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1.
Clay mineral diagenesis and quartz cementation in mudstones: The effects of smectite to illite reaction on rock properties 总被引：1，自引：0，他引：1
The Late Cretaceous to Early Tertiary sequence of the Vøring and Møre Basins from the Norwegian Sea has been examined with respect to mineralogy based on 319 cutting samples from five wells. A clear relationship between mineralogy and well log data is demonstrated. A significant change with respect to velocity, porosity and density occurs within the depth interval corresponding to 80–90 °C. At shallow depths/temperatures (<2.0 km/70 °C), compaction is mainly mechanical and the physical properties are similar to what has been measured by experimental compaction of mudstones. At greater depths, however, the log derived velocities and densities are higher than those produced by experimental compaction indicating significant chemical compaction. XRD analyses show a progressive alteration of smectite to illite (S–I) within this depth/temperature interval which results in the release of significant amounts of silica into solution. Detrital silt and fine-grained quartz showed no secondary quartz overgrowths. These grains are isolated within a clay matrix and surrounded by clay minerals, thus limiting the available surface area and pore space for quartz overgrowths. Chemical analyses (XRF) indicate that silica is conserved within this depth interval, and the amount released from S–I alteration was locally precipitated. Field emission gun-scanning electron microscopy (FEG-SEM) and cathode luminescence (CL) identified authigenic micro-crystalline quartz cement within the clay matrix at temperatures above ∼85 °C. This is accompanied by an increase in velocity and density indicating that the S–I reaction and the precipitation of authigenic quartz caused a significant change in the rock stiffness. 相似文献
2.
The tight sandstones of the Cretaceous Quantou formation are the main exploration target for hydrocarbons in the southern Songliao basin. Authigenic quartz is a significant cementing material in these sandstones, significantly reducing porosity and permeability. For efficient predicting and extrapolating the petrophysical properties within these tight sandstones, the quartz cement and its origin need to be better understood. The tight sandstones have been examined by a variety of methods. The sandstones are mostly lithic arkoses and feldspathic litharenites, compositionally immature with an average framework composition of Q43F26L31, which are characterized by abundant volcanic rock fragments. Mixed-layer illite/smectite (I/S) ordered interstratified with R = 1 and R = 3 is the dominating clay mineral in the studied sandstone reservoirs. Two different types of quartz cementation modes, namely quartz grain overgrowth and pore-filling authigenic quartz, have been identified through petrographic observations, CL and SEM analysis. Homogenization temperatures of the aqueous fluid inclusions indicate that both quartz overgrowths and pore-filling authigenic quartz formed with a continuous process from about 70 °C to 130 °C. Sources for quartz cement produced are the conversion of volcanic fragments, smectite to illite reaction and pressure solution at micro stylolites. Potassium for the illitization of smectite has been sourced from K-feldspar dissolution and albitization. Silica sourced from K-feldspars dissolution and kaolinite to illite conversion is probably only minor amount and volumetrically insignificant. The internal supplied silica precipitate within a closed system where the transport mechanism is diffusion. The quartz cementation can destroy both porosity and permeability, but strengthen the rock framework and increase the rock brittleness effectively at the same time. 相似文献
3.
The Upper Cretaceous Mesaverde Group in the Piceance Basin, western Colorado, contains thick sections of low porosity, low permeability sandstones that are reservoirs for large accumulations of hydrocarbon gas. The Mesaverde sandstones are lithic arkoses and feldspathic litharenites, containing quartz, plagioclase, variable K-feldspar, chert, and volcanic rock fragments. Important diagenetic processes that have affected the sandstones include compaction, dissolution of feldspar and/or alteration to clay, precipitation of carbonate and quartz cements, precipitation of illite, and alteration of detrital clays (mixed-layer illite–smectite). Porosity is relatively constant; a decrease in primary porosity downward is approximately balanced by an increase in secondary porosity, with significant microporosity in authigenic and diagenetic clays. K-feldspar is almost completely absent below 5500 feet (1675 m). Fibrous illite is relatively abundant above this depth and variable in abundance below. The K–Ar ages of the clays increase with depth, from 40 m.y. at the top of the sampled section to 55 m.y. at the base, indicating illitization of a precursor smectite at approximately the 100 °C isotherm. Samples with abundant fibrous illite have relatively smaller age values. Mass balance calculations indicate that dissolution of K-feldspar, illitization of smectite and precipitation of fibrous illite were coupled. These reactions suggest the transport of dissolved potassium upward hundreds of feet (100–300 m) in the section, possibly associated with water driven vertically by the migration of gas. 相似文献
4.
