间层伊利石—蒙皂石粘土中四面体和八面体置换的红外光谱研究

本文用红外光谱研究了一种间层伊利石－蒙皂石粘土中四面体和八面体的置换，Ｈｏｆｆｍａｎｎ－Ｋｌｅｍｅｎ（Ｌｉ）实验表明，在２５０℃时经过热处理后，Ｌｉ优先占据ＡｌＭｇ和ＦｅＭｇ的八面体空位，氨（Ｃｈｏｕｒａｂｉ－Ｆｒｉｐｉａｔ）实验表明，由于脱氨作用中形成了两个ＯＨ伸缩模式，因而出现了贝得石特征。由于Ｋ是不可交换的，因此伊利石层没有受到影响。     

湘西晚前寒武纪层状硅质岩的热水沉积地球化学标志及其环境意义

湘西晚前寒武纪层状硅质岩化学成分纯净,硅质矿物平均含量９５％以上。岩石富Ｆｅ、Ｍｎ,相对贫Ａｌ、Ｔｉ、Ｍｇ,富含Ｂａ、Ａｓ、Ｓｂ、Ａｇ、Ｕ等微量元素。Ｆｅ／Ｔｉ、（Ｆｅ＋Ｍｎ）／Ｔｉ、Ａｌ／（Ａｌ＋Ｆｅ＋Ｍｎ）、Ｕ／Ｔｈ比值及ＡｌＦｅＭｎ、ＦｅＭｎ（Ｎｉ＋Ｃｏ＋Ｃｕ）三角图均表明岩石为热水来源沉积岩。稀土元素总量低,Ｃｅ负异常,重稀土相对富集,显示主要为热水沉积作用的产物。δ３０Ｓｉ、δ１８Ｏ值及岩石的形成温度清楚地表明组成岩石的二氧化硅来源于热水。岩石的ＭｎＯ／ＴｉＯ２、δＣｅ及δ３０Ｓｉ值分析表明硅质岩沉积于大陆边缘斜坡半深海至大洋盆地深海环境中     

金刚石中岩浆熔融包裹体

在我国数颗金刚石发现了罕见的岩浆熔融包裹体。包裹体质由球粒和基体组成，球粒主要为Ｆｅ质球、Ｓｉ－Ｆｅ质球和Ｓｉ－Ｆｅ－Ｍｇ质球，基体成成Ｓｉ－Ａｌ－Ｋ质、Ｓｉ－Ｍｇ－Ｆｅ质和Ｓｉ－Ｆｅ－Ｃａ质等。不同金刚石中包裹成分变化较大，推测包裹体（球体和基体）是经熔离作用的岩浆熔体在温度下降、氧速度很低和淬火作用条件下形成的。金刚石的结晶可能与火山喷发作用有关。     

新疆尉犁金云母和金云母—蛭石的成分特征

对６个金云母和１０个金云母－蛭石间层矿物样品进行Ｘ－射线荧光光谱分析，并对分析进行了研究。所获分析数据可靠、相对误差小；金云母较金云母－蛭石样品含较高的Ｋ２Ｏ、ＦｅＯ、Ａｌ２Ｏ３、ＴｉＯ２，而含较低的ＳｉＯ２、Ｆｅ２Ｏ３、ＭｇＯ、Ｈ２Ｏ＾＋。结合离子占位特点，讨论了金云母－蛭石在成分上与金云母的区别及由金云母变化成金云母－蛭石过程中，元素的带入、带出规律。     

雪宝顶绿柱石的谱学研究

本文对雪宝顶绿柱石的晶体化学、矿物谱学、热释光和流体包裹体特征等进行了分析讨论。结果表明,雪宝顶绿柱石化学成分具有富碱、富水、过渡金属离子以Ｆｅ＾３＋、Ｆｅ＾２＋为主的特点。碱金属离子,水和Ｆ＾２＋存在于绿柱石结构隧道中,隧道水分为Ⅰ型和Ⅱ型两类,Ⅰ型水可以进一步区分为Ⅰ１和Ⅰ２两亚类,Ｆｅ＾２＋主要与隧道水结合形成水合离子「Ｆｅ＾２＋（Ｈ２Ｏ）」。Ｆｅ＾３＋主要占位于绿柱石ＡｌＯ６八面体中的Ａｌ     

