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1.
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
2.
The Lower Jurassic section at Makhtesh Ramon, in the northeastern Negev of Israel, comprises a sequence of fluviatile sediments of laterite composition. Post-depositional chemical weathering has resulted in marked facies changes whereby the clastic sequence passes laterally into high-alumina flint clays and bauxites (Goldbery, 1979). A geochemical and mineralogical investigation was initiated on 216 samples from several key sections of the facies change to obtain a more refined definition of the diagenetic overprint, to reconstruct the history of chemical weathering and finally to recognize the parent material of the unaltered laterite sediments.Results are presented herein on major and trace-element composition, normative mineralogical composition, kaolinite crystallinity and porosity and density measurements. Kaolinite crystallinity values proved to be a good indicator of intensity of leaching, showing a marked decline in ordering with increase of diagenetic reorganization. On the basis of mineralogical parameters it was possible to subdivide the section of flint clays and bauxites, generated under karstic conditions, into four units. Bivariate plots of Al2O3 vs. several elements within the section, plotted into four distinctive fields coinciding with the subdivision. Enrichment/depletion ratios, calculated from the element concentrations within these flint clays against element concentrations of the clastic parent material of the karstic infill, led to the reconstruction of a multi-cyclic leaching event, whose “signature” is left in each of the four units. At least 3 individual episodes of leaching, related to a rising water table and punctuated by “still-stands” could be recognized.Zr/TiO2: Nb/Y plots of stable elements, using the diagram of Floyd and Winchester (1978) for determination of source rocks, indicated a rhyolite or alkaline rhyolite provenance for the clastic laterite detritus. 相似文献
3.
Field and laboratory investigations of the Triassic Budra Formation of Wadi Budra, south-west Sinai, have demonstrated the existence of surface pedogenic laterites developed within‘overbank facies’of fluviatile sediments during times of hiatus. The laterite profiles, up to 7 m thick, comprise a zone of high-iron concentrations (21.47–73.17%) which includes a concretionary unit and either overlies a zone of slightly mottled host rock or rests directly upon unaltered sandstone; a pallid zone is noticeably absent. The primary depositional horizontal fabric of the finely laminated sediments of the‘overbank facies’ has strongly influenced the final fabric of the laterite. The pronounced alternations of iron-rich pisolitic and iron-deficient laminae highlight the influence of inherent fabric (primary bedding) on pedogenesis. The micromorphology of the laterites is characterized by bimasepic plasmic fabrics, abundant elongate voids partially infilled with cryptocrystalline kaolinite and an abundance of randomly oriented skew planes. Illuviation of clay minerals to considerable depths is evident. Sesquioxidic and kaolinitic glaebules, concentrated within the concretionary units of the laterite have a flattened ellipsoidal shape and occur as both massive and concentrically structural varieties. At Gebel Mussaba Salama to the north, zoned iron mineralization occurs at various levels within the fluviatile sandstones which underlie the‘overbank facies’. This is interpreted as being a non-pedogenic, ground water alteration phenomenon induced by a rising water table within the buried alluvial channels. Iron mineralization, probably records minor fluctuations of the water table during standstill periods. Lateritization in the Triassic Budra Formation provides important evidence that the widely recorded late Triassic lateritization and bauxitization event of the neighbouring East Mediterranean countries, extended south to the continental areas bordering the Tethyan Ocean. 相似文献
4.
第四纪红色粘土在我国南方分布很广,最典型的分布在华中岗地上,土层较厚,上部土质均匀,下部具有红白网纹并含砾石,大都是中更新世的洪积-冲积或残积-坡积物,笔者认为可能是间冰期比较暖热气候条件下的产物。熊毅早就指出:各地环境殊异,地形复杂,母岩不同,其理化特征将随之而异。第四纪红色粘土来自不同的堆积相,和经受不同的风化和成土过程,这将在矿物组成方面反映出来。土壤普查的结果表明,第四纪红色粘土按其分布的地形部位,成因和物质来源,可分成两类:一类是残积坡积相，为中更新世较早的暗红色沉积物，即Q2另一类是冲积相，为中更新世较晚的红化程度较轻的淡红色沉积物。它们都经历了中更新世至今的成土过程1)”。为了查明它们的差异，并有助于第四纪沉积物的研究，笔者用部分标本进行矿物分析，并对初步结果进行讨论。 相似文献
5.
