Geochemistry of arsenic in uranium mine mill tailings,Saskatchewan, Canada

The Rabbit Lake U mine in-pit tailings management facility (TMF) (425 m long×300 m wide×91 m deep) is located in northern Saskatchewan, Canada. The objectives of this study were to quantify the distribution of As phases in the tailings and evaluate the present-day geochemical controls on dissolved As. These objectives were met by analyzing pore fluid samples collected from the tailings body for dissolved constituents, measuring Eh, pH, and temperature of tailings core and pore fluid samples, conducting sequential extractions on solid samples, conducting geochemical modeling of pore fluid chemistry using available thermodynamic data, and by reviewing historical chemical mill process records. Dissolved As concentrations in 5 monitoring wells installed within the tailings body ranged from 9.6 to 71 mg/l. Pore fluid in the wells had a pH between 9.3 and 10.3 and Eh between +58 and +213 mV. Sequential extraction analyses of tailings samples showed that the composition of the solid phase As changed at a depth of 34 m. The As above 34 m was primarily associated with amorphous Fe and metal hydroxides while the As below 34 m was associated with Ca, likely as amorphous poorly ordered calcium arsenate precipitates. The change in the dominant As solid phases at this depth was attributed to the differences in the molar ratio of Fe to As in the mill tailings. Below 34 m it was <2 whereas above 34 m it was >4. The high Ca/As ratio during tailings neutralization would likely precipitate Ca₄(OH)₂(AsO₄)₂:4H₂O type Ca arsenate minerals. Geochemical modeling suggested that if the pore fluids were brought to equilibrium with this Ca-arsenate, the long-term dissolved As concentrations would range between 13 and 126 mg/l.     

Growth of rigid high-relief patch reefs, Mid-Silurian, Gotland, Sweden

Patch reefs up to 35 m thick and generally 100–150 m wide, separated by bedded inter-reef sediment, dominate the Högklint Formation (Lower Wenlock) of north-west Gotland. The spacing between adjacent patch reefs is variable, but is commonly 150–350 m. The Högklint is a shallowing sequence, and the patch reefs exhibit a well-developed vertical succession: (1) Axelsro-type patch reefs developed in the underlying Visby Formation; (2) halysitid tabulates capped by laminar stromatoporoids; (3) domical and bulbous stromatoporoids and red algae; (4) cyanobacterial–algal reef crest. The patch reefs expand upwards from an initial bioherm phase with a small base to a laterally extensive biostrome phase. This gives them a thumb-tack appearance. In stage 2 of the bioherm phase, rigid framework development and high reef relief resulted in breakage of angular blocks up to 15 m long, which were incorporated into the reefs or fell into adjacent sediments. Poorly sorted talus haloes (Millingsklint Member) also developed adjacent to stage 2 of the bioherm phase. These include angular blocks and exhibit depositional slopes up to 40° away from the reefs. Stage 3 biostrome development was mainly non-rigid cluster reef, which shed skeletal debris (Domkyrka Member) but few lithified blocks. Stage 4 biostrome development was a reef crest with open to closed frame structure. Storm breakage and overturning produced large blocks with complex cavity fill sequences including double geopetals. Relief during the bioherm phase, indicated by fallen blocks and talus slopes, was up to at least 15 m; during the biostrome phase, it was up to 10 m.     

Cisuralian coals of the Mullaley Sub-basin,northern New South Wales

The Mullaley Sub-basin of the Gunnedah Basin extends from Quirindi in the southeast, to north of Narrabri, to west of Dunedoo in northern New South Wales. There have been more than 100 boreholes sunk to basement investigating the (lower Permian) Cisuralian coal and coal seam gas resources of the Mullaley Sub-basin since the early 1990s. A desktop review of this open file information has allowed the formal correlation and naming of six Cisuralian coal members attaining a maximum 35 m of cumulative thickness within an upward coarsening sedimentary package totalling no more than 150 m. In ascending order, the coal members are: Bibblewindi (0–10 m), Bohena (3–18 m), Collygra (0.5–3 m), Coxs (1.5–4 m), Tullamullen (0.5–4 m) and Mooki (0.5–3 m).

