广西靖西红黏土及其击实后的水稳定性试验研究

为分析红黏土地基及其强夯法加固后的水稳定性问题,对红黏土及其击实样在饱和前、饱和后的固结特性以及剪切特性进行了室内试验。研究表明,土样经过击实后,压缩稳定后的应变值比较小,压缩稳定再浸水后土样的变形只有少量增加;原状土样在剪切过程中一般呈现应变软化的特征;固结饱和后快剪试验强度明显要比固结未浸水试验强度要小。因此,浸水效应对红黏土强度的影响是很明显的。     

不同破坏形式加筋红土强度分析

从加筋土体的等效围压概念出发,根据加筋土体发生拉裂破坏和剪切破坏时筋材所发挥的作用不同,提出了两种破坏形式下考虑等效围压折减系数的等效围压表达式,并根据加筋土体的极限平衡条件,确定了加筋土体的强度参数,分析了不同排水条件对加筋土体强度参数的影响。结合临界围压,建立起加筋土体强度破坏标准。按照一般加筋土体的广义等效围压,给出了两种破坏形式下等效围压折减系数的确定方法,并用实例进行验证。     

苏南及沿江地区柏山组,下蜀组的时代及成因

柏山组与下蜀组是江苏西南部丘陵山区的两个岩石地层单位,也是第四纪特定气候环境下形成的两类土状堆积。经与平原区第四纪地层对比,柏山组的层位与平原区的海门组上段至启东组下段相当,沉积时代为早更新世晚期到中更新世早期;下蜀组与平原区的启东组至湖组相当。沉积时代为中更新世晚期至晚更新世。柏山组网纹红土是早期干凉气候环境下堆积的黄土,经后期强烈湿热、氧化及流水冲刷后的产物,成因以洪冲积为主;下蜀组黄土是干凉气候环境下的产物,是风尘物质经流水改造后的产物,具多成因特点。     

元谋盆地的第四纪红土

本文阐述了元谋红土的分布规律，物理化学性质，红土化作用时期以及红土对环境的解释。按成因观点，元谋红土可分风化壳型红土，地下水型红土，坡积红土三种。中更新世中期，晚更新世早期，全新世最佳期，是元谋红土的主要形成特期。作为岩石圈，大气圈，生物圈相互作用的产物，红土的形成发育，与盆地的第四纪发育历史密切相关。同时，红土也记录了盆地过去的环境演化，因而有可能提取红土储藏的信息重塑第四纪环境。     

New insights into nanomineralogy and geochemistry of Ni-laterite ores from central Greece (Larymna and Evia deposits)

Nickeliferous laterite ores from two typical central Greece deposits (Larymna and Evia), currently used in the LARCO GMMSA smelting plant to produce ferronickel, were characterized using a combination of diffraction, microscopic, and analytical techniques. X-ray diffraction patterns of various fractions, with emphasis to the clayey material (<2 μm), after glycolation and heating at 550 °C, indicated that both materials contain crystalline Fe³⁺ oxide (hematite) and chlorite-group phyllosilicates, whereas the Evia sample contains additional illite. Transmission electron microscopy investigations revealed that the LARCO laterite ores consist of complex nanoscale aggregates of the above-mentioned phases. Different Ni-bearing Mg-Fe-phyllosilicates (mainly chlorite-group minerals), occur in mixture with hematite. Nickel is present in all examined phases, and therefore the separation of pure Ni-phases, by physical or chemical methods, is practically unfeasible. Trace element bulk analyses showed that there no significant differences, with regarding to Ni content concentrations (ca. 0.6–0.7 wt.%), between the initial ore and the clay fraction, for both the Larymna and Evia laterites (ca. 30% and 26% wt.% enrichment respectively). However, the Larymna ore contains double quantities of Co and it is enriched in rare earths compared to Evia (ΣREE = 774 ppm and 76 ppm respectively), while Sc concentrations are comparable in both mining areas (64 ppm and 42 ppm respectively). Discrimination diagrams (e.g. Th/Sc vs. Zr/Sc and Ce/Ce* vs. Eu/Eu*) showed that LARCO laterite Ni-ores do not exclusively originate in ultrabasic -ophiolitic- rocks as previously considered.     

盐酸-硫酸镍混合溶液热力学性质

在HCl-NiSO4-H2 O混合溶液中 ,以标准氢电极和银—氯化银电极组成无液接电池 ,恒定溶液总离子强度I和NiSO4在溶液中的离子强度分数yB 的条件下 ,在 2 78 1 5～ 3 2 3 1 5K温度范围内测定下列电池的电动势Pt,H2 ( 1 0 1 3 2 5kPa) |HCl(mA) ,NiSO4(mB) ,H2 O|AgCl-Ag由于体系存在硫酸的二级解离 ,应用数学迭代方法确定平衡体系氢离子的浓度 ,计算了混合溶液中HCl的活度系数γA,结果表明 ,在溶液总离子强度保持恒定时 ,HCl的活度系数服从Harned规则。在溶液组成恒定时 ,盐酸的活度系数logγA 对热力学温度l/T作图 ,是一条直线     

