Journal articles on the topic 'Illite rich rocks'
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1
Bozkaya, Ö., H. Yalçin, and P. A. Schroeder. "Two-step mode of clay formation in the extensional basins: Cambrian–Ordovician clastic rocks of the Antalya unit, SW Turkey." Clay Minerals 52, no. 3 (September 2017): 365–89. http://dx.doi.org/10.1180/claymin.2017.052.3.07.
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AbstractOrdovician clastic rocks of the Antalya unit in SW Turkey bear mineralogical/geochemical evidence of Triassic extensional rift timing and spatial relations. The crystal chemistry of the phyllosilicate assemblages (illite, chlorite, kaolinite, mixed-layer illite-smectite, chlorite-vermiculite and chlorite-smectite) is consistent with the rock experiencing a multi-generational burial history. The appearance of kaolinite and illite-smectite-bearing rocks in the Antalya unit is characteristic of diagenetic-anchimetamorphic conditions and is of higher grade than their anchi-epizonal equivalents in other regions of the Tauride belt. Illites and chlorites are of both detrital and authigenic origin, whereas I-S and kaolinites are authigenic. Detrital micas have been altered to chlorite and K-white mica stacks in which relicts suggest the chlorites were derived from detrital biotites. The broad X-ray diffraction illite peaks show that they are composed both of illite and illite-smectite. Na,K-mica and paragonite occur within the chlorite-mica stacks as replacements of muscovite, probably driven by Na-rich solutions. The authigenic clays were formed within the microporous matrix and the interplanar spaces of {001} planes of chlorite-mica stacks, with textures independent of the bedding and foliation planes of the rocks. The authigenic chlorites exhibit higher Si and Fe and lower Mg contents than their detrital counterparts. Authigenic chlorite thermometry indicates rift-related temperatures of 50–150°C, whereas pre-rift detrital chlorites formed at temperatures of >200°C. Authigenic illite and illite-smectite are phengitic in composition and contain more Si, Mg, Fe and Ca and less Al and K than detrital K-white micas. The textural, mineralogical and chemical characteristics support the hypothesis that the mineral assemblages were a result of a two-step mode of formation with diagenetic overprints of previously anchizonal rocks in extensional basin conditions.
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Papoulis, D., and P. Tsolis-Katagas. "Formation of alteration zones and kaolin genesis, Limnos Island, northeast Aegean Sea, Greece." Clay Minerals 43, no. 4 (December 2008): 631–46. http://dx.doi.org/10.1180/claymin.2008.043.4.08.
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AbstractKaolin deposits extending over an area of ~10 km2in the western and southern parts of Limnos Island, northeast Aegean Sea, Greece, were studied. The kaolin deposits are alteration products of volcanic rocks, mainly trachytes, trachyandesites, andesites and dacites. Study of the collected samples was carried out using X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), energy-dispersive scanning electron microscopy (SEM-EDS), Fourier transform Raman spectroscopy (FT-Raman), Fourier transform infrared (FTIR) techniques and inductively-coupled plasma (ICP) bulk rock chemical analyses for major, trace and rare earth elements. The extensive alteration of the parent rocks resulted from the circulation of hydrothermal fluids through faults and fractures. The development of the various assemblages depends not only on the temperature and composition of the hydrothermal fluids but also on the distance of the rock from the fault or the channel of the ascending hydrothermal fluids.Kaolinite, dickite, halloysite, illite, smectite and mixed-layer illite-smectite and jarosite were detected in the altered volcanic rocks forming locally various alteration zones. Smectite-rich zones and illite-rich zones are relatively infrequent. In the halloysite-rich zones, the kaolinization of feldspars is accomplished in four stages. The kaolinizaton of feldspars in the kaolinite-dickite-rich zones follows five discrete stages. In the less altered rocks, thin layers of kaolinite are formed on the surface of feldspars. With increasing kaolinization, kaolinite is developed on the surface of feldspars forming extended parallel booklets of newly formed kaolinite. In the third stage, feldspar crystals are partially altered to kaolinite booklets. As kaolinization advances, kaolinite becomes well formed and, in the most altered rocks, feldspars are partially or completely altered to dickite books, depending on the temperature of the hydrothermal fluids.
