碳酸盐岩红土中1．4nm间层矿物及其环境意义

碳酸盐岩红土中１．４ｎｍ间层矿物及其环境意义朱立军（贵州工学院，贵阳５５０００３）关键词红土，间层矿物，土壤环境１．４ｎｍ间层矿物是指由绿泥石晶层与２：１型含水膨胀层交互连生所构成的不规划间层粘土矿物，其中２：１型含水晶层可以是蒙脱石层，也可以是蛭石...     

红土型金矿床综述(英文)

近二十年来 ,热带地区普遍存在的红土型风化作用及其对矿床与矿化带的影响引起了普遍的关注。红土型风化壳的主要矿物成分是以铁铝的氧化物及氢氧化物和粘土矿物为主 ,如针铁矿、赤铁矿、铝土矿、高岭石及石英等 ,与其未风化的母岩相比 ,含有相当高的铁和铝。红土型风化过程中 ,易溶元素均不同程度地被淋滤 ,而难溶元素则相对富集。红土型金矿床就是在这样强烈的风化作用中由原生的金矿化带进一步富集而成 ,并可形成极富的矿体。金矿体常常赋存于风化壳的上部 ,易于露天开采。目前 ,在澳大利亚、巴西、巴布亚新几内亚、印度以及非洲的一些国家均发现了红土型金矿床。红土型风化剖面一般可分为 5个特征带 ,由上而下为 :表土带、铁质带、斑点带、浅色带、腐岩带 ,下面即为未风化的母岩 ,金矿体主要赋存于铁质带和斑点带中。红土型风化壳厚度变化很大 ,薄则几米 ,厚可达数百米。金在风化过程中往往向矿化带两侧运移 ,矿体常呈上宽下窄状。次生金常呈自形晶、树枝晶、浑圆状及不规则状产出 ,并常常与铁质结核共生。一般地说 ,次生金的成色很高 ,因为红土型风化作用常常是在氧化并且酸性的地球化学环境中进行 ,金和银主要以氯化物的形式运移 ,局部地球化学环境的变化可导致金的沉淀 ,而银的氯化物则较稳定 ,?     

碳酸盐岩红土风化壳主要特征及红土成因探讨--以贵州典型剖面为例

本文总结提出了碳酸盐岩风化壳成因证据及其演化特点,对风化壳红土成因进行了讨论.     

库岸边坡倾角及水位变化对红土型库岸稳定性影响研究

水库库岸失稳对水库安全运行有重大影响。采用土工试验和干湿循环试验,结合数值计算及理论分析,研究红土型库岸边坡倾角和库水位升降与库岸稳定性的关系。结果表明:(1)在一定初始干密度条件下,红土抗剪强度随水位升降循环次数增加而非线性减小,且在水位升降循环约10次时趋于稳定。(2)在一定水位升降速率、升降幅度和升降循环次数条件下,红土型库岸稳定安全系数随库岸边坡倾角的增加总体上呈减小的趋势,且在边坡倾角为50°左右存在稳定安全系数极小值。(3)在一定水位升降循环次数条件下,水位上升到坡高的60%左右为上升阶段的相对危险区域,且水位上升速率对库岸稳定安全系数影响很小;水位下降至坡高的70%左右为库水位下降阶段的相对危险区域,且水位下降速率越大,库岸稳定安全系数越小。(4)针对一定初始干密度,库岸稳定安全系数先随水位升降循环次数的增加而减小,但在水位升降循环次数约10次后逐渐趋于稳定。库岸岩土体性质及库岸边坡倾角、水位变化都会对库岸稳定产生影响。     

