of toxic elements onto natural zeolite,synthetic goethite and modified powdered block carbon

Inorganic elements analyses of Carapicuíba lake reveal that As, Cr, Pb and Mn are above the recommended drinking water standards. The mean total concentrations of toxic elements in surface water decrease in the order Mn > Cr > Pb > As. At elevated concentrations, toxic elements like Cr can accumulate in soils and enter the food chain, leading to serious health hazards and threatening the long-term sustainability of the local ecosystem. Absorbing materials has often been used to improve water quality. In this investigation three types of material were studied: the natural zeolite (mordenite); synthetic goethite and the powdered block carbon modified. The adsorption of Pb²⁺ and Mn²⁺ onto natural zeolite as a function of their concentrations was studied at 24°C by varying the metal concentration from 100 to 400 mg L⁻¹ while keeping all other parameters constant. The low-cost zeolites removed Pb from water without any pretreatment at pH values <6. The maximum adsorption attained was as follows: Pb²⁺ 78.7% and Mn²⁺ 19.6%. The modified powdered block carbon effectively removed As(V) and Cr(VI) while goethite removed more chromate than arsenate in the pH range 5–6. Results of this study will be used to evaluate the application these materials for the treatment of the Carapicuíba lake’s water.     

Mineral/melt partitioning of trace elements during hydrous peridotite partial melting

This experimental study examines the mineral/melt partitioning of incompatible trace elements among high-Ca clinopyroxene, garnet, and hydrous silicate melt at upper mantle pressure and temperature conditions. Experiments were performed at pressures of 1.2 and 1.6 GPa and temperatures of 1,185 to 1,370 °C. Experimentally produced silicate melts contain up to 6.3 wt% dissolved H ₂O, and are saturated with an upper mantle peridotite mineral assemblage of olivine+orthopyroxene+clinopyroxene+spinel or garnet. Clinopyroxene/melt and garnet/melt partition coefficients were measured for Li, B, K, Sr, Y, Zr, Nb, and select rare earth elements by secondary ion mass spectrometry. A comparison of our experimental results for trivalent cations (REEs and Y) with the results from calculations carried out using the Wood-Blundy partitioning model indicates that H ₂O dissolved in the silicate melt has a discernible effect on trace element partitioning. Experiments carried out at 1.2 GPa, 1,315 °C and 1.6 GPa, 1,370 °C produced clinopyroxene containing 15.0 and 13.9 wt% CaO, respectively, coexisting with silicate melts containing ~1–2 wt% H ₂O. Partition coefficients measured in these experiments are consistent with the Wood-Blundy model. However, partition coefficients determined in an experiment carried out at 1.2 GPa and 1,185 °C, which produced clinopyroxene containing 19.3 wt% CaO coexisting with a high-H ₂O (6.26±0.10 wt%) silicate melt, are significantly smaller than predicted by the Wood-Blundy model. Accounting for the depolymerized structure of the H ₂O-rich melt eliminates the mismatch between experimental result and model prediction. Therefore, the increased Ca ²⁺ content of clinopyroxene at low-temperature, hydrous conditions does not enhance compatibility to the extent indicated by results from anhydrous experiments, and models used to predict mineral/melt partition coefficients during hydrous peridotite partial melting in the sub-arc mantle must take into account the effects of H ₂O on the structure of silicate melts.     

蛇纹石化和俯冲带蛇纹岩变质脱水过程中流体活动性元素的行为

蛇纹石是大洋岩石圈和俯冲带内水和流体活动性元素最重要的载体之一。研究蛇纹石化和蛇纹岩变质脱水过程中流体活动性元素的行为是认识俯冲带元素地球化学循环的关键。蛇纹岩是指主要由蛇纹石类矿物构成的岩石,包括利蛇纹石、纤蛇纹石和叶蛇纹石。蛇纹石化过程中会造成流体活动性元素(B、Li、As、Sb、Pb、Cs、U、Sr和Ba等)的显著富集,并且由于原岩性质、流体成分和氧逸度等条件的不同,大洋岩石圈蛇纹岩和弧前蛇纹岩的特征也略有不同。例如,弧前蛇纹岩具有相对高的As、Sb、B和相对低的U,这反映了俯冲沉积物来源流体的贡献。在俯冲带蛇纹岩的变质脱水过程中,利蛇纹石向叶蛇纹石的转变伴随着矿物内超过50%F和Cl的释放,以及一些流体活动性元素(如B和Li)的迁出;此外,蛇纹石分解形成的变质橄榄石中的流体包裹体指示,蛇纹石脱水分解所产生的流体具有高于原始地幔几个数量级的Cl、Cs、Pb、As、Sb、Ba、Rb、B、Sr、Li和U含量。由于利蛇纹石中的Fe~(3+)含量较叶蛇纹石高,这种矿物相转变过程中也伴随着俯冲通道内的一系列氧化还原过程,从而影响流体性质和新形成的叶蛇纹石的成分。蛇纹岩与岛弧岩浆在流体活动性元素富集规律上的相似性说明蛇纹岩在俯冲带元素循环中扮演着重要的角色。此外,蛇纹石矿物相转变过程中F、Cl、B等元素的释放,可能对于斑岩型金矿、蛇绿岩中的金矿和某些蛇纹岩作为赋矿围岩的硼矿的形成起到重要的作用。     