This paper analyses the diagenetic evolution of sandstones belonging to the Bajo Barreal Formation (Cretaceous) in the Golfo de San Jorge Basin (Patagonia, Argentina). The Bajo Barreal Formation includes the main reservoirs, which are located along the western area of the basin and is composed of sandstones, conglomerates, mudstones, tuffaceous mudstones and some layers of tuffs. The principal reservoirs comprise medium-to coarse-grained sandstones, which are dominated by feldspathic litharenites and contain minor amounts of litharenites and lithic arkoses. The authigenic minerals include kaolinite, smectite, chlorite, quartz overgrowths, microquartz and calcite, with minor proportions of megaquartz, siderite, analcime, laumontite, feldspar overgrowths and illite/smectite and chlorite/smectite mixed layers. Secondary porosity is much more important than primary porosity and is produced by the dissolution of feldspar, lithic clasts and clay cements. The diagenetic history of the Bajo Barreal sandstones can be divided into seven diagenetic stages, each of which is characterized by a specific assemblage of authigenic minerals and diagenetic processes. Eogenetic conditions occur in stages 1, 2, 3 and 4. Stage 1 corresponds to shallow burial characterized by the physical reduction of primary porosity by compaction; during stage 2, rim clay cements of chlorite, smectite and clinoptilolite, as well as thin quartz overgrowths, were formed. The precipitation of pore-filling cements of kaolinite, chlorite and smectite occurred during stage 3, while stage 4 records the intense dissolution of feldspar, lithic fragments and kaolinite cements. Mesogenesis occurs in diagenetic stages 5 and 6. The former corresponds to a new phase of authigenic kaolinite, while the latter records the significant dissolution of feldspar, lithic clasts and previous cements, which produced the highest values of secondary porosity. Finally, stage 7 corresponds to the highest degree of diagenesis in the Bajo Barreal Formation (mesogenesis), which resulted in the precipitation of cements of zeolites and calcite, as well as quartz and plagioclase overgrowths. 相似文献
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南海粘土矿物组合特征及其环境意义 总被引：1，自引：0，他引：1
利用X射线衍射法(XRD)对南海12个海底表层沉积物和20个悬浮物样品中粘土矿物组成和分布特征进行了综合分析。结果表明:(1)研究区的表层沉积物粘土矿物以伊利石为主,其次为绿泥石、高岭石、伊/蒙间层矿物以及蒙皂石;悬浮物粘土矿物是以绿泥石为主,其次为高岭石、蒙皂石、伊利石以及伊/蒙间层矿物。(2)粘土矿物的组成和分布特征主要受气候条件、物质来源、水动力条件及相互间稀释作用的制约。伊利石的含量随离岸距离和水深的增加呈增大趋势;高岭石则在近岸区特别是河口区富集;绿泥石在西部沿岸海区的含量较低,在东部岛弧和北部台湾岛附近海区的含量较高;蒙皂石与火山作用密切相关,在东部火山岛弧附近海区含量较高。(3)粘土沉积物的来源以河流输入为主,海洋自生和风尘搬运对该区的沉积影响不大。(4)深海悬浮物粘土矿物的组成变化能够很好地指示短尺度气候环境的变迁,伊利石的结晶程度对气候和环境变化反映灵敏,其随所处环境的压力增大而变差。 相似文献
7.
北极圈海域表层沉积物的黏土矿物特征及其环境意义 总被引：2，自引：0，他引：2
应用X射线衍射(XRD)分析技术对北极圈海域15个表层沉积物的黏土矿物进行了研究。结合伊利石的结晶度指数综合分析了研究区黏土矿物的组成和分布特征及其物质来源、沉积环境和水动力条件。结果表明,北极圈海域研究区的黏土矿物以伊利石为主(33%),其次为伊/蒙间层矿物(25%)、绿泥石(23%)、高岭石(15%)以及蒙皂石(4%)。伊利石的开形指数(Ns)都比较小,大多在1~2之间,Ns的分布对物源有一定的指示意义。楚科奇海区具较弱的水动力条件,沉积环境较稳定;白令海具强烈的水动力条件,属于冲刷环境。认为北极圈海域研究区的黏土沉积物均有三方面来源,即河流输入、海洋自生和冰筏搬运物。 相似文献
8.