雅鲁藏布缝合带硅岩的地球化学成因标志及其地质意义

通过西藏雅鲁藏布缝合带所产硅岩的化学组分中具有成因标志的不同元素组合比值（ＭｎＯ/ＴｉＯ_２、Ａｌ/（Ａｌ＋Ｆｅ＋Ｍｎ）及Ｆｅ/Ｔｉ-Ａｌ/（Ａｌ＋Ｆｅ＋Ｍｎ）的相关图解、Ａｌ-Ｆｅ-Ｍｎ的三角图和硅岩原子量进行对比研究，从一个侧面反映硅岩的成因及其雅鲁藏布缝合带形成和演化关系。     

浙西石炭纪层状硅质岩地球化学特征及其意义

在浙西石炭纪地层中存在与地层整合产出的层状硅质岩。硅质岩中ＦｅＯ、ＭｎＯ、ＴｉＯ２、Ａｌ２Ｏ３、ＭｇＯ、ＣａＯ、Ｎａ２Ｏ、Ｋ２Ｏ等含量相对较高，富集Ａｓ、Ｓｂ、Ｂｉ、Ａｕ、Ａｇ、Ｇａ，Ｆｅ２Ｏ３／ＦｅＯ、ＳｉＯ２／Ａｌ２Ｏ３、ＳｉＯ２／（Ｎａ２Ｏ＋Ｋ２Ｏ）、ＳｉＯ２／ＭｇＯ比值较小，稀土元素总量低，Ｃｅ弱负异常，重稀土相对富集，包裹体富含气相组份ＣＨ４、ＣＯ２、Ｎ２、ＣＯ、Ｈ２，具热水沉积硅质岩的地球化学特征。在Ｆｅ—Ｍｎ—（Ｎｉ＋Ｃｏ＋Ｃｕ）三角图及ＳｉＯ２—Ａｌ２Ｏ３、ＳｉＯ２—Ｆｅ２Ｏ３图上均属于热水沉积硅质岩。硅质岩中硅、氧同位素也显示其热水成因之特点。硅质岩的硅同位素和稀土元素Ｃｅ／Ｃｅ※值表明本区层状硅质岩主要是在浅海环境下沉积的。硅质岩的形成温度较高，为９８℃～１５２℃     

集安岩群黑云母的化学成分及意义

黑云母系集安岩群主要变质矿物之一，其化学组成ＴｉＯ＿２平均含量３．３１％，Ａｌ＿２Ｏ＿３１８．２９％，Ａｌ￣Ⅵ０．３１、Ｘ＿Ｍｇ值０．５４，形成于高角闪岩相。黑云母微区成分不均匀，周围与长英质矿物相接触的黑云母，内部成分受变质峰期后扩散作用的影响甚微，与石榴石相邻的黑云母边缘具有扩散环带。因此，通过黑云母和石榴石晶体中心成分及两者的边缘成分，可以分别获得接近变质峰期和Ｆｅ－Ｍｇ交换反应封闭时的温度。     

新疆莫托萨拉铁锰矿硅质岩特征及其成因探讨

莫托萨拉铁锰矿硅质岩呈层状产于铁矿中,含热水沉积矿物。岩石的Ｆｅ２Ｏ３,Ａｕ,Ａｇ,Ｃｕ,ｐｂ,Ｚｎ,Ａｓ,Ｓｂ,Ｈｇ质量分数高,Ｃｒ,Ｎｉ,Ｃｏ,ＦｅＯ,Ａｌ２Ｏ３质量分数低,ｅ（Ａｌ）／ｗ（Ａｌ＋Ｍｎ＋Ｆｅ）比值低,这些元素组合指示出其热水 成因,在判别硅质岩形成作用的主元素和微量元素关系图上,硅质岩主要位于热水沉积作用的范围内或接近于热水沉积作用。岩石的稀土元素和Ｏ,Ｓｉ同位且成表明硅质岩是     

