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1.
Concentration of Fe-oxides and alumina in weathering processes are main geological reactions for lateritization and bauxitization, respectively. In western Japan, red-coloured soil formed by weathering processes developed in many places. This soil is composed of hydrous Fe-oxide minerals, hydrous alumina minerals and other minerals. It was formed in the upper part of deep weathering crust by weathering processes under some kind of sub-tropical climate, probably in the Pliocene. One of these occurrences is observed in the upper part of Goshikidai and Konodai, west part of Takamatsu city, northeast Shikoku Island, west Japan. A deep weathering crust is distributed on wide hilly plains ranging from 250 to 400 m a.m.s.l. in the northwestern region of Takamatsu city. Original rock of the weathering crust is bronzite andesite and glassy bronzite andesite, so-called ‘sanukite’. The andesites had been weathered under some special climate, and the geological age of the weathering is the same as above. The mineral assemblage and formation mechanism are similar to those of laterite and bauxite. The weathering crust developing in this region are subdivided into the three following zones: (1) A zone, composed of hydrous Fe-oxides and metahalloysite with small amounts of gibbsite and it is associated with white veins of metahalloysite; (2) B zone, composed of hydrous Fe-oxides and metahalloysite (some material is associated with -cristobalite); and C zone, composed of metahalloysite or halloysite and -cristobalite with relict crystals of feldspar and quartz, and some material is associated with montmorillonite. Chemical analyses of the materials of the three zones show the formation mechanisms of the weathering crust. 相似文献
2.
福建郭山高岭土矿床中高岭矿物的研究 总被引：1，自引：0，他引：1
本文运用X射线衍射、红外吸收光谱、分析电子显微术和化学分析等多种方法对福建郭山高岭土矿床中的高岭矿物(高岭石和埃洛石)的矿物学性质、分布及矿物形成的阶段性变化进行了系统研究。结果表明,根据高岭石和埃洛石相对含量的多少,花岗岩风化剖面全风化带划分的4个矿物段可以反映这两种矿物的分布特点。埃洛石为具有管状和多面体球状的7?型以及10?—7?、7?-高岭石过渡型。高岭石晶体形态和结晶有序度在风化剖面垂直方向上的规律性变化与高岭石的形成经历了初始结晶——强烈高岭土化——风化作用后期的阶段性变化有关。 相似文献
3.
R. L. Brathwaite A. B. Christie K. Faure M. G. Townsend S. Terlesk 《Mineralium Deposita》2012,47(8):897-910
At the Matauri Bay halloysite deposit, economically valuable halloysite-rich clays are hosted by a sanidine rhyolite dome (Ar–Ar dated at 10.1?±?0.03?Ma). The rhyolite dome intrudes an older basalt and is overlain by alluvial sediments and a younger basalt (4.0?±?0.7?Ma). A blanket-like, halloysite-rich zone is restricted to depths of 10–30?m from the present day erosion surface. Primary sanidine and plagioclase phenocrysts in rhyolite are completely leached out in the halloysite-rich zone but are only partially leached out at greater depth. Halloysite was formed by hydrolysis and cation leaching of sanidine and plagioclase phenocrysts and groundmass glass in the rhyolite, resulting in loss of K, Ca, Na and Si and enrichment in OH (LOI 6–10%) and Al2O3 (20–30%) relative to least-altered rhyolite with 1.8% LOI and 14.5% Al2O3. Oxygen and hydrogen isotope data indicate the halloysite is supergene rather than hydrothermal in origin, which is consistent with the absence of pyrite, alunite and other acid-sulphate type hydrothermal minerals, and with the blanket-like alteration profile. The dominance of halloysite over kaolinite was favoured by water-saturated weathering conditions during the late Miocene-Pliocene subtropical weathering regime in Northland. 相似文献
4.