Heavy metal contamination of an arid river environment: Gruben River, Namibia

The dispersal of metalliferous pollution from several spoil heaps produced during 20th century copper mining in the Gruben River valley, Namibia is examined. The Gruben River flows through an extremely arid environment with an average rainfall of ˜25 mm p.a. The potential for physical and chemical remobilisation of Cu, Zn and Ni is assessed by examining the spatial and temporal distribution of metal-contaminated sediment deposited within the confines of the channel. The relationships between metal content, grain size, geomorphic environment and the downstream distribution of metals are discussed. The phase-specific heavy metal concentrations of sediments, collected as part of the downstream sampling programme, are also examined using progressively more aggressive sequential acid extractions. In addition, metal concentrations are compared with Dutch guidelines for soil contamination to ascertain the extent of environmental risk.Total metal concentrations show that the Gruben valley is highly contaminated, particularly with respect to Cu and Ni concentrations, which exceed Dutch target values for Cu (36 ppm) in 94.7% and Ni (35 ppm) in 90.5% of samples, respectively. Zn concentrations are much lower with only 6.3% of the samples exceeding the target value (140 ppm). As might be expected, the metal–sediment concentrations of Cu are the most highly elevated, with a peak value of 10,500 ppm being recorded from material collected from suspended sediment transported during a minor flow event that occurred in March 1999. Lower energy and fine-grained sedimentary environments are shown to be clearly associated with higher metal concentrations. Sequential extractions of metals show that of the three principal elements considered in this study, only a negligible proportion of Cu (0.41%) is held in the exchangeable phase. Ni and Zn were below detection limits. Although the total metal concentrations in the Gruben River valley sediments are extremely high and are in themselves a concern, the small percentage of metals held in the exchangeable phase and the low potential for remobilisation under the arid conditions would suggest that they pose only a minor risk to the environment.     

Effect of chemical fertilizers on the fractionation of Cu,Cr and Ni in contaminated soil

Effect of chemical fertilizers (urea, NH₄Cl, Ca(NO₃)₂, KCl and KH₂PO₄) on the fractionation of Cu, Cr and Ni was studied by a 4-month incubation experiment. Using sequential extraction procedure, it was found that the application of fertilizers could change the distribution of Cu, Cr and Ni in the fractions of soil. Applying urea (CO(NH₂)₂) significantly decreased the concentrations of Cu, Cr and Ni in water soluble plus exchangeable (WE) fraction, but increased those in Fe–Mn oxides bound (FM) fraction (p < 0.01). However, application of NH₄Cl caused an increase in the WE fraction by 27.7% for Cu, 111.5% for Cr and 20.4% for Ni. The CO(NH₂)₂ raised the soil pH from 4.51 to 4.96, whereas NH₄Cl lowered the pH of soil by 0.44 units. The WE fraction of the three heavy metals was significantly increased, while the FM fraction was significantly decreased by adding KCl (p < 0.01). Moreover, the supply of KH₂PO₄ reduced the WE and carbonate bound (CB) fractions of Cu, Cr and Ni in the soil, however, it raised Cu and Ni in the residual (RS) fraction and Cr in the FM fraction. In addition, the mobility index indicated that KCl and NH₄Cl increased the mobility of Cu, Cr and Ni in the soil, whereas urea and KH₂PO₄ decreased the mobility of the three metals in the soil. These results suggest that applying chemical fertilizers does not only provide plant nutrients, but may also change the speciation and mobility of heavy metals in the soil.     

石灰稳定红黏土强度的长期碳化效应

碳化效应是石灰稳定土强度增长机理之一,但长期的碳化作用是否对其强度一直起促进作用？如果没有压实作用,碳化效果到底如何？这些关键问题还没有得到充分的论证。采用灰土拌和后击实养护和养护后再击实的不同制样方法,通过承载比CBR试验,探讨压实作用对碳化效应的影响。制备4种初始含水率的击实试样,开展碳酸溶液和纯水浸泡下的CBR试验,论证长期碳化对石灰稳定土强度的作用效果。结果表明,自然养护90 d后再击实试样的CBR值明显低于击实后养护的试样;初始含水率为34%时前者约为后者的12倍。另外,碳酸溶液浸泡15 d后的试样CBR值均小于纯水浸泡的试样CBR值,但初始含水率越大其影响程度越小,当初始含水率大于34%后两者之间的强度基本没有差别。为进一步佐证长期碳化作用能弱化石灰稳定土的强度,开展不同浸泡时间的无侧限抗压强度试验,发现石灰土的强度呈现先增大后减少的变化趋势,再次证实长期的碳化作用弱化石灰稳定土的强度。最后,利用热重分析法测试经过碳酸溶液浸泡前后的石灰稳定土,发现长期碳化溶解了部分石灰土中的碳酸钙和硅酸盐类胶结物。借助扫描电镜图片和孔隙尺寸分布曲线,从微观角度揭示不同击实和养护方式对石灰稳定土强度的影响机制。     

