湘潭石潭海泡石粘土矿床特征及找矿方向

赋存于茅口组下部含泥质灰岩段的矿体呈似层状、透镜状，长3500－5600m，平均厚4.39-5.15m，矿石品位一般8%-20%，最高可达65％。矿石有原岩型和粘土型两类，粘土型矿石一般呈灰－深灰色，干燥后呈灰白色，硬度1－2，比重1.6-2.3t/m^3，粘性强，可塑性好，透水性强。主要矿物成分有海泡石、石英、方解石、滑石、蒙脱石、伊利石和氟磷石等,矿石富Si、Mg、贫K、Na,CaO、Al2O3含量偏高。早二叠世江南古陆两侧局限（浅）海或海湾环境有利于海泡石沉积。在永顺－石门、安化－浏阳、怀化－浏阳成矿带，具有良好的找矿前景，估计海泡石资源量在3000万吨以上。     

包心构造是铝土矿床的成因标志

铝土矿床的包心构造,即粘土岩层包裹铝土矿体,是腐植酸长期分解土壤硅酸盐,而导致土壤剖面的垂直分层。具备垂直渗水系统的地形,如岩溶洼地、平顶山丘,是成矿的先决条件之一。铝岩系是一套陆相地层,夹在地层剖面的基底岩层风化侵蚀面之上,和其上发育植被的沉积间断面之下。铝土矿是陆上成矿,是植物化学风化残积矿床。     

The relations between modulus of elasticity and temperature in the context of the experimental simulation of rock weathering by fire

Fires occur frequently in many biomes and generate high temperatures on the ground surface. There are many field examples of fire causing rock disintegration. The simulation of fire in the laboratory (using a furnace) and the monitoring of changes in rock modulus of elasticity (with a Grindosonic apparatus), reveal that different rocks respond differently to heating. Significant decreases in elasticity occur at temperatures as low as 200°C and granites display particularly marked reductions. Extended periods of heating are not required for significant reductions to occur. It is postulated that the degree of change in elasticity as a result of simulated fire is such that rock outcrops subjected to real fires are likely to be sufficiently modified as to increase their susceptibility to erosion and weathering processes.     

Differential diatom dissolution in Late Quaternary sediments from Lake Manyara,Tanzania: an experimental approach

Diatom dissolution in saline lakes represents an important obstacle to the quantitative reconstruction of water chemistry and climate from lake sediment archives. This problem is here approached experimentally by artificially dissolving diatom-bearing core sediment from Lake Manyara, Tanzania. Manyara holds one of the longest continuous palaeolimnological records from tropical Africa although its interpretation is based on a fragmentary diatom record due to frustule dissolution. These experiments have revealed clear changes in assemblage composition as dissolution operated differentially with respect to diatom taxa. Differential dissolution has considerable impact on the water chemistry estimates derived from transfer functions. Taphonomy, rather than environmental change, may have been responsible for minor fluctuations in the diatom assemblages from Manyara, although major palaeohydrological changes during the Late Pleistocene and Early Holocene can be identified. Particularly well represented by MANE-87 is a period of intermediate lake level between 27 500 and 23 000 ¹⁴C yr BP which has regional palaeohydrological significance.     

新疆尉犁县蛭石矿床成因及矿床模式探讨

本文通过新疆尉犁县蛭石矿床的研究指出,与蛭石成矿密切相关的云母岩是碱性超基性岩经同源高温气液多次反复交代所形成之蚀变岩。并证实,在热液阶段,不能直接形成蛭石矿,只有在风化作用阶段,金(黑)云母经水化之后才铲最终成矿。在搞清成矿地质背景、成矿机制、成矿过程的基础上,确定该蛭石矿床成因类型为:与碱性超基性岩有关的气化—高温热液交代—风化壳型蛭石矿床,并初步构想了该蛭石矿床之成矿模式。     

Geochemical mass balances of major chemical constituents in the watershed of the Changhuajian River in China

Based on the geological background, R-mode factor statistics, and the analysis of the stability diagram for the corresponding system, five weathering reactions controlling the surface-water chemical composition in the watershed of the Changhuajiang River are deduced. In the mass balance model, the precipitation accounts for some solute input, since the rainwater is dilute without pollution. Most of the Ca²⁺ and HCO ₃ ^– ions are from the dissolution of calcite, K⁺, Na⁺, H₄SiO₄ and some of the Mg²⁺ and HCO ₃ ^– come from albite and biotite weathering to kaolinite. The dissolution of dolomite and gypsum controls the mass balances of Mg²⁺ and SO ₄ ^2– . The dissolution of calcite is the dominant chemical weathering reaction in the watershed because of its reactivity and high concentration. In the watershed in 1986, the chemical weathering rate was 0.073 (kg/m² a), and the mechanical denudation rate is 0.093 (kg/m² a). The chemical weathering mass output proportion of carbonate rocks to silicate rocks was about three to one.     

Differences of granitic weathering at the northern and southern feet of Dabie Mountains,Central China: Implication for tectonic and climatic environments

Previous studies of weathering generally started with geochemistry[1—8] and mineralogy[9—12], and have been focused on chemical weathering rates[1—3], removability-enrichment of elements[3—6] during chemical weathering, and the age of weathering profi…     

Modeling Biogeochemistry,the Key for Understanding Environmental Chemistry of a Semi－Arid Soil in Egypt

1IntroductionThecomponentsoftheenvironmentaredamagedbyagriculturalpractices.Soilslosstheirfer tilityandwaterdeterioratesduetopollution .Chemicalweatheringofmineralandsoiloccursattheinterfacesbetweentheliquidandsolidphases;consequentlythesurfaceareaandcompositionofthemineralsplayanimportantroleinthisprocess.GarrelsandMackenzie ( 1 96 7)suggestedthatincon gruentweatheringreactionswouldproducedissolvedspeciesandnewsolidsthataremorestableintheweatheringenvironmentthantheoriginalbedrockminerals.Ro…     

Incipient weathering rind development on introduced machine‐polished granite discs in an Arctic alpine environment,northern Scandinavia

Weathering rinds, zones of alteration on the exterior surfaces of rock outcrops and coarse unconsolidated surficial debris are widely used by geomorphologists and Quaternary geologists as indicators of the relative age of landforms and landscapes. Additionally they provide unique insights into the earliest stages of rock and mineral weathering, yet the origin of these alteration zones is relatively poorly understood. This lack of understanding applies especially to the initial stages of rind formation. The study reported in this paper has two principal objectives. The first is to use lightly polished granite discs inserted in soil profiles under several different plant communities in an Arctic alpine environment for a period of four or five years to investigate the nature of incipient weathering rind development. The second is to investigate the factors responsible for spatial variability in the nature and rates of rind formation. Incipient weathering rind development on the outer edges of the granite discs is observable and measurable over a period of time as short as four years in the mild Arctic alpine environment of Swedish Lapland. The earliest stages of rind development involve the development of a porous structure consisting of a combination of pits and fractures which have been solutionally enlarged and modified. Solution appears to be preferentially concentrated on the surfaces of feldspars and, to a lesser extent, quartz. In addition, iron oxides are present along grain boundaries and in grain interiors and are interpreted to have been derived from the oxidation of ferromagnesian minerals. Spatial variability in weathering rind development appears to be particularly driven by differences in moisture but is not related to soil pH. Copyright © 2005 John Wiley & Sons, Ltd.