The significance of trace elements in solving petrogenetic problems and controversies

In contrast to the cases of interpolation, in the cases of extrapolation trace elements and trace-element ratios can be used as evidence in solving petrogenetic problems. Despite of the many instances of successful employment of trace elements in solving genetic problems and in differentiating cases, on the whole trace elements should only be used as contributory evidence, together with geological, structural and textural data.     

榴辉岩退变质过程中的微量元素地球化学行为：对CCSD主孔退变质榴辉岩的研究

对中国大陆科学钻探工程主孔榴辉岩退变质过程中的微量元素地球化学行为进行了研究。对退变质程度连续变化样品的不同部分的对比研究表明，流体作用下的退变质过程中大离子亲石元素（Cs、Rb、Ba、Sr、K、Th、U）和轻稀土元素表现出较大的活动性，重稀土元素和高场强元素变化相对较小。退变质后大离子亲石元素的显著增加和高场强元素、重稀土元素的轻微变化（甚至相对降低），表明与退变质作用有关的流体中的络阴离子含量很少，并不富集高场强元素和重稀土元素。退变质后总体上表现出的Si、大离子亲石元素和轻稀土元素的明显变化，表明外来流体参与了榴辉岩的退变质过程，带入和带出了一些元素。结合榴辉岩中单矿物微量元素组成以及前人对D^Mineral/Fluid的研究成果，对流体-榴辉岩作用形成的退变质分带（富石英条带→角闪岩→退变质榴辉岩→新鲜榴辉岩）的微量元素组成变化进行了详细研究。结果表明在流体作用下的榴辉岩退变质过程中，大离子亲石元素、轻稀土元素和高场强元素含量的变化除了受退变质流体性质的影响外，更大程度上取决于退变质过程中的矿物相（尤其是副矿物）的变化。     

活体珊瑚微量元素对硼同位素组成影响及硼掺入珊瑚的形式

为确定元素 B 掺入进珊瑚的形式、B(OH)与 B(OH)3间的分馏系数及珊瑚中微量元素对硼同位素?4组成的影响,对北海涠洲岛、海南三亚和雷州半岛灯楼角三地活体珊瑚的 Mg、Sr、Na、Ca、B 浓度及硼同位素组成(δ11Bcoral)进行了测定.结果表明,涠洲岛、三亚和灯楼角三地珊瑚的 Mg、Sr、Na 和 Ca 浓度平均值分别为40.1 mmol/L、86.1 mmol/L、449 mmol/L 和12.1 mol/L.珊瑚中 B 浓度的变化范围为4.4~8.4 mmol/L,平均值为5.9 mmol/L.Ca、Sr 在珊瑚中明显富集,而 Mg 在珊瑚中贫化.珊瑚 B 浓度的变化主要反映了珊瑚生长时海水 pH 值的变化.δ11Bcoral 的变化范围为22.8‰~27.9‰,平均为25.2‰.除与 B 浓度呈弱正相关关系外,δ11Bcoral 与其他四种元素不相关.应用珊瑚硼同位素组成恢复古海水 pH 值时选择同属种珊瑚和判别是否有 Mg(OH)2的存在是必要的.涠洲岛、灯楼角和三亚三地珊瑚与海水间的硼同位素分馏系数αcoral-sw 分别为0.9839、0.9847和0.9850.计算得到的珊瑚与海水 B(OH)3间的分馏系数αcoral-3的变化范围为0.9772~0.9800,平均值为0.9788.该新的α4-3值是准确的,可以用来反演古海水 pH 值.αcoral-sw 和αcoral-3随pH 值的升高分别呈现出增大和减小的变化趋势.珊瑚的平均δ11Bcoral 位于理论计算的δ11B4和δ11B3曲线之间,而且都低于原始合成海水的δ11B.这些都表明 B 以 B(OH)3和B(OH)两种形式以变化的比例同时掺入进?4珊瑚,并以B(OH)优先掺入为主.计算得到有0.1%~5.5%(平均值为2.2%)的 B(OH)3掺入进珊瑚中.由于?4 B(OH)3同时掺入进生物碳酸盐,δ11Bcarb=δ11B4的假设不能成立,由所测生物碳酸盐δ11Bcarb 值计算的海水 pH值将产生误差,使δ11B-pH 技术变得更为复杂.通过无机碳酸盐沉积或有孔虫或珊瑚的养殖实验(或者野外观测实验)建立用于重建古海水 pH 值的δ11Bcarb-pH 经验方程是今后的一项重要任务.