The lateral and vertical growth of laterite weathering profiles,Hawaiian Islands,USA

The Hawaiian Islands permit investigation of tropical chemical weathering rates and processes on a single rock type, basalt. Chronosequences are investigated as a function of rainfall due to the varying age of each island, including Kauai (~4 Ma), Oahu (~2 Ma), and Hawaii's Kohala Peninsula (~0.3 to 0.17 Ma). Understanding tropical critical zone (CZ) development is vital given the large populations in developing countries that rely on it. HVSR (horizontal-to-vertical spectral ratio) seismic soundings on Kauai indicate that ~60% of the variability in laterite thickness is due to gradients in precipitation, with errors in erosion corrections and variability in the original permeability structure of the volcanic sequence playing important roles. Basalts have higher horizontal than vertical hydraulic conductivity (K_h > K_v) , and local variability in likely drives much of the remaining differences in laterite thickness. HVSR is well suited for estimating laterite thickness as it has been shown to reliably detect the base of the weathering profile, is rapid (20 min/sounding), highly portable, and occupies a very small footprint. Comparison of Kauai and Oahu weathering profiles suggests that the Oahu laterites are fully or nearly fully formed, despite being half the age of Kauai. By contrast, the young laterites on Kohala (~170 to ~300 ka) exhibit greatly contrasting thicknesses, where coastal laterites are thick and interior laterites are thin, suggesting that early weathering on shield volcanoes produces wedge-shaped laterites near the coast. With time, the thick (coastal) end of the wedge propagates upslope such that a fully developed, constant-thickness laterite carapace can form in ~2 Ma or less. The development of thickened coastal laterites on young substrates depends on greater water–rock ratios as vertically infiltrating water upslope is diverted laterally. This view of laterite development is very different compared to endmember models of continental weathering and CZ development. © 2020 John Wiley & Sons, Ltd.     

浅析东南亚地区红土型镍矿地质特征及成矿规律

东南亚地区红土型镍矿分布较广,成矿地质条件优越。该类矿床产于超基性岩带顶部红土型风化壳内,矿石多为含镍的褐铁矿化黏土,其产出规模、分布范围和品位高低与原岩类型、气候变化、地形地貌和构造条件关系密切。成矿物质主要来源于超基性岩体,是镁铁质-超镁铁质岩体风化-淋滤-淀积的产物,矿石的矿物组分与风化土的矿物组分大体一致,属黏土硅酸盐镍矿床。本文在收集前人资料的基础上,系统地阐述了矿床区域地质背景、矿床地质特征及成矿分布规律初步研究,总结出了该类矿区找矿标志及成矿规律,对寻找红土型镍矿床具有一定的指导作用。     

Geostatistical modelling of lateritic bauxite orebodies in Surinam: effect of the vertical dimension

Lateritic bauxite deposits in Surinam have until now been modelled in two dimensions. The samples collected by auger drill are composited into 1 m (3 ft) intervals and the accumulated grade per hole used as the input for statistical and geostatistical studies. The aim of the study presented in this paper is to quantify the information lost by working with accumulated grades. In other words, the third dimension is taken into account, by considering successive slices with a thickness of 1 m. The composition of the bauxite orebody is characterised by the loss on ignition (LOI), silica, titanium oxide, iron oxide and aluminium oxide contents.The average grade of silica increases significantly with depth, whereas the decrease in the average LOI is only minor. The statistical study indicates two populations for silica and LOI, at least for the fourth slice (at 3–4 m from the top of the orebody) and deeper. For iron oxide a significant decrease with depth is observed, but for each slice only one population could be distinguished. For titanium and aluminium oxide no significant variation with depth and no multi-populations are observed. All these observations are linked to the weathering process, which is the process of genesis of bauxite. The higher the samples are in the profile, the more intense the weathering has been, as indicated by the leaching of silica. These observations confirm that a horizontal zoning is present.For all five parameters studied, a spatial correlation in the horizontal plane is noted for the successive slices. The range of this correlation is on average 200–250 m, and a relative nugget of 35–80% is calculated depending on the parameter and the depth position.The study presented shows clearly that there is a variation with depth. By considering accumulated values, some of this information is lost. For example, for the accumulations of silica and iron oxide no spatial correlation is observed, whereas for the individual slices a distinct spatial correlation is present.     

安徽省沿江地区网纹红土和下蜀土的形成环境及其年龄

通过对安徽省沿江地区的网纹红土和下蜀土的岩性、地球化学特征、古地磁和热释光测年等综合研究，认为网纹红土形成于山地、丘陵古地理景观和热带－亚热带湿热气候环境中．年龄介于０．４５－２．５ＭａＢ．Ｐ．之间，其底界年龄与我国北方午城黄土的底界基本一致；下蜀土形成于山前垅岗状倾斜平原古地理景观和干旱－半干旱的温带－暖温带气候环境中．年龄介于０．１３－０．４５ＭａＢ．Ｐ．之间．与我国北方上离石黄土大体相当，以往与马兰黄土对比并不合适。