Weathering profile of non-welded ignimbrite and the water infiltration behavior within it in relation to the generation of shallow landslides 总被引：1，自引：0，他引：1
The mechanism underlying rain-induced shallow landslides of non-welded ignimbrite is found to be a special type of weathering profile and the behavior of water infiltrating through that profile, according to our study of Ito ignimbrite in southern Kyushu, Japan. Rhyolitic volcanic glass, the primary component of ignimbrite, is first hydrated and dissolved, forming halloysite. Halloysite near ground surface is then transported through the ignimbrite by infiltrating water and becomes clogged in interstices to form clay bands. Suction monitoring across a weathering profile indicated that downward infiltration of water is disrupted once by a zone of less-permeable clay bands and again at the weathering front. This disruption at the front is caused by a capillary barrier effect caused by the structure where finer, weathered material overlies coarser, fresh material. This results in a well-defined weathering front, particularly beneath a slope where water flux is parallel to the front, whereas the front is transitional beneath a ridge top where the front is nearly horizontal and the water flux is normal to the front. Infiltrating water from rain increases the weight of weathered material and decreases the suction within the material, which is the final trigger of a shallow landslide of non-welded ignimbrite; long-term weathering, which proceeds on the order of years, provides slide material. 相似文献
5.
本区燕山早期花岗岩发育的风化壳中的粘土矿物以高岭石和埃洛石(7Å)为主;蒙脱石、三水铝石及其它为新查明矿物。据粘土矿物组合特征,自风化剖面深部到地表分为三个带:含蒙脱石带,高岭石和埃洛石(7Å)带,含三水铝石带。本文探讨了矿物在风化过程中的生成演化顺序,并进行了热力学的解释。据各带粘土物质的阳离子交换量与稀土含量变化的不一致关系认为,稀土在C带中的富集是化学风化的结果,与粘土矿物组合无关。 相似文献
6.
A new method to estimate strain and competence contrast from natural fold shapes is developed and verified by analogue and numerical experiments. Strain is estimated relative to the nucleation amplitude, AN, which is the fold amplitude when the amplification velocities caused by kinematic layer thickening and dynamic folding are identical. AN is defined as the initial amplitude corresponding to zero strain because folding at amplitudes smaller than AN is dominantly by kinematic layer thickening. For amplitudes larger than AN, estimates of strain and competence contrast are contoured in thickness-to-wavelength (H/λ) and amplitude-to-wavelength (A/λ) space. These quantities can be measured for any observed fold shape. Contour maps are constructed using existing linear theories of folding, a new nonlinear theory of folding and numerical simulations, all for single-layer folding. The method represents a significant improvement to the arc length method. The strain estimation method is applied to folds in viscous (Newtonian), power-law (non-Newtonian) and viscoelastic layers. Also, strain partitioning in fold trains is investigated. Strain partitioning refers to the difference in strain accommodated by individual folds in the fold train and by the whole fold train. Fold trains within layers exhibiting viscous and viscoelastic rheology show different characteristic strain partitioning patterns. Strain partitioning patterns of natural fold trains can be used to assess the rheological behaviour during fold initiation. 相似文献
7.
绝大部分的亚硝酸盐和氰化物属于钙钛矿型结构,但有部分化合物为“反”钙钛矿型结构,充填空洞A位的阳离子的拓扑体积为0。阴离子团NO2-和CN-的拓扑体积都近乎常数,分别为41.73Å3和40.03Å3,标准方差σn-1=1.516和σn-1=1.25。由此,进一步证明了原来的一套离子拓扑体积数值的普适性。“反”钙钛矿型结构中A位阳离子的平均半径rA>1.00Å时,三价阳离子会产生扩容效应,其扩容系数大约是其本身拓扑体积的2倍;正钙钛矿型结构中,当A位是由半径较大的Cs+充填时,Cs+也会产生扩容效应,其扩容系数约为24Å3。氰化物中结晶水分子的拓扑体积近乎常数,为24Å3或0。 相似文献
8.
Trace-element contents in leucite and its alteration mineral phases from the Quaternary potassic rocks of the Roccamonfina volcano have been determined. The dominant weathering phase of leucite is analcite. In the early stages of the conversion process, it concentrates mainly Rb and Sr with minor amounts of Ba, Ni, V, Zn, La, Ce and Zr. At more advanced stages of the conversion process, only Rb and Y persist, while all other elements (except Cu and Cr that are essentially immobile) are lost, particularly Zn and to a lesser extent La, Ce and Nd. Besides analcite, leucite may also subordinately alter to halloysite. This probably occurs by interaction of waters of low cation/H+ ratio. Halloysite concentrates mainly Sr and, to a lower extent, Ba. Environmental implications are significant only for K, as the release of this element to groundwaters increases greatly the fertility of soils. 相似文献
9.
