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柴达木盆地察尔汗盐湖的成盐建造可分为:浅部构造层(Q2—Q4);中部构造层(R—Q1);深部构造层(K以前)。其成盐作用可分为:泛湖阶段(Q1);盐渍阶段(Q2);盐沼阶段(Q3);干盐湖阶段(Q4)。从地层建造、变形特征、继承关系、富盐程度讨论了构造层次的生成关系。由成盐物质侧向补给的盐筛效应、垂向补给的构造膜效应讨论了构造的成盐规律,并确立了盐湖不完全对称地堑式的沉积模式。 相似文献
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近些年来,人们广泛地利用火山岩的主元素或微量元素的特征对火山岩进行地球化学、成因岩石学和构造岩石学的研究。Mullen(1983)利用玄武岩的 MnO、TiO2和P2O5建立大洋型玄武岩的 MnO×10-TiO2-P2O5×10的构造背景判别图(以下简称MTP图)和圈出了大陆拉斑玄武岩在 MTP 图中的分布范围。他选择了能反映玄武岩形成过程中的重要地球化学特征和成因机制的元素组作为该图的端元组分。 相似文献
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赣北鄱阳湖地区土塘剖面发育第四纪红土,自下而上可分为强网纹红土层、弱网纹红土层、微网纹红土层、均质红土层和下蜀黄土层。基于常量元素、粒度分析数据以及前人年代框架,初探土塘剖面化学风化特征及其古气候意义。(1)土塘剖面粒度组分均一,常量元素含量相近,风化淋溶强烈。(2)土塘剖面各地层间化学风化强度存在差异:下蜀黄土层为初期的去Na、Ca阶段;均质红土层为中期的去K阶段;微网纹红土层由去K阶段向去Si阶段过渡;网纹红土层已完全进入晚期去Si阶段。剖面常量元素的相对迁移能力为:Na2O>MnO2>CaO>P2O5>MgO>K2O>SiO2>Al2O3>TiO2>Fe2O3。(3)中更新世以来赣北鄱阳湖地区气候总体上由暖湿趋于干冷,期间伴随多个明显的干湿旋回佐证强烈的淋溶与干湿交替作用是网纹红土发育的重要驱动因子。 相似文献
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湖北均县风化淋滤型高岭土矿床赋存在与一定风化母岩岩性相依存的同一时代层位中。矿体产于寒武纪下统（∈1）和震旦系上统灯影组（Zbdn）之间的平行不整合面上,呈断断续续的含矿带。风化母岩为寒武系下统暗色含硫有机质、硅质页岩,含矿带的下盘岩性为灰白色厚层状白云岩。 相似文献
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华南地区广泛分布中更新世红土。目前, 对其物质来源尚有争议。九江红土剖面的沉积时代已得到很好限定, 同时由于其沉积连续、地层出露较好, 是开展中更新世红土物质来源研究的理想剖面。通过对九江中更新世红土2件碎屑锆石样品的分析, 共获得177颗谐和锆石U-Pb年龄, 主要峰值集中在新元古代(816 Ma、801 Ma和991 Ma)、古元古代(2019 Ma、2022 Ma和2481 Ma)和新太古代(2502 Ma), 并具有不显著的中生代峰值(135 Ma)。将其与潜在远源和近源物源区的锆石U-Pb年龄组成进行对比, 结果发现中国北方戈壁、沙漠和黄土高原、塔里木盆地、华北平原并不是九江中更新世红土的主要源区。庐山北麓早更新世发育的洪积扇为九江中更新世红土发育提供了充足物质。九江中更新世红土和九江晚更新世黄土的碎屑锆石U-Pb年龄组成存在明显差别, 后者主要来自长江河漫滩的碎屑物质。不同的气候条件主导了九江地区红土和黄土的发育, 二者都受控于青藏高原构造隆升产生的环境变化。 相似文献
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贵州晴隆沙子矿床是近年来我国的发现1处大型独立钪矿床,本文对矿区新鲜玄武岩、风化玄武岩及矿化红土中磁铁矿铁同位素组成进行研究。结果表明,新鲜玄武岩和风化玄武岩的w(Fe_2O_3)分别变化在15.41%～15.51%和14.60%～15.12%的范围内,而磁铁矿δ~(56)Fe的变化范围分别为0.23‰～0.29‰和0.02‰～0.07‰。红土具有最高的铁含量,w(Fe_2O_3)在23.53%～28.95%的范围内,但δ~(56)Fe与风化玄武岩相差不大,变化范围在-0.09‰～0.03‰之间。风化玄武岩和红土中铁同位素组成的变化,与单斜辉石的水解有关。结合已有的研究成果,认为沙子钪矿的成因与峨眉山玄武岩的深部原位水解和地表风化淋滤有关。 相似文献
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氟碳钡铈矿(Cordylite)BaCe2(CO3)3 F2本世纪初首先发现于格陵兰纳尔萨尔苏克(Narssarssuk)的碱性正长伟晶岩脉中,与霓石、氟碳铈钙矿、柱星叶石和碳锶铈矿共生。1965年该矿物又发现于我国白云鄂博西矿区热液交代的元古代白云岩中。1975年,加拿大魁北克省圣赫莱山(Mont st. Hilaire,Quebec)的霞石正长岩中的伟晶岩脉中也发现了这一矿物,它与方沸石、霓石和钠闪石共生。 相似文献
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Geology of Ore Deposits - A ferruginous laterite horizon was established for the first time as a result of the detailed study of the profile of the bauxite-bearing lateritic weathering crust in the... 相似文献
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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
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Subaerial leaching process of sedimentary bauxite and the discussion on classifications of bauxite deposits 
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下载免费PDF全文 Bauxite is the ultimate fine-grained products of chemical weathering,and thus it is closely linked with the intense chemical weathering. Based on variations of parent rock and weathering processes,the weathering products can be subdivided into laterite and terra rossa,of which the former is formed by weathering of aluminosilicates and the latter is produced by the weathering of carbonates. During the intense chemical weathering,minerals in original subaerial sediments(parent rocks)would suffer a series of processes(dissolution,hydrolyzation,hydration,carbonation,and oxidation)and be destroyed or transformed,leading to formation of new minerals. In the favorable environment,continuously intense chemical weathering would cause the loss of most mobile elements(e.g., K,Na,Ca,Mg,Si)and the enrichment of Al,resulting in the formation of bauxite. Although sedimentary bauxites are closely linked