The <2 μm fraction of 45 sediment samples from the Elbe and Weser rivers and from the southeastern North Sea (German Bight) was analyzed for its contents of clay minerals and selected chemical elements. This was done to provide new information to the controversial question about the origin and distribution of clays in this near-shore marine region. The proportions of smectite, chlorite, illite and kaolinite were determined from intensities of the (001) basal reflection of the XRD pattern using weighted integrated factors and IR-mineral spectra, which were fitted to the values of the chemical analyses. Illite – the major clay mineral – was characterized by its K/Rb ratios and K-Ar ages. Anthropogenic metal contamination was demonstrated by the Cu, Pb and Zn contents. 相似文献
9.
Fine fractions (<2 μm) from smectite-rich flood-plain sediments from the Elbe and Weser rivers in Germany were treated in the laboratory with synthetic sea salt solutions at different concentrations and for different periods of time to document sheet delamination of smectite particles at the fluvial/marine interface and thus simulate changes in clay minerals at the mouth of a river. The project consisted of two steps: (1) Pilot tests were made in 0.5% salt solutions (brackish environment) showing a nearly 2-min delay of the clearing of the clayey suspensions, when the suspension was redispersed 15 and 30 min later after the first measurement. This was due to an obviously increased number of fine laminae from disintegrated smectite particles. (2) X-ray diffraction studies (XRD) of the clayey material from suspensions in 0.0, 0.5, 1.0, and 3.0% salt solutions after standing 10 min, and one and three weeks were made to document alteration reactions of smectite. An aliquot was pipetted periodically from each series, and oriented clay-mineral specimens were analyzed by XRD in air-dried, glycol- and glycerin-solvated states. The peak intensities in the XRD patterns of the clay minerals smectite, random-ordered mixed-layer illite/smectite (I–S), kaolinite, chlorite, and illite did not change in the salt-free series during the experiments. In contrast the peak intensities of smectite and I–S mineral in the air-dried and glycerin-solvated states after suspension in saline solutions decreased significantly. The d-values of the smectitic materials in the air-dried state also decreased after contact with the saline solutions, and in the glycerin-solvated state the full-width-at-half-maximum (FWHM) of the 001 smectite reflection increased by about 20%, indicating a reduction in grain size. 相似文献
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南海南部沉积物中黏土矿物组成变化及其古沉积信息记录初探 总被引：7，自引：1，他引：6
通过对南海南部2个代表13万a以来柱状沉积样品高分辨率的黏土矿物组成分析,认为所研究的黏土矿物主要为陆源碎屑成因,埋藏过程中的成岩变化或黏土矿物自生特征不明显,而以采样点南面加里曼丹岛、菲律宾东、西两侧的火山群岛和湄公河流域为主要陆源的地质条件、风化环境及物质迁移途径的差异控制了南海南部沉积物中黏土矿物组成的空间和时间变化.研究发现,沉积物样品中较高的蒙皂石含量对应于地质历史上的暖期,而较低的蒙皂石含量对应于冷期.伊利石的行为及其古海洋指示意义则与蒙皂石相反.将柱状沉积物样品上高分辨率的黏土矿物组成分析作为一种研究方法,有助于研究晚第四纪以来南海陆源碎屑物的源区特征、迁移途径及海区古环境演变. 相似文献
12.
Ruarri J. Day-Stirrat Kitty L. Milliken Shirley P. Dutton Robert G. Loucks Stephen Hillier Andrew C. Aplin Anja M. Schleicher 《Marine and Petroleum Geology》2010
Wilcox Group mudstones have been mechanically and geochemically transformed over a temperature range of 20–200 °C. Our research controlled for provenance and age by sampling from five wells, parallel to the paleodepositional axis, all within the Houston delta system. Across the sampled depths, mudstone porosity has been reduced from ∼25 to <10% and bulk mineralogical change as documented by quantitative X-ray diffraction includes decreases in quartz, K-feldspar and kaolinite content whereas illite + illite − smectite, chlorite, and plagioclase increase. These mineral transformations transfer elements at a scale of less than 1 mm from one mineralogical form to another, however, X-ray fluorescence data suggest that among major elements only Al2O3 and TiO2 are fully conserved within the system (trace-element ZrO2 is also conserved). K2O has been added to and SiO2 released from the Wilcox Group mudstones. Cathodoluminescence and secondary electron imaging did not find this SiO2 locally precipitated. We, therefore, document an open-system geochemical behavior. 相似文献
13.