皖南地区花岗岩风化壳中稀土元素普遍富集，局部已成为矿床，其中，郎溪县姚村岩体风化壳富集程度较高。LA- ICP- MS锆石U- Pb定年表明，姚村花岗岩体的形成年龄为127.9±1.4 Ma，属于皖南地区燕山期晚期岩浆作用的产物。风化壳可细分为残坡积层（A）、强半风化层（C1）、过渡层（C2）、弱风化层（C3）和基岩（D）五层。稀土总量在纵向剖面上呈“波浪式”分布，各层稀土分布型式表现出对原岩的继承性。风化壳稀土配分型式与基岩一致， 富集LREE，轻重稀土分馏明显(La/Yb)N=15.6），但总含量明显更高。基岩∑REE为338×10-6，半风化层∑REE最高达642×10-6，富集约两倍。风化壳物质由风化残余主矿物（石英、钾长石、斜长石、黑云母）、黏土矿物（高岭石、埃洛石、伊利石、三水铝石等）和副矿物（锆石、磷灰石、榍石等）等组成。黏土矿物以伊利石含量最高，指示风化壳发育不成熟。REE与埃洛石含量明显正相关，与其他黏土矿物关系不明显。（含）稀土矿物（尤其是榍石）对风化壳中稀土元素的贡献量超过百分之五十，其次为斜长石，是风化壳中REE的重要来源。 相似文献
10.
皖南地区花岗岩风化壳中稀土元素普遍富集，局部已成为矿床，其中，郎溪县姚村岩体风化壳富集程度较高。LA- ICP- MS锆石U- Pb定年表明，姚村花岗岩体的形成年龄为127. 9±1. 4 Ma，属于皖南地区燕山期晚期岩浆作用的产物。风化壳可细分为残坡积层（A）、强半风化层（C1）、过渡层（C2）、弱半风化层（C3）和基岩（D） 5层。稀土总量在纵向剖面上呈“波浪式”分布，各层稀土分布型式表现出对原岩的继承性。风化壳稀土配分型式与基岩一致， 富集LREE，轻重稀土分馏明显\[(La/Yb)N=15. 6\]，但总含量明显更高。基岩∑REE为338×10-6，半风化层∑REE最高达642×10-6，富集约两倍。风化壳物质由风化残余主矿物（石英、钾长石、斜长石、黑云母）、黏土矿物（高岭石、埃洛石、伊利石、三水铝石等）和副矿物（锆石、磷灰石、榍石等）等组成。黏土矿物以伊利石含量最高，指示风化壳发育不成熟。REE与埃洛石含量明显正相关，与其他黏土矿物关系不明显。（含）稀土矿物（尤其是榍石）对风化壳中稀土元素的贡献量超过 50%，其次为斜长石，是风化壳中REE的重要来源。 相似文献
11.
Eurybiades Busenberg 《Geochimica et cosmochimica acta》1978,42(11):1679-1686
Chemical analyses of 300 solutions produced by the artificial weathering of eight different feldspars in fourteen experiments of up to 1200hr duration were used to study the evolution of water during weathering. The range of pH was between 4 and 5·5. Within 4 hr of dissolution, the activity of Al was controlled by the pH and the solubility of microcrystalline gibbsite. After 100 hr of dissolution, the pH and microcrystalline halloysite controlled the activities of Al and silicic acid in all of the solutions.Microcrystalline halloysite was the only phase identified in the weathering of plagioclases in distilled water and 1 atm CO2 partial pressure. Montmorillonites, halloysite and other clay minerals were produced from oligoclase in aqueous solutions containing high initial concentrations of Ca. Mg, K and SiO2.The experimentally determined log solubility product of microcrystalline gibbsite was ?32·78 ± 0·04 and log for the hydrolysis of microcrystalline halloysite was 11.58 ± 0·05. The results suggest that very poorly crystalline metastable phases may control the initial compositions of some waters in contact with rocks containing feldspar minerals. 相似文献
12.