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Almeida, Delia Del Pilar M. de, Vitor P. Pereira, Adriane Machado, Henrique Zerfass, and Ricardo Freitas. "Late sodic metasomatism evidences in bimodal volcanic rocks of the Acampamento Velho Alloformation, Neoproterozoic III, southern Brazil." Anais da Academia Brasileira de Ciências 79, no. 4 (December 2007): 725–37. http://dx.doi.org/10.1590/s0001-37652007000400012.
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A mineralogical study was carried out in mafic and felsic volcanic rocks of the Acampamento Velho Alloformation at Cerro do Bugio, Perau and Serra de Santa Bárbara areas (Camaquã Basin) in southern Brazil. The Acampamento Velho bimodal event consists of two associations: lower mafic at the base and upper felsic at the top. Plagioclase and alkali-feldspar were studied using an electronic microprobe, and magnetite, ilmenite, rutile, illite and alkali-feldspar were investigated through scanning electron microscopy. The rocks were affected by a process of late sodic autometasomatism. In mafic rocks, Ca-plagioclase was transformed to albite and pyroxenes were altered. In felsic rocks, sanidine was partially pseudomorphosed, generating heterogeneous alkali-feldspar. In this association, unstable Ti-rich magnetite was replaced by rutile and ilmenite. In mafic rocks, the crystallization sequence was: (1) Ti-rich magnetite (?), (2) pyroxene and Ca-plagioclase, (3) albite (alteration to Ca-plagioclase), (4) sericite, chlorite and calcite (alteration to pyroxene), and kaolinite (alteration to plagioclase/albite). In felsic rocks: (1) zircon, (2) Ti-rich magnetite, (3) sanidine, (4) quartz. The introduction of late Na-rich fluids, generated the formation of (5) heterogeneous alkali-feldspar, (6) ilmenite and rutile from the Ti-rich magnetite, (7) albite in the spherulites. Finally, alteration of sanidine, vitroclasts and pumice to (8) illite.
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Brattli, B. "A rectorite-pyrophyllite-chlorite-illite assemblage in pelitic rocks from Colombia." Clay Minerals 32, no. 3 (September 1997): 425–34. http://dx.doi.org/10.1180/claymin.1997.032.3.05.
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AbstractIn samples of slate from the Fomeque Formation near Bogota, Colombia, pyrophyllite was found to occur together with mixed-layered illite-smectite, chlorite and illite. Other minerals were quartz, K-feldspar, dolomite and pyrite. X-ray diffraction patterns revealed that the mixed-layer represents an R1 ordered rectorite with 80–90% illite layers. The microfabric is developed as a closely spaced cleavage in the phyllosilicate-rich rocks, and grades into a fracture cleavage with coarsening of the grain size. No cleavage was observed in the interbedded siltstones. It is suggested that the microfrabrics developed in these rocks correspond to high diagenetic to anchizonal conditions. The illite crystallinity from the slate has been measured on glycolated samples and ranges from 0.47 to 0.55°Δ2θ with a mean of 0.52°Δ2θ Based on the stability of R1 ordered rectorite, the illite crystallinity and the microfabric development, it is proposed that the rocks have been subjected to a temperature of ∼200°C at low pressure. At this temperature, pyrophyllite can only be stabilized at the expense of kaolinite and quartz if aH2O ≪ 1.
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Zhang, Jie, En Lin Yang, Yong Ning Di, Fei Xie, and Guo Feng Yang. "Study of Material Characteristics about Lower Cambrian Black Shale in ZhiJin-KaiYang-XiFeng, Guizhou." Applied Mechanics and Materials 170-173 (May 2012): 1162–66. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.1162.
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The high cambrian black rock series of clay under Zhijin, Kaiyang, Xifeng and other areas of Guizhou , are high carbon black shale - clay rocks characterized by containing illite ores[1]. After deep processing, it will be served as illite ores belonging to a useful clay minerals, and the main directions of development and application include filler, new building materials and ceramics. After the activation, potassium can be extracted from illite that is often rich in potassium which can be prepared for potash fertilizer. Carrying out the study of mineral material science of high carbon black clay mineral rock , the aim is developing and using this type of non-metallic mineral. Based on this study, recoverying useful metal elements by exploring the reasonable technical process will be significant to enhance the comprehensive value of the type of deposit and improve its economic efficiency.