Th. Leipe A. Loeffler K. -C. Emeis S. Jaehmlich R. Bahlo K. Ziervogel 《Estuarine, Coastal and Shelf Science》2000,51(6):789
Suspended particulate matter samples were collected from the water column, the bottom nepheloid layer and the ‘ fluffy layer ’ from four stations along a coastal-basin transect in the Pomeranian Bight, western Baltic Sea. Sampling was performed nine times between October 1996 and December 1998 for various analyses, including electron probe x-ray micro analysis for detailed mineralogical investigations.Specific vertical patterns of clay mineral distributions were found. Suspended particulate matter (SPM) in the bottom nepheloid layer and the ‘ fluffy layer ’ overlying sediments was enriched in organic carbon and hydrated three layer clay minerals, whereas the non-aggregated SPM was dominated by quartz and biogenic opal. It appears that separation effects operate during aggregation of mineral particles and organic matter in repeated cycles of resuspension and settling. No clear seasonal variations in the composition of the SPM were found, in spite of high spatial and temporal variability of biological and physical variables. The results suggest that preferential incorporation, possibly aided by microbiological colonization, of hydrated three layer silicates into the organic flocs is a process that occurs under a wide range of conditions. Because aggregates sink faster than individual particles, aggregate formation led to a relative enrichment of illite and smectite in the near-bottom layers. Considering the affinity of organic contaminants and heavy metals to organic matter, the selective removal of aggregated organic matter and hydrated three-layer clay minerals from the water column and enhanced transport in the near-bottom fluffy layer may be a natural cleansing mechanism operating in the shallow waters of the bight. 相似文献
14.
The Stø Formation is the most important reservoir interval in the Norwegian Barents Sea, however the reservoir quality can be highly affected by the detrimental effects of quartz cement where there have been extensive post depositional burial. Core plug data from well 7219/8-2 in the Southwestern Barents Sea shows abnormally high porosity and permeability values in certain units of the deeply buried and otherwise highly quartz cemented Stø Formation. The amount of quartz cement in the samples is inversely proportional to the porosity. Samples with high and low porosities are similar texturally and mineralogically, but the high porosity samples have a layer of illitic clay coating the majority of the detrital quartz grains. Illitic clay coating present at grain contacts can result in a lowered IGV given they aid in the dissolution of quartz at interfaces, also creating a source of dissolved silica. Clay induced dissolution means that silica saturation is not a limiting factor in quartz cementation in these samples. The results show that the illitic clay coating is capable of limiting the amount of authigenic quartz overgrowth from 20 to 23% in samples with negligible grain coating to 5–11% in the intervals with high coating coverage. The illitic clay coating inhibits quartz overgrowth by limiting the surface area available for nucleation on detrital grains. The Stø Formation comprises mainly shallow marine deposits of highly reworked clean sandstone. Abnormally high porosities appear to be linked to settings where sediments of a more proximal location are preserved without extensive reworking. The grain coating clay is illitic and most likely originates from clay infiltration processes prior to final deposition. The difference in extent of clay coating in similar facies can mostly be correlated with varying amount of post depositional reworking. This study suggests that there is a potential for considerable porosity and permeability to be preserved in deeply buried sandstones in the Barents Sea. This study could be important in the future exploration activity of deeply buried structures in the area. 相似文献
15.