Cisuralian coal seams in the Maules Creek Formation of the southern Mullaley Sub-basin are here correlated with those of the Greta Coal Measures at Werris Creek and Muswellbrook. It is apparent that basement paleotopography played a significant role in the Cisuralian coal development as coals are best developed where the sedimentary sequence is greater than 60 m thick, as there the thick seams (Bohena and Bibblewindi coal members) occur towards the base of the sequence. The maximum western limit of the Cisuralian coals (Rocky Glen Ridge) is further east than previously inferred with new drilling information showing the Porcupine Formation directly overlying the barren pelletoidal claystones of the Leard Formation or the underlying volcanics (Boggabri Volcanics/Werrie Basalt). Early marine transgressions at the top of the Maules Creek Formation have stopped development of the Mooki, Tullamullen and Coxs coal members in the northern and eastern Mullaley Sub-basin and allowed the development of localised paraconglomerate (diamictite) intervals up to 10 m thick. Thick (>20 m cumulative) coal occurrences are localised to the Jacks Creek and Pilliga East State Forest areas southwest of Narrabri. The coal resource potential of the Mullaley Sub-basin is estimated at 13–28 billion tonnes.     

Analysis of waves generated by Gongjiafang landslide in Wu Gorge, three Gorges reservoir, on November 23, 2008

At 4:40p.m. on November 23, 2008, the Gongjiafang slope collapsed on the north bank of Yangtze River in Wu Gorge of Three Gorges Reservoir. The 380,000-m³ sliding mass consisted mainly of cataclastic rock. A video record of the major sliding incident was analyzed using the general laws of physical motion. The analysis indicated that the maximum speed and maximum acceleration of the sliding mass were 11.65?m/s and 2.23?m/s², respectively, and that the maximum amplitude and the propagation velocity of the water wave near the landslide were 31.8?m and 18.36?m/s, respectively. Wave run-up investigation indicated that the maximum run-up on shore was 13.1?m, which declined to 1.1?m at Wushan dock 4?km away. The incident causes no casualties, but did result in economic losses of RMB five million. The numerical simulation model GEOWAVE was used to simulate and reproduced the impulse wave generated by the landslide; the results were in good agreement with the observed incident. The numerical simulation data were then applied to analyze the decay and amplification effects of the landslide wave in the river course. The field investigations and witness information provide valuable materials for the studies of landslide kinematics and impulse waves generated by landslides. In addition, the research results provide a useful reference for future similar waves generated by landslides in reservoirs.     

Consolidation and incipient oxidation of alkaline arsenopyrite-bearing mine tailings,Macraes Mine,New Zealand

Fine grained (ca. 15 μm), arsenopyrite-bearing mine tailings have been exposed to drying and oxidation for 4 a pending relocation. The tailings are still partly covered by a pond of decanted pore waters. The water table in drying tailings has lowered by 1–3 m and desiccation cracks up to 2 cm wide have formed on the 1 m scale, extending through the unsaturated zone. Tailings in the unsaturated zone have similar pore water contents to saturated tailings: typically 16–32 wt% water. Saturated tailings retain alkaline pH (ca. 10) from the mine cyanidation plant, but pH lowers progressively towards ca. 7 near the surface, or near desiccation cracks, in the unsaturated zone. The redox state of the tailings changes in parallel with pH, with an empirical relationship: Eh(mV)=−55 pH+290. Water in the remnant decant pond reflects this relationship also. Unsaturated tailings have variable but low permeabilities, typically 10⁻³ to 10⁻⁴ m/day, and more permeable horizons have allowed incursion of oxygenated air and/or rain water from desiccation cracks. Sulphide grains in all tailings examined are unaltered. Sulphides and solutions in the tailings are out of thermodynamic equilibrium predicted from the redox–pH conditions, due to kinetic constraints. Incursion of rain water locally facilitates deposition from pore waters of insoluble Fe oxide and arsenate minerals, thus fixing As in the dry unsaturated tailings.     