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Mahmoud, Soliman Abu Elatta A., and Hani H. Ali. "Geology and genesis of vein-type corundum deposits in the Hafafit-Nugrus area, South Eastern Desert, Egypt." Geologos 26, no. 3 (December 1, 2020): 181–97. http://dx.doi.org/10.2478/logos-2020-0018.
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Abstract Unusual deposits formed by corundum are described from two separate pegmatitic veins in the Hafafit-Nugrus area of the South Eastern Desert of Egypt. Other related minerals are described too. The vein-type of corundum at Locality 1 (Vein 1) crosscuts through exposed rocks of an ophiolitic mélange, whereas at Locality 2 (Vein 2), it crosscuts through exposed serpentinised ultramafic rocks. The main minerals in Vein 1 are plagioclase, corundum, grossular, phlogopite, muscovite and clinochlore, while almandine, xenotime-(Y), allanite-(Ce), zircon, Cr-rich spinel, apatite, titanite, fergusonite-(Y), meta-ankoleite, U-rich thorite (uranothorite), carbonate and illite are the accessories. In Vein 2, the main minerals are plagioclase, corundum, phlogopite and chlorite, while clinochlore, euxenite-(Y), Nb-rich rutile, almandine, xenotime-(Y), allanite-(Ce), zircon, spinel, apatite, titanite, kasolite, dickite, illite, carbonate, antigorite and talc are accessories. The two types of corundum veins differ in their concentrations of Th, U, Zr, Nb, Ta, REE, Y and Li in whole-rock compositions. Field observations, mineralogy and chemical analyses of samples from the two veins of corundum deposits, as well as concentrations of chromophore elements in corundum crystals, suggest metasomatic origins. The present study suggests that the two types of corundum veins formed at different ages from different residual magmas that underwent in-situ hybridisation with the host rocks.
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Xiao, Zhenghui, Yunjiang Cao, Wei Jiang, Ping Zhou, Yanran Huang, and Jisong Liu. "Minerals and Enrichment of W, Rb, and Cs in Late Permian Coal from Meitian Mine, Meitian Coalfield, Southern China by Magmatic Hydrothermal Fluids." Minerals 8, no. 11 (November 5, 2018): 504. http://dx.doi.org/10.3390/min8110504.
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We report on the effects of magmatic hydrothermal fluids on the mineralogical and geochemical compositions of 12U and 12L Coals from the Meitian Mine in the Meitian Coalfield, southern China. The minerals in 12U Coal are predominantly chlorite, quartz, and calcite, while the minerals in 12L Coal consist mainly of illite, quartz, chlorite, kaolinite, and mixed-layer illite/smectite (I/S). The vesicle- and fracture-filling illite, chlorite, I/S, pyrite, and fluorite, cleat- and fracture-filling carbonate minerals (i.e., calcite, and dolomite), and cleat-filling tremolite, diopside, and talc have epigenetic hydrothermal origins. Tremolite, diopside, and talc were probably formed from the reaction between dolomite and Si-rich magmatic hydrothermal fluids. Elevated Pb–Zn–Sn–Cd assemblages are characteristic for the 12U Coal, while 12L Coal is enriched in W, Rb, Cs, Th, V, Zn, and Zr, most notably W, Rb, and Cs. REY (Rare Earth Elements and Yttrium) plots for almost all coals, partings and host rocks are similar, showing an M-type REY distribution, Gd-maximum, positive Y anomalies, and negative Ce anomalies, suggesting acid hydrothermal circulation in the coal-bearing strata. Rubidium and cesium in the coal is clearly associated with K-rich clay minerals (illite + I/S), and to a lesser extent with silicate minerals that were precipitated from hydrothermal solutions. W in the coals mainly occurs in the inorganic constituents of illite and pyrite, especially illite. Enrichment of W, Rb, and Cs in the coal and host rocks is genetically associated with magmatic hydrothermal fluids. Specifically, magmatic hydrothermal fluids of relatively high temperatures that are rich in volatile matter can extract abundant W, Rb, and Cs from granitic melts. The enrichment of these rare metals in the coal is mainly related to illitization. Our study results suggest that, for coal intruded by magmatic rocks, the type of hydrothermal alteration may greatly influence the enrichment of elements.