湖南辰溪仙人湾埃洛石型高岭土矿床特征及成因分析 总被引：1，自引：0，他引：1
在野外地质矿化特征调查的基础上,通过化学成分分析、光学显微镜、红外吸收光谱、X射线衍射、扫描电镜等手段,对新发现的湖南辰溪仙人湾埃洛石型高岭土矿床特征及成因进行研究发现:此高岭土矿体呈似层状与囊状形态,就位于二叠系/石炭系角度不整合面及二叠统/下二叠统假整合面上,分布在岩溶洞穴体系中。矿石中主要矿物为1nm管状埃洛石,部分为0.7 nm管状埃洛石,原生带矿石中埃洛石的含量达95%以上。该高岭土矿床为次生淋滤胶体溶液沉积-重结晶成因高岭土矿床矿床,系温暖湿润、岩溶发育的环境中,受强淋滤作用,由来自上覆地层砂页岩、煤层、泥灰岩及泥质灰岩中的硅铝物质经过相对富集,形成硅铝溶胶,迁移,在岩溶洞穴中沉淀并再次富集成为凝胶体,脱水老化形成埃洛石。 相似文献
13.
14.
In the Middle Atlas of Morocco, alkali basaltic flows record successive weathering phases during the Quaternary. In fresh basalt interior and intermediate external zones, the first weathering stage is characterised by glass dissolution and the formation of a Si-Al poorly-crystallised product. Advanced weathering phases are characterised by 10 Å halloysite, kaolinite and goethite, located within the primary minerals or as secondary products in fissures. Olivine and iddingsite are transformed into Si-rich goethite, plagioclase into halloysite and pyroxene into a mixture of halloysite + geothite. Dissolution of Ti-magnetite and ilmenite yielded Ti-rich products. In these conditions, the weathering of basalts and development of a soil matrix are accompanied by the elimination of certain chemical elements, such as Si, Ca, Na and K, and the concentration of Fe and Al. In the soil, clay minerals such as illite and vermiculite, do not have any genetic relationship with weathered basalt and were probably introduced externally. 相似文献
15.
通过对我国南方许多风化型高岭土矿床研究查明,在表生条件下形成高岭石-多水高岭石矿物的基本因素是决定于风化母岩的岩性和水介质的物化性质。水介质的物化性质又明显地受到风化母岩的岩性类型和结构构造、动力裂隙的发育程度、围岩的稳定性和透水性、气候、地形地貌和植被等因素的综合性制约。 相似文献
16.
《Applied Geochemistry》2002,17(7):885-902
An ancient saprolite has developed on the Palaeoproterozoic granulite, granite gneiss and amphibolite bedrock of the Vuotso–Tankavaara area of central Finnish Lapland. The present day climatic regime in Finnish Lapland lies within the northern boreal zone and so the saprolite there can be regarded as fossil. Cores of saprolite were collected from 4 sections (42 samples) and analyzed chemically and mineralogically. In the study area, progressive weathering of the rocks has been marked by gradual enrichment in Al, Fe and Ti; and depletion of Na, K and Ca. The higher concentration of Fe(III) and water and reduced Na and Ca in weathered bedrock in the 4 sections are indicative of oxidation, hydration and leaching processes involved during weathering. The primary minerals in the saprolite are plagioclase feldspar, K-feldspar, quartz, garnet (almandine) and hornblende; the common secondary minerals are kaolinite, halloysite, and vermiculite in addition to minor amounts of sericite. Intense weathering is indicated by: (1) the presence of kaolinite and halloysite in 4 sections of different bedrock types, and (2) the comparatively lower SiO2/Al2O3 (wt.%) ratio (2.30) of weathered granulites (3 sections) as compared to fresh granulite (4.33) and that of weathered amphibolite (2.68) as compared to fresh amphibolite (3.56). In general, kaolinite and halloysite have formed through the weathering of feldspars, garnet, and biotite. Vermiculite is the most probable alteration product of biotite. The formation of kaolinite and halloysite in Finnish Lapland indicates wetter and warmer climatic conditions during the time of their formation than at present. The possible time for formation of the saprolite is early Cretaceous–early Tertiary into Middle Miocene. 相似文献
17.