Oedometric mechanical compaction tests were performed on brine-saturated synthetic samples consisting of silt-clay mixtures to study changes in microfabric and rock properties as a function of effective stress. The silt consisted of crushed quartz (∼100%) with grain size range between 4 and 40 μm, whereas the clay consisted of 81% kaolinite, 14% mica/illite and 5% microcline of grain size between 0.4 and 30 μm. Five sample pairs ranging in composition from pure silt to pure clay were compacted to 5 and 50 MPa effective stress respectively. SEM studies were carried out to investigate microfabric changes in the mechanically compacted silt-clay mixtures. The degree of alignment of the different minerals present (quartz, mica/illite and kaolinite) were computed by using an image analysis software. Experimental compaction have measured the changes in the rock properties such as porosity and velocity as a function of effective stress for different mixtures of clay and silt. Clay-rich samples showed a higher degree of mineral orientation and lower porosity compared to silt-dominated samples as a function of effective stress. Pure clay sample had 11% porosity at 50 MPa effective stress whereas the pure silt sample retained about 29% porosity at the same effective stress. The experiments showed that low porosity down to 11% is possible by mechanical compaction only. A systematic increase in strain was observed in the silt-clay mixtures with increasing clay content but the porosity values found for the 50:50 silt-clay mixture were lower than that of 25:75 silt-clay mixture. No preferential mineral orientation is expected before compaction owing to the high initial porosity suggesting that the final fabric is a direct result of the effective stress. Both P- and S-wave velocities increased in all silt-clay mixtures with increasing effective stress. The maximum P- and S-wave velocities were observed in the 25:75 silt-clay mixture whereas the minimum Vp and Vs were recorded in the pure silt mixture. At 50 MPa effective stress P- wave velocities as high as 3 km/s resulted from experimental mechanical compaction alone. The results show that fine-grained sediment porosity and velocity are dependent on microfabric, which in turn is a function of grain size distribution, particle shape, sediment composition and stress. At 5 MPa effective stress, quartz orientation increased as a function of the amount of clay indicating that clay facilitate rotation of angular quartz grains. Adding clay from 25% to 75% in the silt-clay mixtures at 50 MPa effective stress decreased the quartz alignment. The clay mineral orientation increased by increasing both the amount of clay and the effective stress, the mica/illite fabric alignment being systematically higher than that of kaolinite. Even small amount of silt (25%) added to pure clay reduced the degree of clay alignment significantly. This study demonstrates that experimental compaction of well characterized synthetic mudstones can be a useful tool to understand microfabric and rock properties of shallow natural mudstones where mechanical compaction is the dominant process. 相似文献
16.
黏土矿物研究在示踪物源、源区风化历史乃至洋流变迁能力等方面具有重要的作用,尽管目前对南海表层沉积物黏土矿物宏观分布特征已获得了较系统的认识,但在受珠江和海南岛物源共同影响的南海西北部其高分辨率的黏土矿物学工作还未开展。本文对南海西北部表层沉积物中的黏土矿物组成、结晶学特征进行了分析,讨论了研究区黏土矿物的物质来源。结果表明,南海西北部表层沉积物的黏土矿物组成以伊利石为主（平均45%）,蒙脱石（平均27%）与高岭石（平均21%）次之,绿泥石含量最少（平均6%）。在区域空间分布上,蒙脱石含量呈现西南高东北低的特征,伊利石含量则与之相反;高岭石含量表现为近岸高离岸低,而绿泥石含量呈现离岸高近岸低的特征。总体上,研究区表层沉积物黏土矿物组成与现代珠江沉积物组成差异较大,而与珠江口2.5 ka前的沉积物黏土矿物组成比较接近,并且结合研究区岩心揭露的全新世以来极低的沉积速率（4 cm/ka）以及上部很薄（小于0.6 m）的泥质沉积,推测该区表层沉积物可能并非是现代沉积的结果,更可能主要来自全新世末期古珠江输送的沉积物。除古珠江作为研究区表层沉积物中蒙脱石的一个主要来源外,海南岛北部河流也贡献了少量蒙脱石到其邻近的东南海域。运用高岭石/伊利石比值和伊利石化学指数等进一步对比分析表明,珠江是研究区沉积物中伊利石、高岭石和绿泥石的主要物源,其次台湾和海南岛也可能分别提供了少量富含伊利石/绿泥石和高岭石的沉积物。本工作对于南海西北部沉积物源-汇过程和相应的古环境研究有重要的参考意义。 相似文献
17.