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Clauer, Norbert. "How Can Technical Aspects Help Improving K-Ar Isotopic Data of Illite-Rich Clay Materials into Meaningful Ages? The Case of the Dominique Peter Uranium Deposit (Saskatchewan, Canada)." Geosciences 10, no. 8 (July 27, 2020): 285. http://dx.doi.org/10.3390/geosciences10080285.
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Previously published K-Ar dating results of <2 μm illite separates from uranium-hosting and associated barren rocks from Dominique Peter district of the Carswell circular structure in the Athabasca Basin (Canada) were considered to trace four distinct tectonic-thermal events at 1447 ± 45, 1282 ± 40 and 1184 ± 15 (all errors at ± 2 Ma, with a younger, less constrained episode at ~900 Ma. Recent analyses of K-Ar ages of additional <0.2 μm illite fractions from a few initial samples demonstrate that the intermediate ages at ~1280 and ~1185 Ma result, in fact, from mixing of two generations of illite that precipitated at ~1450 and ~900 Ma. They have, therefore, no stratigraphic value, while the two tectonic-thermal episodes at 1448 ± 48 and 937 ± 39 Ma appear to be historically sound. In fact, the analytical procedure of isotopic dating clay materials is of more importance than is often stated. For instance, a safe way to evaluate and constrain best numerical isotopic data of clay separates into ages is combining data of two size splits from several samples. If such age data, especially from size fractions of indurated host rocks, are scattered and point towards the higher data of the coarser fractions, they are potentially enriched in earlier crystallized K-rich components, and should consequently be discarded. The occurrence of detrital or early-crystallized components in clay-rich separates becomes a serious concern when comparing ages generated by various isotopic methods on mineral separates of various whole rocks. It is especially verified in very old, metal-rich deposits such as the uranium-rich deposits of the Saskatchewan Basin. These deposits and their host rocks were studied extensively by a large spectrum of isotopic methods on many types of rocks in a widely dispersed area, and for which the numerical statistics became, sometimes, more central in the interpretation than the specificity of the successive events in the host rocks.
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Velde, B. "Possible chemical controls of illite/smectite composition during diagenesis." Mineralogical Magazine 49, no. 352 (June 1985): 387–91. http://dx.doi.org/10.1180/minmag.1985.049.352.09.
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AbstractRe-interpretation of the significance of phase assemblages present in two sequences of rocks having experienced similar burial diagenesis allows one to establish that the change of oxidation state of iron in sediments could have the effect of changing the smectite content of the mixed layer mineral. This is used to explain an almost isothermal change in the composition of a sequence while others do not show such a rapid change. An indicator of the reaction is seen in the composition of the chlorite present in the rocks which is iron-rich and alumina-poor compared to chlorites in rocks showing a slower rate of change in the smectite content of the mixed-layered mineral. In order to reveal such a relation, one must make an analysis of the clay mineral assemblage, especially in the number of phases present during the course of diagenesis.
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Clauer, N., N. Liewig, and I. Bobos. "K-Ar, δ18O and REE constraints on the genesis of ammonium illite from the Harghita Bãi hydrothermal system, Romania." Clay Minerals 45, no. 3 (September 2010): 393–411. http://dx.doi.org/10.1180/claymin.2010.045.3.393.
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AbstractAmmonium illite and ammonium illite-smectite mixed layers, together with potassium illite, smectite and minute amounts of kaolinite were identified in hydrothermally altered andesite rocks from the Harghita Bãi area of the Eastern Carpathians, Romania. K-Ar dating and oxygen isotope tracing, as well as rare-earth elemental analyses were made to provide new information on the timing and crystal-chemical processes characterizing the crystallization and further evolution of these illite-type mineral phases.The combined results suggest the occurrence of hydrothermal activity in two distinct episodes with nucleation of two generations of illite-type particles of different chemistry and morphology. About 9.5 Ma ago, potassium illite crystallized in alteration halos of the porphyry Cu system, probably at a temperature of ~270ºC from fluids having a δ18O of ~2.9% (V-SMOW). Associated smectite seems to have precipitated slightly later in external alteration halos at a similar temperature, but from fluids depleted in alkalis and with a different δ18O. Alternately, ammonium-rich illite-smectite mixed layers formed very recently, less than ~1 million years ago at a temperature of ~90ºC from fluids of probable meteoric origin that altered the previously crystallized potassium illite, resulting in the crystallization of a new generation of ammonium illite-smectite mixed layers. Evidence of this dissolution-precipitation process is provided by a significant increase in the δ18O of the mixed-layer structures and by a significant change in their REE contents and distribution patterns. Occurrence of potassium in the ammonium-rich mixed layers probably relates to the progressive alteration of the first-generation potassium illite and a discrete concomitant take up of released K by the new NH4-rich interlayers of the ammonium mixed layered sequence.