甘肃临洮晚更新世黄土环境变迁

对甘肃临洮县塔湾乡晚更新世黄土-古土壤序列的粒度、磁化率两个环境代用指标进行综合分析, 可划分出以下7个气候阶段: (1) 距底18.5m (92.478.8ka), 平均粒径24.42μm, 平均磁化率716.8×10-6SI, 年均温度7.8℃, 年均降水量500mm, 气候温暖较湿; (2) 距底8.514.8m (78.865.3ka), 平均粒径26.83μm, 平均磁化率为442.3×10-6SI, 年均温度5.2℃, 年均降水量370mm, 气候温干; (3) 距底14.820.3m (65.357.3ka), 平均粒径25.94μm, 平均磁化率320.7×10-6SI, 年均温度3.5℃, 年均降水量280mm, 气候温干偏凉; (4) 距底20.324.9m (57.347.7ka), 平均粒径25.23μm, 平均磁化率516.4×10-6SI, 年均温度6.0℃, 年均降水量410mm, 气候温干偏湿; (5) 距底24.929.4m (47.740.9ka), 平均粒径25.46μm, 平均磁化率299.4×10-6SI, 年均温度在3.1℃, 年均降水量270mm, 气候温干偏凉; (6) 距底29.434.2m (40.932.4ka), 平均粒径21.46μm, 平均磁化率405.5×10-6SI, 年均温度4.7℃, 年均降水量350mm, 气候温干偏湿; (7) 距底34.239m (32.4ka以后), 平均粒径188.89μm, 平均磁化率381.1×10-6SI, 年均温度4.4℃, 年均降水量330mm, 气候温干.这些环境变迁阶段与区域环境变迁具有较好的可对比性, 其中Ⅰ阶段相当于MIS5温暖期; Ⅱ阶段和Ⅲ阶段相当于MIS4降温期; Ⅳ阶段、Ⅴ阶段和Ⅵ阶段相当于MIS3的气候温暖期; Ⅶ阶段相当于MIS2降温期.但与邻区兰州九洲台和若尔盖RM孔相比, 同时期临夏地区气候明显偏温偏湿.      

The Precambrian geology of El Cristo,southern Tandilia Region,Argentina

Metamorphic and granitoid rocks of the El Cristo area, southern part of Tandilia Range, are considered in terms of structural, lithological and geochronological data.The abovementioned area was affected before 2000 m. y. by a first tectono-thermal event that was followed by a second episode of intense SW-NE folding. The latter accompanied or followed by a metamorphism of almandine grade and strong synkinematic to latekinematic granitization during the span 1800-1520 m. y.Succeeding episodes of metamorphism and deformation were less intense and culminated in the local development of a 900 m. y. granite, chloritization and some brittle deformation.

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Zusammenfassung Tektonische, lithologische und geochronologische Daten der metamorphen und granitischen Gesteine der El Cristo Gegend im südlichen Teil des Tandilia Gebirges werden diskutiert.Vor mehr als 2000 Ma wurde dieses Gebiet erstmals von einem tektonothermalen Ereignis erfa\t, gefolgt von einer zweiten Episode starker SW-NE gerichteter Faltung. Letztere wurde begleitet oder gefolgt von einer Almandingrad Metamorphose und starker synbis spÄtkinematischer Granitisierung wÄhrend der Zeitspanne 1800 bis 1520 Ma.Darauffolgende Metamorphosen und Deformationsereignisse waren weniger intensiv und endeten um 900 Ma in Lokaler Granitintrusion, Chloritisierung und spröder Deformation.