花园沟硼矿床中硼铝镁石的发现及其地质意义

在对辽宁省宽甸县花园沟硼矿床的研究中，发现了硼铝镁石，它与遂安石、袁复礼石、硬石膏等并生，产于硼矿体中．硼铝镁石是一种比较稀少的硼酸盐矿物，为此，对其进行了矿物特征的研究．硼铝镁石为黄色，粒状；晶体形态呈短柱状和权状，类似于橄榄石的晶体形态，弱多色性、Ｎｇ－淡黄、Ｎｐ－近于无色；折射率Ｎｇ＝１．７０７６，Ｎｐ＝１．６７０８，Ｎｍ＝１．６９６２；－２Ｖ＝５４°，Ｈ＝６－７，ＶＨＮ１００＝１２１５ｋｇ／ｍｍ２；Ｄ测＝３．５０．化学成分除Ａｌ和Ｍｇ外，其次是Ｆｅ２＋和Ｆｅ３＋，且Ｆｅ２＋＞Ｆｅ３＋晶体化学式为：晶体结构属斜方晶系，空间群ｐｎｍａ，ａ＝９．８９３（６）Ａ，ｂ＝５．０７６（４）Ａ，ｃ＝４．３３５（３）Ａ，Ｚ＝４．成因分析表明，硼铝镁石富Ａｌ、Ｍｇ、Ｂ，经角闪岩相区域变质作用形成．     

Regional retrograde alteration of sub-greenschist facies chlorite to smectite

Dioctahedral smectite is present as a retrograde alteration product of chlorite in Permian-Triassic red slates of the Malaguide Complex in Sierra de Espuña (Betic Cordillera). Mineral assemblages and textures, illite crystallinity indices, and fluid inclusion data indicate sub-greenschist facies conditions that reached at least 180°C in the higher-grade tectonic unit of the Malaguide Complex, preceding formation of smectite. Smectite, having K as the dominant interlayer cation, occurs ubiquitously intercalated with trioctahedral chlorite as thin packets of layers and as individual layers that commonly change to chlorite along layers. Although some chlorite is typically homogeneous and trioctahedral, much chlorite shows signs of alteration and has compositions corresponding to different degrees of smectite contaimination. The incompatibility of metamorphic grade with the occurrence of smectite, the general association of chlorite and smectite, and the textural relations collectively show that dioctahedral smectite is derived through replacement of trioctahedral chlorite. Such replacement occurs on a regional basis and demonstrates that caution must be used in interpreting the occurrence of smectite in pelites as being due to prograde processes. Alteration of trioctahedral chlorite under oxidizing conditions due to introduction of phreatic water after uplift of the Betic Cordillera is proposed as the cause of formation of smectite.     

Compositional variation within some glauconites and illites and implications for their stability and origins

Textural, mineralogical and chemical data are presented for glauconites and illites from the Lower Cretaceous Glauconitic Sand Formation, Alberta, Canada. Single crystal analyses by scanning transmission electron microscopy (STEM) indicate that both glauconite (29 analyses) and illite (44 analyses) correspond very closely to ideal dioctahedral structures. Al dominates the octahedral sheet in illite. Very extensive A1 for Fe^III substitution was also found in some of the glauconites, much more than previously recorded. The dioctahedral mica structure is clearly very stable and flexible with respect to A1 for Fe^III substitution. Iron-poor glauconites were found associated with pyrite. We believe that glauconites tend to lose iron progressively during burial diagenesis, especially where pore water iron activities are low (high HS^? activity and low Eh). It seems probable that A1 for Si tetrahedral substitution also takes place during diagenesis with consequent loss of swelling properties. This is the same trend which is responsible for conversion of smectite to illite. Glauconite forms only where sediments reside for lengthy periods at the interface between oxidizing and reducing environments, where Fe³⁺ is transiently available in solution. Related marine and terrestrial nontronites also form only in similar ‘interface’ environments.     