红土型铝土矿是加纳共和国铝土矿资源的主要矿床类型。阿瓦索铝土矿床产于西非克拉通古元古界比理姆岩系(泥板岩类)的表层红土中,是典型的红土型铝土矿。通过分析阿瓦索铝土矿的成矿地质背景、矿体特征以及矿石地球化学元素特征发现,铝土矿石的化学组分以Al_2O_3、SiO_2、TFe_2O_3为主,TiO_2次之,碱金属元素含量极低;风化过程中Zr、Hf、Nb、Ta等微量元素含量稳定;Cr—Ni关系图显示比理姆岩系为铝土矿的矿源岩,三水铝石主要由比理姆岩系中的黏土矿物经过风化淋滤形成,表层铝土矿在后期风化和红土化作用下结构构造发生一定的变化,铁氧化成以赤铁矿为主的铁壳,最终形成一个大型的红土型铝土矿。 相似文献
6.
我国铝土矿成因及矿层沉积过程 总被引：8，自引：3，他引：8
我国铝土矿床按最近作者等（1984,1985）的意见主要的是风化壳沉积型（Ⅰ型）,占我国铝土矿石储量98.83%,其次是红土型（Ⅱ型）,占我国矿石储量1.17%。前者又分三个亚型即Ⅰ1修文式--碳酸盐古风化壳沉积亚型,占Ⅰ型矿石储量83.2%,分布在山西、贵州、河南、四川、山东、河北、陕西、辽宁、江西、新疆等省（区）;Ⅰ2苹果式--碳酸盐古风化壳沉积--近代卡斯特堆积亚型,占Ⅰ型矿石储量13.04%,分布在广西、云南等省（区）;Ⅰ3乐山式--硅酸盐古风化壳沉积型,分布在四川、贵州北部、湖北、湖南等省。红土型（Ⅱ型）分布在福建、广东。是第三纪到第四纪玄武岩在近代气候条件下风化作用形成的三水铝石矿床。其成因已得到我国铝土矿床地质工作者的公认,与国外的意见也一致,本文不再讨论。但是我国对于古风化壳沉积型铝土。 相似文献
7.
Peter Turner 《Sedimentary Geology》1974,12(3):215-235
The Ringerike Group is a meandering fluviatile succession which is about 60% red. Most of the red zones are formed of mudrocks and siltstones and correspond to the fine members of fining-upwards cyclothems. The majority of coarse members are drab coloured.Textural studies of thin and polished sections show that the red colour is caused by finely crystalline hematite as matrix and grain-coatings. This hematite apparently crystallized post-depositionally. Hematite also occurs in other textural sites: within altered phyllosilicates, as detrital grains and as totally pseudomorphed phyllosilicates. This, and the lack of consistency between colour and clay mineralogy, suggests that the red beds have had a long and complex diagenetic history.Iron analyses indicate that the red beds are enriched in Fe3+ and total iron (FeO) by about 1%. This is thought to have been derived from the pre-depositional weathering of iron minerals and introduced into the sediments as amorphous iron hydroxide or iron-bearing clays. Crystallization of iron hydroxide under oxidizing conditions and the post-depositional alteration of iron-silicates and oxides is thought to be responsible for the formation of the red beds. 相似文献
8.
论铝土矿床成因及矿床类型 总被引：11，自引：0，他引：11
廖土范 《华北地质矿产杂志》1994,9(2):153-160
铝土矿全部是风化作用形成的，无一例外。地球上含铝（含少量铝质也可以）岩石在适宜的气候和地形条件下，风化成红土矿物，包括铝土矿物及少量粘土矿物、含铁矿物及少量含钛矿物等风化壳铝土物质（红土铝土物质）。第四纪以前的古风化作用形成的是古风化壳铝土物质（古红土铝土物质），迁移就位以后便形成风化壳铝土矿床（红土铝土矿床）。深埋地下经过成岩变化，再随地壳抬升进入地壳浅部，或地表的叫古风化壳铝土矿床。我国９８％是古风化壳铝土矿床，即国外所称的喀斯特铝土矿床。由于其迁移就位方式不同，便形成了不同的风化壳和古风化壳（亚型）矿床 相似文献
9.