Composition and origin of the Çaldağ oxide nickel laterite,W. Turkey

The Çalda? nickel laterite deposit located in the Aegean region of W. Turkey contains a reserve of 33 million tons of Ni ore with an average grade of 1.14% Ni. The deposit is developed on an ophiolitic serpentinite body which was obducted onto Triassic dolomites in the Late Cretaceous. The deposit weathering profile is both laterally and vertically variable. A limonite zone, which is the main ore horizon, is located at the base of the profile. A hematite horizon is located above the limonite, which in the south of the deposit is capped by Eocene freshwater limestones and in the north by a siliceous horizon. The deposit is unusual in lacking a significant saprolite zone with little development of Ni-silicates. The boundary between the limonite zone and serpentinite below is sharp with a marked decrease in concentrations of MgO from 13 to 1 wt.% over a distance of 2 mm representing the ‘Mg discontinuity’. Ni concentrations within goethite, the main ore mineral, reach a maximum of ~3 wt.% near the base of the limonite zone. Silica concentrations are high throughout most of the laterite with up to 80 wt.% silica in the upper portion of some profiles. The combination of a serpentinite protolith and a high water table at Çalda?, in association with an aggressive weathering environment in a tropical climate, resulted in the formation of an oxide-dominated deposit. The precipitation of silica may coincide with a change in climate with silica precipitation linked to an increase in seasonality. Additional variations within profile morphology are attributed to transportation during and after laterite development as a result of faulting, pocket type laterite formation and slumping, each of which produces a contrasting set of textural and geochemical features.     

超基性岩红土风化壳中镍的表生富集规律及矿化结构研究 ——以印尼苏拉威西岛Kolonodale矿区为例

文章选取印尼苏拉威西岛Kolonodale红土型镍矿区为研究区,对201个浅井剖面共采取3 161件风化壳样品,进行了w(Ni)值的测试,以揭示超基性岩红土风化壳中Ni的表生富集规律及矿化结构特征。研究结果表明,在平面上,矿区内风化壳的w(Ni)平均值的高低与地形地貌关系密切。斜坡带、坡脚堆积带的风化壳为含镍高值区,其w(Ni)值为0.8%~1.8%;山顶平台区、山脊的风化壳为含镍低值区,其w(Ni)值为0.7%~1.4%。在垂向上,风化产物的w(Ni)值的高低与取样深度及样品属性密切相关。w(Ni)值随着红土带→腐岩带→基岩带的变化出现低值(0.85%~1.55%)→高值(1.15%~4.75%)→低值(≤0.55%)的波动变化规律。矿层的产状(分布、深度、厚度)与风化壳产状之间表现出明显的正相关关系。矿区内的低品位矿层〔1.5%≤w(Ni)≤2.0%〕和高品位矿层〔w(Ni)≥2.0%〕单独或组合发育,产出"正常型双层矿化"、"倒置型双层矿化"、"低品位单层矿化"、"高品位单层矿化"和"叠层矿化"等5种矿化结构类型。综合分析认为,富镁及中等程度蛇纹石化的超基性岩母岩、热带雨林气候环境是矿区内发育富镍红土风化壳的首要条件。吸附、离子交换以及次生沉淀等3种成矿作用的共同发育,导致了红土风化壳中Ni表生矿化的连续性、矿石类型的多样性及特高品位矿石的形成。矿床中矿化结构类型的多样化是区域构造背景、地形地貌、构造发育、水文条件等诸多因素耦合作用的结果。文章指出,在今后的红土型镍矿床的找矿勘查过程中,需要综合考虑各类内、外生控矿因素对矿床发育的影响,总结矿区尺度的矿化结构规律,可有效地指导矿床勘查工作。     

昆明红土微观结构特征参数分析

红土的特殊物理力学性质主要是由它的微观结构特征决定的。分析了昆明红土在电子显微镜下的微观结构特征,从经过处理的红土微观结构照片中提取了面积比例、平均周长、最大面积、圆形度、复杂度、定向度和分布分维等定量化参数,并将这些定量化参数与红土的物理力学性质之间建立了联系。