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Cementation (geology)

About: Cementation (geology) is a research topic. Over the lifetime, 3123 publications have been published within this topic receiving 61938 citations.


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TL;DR: In this article, the results of a study in which natural microbial biological processes were used to engineer a cemented soil matrix within initially loose, collapsible sand were presented, using the microorganism Bacillus pasteurii, an aerobic bacterium pervasive in natural soil deposits.
Abstract: Current methods to improve the engineering properties of sands are diverse with respect to methodology, treatment uniformity, cost, environmental impact, site accessibility requirements, etc. All of these methods have benefits and drawbacks, and there continues to be a need to explore new possibilities of soil improvement, particularly as suitable land for development becomes more scarce. This paper presents the results of a study in which natural microbial biological processes were used to engineer a cemented soil matrix within initially loose, collapsible sand. Microbially induced calcite precipitation (MICP) was achieved using the microorganism Bacillus pasteurii, an aerobic bacterium pervasive in natural soil deposits. The microbes were introduced to the sand specimens in a liquid growth medium amended with urea and a dissolved calcium source. Subsequent cementation treatments were passed through the specimen to increase the cementation level of the sand particle matrix. The results of both MICP- and ...

1,149 citations

Journal ArticleDOI
TL;DR: In this article, a set of carbonate minerals are stained with alizarin red-S and potassium ferricyanide only if they will react with dilute hydrochloric acid solution, with which the stain is prepared.
Abstract: Carbonate minerals are stained over a set period of time with alizarin red-S and potassium ferricyanide only if they will react with dilute hydrochloric acid solution, with which the stain is prepared. The rates of solution of carbonates in the acid control the intensity of color development. For calcite, the rate of solution varies with the optic orientation of the section. The speed of carbonate solution is changed if the acid concentration is altered, but only at concentrations of about 0.1 N is the optic orientation of calcite differentiated by the stain. Etching reduces thin section thickness and clarifies rock texture. Staining with alizarin red-S differentiates carbonate minerals into two groups. Aragonite, calcite, witherite, and cerussite, which dissolve rapidly in dilute hydrochloric acid, are stained, while dolomite, siderite, magnesite, and rhodochosite, which react much more slowly with the acid, remain unstained. The distribution of ferrous iron, as distinguished by staining with potassium ferricyanide, has proved to be highly significant in the genesis of cements. Ferrous iron can be introduced at any one stage in cementation, or repeatedly, forming zoned patterns. The paragenesis of zoned ferroan cements can be reconstructed after staining. Solution of the more soluble original constituents can sometimes be dated in relation to cementation. Ferroan calcite can be secondary in origin and is usually associated with replacement minerals.

847 citations

Journal ArticleDOI
TL;DR: In this article, the authors identify the processes and products of carbonate diagenesis, and the distribution of porosity in subsurface carbonates can often be predicted by identifying the environments in which those processes acted.
Abstract: Understanding the processes and products of carbonate diagenesis is essential to exploration for, and optimum development of, hydrocarbon reservoirs in carbonate rocks. Much (and perhaps most) cementation and formation of secondary porosity (except fractures) in carbonates occurs at relatively shallow depths in one of four major diagenetic environments: the vadose zone, meteoric phreatic zone, mixing zone, and marine phreatic zone. Each of these zones may be divided into several parts on the basis of rate of water movement and saturation of the water with respect to calcium carbonate. Most carbonates are deposited in and begin their diagenetic history in the marine phreatic environment. This zone may be divided into two end members of a continuous spectrum: a zone of relatively little water circulation in which micritization and minor intragranular cementation occur, and a zone of good water circulation near the sediment/water interface of shelf margins or the upper shoreface in which extensive intergranular and cavity-filling cementation occur. Fibrous aragonite and micritic Mg-calcite are the dominant cements. With subaerial exposure, fresh water will replace sea water in the pores of shallow-water carbonates, and a zone of mixed fresh and marine waters may form. In long-lived mixing zones, dolomite may form if the water is of relatively low salinity, whereas bladed Mg-calcite may form if the water is relatively marine. Active water circulation in the mixing zone, which may be caused by seasonal rainfall, is necessary for dolomitization or cementation. Diagenesis in the freshwater phreatic environment may involve leaching in the zone of solution, neomorphism of grains accompanied by extensive intergranular calcite cementation in the active saturated zone, or neomorphism of grains without cementation in the stagnant saturated zone. Syntaxial overgrowths on echinoderm fragments and interlocking crystals of equant calcite that coarsen toward pore centers are typical of cementation in the active freshwater phreatic zone. The freshwater vadose environment is the zone with both air and meteoric water in the pores and may be divided into the zone of solution and the zone of precipitation. CO2 from the atmosphere and soil contributes to solution which generally occurs near the soil zone and forms vugs, molds, and etched grains. When the water becomes saturated with respect to calcite, evaporation or CO2 loss may cause precipitation of fine equant calcite in the form of pendant and meniscus cements. Grains may be altered to calcite, particularly in humid climates, and caliche crusts may be produced by evaporation and/or biologic (generally algal) factors. Climate plays an important role in early diagenesis if subaerial exposure occurs. In arid climates, cementation in freshwater environments may be limited and primary intergranular porosity may be preserved. In humid climates, little primary porosity is likely to escape cementation, but significant amounts of secondary moldic and vuggy porosity may form. Interpretation of diagenesis in carbonates is complicated by the fact that diagenetic environments may change many times in the history of a carbonate rock. By recognizing the processes leading to the formation or preservation of porosity, and the distribution of diagenetic End_Page 461------------------------------ environments in which those processes acted, the distribution of porosity in subsurface carbonates can often be predicted.

616 citations

Journal ArticleDOI
TL;DR: Impure reworked evaporitic sandstones, preserved on Meridiani Planum, Mars, are mixtures of roughly equal amounts of altered siliciclastic debris, of basaltic provenance (40−±10% by mass), and chemical constituents, dominated by evaporitic minerals (jarosite, Mg, Ca-sulfates, chlorides, Fe-, Na-solves), hematite and possibly secondary silica (60−± 10%).

541 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023353
2022693
2021193
2020129
2019158
2018154