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Résumé Des roches métamorphiques et granitoÏdes de la région de Cristo font ici l'objet d'une discussion sur la base de données structurales, lithologiques et géochronologiques.La région mentionnée a été marquée d'abord, il y a plus de 2000 millions d'années, par une phénomène thermo-tectonique, suivi, dans une seconde phase, d'un plissement important dirigé SO-NE. Celui-ci a été accompagné ou suivi par un métamorphisme à almandin et par une intense granitisation syncinématique à tardicinématique au cours de la période 1800-1500 m. a.Des épisodes de métamorphisme et de déformation moins intenses s'ensuivirent, qui aboutirent au développement local, vers 900 m. a., d'une intrusion granitique, avec chloritisation et déformations cassantes.

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, - , 2000 - , SW-NE. 1800 1520 . , 900 .

     

Diagenetic transformation of clinoptilolite to analcime in silicic tuffs of Hokkaido, Japan

Diagenetic clinoptilolite and analcime are present in the diagenesis of Tertiary marine silicic tuffs in the MITI-Toyokoro borehole, Hokkaido, Japan. Chemical analysis, SEM and petrographic observations show the mechanism of clinoptilolite to analcime transformation. Na-K clinoptilolite (NaK=6:4), an alteration product of volcanic glass, is detected at depths of 1230 to 2710m. A more Na-rich clinoptilolite (Na: K = 9:1) discovered at depths between 2590 and 2710 m is a result of a cation exchange mechanism. The formation of analcime at greater depths is due to a microdissolution-precipitation mechanism, that is Na-rich clinoptilolite dissolved and analcime precipitated as a result of increasing burial. At 2710 m analcime occurs next to the Na-rich clinoptilolite and it is assumed that the Na-rich clinoptilolite is an intermediate phase.     

Time variability of pore water chemistry in recent carbonate sediments,Devil's Hole,Harrington Sound,Bermuda

Chemical analyses of pore waters from recent marine carbonate sediments, Devil's Hole, Harrington Sound, Bermuda, have been obtained at intervals over a four year period. Interstitial waters were systematically analyzed for pH, titration alkalinity, dissolved sulfides, NH₄⁺, Ca²⁺, Mg²⁺ and Na⁺ or Cl^?. Additional analyses on some cores included SO₄^2?, PO₄^3?, dissolved CH₄ and N₂, and C:N:H ratios in the detrital organic material. The following general trends with depth (to ～ 1 m) are observed: (1) major cations show little or no change; (2) pH decreases; (3) alkalinity, sulfides, NH₄⁺ and PO₄^3? increase; (4) dissolved CH₄ is consistently low. The chemical changes with depth can be modelled theoretically and are consistent with experimental data.Significant seasonal changes in pore water chemistry are observed. The data suggest an annual exchange between the pore waters (to a depth of ～ 1 m) and the overlying water of Harrington Sound; the exchange occurs between August and January. The nutrient flux out of the sediments during this process may be a major factor in the plankton ecology of Harrington Sound.     

南海珠江口盆地LH-19-4-1井新近纪有孔虫生物地层研究

标准化石的末现面(LAD)被广泛用于全球性地层划分和对比,但是,只有像白垩纪与第三纪之间的撞击事件所引起的全球性生物集群绝灭(LAD)才具有全球等时间的性质。标准浮游有孔虫化石带的LAD,可能与白垩纪与第三纪之间的撞击事件所引起的LAD一样、具有全球等时面的性质,所以它可以用于全球地层的划分和对比。依据标准浮游有孔虫带的研究,南海珠江口盆地LH-19-1-1井的岩屑地层(430m-2 630m)一共识别出20个带(N_(22)-N_3)。更新世:N_(22)带(430m-620m);晚上新世:N_(21)-N_(20)带(620m-680m);早上新世:N_(19)-N_(18)带(680m-790m);晚中新世:N_(17)-N_(16)带(790m-1 139m);中中新世:N_(15)-N_8带(1 139m-1 898m);早中新世:N_7-N_4带(1 898m-2 588m);晚渐新世:N_3带(2 588m-2 630m)。它们可以和世界其他地区的地层作准确的对比。     

The duisburg method of metro-construction, a successful application of the gap freezing method

Between March 1977 and August 1979 contract No.4 of the Stadtbahnbau (Metro-construction) in Duisburg was executed, making successful use of gap freezing.