铝土矿的形成受到气候条件的严格限制。通过对黔北务川—正安—道真地区下二叠统铝土矿层钻孔岩心样品主量元素和黏土矿物的综合研究,探讨了铝土矿层形成时期黔北地区的古气候环境以及淋滤作用对矿层的改造。从下至上,铝土矿层化学蚀变指数(CIA)由80左右上升至大于90,成分分异指数(ICV)由0.8下降至0.1。X射线衍射分析发现,研究区铝土矿层中的黏土矿物组分为高岭石、伊利石与绿泥石,其中高岭石在各个钻孔中广泛存在且在大部分层位中含量较高,平均含量为34.2％,并呈机械碎屑或基质形态产出且有进一步风化成为铝矿物的现象;伊利石主要以机械碎屑形式产出,平均含量为21.5％,赋存于矿层的黏土质部分,结晶度变化范围为0.22°～0.71°;绿泥石多为基质,部分层位中含量极高且伴随ICV值上升,平均含量为44.3％,为后期成岩过程中由高岭石转化而成。矿层内极高的CIA值与广泛存在的高岭石证明,铝土矿形成时为炎热潮湿的古气候。而矿层内部ICV值的波动可能与淋滤作用所引起的矿层内元素迁移活动有关。 相似文献
10.
11.
Chemical weathering in Luzon, Philippines from clay mineralogy and major-element geochemistry of river sediments 总被引：3，自引：0，他引：3
Zhifei Liu Yulong Zhao Christophe Colin Fernando P. Siringan Qiong Wu 《Applied Geochemistry》2009,24(11):2195-2205
Clay mineralogy and major-element geochemistry of 35 surface sediment samples collected in 21 major to moderate rivers of Luzon, Philippines are used to evaluate the present chemical weathering process. The clay mineral assemblage consists mainly of smectite (average 86%) with minor kaolinite (9%) and chlorite (5%) and very scarce illite (1%), and does not show strong island-wide differences. The major element results of both bulk and clay-fraction sediments indicate that the formation of clay minerals is accompanied by leaching of Ca and Na first and of Fe and Mn thereafter during the chemical weathering process. A low-moderate chemical weathering degree of bulk sediments and a moderate-intensive degree of clay-fraction sediments are obtained in Luzon rivers based on proxies of chemical index of alteration (CIA) and smectite crystallinity. It is suggested that the majority of andesitic–basaltic volcanic and sedimentary rocks along with the tectonically active geological setting and sub-tropical East Asian monsoon climate are responsible for the predominance of smectite in the clay mineral assemblage. 相似文献
12.
河南铝土矿矿物成因及其演化序列 总被引：2，自引：0，他引：2
[摘 要]豫西铝土矿是我国喀斯特型铝土矿的典型代表。本文选取豫西典型的喀斯特型铝土矿为研究对象,通过XRD 分析、扫描电镜-能谱分析、电子探针分析和差热分析多种手段,探测铝土矿的物质组成及其赋存状态,并且分析其矿物成因,总结矿物演化序列。研究显示,豫西铝土矿的主要矿物成分包括硬水铝石、伊利石、锐钛矿、高岭石、针铁矿、赤铁矿、金红石等。硬水铝石主体为简单结晶成因。伊利石主体为风化过程中产物,部分为后期硬水铝石硅质交代的结果。锐钛矿和硬水铝石同期结晶形成于还原环境下。大部分高岭石形成于陆源期风化阶段,少部分为后期硬水铝石硅化转变形成。针铁矿和赤铁矿形成于两个阶段,第一阶段为成矿前风化作用形成的铁质风化壳;第二阶段为铝土矿成岩晚期出现了一期铁质流体活动形成了大量的赤铁矿和针铁矿。重砂矿物金红石和锆石等主要是母岩风化作用的残留物。豫西铝土矿中矿物形成演化可归纳为如下五个阶段:陆源期、同生期、成矿期、成矿后期和表生期。 相似文献
13.
南黄海北部晚更新世以来常量元素记录的化学风化作用 总被引：1，自引：0，他引：1
以南黄海北部高沉积速率柱状样DLC70-3孔作为研究对象,对沉积物的黏土矿物和常量元素地球化学组成进行了综合分析。结果显示,DLC70-3孔沉积物中黏土矿物组合以伊利石为主,其次为蒙皂石,绿泥石和高岭石含量较低;绝大部分样品中伊利石与蒙皂石含量的比值<6,表明沉积物主要来源于黄河物质的输送。研究认为DLC70-3孔沉积物的化学风化指标CIA值受到海平面变化和源区气候变化共同控制,其中源区的气候变化为主要控制因素,而海平面变化造成的机械沉积分异作用主要影响27.80~38.00 m（MIS 4）层位沉积物的CIA值。CIA值显示在MIS 5和MIS 3期大陆化学风化作用较强,与内陆黄土高原地区夏季风和化学风化指标的变化趋势一致,尤其是在MIS 3早期（40~60 ka）记录的化学风化作用非常强,反映了黄河流域地区出现强夏季风降雨过程。 相似文献
14.