with the weathering curst,they show obvious differences in formation processes. Sedimentary bauxites are composed of intense chemical weathering products that are transported from outside of the basin and re-deposited in the basin,while most weathering crusts are transformed from saprolite and/or deluvium in-situ,and they can only form low-grade bauxites. Sedimentary environments also differ in bauxite ore layers and bauxitic claystone layers. Bauxite ore layers are formed in the subaerial environment and controlled by the leaching process of groundwater in the vadose zone. Based on the analysis of bauxitization,this study proposes to use multiple parameters,such as provenance,sedimentation and mineralization,to build the new classification of Chinese bauxite deposits. In this classification,lateritic and karstic types of bauxite deposits are autochthonous or parautochthonous saprolite and/or deluvium,while sedimentary type is dominated by heterochthonous provenance. 相似文献
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Lateritization processes of ultramafic rocks in Cretaceous times: The fossil weathering crusts of mainland Greece 总被引：1，自引：0，他引：1
The lateritic weathering crusts exposed in mainland Greece were developed on ophiolitic ultramafic lithologies during lower Cretaceous times. The lateritic profile consists of four zones: bedrock, saprolite clay (nontronite) and goethitic. The profiles show large variations in thickness, continuity, mineralogy and chemical characteristics. They are broadly similar to clay nickel laterite deposits. The uppermost gravelly ferruginous sector was eroded and the material reworked and redeposited partly on the lateritic crust. Silcrete layers, characteristic of groundwater silcretes, were formed into the clay and goethitic zones. Significant supergene nickel enrichments occur in the clay and saprolite zones, indicating that water moved downward to a very low water table. The structure and mineralogy of the weathering crusts indicates that environmental conditions were likely to have been dominated by alternating wet and dry periods. 相似文献
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The mineral chemistry and crystal morphology of kimberlite pyropes from the Billyakh River placer in the northeastern Siberian craton are characterised in terms of the placer history. The pyropes bear signatures of chemical weathering (dissolution), presumably in a Middle Paleozoic laterite profile, and therefore were originally hosted by Middle Paleozoic kimberlites. The broad occurrence of placer pyropes with lateritic dissolution signatures points to the presence of Middle Paleozoic diamond-bearing kimberlites in the study area. 相似文献
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铝土矿是化学风化作用的细粒终极产物,与强烈的化学风化作用密切相关。根据母岩的类别及作用过程,风化作用进一步分为铝硅酸盐岩强化学风化形成的红土化作用和碳酸盐岩强化学风化形成的钙红土化作用。在强烈的化学风化过程中,地表的原始沉积物(母岩)的原生矿物发生溶蚀、水解、水化、碳酸化、氧化,破坏原始的矿物结构,形成新的细粒矿物(主要是黏土质矿物)。在适合的地质条件下,持续的强烈化学风化作用会造成大部分活动的元素(如K、Na、Ca、Mg、Si)的流失与Al的残留富集从而形成铝土矿。现在观察到的沉积型铝土矿,虽然与古风化壳具有密切联系,但沉积型铝土矿多数是由沉积过程搬运到沉积盆地中所形成的强化学风化产物的沉积层,与古风化壳的残坡积层具有显著差别,只有少数工业价值不大(品位低、品质差)的残坡积相铝土矿。铝土矿含矿岩系的沉积环境与铝土矿(尤其是高品位、高品质的铝土矿)的成矿环境不尽相同。铝土矿主要形成于暴露于大气中的陆表环境(而非水下环境),由地下水淋滤作用形成(在渗流带由活动元素流失、Al等稳定元素残留富集而成)。本研究在铝土矿成矿作用分析等基础上,提出了以铝土矿沉积物等物源和沉积、成矿作用为依据的中国铝土矿床分类方案,包括原地或准原地残坡积物成因的红土型和喀斯特型,和异地物源沉积成因的沉积型。 相似文献