The gap freezing was necessary because the Metro-tunnel is crossed by a groundwater stream (flow velocity up to 15 m/d) and it had to be assured that open cut construction of the tunnel was possible and that the original situation could be reinstated as far as possible after completion.

The Duisburg building ground also made a special construction method necessary. Ground strata: from surface to 2–4 m, civilisation deposits; from ˜ 4 m to ≈ 25–28 m below surface, glacial sand and gravel deposits, containing stones with a diameter > 20 cm and even boulders of 1 m³ and more; from approximately 28 m below surface, layers of Tertiary clay and silt; the groundwater table is ˜ 8 m below the surface, the stream flowing within the sand and gravel deposits from SE to NW (towards the Rhine).

Installing a groundwater barrier, for instance by erecting a continuous diaphragm wall enclosure, was already ruled out in early design stages as was the use of driven steelpiles.

At the inception of the design in 1974, it was decided first to carry out a measuring scheme to establish the groundwater flow velocity. This was followed by a large scale (1:1) trial freezing to ascertain the feasibility of the gap-freezing method.

When these experiments were scientifically valued it was established, that the risk involved was acceptable. The contract documents were prepared prescribing a combination of “cover and cut” with gap-freezing, which is tentatively called the “Duisburg method of Metro-construction”.

During the construction a large scale measuring and scientific research programme was carried out.     

Delineation of groundwater prospective zones from a delta region of India,using geoelectrical and water quality approach

Geoelectrical survey was carried out in the western delta region of River Vasista Godavari, Andhra Pradesh, India, for delineation of groundwater prospective zones due to acute shortage of water supply for various purposes. Forty-six vertical electrical soundings (VES) were done, employing the Schlumberger configuration with a maximum AB/2 of 160 m. The interpreted results of VES show four to five layers with variable thicknesses, such as topsoil zone (1.5–3 m), clay zone (0.84–32 m), finer sand zone (2–72 m), medium to coarse sand zone (4 to 28.8 m) and clay zone (1.2–∞ m), indicating a multi-aquifer system. These results are corroborated with the known lithologs of the study area. Further, the resistivity is also compared with electrical conductivity (EC) of groundwater observed nearby shallow wells representing buried channel (BC), flood plain (FP) and coastal (C) zones, which indicate slightly brackish to brackish water (EC: 1470–6010 µS/cm), whereas the groundwater observed from deep wells shows the fresh (EC: 726–1380 µS/cm), fresh to brackish (EC: 1010 to 3250 µS/cm), and brackish water (EC: 3020 to 4170 µS/cm) located in BC, FP and C zones, respectively. This survey reveals the prospective aquifer zones with potable water at VES locations of 4–6, 8, 10, 11, 14, 16–28, 33–36, 39 and 42–44, where the resistivity values vary from 10 to 40 Ω m. The slightly brackish and brackish water zones are also observed from the resistivity of less than 10 Ω m at shallow depth in BC (VES-22, 37, 38 and 46), FP (VES-1, 2, 7, 29, 30 and 40) and C (VES-3, 4, 9, 12, 13, 15, 31, 32, 41 and 45) zones. As a result, the present investigation has delineated the freshwater zones at shallow (<?12 m) and also at deeper depths (30–45 m) as prospective areas, where BC zone occurs. Freshwater pockets also identified in FP (VES-8 and 39) and C (VES-11, 14 and 15) zones. Thus, this study helps to solve the drinking and irrigation water problems.     