Palaeoenvironmental significance of the clay mineral composition of Olduvai basin deposits,northern Tanzania

Quaternary deposits in the southeastern part of the Olduvai basin, northern Tanzania, consist of lake margin deposits, followed by a series of fluvial sediments. The clay mineral fraction of the lake margin deposits (Bed I and lower part of Bed II) is composed of smectite and subordinate illite. All smectite is largely dioctahedral and shows indications for a limited degree of irregular interstratification by illite. In the overlying fluvial deposits (Beds II–IV), illite is the most abundant clay mineral. Smectite only occurs in lower parts of the fluvial deposits (up to the middle of Bed III), where it generally shows a high degree of irregular interstratification. Differences in clay mineral composition between the lake margin deposits and the fluvial deposits record differences in sediment source area and degree of alteration. Dioctahedral smectite in the lake margin deposits and the oldest fluvial deposits is derived from a region with volcanic material extending to the east and south of the basin, which also supplies a certain amount of illite. Illite in the fluvial deposits of Bed IV originates from an area with a metamorphic bedrock to the west and north. Alteration of detrital clay minerals resulted in Mg-enrichment of dioctahedral smectite in part of the lake margin deposits and partial illitization of smectite in the older fluvial deposits. Formation of clay minerals during diagenesis or soil development is not documented by analysis of the total clay fraction.     

Dating incipient metamorphism using 40Ar/39Ar geochronology and XRD modeling: a case study from the Swiss Alps

Six samples of a single carbonate-rich unit of the Swiss Préalpes, progressively metamorphosed from diagenesis to deep anchizone, yield ⁴⁰Ar/³⁹Ar spectra with variably developed staircase patterns, consistent with mixtures of detrital mica and neocrystallized mixed-layer illite/smectite. The lowest temperature heating steps for different size fractions (2–6?μm and 6–20?μm) converge to ～40?Ma providing an imprecise, maximum age of regional metamorphism. A method is described for distinguishing and quantifying the amount of pre-existing detrital mica versus neoformed illite layer in the illite/smectite formed during Tertiary Alpine metamorphism by comparison of X-ray diffraction patterns with Newmod^© simulations. In the least metamorphosed samples the illite/smectite contains ～65% neoformed illite, and this illite accounts for approximately 17% of all dioctahedral phyllosilicate minerals in the rock (e.g., detrital mica and illite/smectite). In contrast, the illite/smectite from the more strongly metamorphosed samples contains >97% neoformed illite, which accounts for ～70% to >90% of all dioctahedral phyllosilicate minerals. Phyllosilicate morphologies viewed by scanning electron microscopy are consistent with these estimates. A process of dissolution/reprecipitation is inferred as a mechanism for the growth of the neoformed phyllosilicates. A plot of neoformed illite content versus ⁴⁰Ar/³⁹Ar total fusion age yields a near-linear curve with an extrapolated age of 27?Ma for 100% neoformed dioctahedral phyllosilicates. This age is interpreted as the time of incipient metamorphism and is consistent with independent biostratigraphic constraints. Model ⁴⁰Ar/³⁹Ar age spectra constructed with the XRD simulation results correspond well to the experimental data and illustrate the changes in degassing properties of progressively metamorphosed mixtures of detrital mica and neoformed illite.     