Seventy-five surface and subsurface sediment samples collected on the Amazon continental shelf were analyzed by X-ray diffraction
(XRD) in the grain-size fractions smaller than 2 μm. The groups of clay minerals thus identified were smectite, kaolinite,
illite, and mixed-layer illite/smectite. Calculation of relative abundance shows a predominance of smectite (37%) in the whole
area, followed by kaolinite (27%), illite (23%), and a small percentage of mixed-layer illite/smectite (12%). The distal,
northwest region of the continental shelf is characterized by a high abundance of smectite (41%), high salinity values, and
high sediment accumulation rates (10 cm year−1), whereas the proximal region is characterized by a comparatively low abundance of smectite (30%), low salinity values, and
low sediment accumulation rates (<1 cm year−1). This trend of increasing abundance northwestwards documents a preferential settling of smectite in the distal and more
saline regions of this estuarine system.
Received: 17 September 1999 / Revision accepted: 17 January 2000 相似文献
18.
Origin,physical, and mineralogical nature of red clays: The Pacific Ocean Basin as a model 总被引：2，自引：0，他引：2
Extensive examination of North Pacific Basin red clays by scanning and transmission electron microscopy reveals that the mean constituent of the red clays are illite-rich argillaceous or shale clasts, quartz and authigenic smectite. The main source of the shale clasts and quartz are aeolian in nature and are derived mainly from African and Asian shales. Illite-rich argillaceous or shale clasts are identifiable by their morphology (high degree of roundness), selected area diffraction, and their unique fracture characteristics created by an ultra thin-sectioning process. This allows for the identification and differentiation of illite-rich shale clasts from other clays, including detrital illite, kaolinite, and smectite. Geotechnical examination of the red clays indicate that they are overconsolidated: the preconsolidation stress is in all cases larger than the vertical effective stress. The overconsolidation is attributed to the strong bonding of argillaceous or shale clasts, quartz and other particulate matter by x-ray amorphous and well developed crystalline sheets of authigenic smectite characterized by high surface activity. 相似文献
19.
基于409个表层沉积物样品黏土组成的分析测试结果,结合周边河流沉积物黏土矿物组成数据,研究了渤海—北黄海底质沉积物中黏土矿物的分布特征、来源和输运趋势。渤海—北黄海底质沉积物中黏土矿物组分质量分数从高到低依次为伊利石(70%)、高岭石(12%)、绿泥石(11%)和蒙皂石(7%)。根据沉积物黏土矿物的组成和分布特征,可以把研究区分为2个区和6个亚区。I区物质来源主要为黄河,分布在黄河口外,向东北延伸至渤海海盆、东南向经莱州湾再向东北延伸至北黄海南部海域;II区物质来源主要为潍河、六股河、滦河和辽河等,还包括海岸侵蚀物质,主要分布在辽东湾、渤海湾北部和北黄海北部等海域。黏土矿物的输运和分布除了受到物源的影响外,主要受渤海环流的控制。 相似文献
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A 43 cm long E271 sediment core collected near the East Pacific Rise(EPR) at 13°N were studied to investigate the origin of smectite for understanding better the geochemical behavior of hydrothermal material after deposition.E271 sediments are typical metalliferous sediments. After removal of organic matter, carbonate, biogenic opal,and Fe-Mn oxide by a series of chemical procedures, clay minerals(2 μm) were investigated by X-ray diffraction,chemical analysis and Si isotope analysis. Due to the influence of seafloor hydrothermal activity and close to continent, the sources of clay minerals are complex. Illite, chlorite and kaolinite are suggested to be transported from either North or Central America by rivers or winds, but smectite is authigenic. It is enriched in iron, and its contents are highest in clay minerals. Data show that smectite is most likely formed by the reaction of hydrothermal Fe-oxyhydroxide with silica and seawater in metalliferous sediments. The Si that participates in this reaction may be derived from siliceous microfossils(diatoms or radiolarians), hydrothermal fluids, or detrital mineral phases. And their δ30 Si values are higher than those of authigenic smectites, which implies that a Si isotope fractionation occurs during the formation because of the selective absorption of light Si isotopes onto Feoxyhydroxides. Sm/Fe mass ratios(a proxy for overall REE/Fe ratio) in E271 clay minerals are lower than those in metalliferous sediments, as well as distal hydrothermal plume particles and terrigenous clay minerals. This result suggests that some REE are lost during the smectite formation, perhaps because their large ionic radii of REE scavenged by Fe-oxyhydroxides preclude substitution in either tetrahedral or octahedral lattice sites of this mineral structure, which decreases the value of metalliferous sediments as a potential resource for REE. 相似文献