2001-2015年天山山区积雪时空变化及其与温度和降水的关系

采用2001-2015年MODIS积雪和陆表温度数据、中国高时空分辨率降水数据,基于趋势分析和相关分析方法,分析了天山山区积雪时空变化及其与温度和降水的关系。结果表明：（1）年内积雪面积变化受海拔影响,海拔≤4 000 m,呈单峰型分布,积雪面积冬季大,夏季小;海拔介于4 000~≤5 000 m,积雪面积分别在春季和秋季出现两次峰值;海拔>5 000 m,积雪面积变化与低海拔相反,在夏季达到最大,冬季最小。就年际变化而言,全区积雪面积呈略微减少趋势,其中秋季略微增加,春季变化不大,冬季和夏季明显减少。（2）积雪覆盖频率受水汽来向和地形影响,呈西高东低、北高南低分布格局,与海拔呈正相关。山区大部分区域积雪覆盖频率呈减少趋势,其中海拔介于3 600~≤4 600 m的积雪覆盖频率减少最为显著。（3）在春、夏季,温度是决定积雪面积变化的主要因素,与积雪面积呈负相关;在秋、冬季,降水对积雪面积变化的贡献大于温度,与积雪面积呈正相关。（4）积雪覆盖频率整体上与年均温度呈负相关,与降水呈低度正相关,相关程度及显著性水平在空间分布上存在差异,温度对积雪覆盖频率变化的贡献大于降水。     

The origin of carbonate mud in isolated carbonate platforms of Belize,Central America

Carbonate mud from three small isolated carbonate platforms of Belize (Central America) is largely a product of the breakdown of skeletal grains. The composition of the 63-20- and 20-4-µm fractions of 37 samples was determined by point counting under SEM; composition of the <4-µm fraction was assessed qualitatively under SEM. The 63-4-µm fractions are dominated by fragments of mollusks, the codiacean alga Halimeda, and other skeletal types. About one-third of the particles in the 63-4-µm fractions remained unidentified, probably due to obliteration of diagnostic features by early recrystallization processes such as micritization. Nanograins (<1 µm) and short (3-5 µm) aragonite needles are most common in the <4-µm fraction. These grains are interpreted to be largely fragments of codiacean algae (Halimeda, Penicillus). The 20-4- and <4-µm sediment fractions are composed of 80 and 75% aragonite on average, respectively. Trace element composition of strontium averages 7,900 ppm in the 20-4-µm fraction and in codiacean algae samples, and 5,600 ppm in the <4-µm fraction. Geochemical (trace element) data also argue against inorganic aragonite precipitation within the water column, and favor a skeletal origin. The lower strontium contents in the <4-µm fraction as compared with the 20-4-µm fraction may also be a consequence of early recrystallization processes.     

西藏纳木错地区约120kaBP以来的古植被、古气候与湖面变化

西藏纳木错湖相沉积的U系和^11C测年结果表明，湖泊沿岸的6级湖岸阶地及拔湖约48～139．2m的高位湖相沉积形成于约120ka BP以来的晚第四纪。本文根据该套湖相层的发育和其中的孢粉组合特征对纳木错地区约120ka BP以来的湖面变化与古植被、古气候变迁进行了探讨。结果表明，纳木错地区晚更新世以来经历了频繁的湖面波动、气候的冷暖与干湿变化以及森林—草原与草原植被的交替演化。其总体特征是：约115．9ka BP时，纳木错湖面最高。在116～78ka BP期间，该区气候温和凉爽或温和偏湿，植被以疏林草原与森林草原或森林的交替出现为特征，湖面经历了较大幅度的波动，但基本保持在拔湖140～88m之间。在78～53ka BP期间，该区气候干冷，植被以疏林草原为主，湖面大幅度下降，并在拔湖约36～48m之间波动。约53～32ka BP期间，气候转为温暖偏湿或温暖湿润，湖面波动于拔湖约15～28m之间，波动较为频繁。与阶地的发育相对应，该时期内包含了3次明显的暖期和湖面波动过程，区域植被主要以松、蒿、桦为主，为含一定量的冷杉的森林。其中36ka BP左右气候最温暖湿润，区域内可能出现针叶林或针阔混交林。约32～12ka BP期间，该区气候最为干冷，古植被以草原和疏林草原为主，湖面再次发生较大幅度的下降，最低可至拔湖约8m处，但通常维持在拔湖约12～17m之间。约11．8～4．2ka BP期间，气候整体较为暖湿，其中在约8．4～4．2ka BP期间气候最温暖湿润，该区可能发育针叶林或针阔混交林，湖面波动于拔湖2～9m之间，整体波动幅度较小，但波动最为频繁。区域气候对比发现，纳木错地区的冷、暖气候变化过程与整个青藏高原乃至北半球的气候变化基本是一致的，特别是阶地下切所反映的湖面退缩过程与北大西洋的Henrich冷事件之间具有很好的对应关系。     