Occurrence of Fe-Mg-rich smectites and corrensite in the Morrón de Mateo bentonite deposit (Cabo de Gata region, Spain): A natural analogue of the bentonite barrier in a radwaste repository

The Morrón de Mateo bentonite deposit is being studied as a natural analogue of the thermal and geochemical effects on a bentonite barrier in a deep geological repository of high level radioactive wastes. This bentonite deposit and its host rocks were intruded by a rhyodacitic volcanic dome that induced a hydrothermal metasomatic process affecting the biocalcarenite beds close to the dome. In this work, the mineralogical and chemical features of the clay minerals of the hydrothermally altered pyroclastic (white tuffs) and epiclastic rocks (mass flow), located in the NE sector of the Morrón de Mateo deposit are described. White tuffs have a high content of phyllosilicates, mainly composed of dioctahedral smectites, while mass flow have a higher proportion of inherited minerals, the neoformed phyllosilicates are dioctahedral smectites and an interlayer chlorite/smectite mineral of corrensite type. The chemical composition of smectites reflects the different nature of the parent rocks, in such a way that smectites from white tuffs have a quite homogeneous chemical composition and their structural formulae correspond to montmorillonite type, while smectites from mass flow show more chemical variability, higher Fe and Mg contents and a mean structural formulae corresponding to Fe-Mg-rich beidellite and/or to an intermediate smectite member between beidellite and saponite. In addition, chemical composition and textural features of corrensite-like clay minerals in relation to Fe-Mg-rich smectites in the samples have also been studied, suggesting that the former seems to be formed from Fe-Mg-rich smectites. The presence of corrensite in the epiclastic rocks suggests that in the Morrón de Mateo area a hydrothermal alteration process occurred after bentonite formation, which transformed Fe-Mg-rich smectites into corrensite. This transformation was probably favoured by the intrusion of the Morrón de Mateo volcanic dome, which produced a temperature increase in the geological media and a supply of Fe-Mg-rich solutions. These physicochemical conditions were also responsible for the metasomatic transformations observed in the biocalcarenite beds located on the top of the bentonite deposit. All these data suggest that the Morrón de Mateo natural system could be a good natural analogue of both thermal and chemical effects on a bentonite barrier related to the radioactive decay of fission products and the interaction between the corrosion products of steel over-packs and the bentonite. These circumstances would favour the transformation of the candidate Al-rich smectites into Fe-Mg-rich smectites and corrensite, as steps prior to formation of chlorite. In this case, all the physicochemical and mechanical properties of Al-rich smectites would disappear and the clayey barrier would fail.     

Analysis of cation distribution in the octahedral sheet of dioctahedral 2:1 phyllosilicates by using inverse Monte Carlo methods

An inverse Monte Carlo (MC) method was developed to determine the distribution of octahedral cations (Al³⁺, Fe³⁺, and Mg²⁺) in bentonite illite–smectite (I–S) samples (dioctahedral 2:1 phyllosilicates) using FT–IR and ²⁷Al MAS NMR spectroscopies. FT–IR allows determination of the nature and proportion of different cation pairs bound to OH groups measuring the intensities of OH-bending bands. ²⁷Al MAS NMR data provide information about cation configuration because ²⁷Al MAS NMR intensity depends on Fe distribution. MC calculations based on FT–IR data alone show Fe segregation by short-range ordering (Fe clusters within 9 to 15?Å from a given Fe atom). Fe segregation increases with illite proportion. MC calculations based on IR and ²⁷Al NMR simultaneously yield similar configurations in which Fe clusters are smaller. The latter calculations fail to build appropriate cation distributions for those samples with higher number of illite layers and significant Fe content, which is indicative of long-range Fe ordering that cannot be detected by FT–IR and ²⁷Al MAS NMR. The proportion of Mg–Mg pairs is negligible in all samples, and calculations, in which the number of Mg atoms, as second neighbours, is minimised, create appropriate configurations.     