Many physico-chemical variables like rock-type, climate, topography and exposure age affect weathering environments. In the
present study, an attempt is made to understand how the nature of clay minerals formed due to weathering differs in tropical
regions receiving high and low rainfall. Clay mineralogy of weathering profiles in west coast of India, which receives about
3 m rainfall through two monsoons and those from the inland rain-shadow zones (<200 cm rainfall) are studied using X-ray diffraction
technique. In the west coast, 1:1 clays (kaolinite) and Fe—Al oxides (gibbsite/goethite) are dominant clay minerals in the
weathering profiles while 2:1 clay minerals are absent or found only in trace amounts. Weathering profiles in the rain shadow
region have more complex clay mineralogy and are dominated by 2:1 clays and kaolinite. Fe—Al oxides are either less or absent
in clay fraction. The kaolinite—smectite interstratified mineral in Banasandra profiles are formed due to transformation of
smectites to kaolinite, which is indicative of a humid paleoclimate. In tropical regions receiving high rainfall the clay
mineral assemblage remains the same irrespective of the parent rock type. Rainfall and availability of water apart from temperature,
are the most important factors that determine kinetics of chemical weathering. Mineral alteration reactions proceed through
different pathways in water rich and water poor environments. 相似文献
15.
早石炭世九架炉组与晚石炭世大竹园组,皆属黔中—渝南岩溶型铝土矿含矿岩系。按岩溶形态组合特征,主要可分为溶蚀洼地型和岩溶湖泊型,两种类型的含矿岩系下段,皆以铁质黏土岩、绿泥石黏土岩为主,间夹赤铁矿层,时夹白云岩、石灰岩透镜体,二者均为永久性、低能、浅水、海源湖泊沉积产物。溶蚀洼地型含矿岩系上段的铝土矿、铝土岩和黏土岩等,皆产于陆地上各种形态的溶蚀洼地中。岩溶湖泊型含矿岩系上段的各种铝土矿、铝土岩和黏土岩等,皆为间歇性、洪控、高能、浅水、陆源湖泊中沉积而成的。因距海较近,在海泛和强风暴潮的影响下,含矿岩系上段的陆相沉积物中时显海相、过渡相沉积特征。在赤道附近有利的地质、气候、水文、植物等条件下,母岩经红土化形成的风化壳物质,被流水短距离搬运到溶蚀洼地和岩溶湖泊中,沉积形成的岩溶型铝土矿含矿岩系,是在同一时间段内连续发生、发展和演化的过程, 其间没有明显的间断时期。 相似文献
16.
早石炭世九架炉组与晚石炭世大竹园组,皆属黔中—渝南岩溶型铝土矿含矿岩系。按岩溶形态组合特征,主要可分为溶蚀洼地型和岩溶湖泊型,两种类型的含矿岩系下段,皆以铁质黏土岩、绿泥石黏土岩为主,间夹赤铁矿层,时夹白云岩、石灰岩透镜体,二者均为永久性、低能、浅水、海源湖泊沉积产物。溶蚀洼地型含矿岩系上段的铝土矿、铝土岩和黏土岩等,皆产于陆地上各种形态的溶蚀洼地中。岩溶湖泊型含矿岩系上段的各种铝土矿、铝土岩和黏土岩等,皆为间歇性、洪控、高能、浅水、陆源湖泊中沉积而成的。因距海较近,在海泛和强风暴潮的影响下,含矿岩系上段的陆相沉积物中时显海相、过渡相沉积特征。在赤道附近有利的地质、气候、水文、植物等条件下,母岩经红土化形成的风化壳物质,被流水短距离搬运到溶蚀洼地和岩溶湖泊中,沉积形成的岩溶型铝土矿含矿岩系,是在同一时间段内连续发生、发展和演化的过程, 其间没有明显的间断时期。 相似文献
17.