Lateritic soils near Calicut, Kerala, contain halloysite of intermediate hydration, kaolinite, goethite, gibbsite and quartz. The presence of halloysite is responsible for relatively high plasticity and cation-exchange capacity. Fe-hydroxide colloids along with halloysite contribute to significant phosphate uptake by this soil. Composition of local groundwater is consistent with weathering of sodic plagioclase to gibbsite, kaolinite and metastable halloysite. 相似文献
18.
基岩风化体现了构造与气候对地貌演化过程的共同作用。晚新生代的强烈构造抬升和干旱的气候条件,使得祁连山成为研究基岩风化与地貌演化过程的理想场所。借用施密特锤系统地研究了基岩回弹值（R）在黑河流域内不同海拔高度内的变化,结果显示流域平均的R值与侵蚀速率具有较好的相关性,意味着R值可以作为风化强度空间变化的代用指标。研究区内各种岩石类型的R值变化相差不大,说明岩性对R值的影响较小。进一步将R值与气候因子和区域地形进行比较发现：气温、降水与NDVI对R值的影响较强;坡度与局地高差对R值影响较弱,高程与R值在海拔小于3 800 m时呈现负相关关系,在大于3 800 m时呈现正相关关系。 相似文献
19.
We present a numerical approach which accounts for nucleation, growth and/or resorption of particles of fixed composition in aqueous solutions, and which involves functionalities suited to the formation of simple clay minerals in weathering processes, such as: formation of non-spherical particles, heterogeneous/homogeneous nucleation, several growth laws, precipitation resulting from the dissolution of primary minerals. The overall model is now embedded into a new numerical code called NANOKIN, in which several optimization procedures have been introduced in order to allow long dynamics to be followed. NANOKIN was applied to the precipitation of Al- bearing minerals from aqueous solutions: halloysite, kaolinite and Ca-montmorillonite. It allowed us to propose a stable scheme for the competitive precipitation of halloysite and kaolinite under two different types of initial conditions: (1) a given initial super-saturation state of the aqueous solution; (2) progressive super-saturation resulting from the kinetic dissolution of the minerals from a granitic rock under weathering conditions. Both yield particle sizes in the micron range, but with distinct crystal size distribution functions. The interplay between kinetic and thermodynamic effects is discussed. 相似文献
20.
Heat transport in serpentinites 总被引：1，自引：0，他引：1
The thermal transport properties thermal conductivity and thermal diffusivity were examined for a variety of serpentinites as a function of temperature at ambient pressure. The thermal transport properties of serpentinites show an extraordinary behavior. Besides the common 1/T decrease in thermal transport properties with increasing temperature, which can be related to an increase in phonon–phonon interactions with increasing temperature, an oscillation of thermal conductivity is observed with maxima around 450 and 850 K. This oscillation is linkable to water release of surficially bounded water and water in pores (450 K) and the dehydration of serpentinite (850 K). The oscillations are explained by advective heat transfer during dehydration, reaching up to 30% of the overall heat transport. The dehydration of serpentinites was examined by XRD and Thermo-Gravimetry and Differential Thermal Analysis/Differential Scanning Calorimeters (TG/DSC) investigations, indicating that the dehydration reaction is kinetically hindered and the crystallization of the product phases are observed at ≈1060 K, more than 200 K above the equilibrium of dehydration reactions. The conductive heat transfer by phonons shows a minor temperature variation and dominates thermal diffusivity. Ultrasonic sound velocities as a function of temperature [J. Geophys. Res. 102 (1997) 3051] were used to derive the mean free path length of phonons, which decreases from 0.28 to 0.2 nm at high temperatures. This is in the same order of magnitude as the interatomic distance of O–O, Al–O and Si–O restricting the minimum distance for phononic movement. A high anisotropy in thermal transport properties of single crystallites is concluded from its structure and elastic behaviour. However, the examined samples are macroscopically isotropic. The pressure and temperature dependence of conductive heat transport of an average serpentinite is given by λ=(1/(A+BT))(1+βP) W/m K, with A=0.3638 m K/W, B=0.000244 m/W and β=0.148 GPa−1. 相似文献