Microstructures and compositional variation in the intravolcanic bole clays from the eastern Deccan volcanic province: Palaeoenvironmental implications and duration of volcanism

Clay minerals associated with intra-volcanic bole horizons of varied colours and thicknesses contain montmorillonite, halloysite and kaolinite, show distinct microstructures and microaggregates. In kaolinite, Fe³⁺ ions substitute for Al³⁺ at octahedral sites. Most of these clays are dioctahedral type, show balance between net layer and interlayer charges. The interstratified illite — smectite (I/S) mixed layers containing variable proportions of montmorillonite. Illite contains sheet-like, well oriented microaggregates. The parallel stacks of chlorite sheets show chlorite/smectite (C/S) mixed layers. Progressive enrichment of Fe and depletion of Al ions with the advancement of kaolinization process is observed. High order of structural and compositional maturity observed in these bole clays, indicate long hiatus between the two volcanic episodes.     

Miocene silcretes in argillaceous playa deposits, Madrid Basin, Spain: petrological and geochemical features

Four regressive sequences are present in the opaline rocks and related deposits of the Miocene Intermediate Unit of the Madrid Basin. The sequences consist of silty mudstones and argillaceous opals, separated by transitional facies. The silty mudstone consists mainly of dioctahedral smectites, whereas the argillaceous opal is principally opal-CT and variable amounts of sepiolite. In the transitional facies, lamina of dioctahedral smectite co-exist with neoformed opal-CT and sepiolite. Petrological and geochemical features (major, trace and REE elements) indicate that the opaline levels and the transitional facies are related and are a consequence of silcrete formation in an argillaceous playa deposit. The isocon method was used to calculate changes in element concentration associated with silcrete formation. The geochemical data suggest silicification in an arid environment. The silcrete profile occurs four times, possibly as a result of highstand–lowstand fluctuations of the lake level caused by climatic changes. Structures and cements in the silcretes indicate that, although silicification may have commenced at the top of a groundwater table, it continued in the unsaturated zone above the water table.     

Determination of Minor Contents of Smectite Layers in the Dispersed Dioctahedral K-bearing Micaceous Minerals of the Illite,Aluminoceladonite, and Glauconite Composition

A theoretically substantiated technique has been elaborated for the precise determination of minor contents of smectite layers in the dioctahedral mixed-layer structures with a disordered alternation of K-bearing micaceous and ethylene glycol-saturated smectite layers. It is shown that observed positions of the possible mixed-layer mica–smectite structures in the d(003)_obs–d(007)_obs or 2θ(003)_obs–2θ(007)_obs diagrams are distributed along a set of parallel straight lines. Data points of each straight line correspond to the mixed-layer structures with one and the same content of smectite layers. A complete matching of theoretical model was recorded in the positions of d(003)_obs–d(007)_obs and 2θ(003)_obs–2θ(007)_obs pairs of the basal reflections determined in diffractograms simulated for 160 two-component mixed-layer mica–smectite structures differing in the thickness of alternating layers and their relative content. We studied samples of the dioctahedral K-bearing micas of the glauconite, illite, and aluminoceladonite composition with different thickness of micaceous layers. Positions of the mixed-layer structures of the studied samples on the 2θ(003)_obs–2θ(007)_obs and d(003)_obs–d(007)_obs plots make it possible to visually determine the content of smectite layers in each structure accurate to 0.5%. The content of smectite layers in the studied samples varied from 2 to 15%. We obtained equations relating the thickness of smectite and micaceous layers for a specified content of smectite layers. They make it possible to determine the thickness correlation between specified mica and smectite layers. Analogous equations can be used to calculate the Wsm value in each sample for specified experimental values of d(001)_mc and d(001)_sm and d(003)_obs or d(007)_obs. The W_sm values coincide within an error limit of 0.2% with those based on the visual estimates in plots.     

我国一些地区海绿石的矿物学研究

本文对七个地区的海绿石矿物学特征进行了较详细地研究,并讨论了它们之间的变化关系。海绿石样品采集地点和层位见表1。