V. N. Patel R. K. Trivedi S. H. Adil R. B. Golekar 《Arabian Journal of Geosciences》2014,7(9):3505-3512
Bauxite deposits of Mainpat Plateau Surguja District, India, are composed of kaolinite, gibbsite, goethite, anatase, and bohemite. Quartz and micas are absent in the samples. The presence of boehmite and goethite are evidences of intense weathering during the formation of the bauxite deposits. The Mainpat Plateau is a mesa landform, at an elevation of around 1,060 m from msl in comparison to the general elevation of 580, consisting of Archaeans (granite?gneisses, phyllite, etc.) at the base, Gondwanas and Deccan basalt, and at the top having a cover of laterite and bauxite. The extremely high values of the chemical index of alteration, and the low values of the alkali metals and alkali earth metals, support an intense weathering origin for the bauxite deposit. There is evidence of deposition in the deposits based on the presence of pisoids in the bauxite samples and the composition of the parent rock. Kaolin minerals were first produced by the hydrolytic weathering of aluminous sediments and then gibbsite was formed as early kaolin was desilicated. The bauxite is having high TiO2 up to 17 %. The Mainpat laterite/bauxite deposits are characterized by having 50?58 % average Al2O3 and 10?30 % Fe2O3. 相似文献
18.
通过对峨眉山玄武岩古风化壳进行野外调查、取样和分析测试工作,认为: ①贵州西部广泛出露峨眉山玄武岩,晚二叠世古气候温润潮湿,利于峨眉山玄武岩风化形成含Fe、Ti的黏土矿物和铝质黏土矿物的古风化壳,该风化壳受古地理环境和峨眉山玄武岩控制。②相对玄武岩而言,铝质黏土岩主量元素含量特征表现为富TiO2、Al2O3,轻度亏损SiO2,明显亏损TFe,其他主量元素大量流失; 铁质黏土岩主量元素含量特征表现为富TFe、TiO2, 轻度富Al2O3,但相对于铝质黏土岩,TiO2的富集程度偏低,SiO2亏损明显,其他元素亦大量流失。③由于晚二叠世频繁的海侵作用,水位较高的区域,风化壳下部处于较还原的条件下,Fe被还原成易溶的二价状态或在有机质的作用下迁出风化壳,而Ti由于存在形式较为稳定,继续保存在黏土矿物中,与Fe发生分异; 局部水位较浅的氧化环境及重力分异作用下,黏土矿物与铁矿物由于比重差异而分选开来,形成Fe与Al、Ti的分异,并伴随铁矿、钛矿和铝土矿的富集。该富集规律的发现对寻找该区铁、钛和铝土矿有一定的理论指导意义。 相似文献
19.
DOROTHY CARROLL 《Sedimentology》1963,2(2):149-155
Sediments cored to a depth of about 1 m in Bay St. George, Newfoundland, were examined for grain-size distribution and minerals. The sediments are light brown silty clays, the principal minerals of which are chlorite and muscovite mica. The scarce sand consists of fresh detrital grains of blue-green amphibole, biotite, epidote, zoisite, magnetite, garnet, hypersthene, apatite, chlorite, and scarce zircon. Quartz, plagioclase feldspar, and muscovite are abundant. These minerals are all present in the rocks of the adjacent land areas and have been deposited in the sediments with little alteration or change due to weathering. The clay minerals of the sediments are predominantly muscovite and chlorite with a slight admixture of vermiculite and montmorillonite. There is very little mixed-layering of these minerals. Montmorillonite may be due to diagenetic changes after deposition of these clays in the marine environment of the bay. 相似文献
20.
Shilpa Vuba Sadia Farnaaz Netramani Sagar S. Masood Ahmad 《Journal of the Geological Society of India》2013,82(3):217-226
The major, trace and rare earth elements geochemistry and clay mineral compositions in the river bed sediments from lower reaches of Godavari river suggest that they are derived from weathering of felsic rocks. Trace and rare earth elemental compositions indicate evidence of sedimentary sorting during transportation and deposition. Lower concentrations of transition elements, such as V, Ni and Cr imply enrichment of felsic minerals in these bed sediments. The REE pattern in lower Godavari sediments is influenced by the degree of source rock weathering. The light rare earth elements (LREE) content are indicating greater fractionation compared to the heavy rare earth elements (HREE). A striking relationship is observed between TiO2 and gZREE content suggesting a strong control by LREE-enriched titaniferous minerals on REE chemistry. Shale-normalized REE pattern demonstrate a positive Eu anomaly, suggesting weathering of feldspar and their secondary products, which are enriched in Eu. Chondrite-normalised REE pattern is characteristic of felsic volcanic, granites and gnessic source rocks. Trace elemental compositions in sediments located near urban areas suggest influence of anthropogenic activity. Chemical Index of Alteration (CIA) is high (avg. 65.76), suggesting a moderate chemical weathering environment. X-ray diffraction analysis of clay fraction shows predominance of clay minerals that are formed because of the chemical weathering of felsic rocks. 相似文献