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Gilg, H. A., B. Weber, J. Kasbohm, and R. Frei. "Isotope geochemistry and origin of illite-smectite and kaolinite from the Seilitz and Kemmlitz kaolin deposits, Saxony, Germany." Clay Minerals 38, no. 1 (March 2003): 95–112. http://dx.doi.org/10.1180/0009855033810081.
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AbstractResidual clays that developed on Permian and Carboniferous glass-rich silicic volcanic rocks (pitchstones, ignimbrites) at the Seilitz and Kemmlitz kaolin deposits, Saxony, Eastern Germany, contain locally abundant lath-shaped illite-rich illite-smectite mixed-layer minerals (I-S). Analyses by XRD and TEM-AES reveal a large illite percentage (>∼90%) and R3 ordering in I-S from Seilitz (>∼90%) and smaller illite percentage (∼70%) and R1 ordering in I-S from Kemmlitz. The clays never suffered a deep burial and there is no geological, petrographic or fluid inclusion evidence for aeolian input or hydrothermal origin of I-S at either deposit. The I-S formed exclusively at the expense of volcanic glass and not from K-feldspar. Residual quartz phenocrysts in the clays still preserve primary glassy silicate melt inclusions and lack secondary aqueous fluid inclusion trails. The dD and δ18O values of kaolinite and I-S are suggestive of low formation temperatures (<40ºC). Rb-Sr and K-Ar dating of I-S-bearing clay separates yield Lower Cretaceous ages at Seilitz and indicates the presence of excess or inherited 40Ar in illite-rich I-S. In contrast, Triassic to Jurassic Rb-Sr ages are obtained for I-S from the Kemmlitz kaolin deposit.
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Brockamp, O., and N. Clauer. "A km-scale illite alteration zone in sedimentary wall rocks adjacent to a hydrothermal fluorite vein deposit." Clay Minerals 40, no. 2 (June 2005): 245–60. http://dx.doi.org/10.1180/0009855054020170.
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AbstractIn a study of wall-rock alteration in the 1.4 km long Würmtal adit at the Käfersteige hydrothermal vein deposit (northern Black Forest, Germany) illite was found to be the only clay mineral within the Bunter sandstone and intercalated claystone. Illite occurs mainly as a detrital mineral in the claystone, whereas it is hydrothermally neoformed in the sandstone, either in the pores or as an alteration product of K-feldspar. The extensive occurrence of authigenic illite along the entire 1.4 km long profile confirms that the fluids migrated far into the sandstone.The authigenic illite formed during a first pulse of high-temperature fluids (Th of ~220°C) with a low salinity (~1 wt.% NaCleq). These fluids also dissolved Sr and Rb from detrital illite of the claystones at the vein. A later hydrothermal pulse with a lower temperature (~70–150°C) and higher salinity (21–28 wt.% NaCleq) silicified the sandstone adjacent to the vein and caused partial substitution of OH- by F- in the structure of the detrital and neoformed illite along the profile.Within analytical error, the K-Ar dates for the neoformed illite of the <2 µm fraction are the same along the profile (~150 Ma). During this hydrothermal process, the age of the detrital illite within the claystone was reset from 310 to 190 Ma. The illite-rich <0.2 µm fractions yield ages of ~142 Ma (sandstone) indicating a Jurassic origin. The uniform age data for illite in the sandstone and in the claystone are probably due to extensive migration of hot fluids through the wall rocks.The hydrothermal fluids are attributed to recycled meteoric water and brines that ascended from the basement into the cover rocks during the opening of the North Atlantic and/or the nearby Tethys area.
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Do, Thanh Ngoc, Duyen Thi Pham, and Phuong Kim Lieu. "Petrographical characteristics and post-depositional alteration affecting porosity and permeability of Oligocene sandstones, block 15-1/05, Cuu Long basin." Science and Technology Development Journal - Natural Sciences 4, no. 2 (May 24, 2020): First. http://dx.doi.org/10.32508/stdjns.v4i2.856.