Refinement of the crystal structure of beryllonite,NaBePO4

Summary The refined lattice parameters of beryllonite are:a=8.178 (3) Å,b=7.818 (2) Å,c=14.114 (6) Å, =90.00° (2); space groupP2₁/n,Z=12. Integrated Weissenberg photographs were taken by using CuK radiation and multiple film packs. The anisotropic refinement of the crystal structure by means of least-square methods gave a finalR value of 0.063 for the 1388 observed reflections. In the crystal structure PO₄ and BeO₄ tetrahedra, linked by shared oxygen atoms in a three-dimensional network, form pseudo-ditrigonal rings perpendicular to theb axis. The independent Na atoms lying in the channels formed by the rings are coordinated as an irregular nine-cornered polyhedron and as distorted octahedra.

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Verfeinerung der Kristallstruktur des Beryllonits,NaBePO ₄

Zusammenfassung Verfeinerte Gitterkonstanten des Beryllonits lauten:a=8,178 (3) Å,b=7,818 (2) Å,c=14,114 (6) Å, =90,00 (2)°; Raumgruppe:P2₁/n,Z=12. Integrierte Weissenbergaufnahmen wurden mit CuK-Strahlung und multiplen Filmpaketen aufgenommen. Die anisotrope Verfeinerung der Kristallstruktur nach der Methode der kleinsten Quadrate ergab für 1388 beob. Reflexe einen abschließendenR-Wert von 0,063. In der Kristallstruktur bilden PO₄-und BeO₄-Tetraeder, die über gemeinsame Sauerstoffe zu einem dreidimensionalen Gerüst verknüpft sind, pseudo-ditrigonale Ringe senkrecht zurb-Achse. Die kristallographisch unabhängigen Arten von Na-Atomen, welche in den aus Ringen gebildeten Kanälen liegen, sind in der Form eines unregelmäßigen neuneckigen Polyeders bzw. in der Form verzerrter Oktaeder koordiniert.

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With 2 Figures     

Biogeochemical characteristics of the lower Mississippi River, USA, during June 2003

During June 2003, a period of mid level discharge (17,400 m⁻³ s⁻¹), a parcel of water in the lower Mississippi River was sampled every 2 h during its 4-d transit from river km 362 near Baton Rouge to km 0 at Head of Passes, Louisiana, United States. Properties measured at the surface during each of the 48 stations were temperature, salinity, dissolved organic carbon (DOC), total dissolved nitrogen, dissolved macronutrients (NO₃+NO₂, PO₄, Si(OH)₄), chlorophylla (chla; three size fractions: < 5 μm, 5–20 μm, and > 20 μm) pigment composition by HPLC, total suspended matter (TSM), particulate organic carbon (POC), and particulate nitrogen (PN). Air-water CO₂ flux was calculated from surface water dissolved inorganic carbon and pH. During the 4 d transit, large particles appeared to be settling out of the surface water. Concentrations of chla containing particles > 20 μm declined 37%, TSM declined 43%, POC declined 42% and PN declined 57%. Concentrations of the smaller chla containing particles did not change suggesting only large particulate materials were settling. There was no measurable loss of dissolved NO₃, PO₄, or Si(OH)₄, consistent with the observation that chla did not increase during the 4-d transit. DOC declined slightly (3%). These data indicate there was little autotrophic or heterotrophic activity in the lower Mississippi River at this time, but the system was slightly net heterotrophic.     