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A study of lateritic soils and samples of ground and river waters was carried out in the Nsimi-Zoetele, a tropical watershed in the southern Cameroon. The Nd isotopic compositions and concentrations of Nd and Sm were determined. It was found that the Nd isotopic composition of the river waters was much more radiogenic than the parent rocks, and that the Nd in the waters is not homogeneous but is carried by different dissolved and complexed components that are not isotopically homogenized. The soil profile shows a regular increase in εNd going from the parent rock (εNd = −36) to εNd = −18 near the top of the profile. The Nd transported in the river is thus not representative of the parent rock but reflects the results of differential weathering of constituent minerals and the redeposition of REE in phosphates and a significant contribution of radiogenic Nd from dust. The concentration of Nd in the river water is far above that found in temperate climate rivers and thus this type of tropical river may play a dominant role in the marine Nd and REE budget. It is suggested that the correlation of REE with DOC is related to DOC fixing some dissolved REE but that the REE in solution is governed by other mechanisms. No major shifts were found in Sm/Nd; however, a regular progression from the parent rock through the lateritic profile was found. The upper laterite profile shows large, almost uniform depletions in all REE below Tb and enrichment above. Complementary behavior was found in the lower part of the section. The concentration of Nd relative to the immobile elements Zr and Ti in the laterite is depleted by a factor of ∼10. Th, Nd and Sm are enriched in the lowest zone sampled and must reflect redeposition of REE from the upper part of the weathering section and is associated with phosphate formation. It is concluded that the soil evolution involves both differential dissolution of primary phases from the parent rock, significant to major input of REE from atmospheric dust from other regions, and the formation of diagenetic phases, particularly phosphates. 相似文献
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RON GOLDBERY 《Sedimentology》1979,26(2):229-251
Petrographical and mineralogical studies of the Lower Jurassic sequence exposed at Makhtesh Ramon, have shown the domination of a lateritic suite of epiclastic sediments of pisolite conglomerate and laterite arenite composition. Their subsequent modification by epigenetic processes of chemical weathering has given rise to the formation of flint clay, high alumina flint clay, laterite and mottled and variegated claystone. Within the Nahal Ardon area, both the transported laterite accumulates and the autochthonous lithologies occur interbedded within the same section. In all, a total of ten lithofacies have been defined and mapping of the various units, grouped into allochthonous and autochthonous classes, has established the existence of lateral facies changes between Nahal Ardon, where the sequence rests on a broad undulatory Triassic basement, and the zone to the west where it occurs as infillings of Triassic solution cavities, sink holes and irregular depressions. Vertical profile studies of the lithofacies indicate that the vertical range of ground water movements increased westwards from Nahal Ardon and resulted in the transported laterite accumulates being subjected to varying degrees of chemical weathering. The observed lateral facies changes are a direct consequence of this. Within the ‘karstic’ zone, the laterite accumulates in addition to the overlying younger carbonate lithologies have been converted to flint clay and demonstrate the intraformational genesis of the flint clay, whereby vertical ground water movements are related to recharge of aquifer zones within the underlying Triassic Mohilla Formation. 相似文献
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贵州老万场红土型金矿地球化学特征及其成因 总被引：4，自引：0，他引：4
对贵州西南部晴隆老万场红土型金矿与相关岩石（矿石）和喀斯特红土等进行了常量元素、微量元素和稀土元素地球化学比较研究,阐明了矿床的各类元素的地球化学特征,追溯了矿术的物质来源。研究表明,本类红土型金矿的物质来源是高硅质（石英）、富铁质（黄铁矿等）的富金矿（岩）石;具有Ａｕ－Ａｓ－Ｓｂ－Ｈｇ－Ｔｌ－Ｗ－Ａｇ－Ｂａ的微量元素组合特征,与卡林型金矿十分相似,是原始卡林型金矿风化演化的产物。常量元素和稀土元 相似文献