Delineation of saltwater intrusion into the freshwater aquifer of Lekki Peninsula,Lagos, Nigeria

Recently, the deterioration of water quality in the coastal zones of Lekki Peninsula area of Lagos due to saltwater infiltration into the freshwater aquifer has become a major concern. With the aim of providing valuable information on the hydrogeologic system of the aquifers, the subsurface lithology and delineating the groundwater salinity, vertical electrical resistivity (VES) sounding survey was carried out utilizing surface Schlumberger electrode arrays, and electrode spacing varying between 1 and 150 m. The DC resistivity surveys revealed significant variations in subsurface resistivity. Also, the VES resistivity curves showed a dominant trend of decreasing resistivity with depth (thus increasing salinity). In general, the presence of four distinct resistivity zones were delineated viz.: the unconsolidated dry sand (A) having resistivity values ranging between 125 and 1,028 Ωm represent the first layer; the fresh water-saturated soil (zone B) having resistivity values which correspond to 32–256 Ωm is the second layer; the third layer (zone C) is interpreted as the mixing (transition) zone of fresh with brackish groundwater. The resistivity of this layer ranges from 4 to 32 Ωm; while layer four (zone D) is characterized with resistivities values generally below 4 Ωm reflecting an aquifer possibly containing brine. The rock matrix, salinity and water saturation are the major factors controlling the resistivity of the formation. Moreover, this investigation shows that saline water intrusion into the aquifers can be accurately mapped using surface DC resistivity method.     

新疆和田县雪凤岭锂矿床、雪盆锂矿床和双牙锂矿床地质特征及伟晶岩脉群分带初步研究

作为战略性关键金属矿产,锂矿勘查与研究已成为当今矿产勘查和地学研究的热点。项目组2017年以来通过多次野外勘查、系统取样与室内化验分析,确认在新疆和田县白龙山锂多金属矿床东部的雪凤岭一带发现了雪凤岭、雪盆和双牙3处花岗伟晶岩型锂多金属矿床。雪凤岭锂矿床由3个含矿伟晶岩脉群共计47条锂多金属矿体组成,矿体长32~360 m,厚0.9~8 m,走向110°~120°,倾角49°~78°。对雪凤岭矿区伟晶岩脉群研究,发现含矿伟晶岩脉群‒含白云母伟晶岩脉群‒块体石英长石伟晶岩脉群‒含黑色电气石伟晶岩脉群‒块体石英长石伟晶岩脉群‒含白云母伟晶岩脉群‒含矿伟晶岩脉群具对称分带特征,进而在距雪凤岭1550 m南部的双牙山和雪盆沟发现较好的锂矿体,其中双牙锂矿床主矿体长850 m,厚12 m,出露最宽处近100 m;雪盆锂矿床3条锂矿体,长800~1200 m,厚4~8 m,向西合成一个矿体,厚12~20 m。各矿体Li2O品位0.6%~4.02%。伴生BeO品位0.04%~0.15%,Rb2O品位0.10%~0.23%,Nb2O5品位0.007%~0.047%,Ta2O5品位0.003%~0.046%。预测雪凤岭、雪盆、双牙3个矿床334资源量共计Li2O为7.1886×105 t,BeO为2.648×103 t,Rb2O为1.433×103 t,Nb2O5为3.387×103 t,Ta2O5为1.727×103 t,雪凤岭一带有望成为一个超大型锂多金属稀有金属矿产基地。