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Petrographical characteristics and post-depositional alteration studies of sandstones are the two important factors to reservoir rocks, which affect oil and gas storage and permeability of reservoir rocks. This study revealed petrographical characteristics, post-depositional alteration, and their influence on the porosity and permeability of Oligocene sandstones, including C, D, and E and F sequences, block 15-1/05, Cuu Long Basin. The results show that most of the sandstones were arkose, lithic arkose, and sporadically interbedded by feldspathic greywacke. The post-depositional alteration was progressively increasing following the burial depth from early diagenesis of sequence C, to intermediate diagenesis of sequence D and advanced diagenesis of sequence E and F. The post-depositional alterations significantly influenced on the porosity of the Oligocene sandstone were the cementation and mechanical compaction. They reduced the porosity and permeability of the sandstone. Additionally, authigenic clay minerals have a negative effect on permeability in which sandstones were rich illite and illite-smectite clay minerals, and the permeability tended to decrease stronger than others. Our results showed that the potential reservoir rocks of Oligocene sandstones, block 15-1/05 were sequence E and F sandstones that are in well grain sorting, well grain roundness shape, and contained a small number of cement, particularly the absence of illite and illite-smectite.
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Neal, C. "The mineralogy and chemistry of fine-grained sediments, Morphou Bay, Cyprus." Hydrology and Earth System Sciences 6, no. 5 (October 31, 2002): 819–31. http://dx.doi.org/10.5194/hess-6-819-2002.
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Abstract. The mineralogy and chemistry of the less than 20μm fraction of marine sediments at Morphou Bay, north-west Cyprus, are presented to characterise fine-grained sediment supplies from basic and ultrabasic rocks of the Troodos Massif within a typological setting. The sediments comprise a mixture of smectite, illite, kaolinite and iron rich chlorite. They also contain amorphous iron oxides/hydroxides, calcite (with some magnesium substitution for calcium) and an amphibole. Spatial patterns in mineralogy occur: the near-shore sediments are rich in smectite, chlorite, amphibole and amorphous iron oxides/hydroxides, while the offshore sediments are rich in illite and calcite. The sediments are calcium, magnesium, iron, aluminium and potassium bearing, due to the presence of significant amounts of calcite (for Ca), clay minerals and aluminium and iron oxides/hydroxides. Potassium is present within the micaceous mineral illite, but it is also contained within other phases that are difficult to pinpoint. Statistical analysis reveals that the chemical composition of the sediments broadly follows the mineralogy with the dominant feature being related to spatial changes in the mineralogy. The patterns of change reflect a three component mix of clay-sized sediment types: (1) localised lithogenous sources rich in smectite with subsidiary amounts of amorphous iron oxides/hydroxides and amphibole, from Cyprus, the Troodos in particular, (2) illite rich and smectite chlorite and chlorite bearing material of lithogenous origin from other parts of the eastern Mediterranean and (3) calcite, mainly of marine origin. Keywords: smectite, illite, chlorite, kaolinite, calcite, sediments, Morphou Bay, Troodos, Cyprus, Mediterranean, calcium, potassium, magnesium, iron, silicon, phosphorus.
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Pham, Sang Nhu, Bat Van Dang, Hiep Huu Nguyen, Chi Kim Thi Ngo, and Binh Van Phan. "A review on the characterization of sediment provenance sources in the southwestern East Sea." Journal of Mining and Earth Sciences 61, no. 5 (October 31, 2020): 11–19. http://dx.doi.org/10.46326/jmes.2020.61(5).02.
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Characteristics of sediment provenance in the southwestern East Sea The southwestern East Sea is a significant area for investigating marine geology and it has drawn many attentions from geoscientists. In this study, clay mineral assemblages of some sediment cores derived from the southwestern East Sea, which were conducted in previous studies were used to review characterization of sediment provenance in this area. Sediment compositions in the southwestern East Sea consist mostly of smectite (11÷58%), illite (19÷45%), and less abundance kaolinite (11÷29%), chlorite (10÷25%). Based on clay mineral assemblages, provenance analysis indicates that the Mekong River can mainly transport terrigenous sediments to the southwestern East Sea. Illite and chlorite have likely been reduced by physical weathering of the metamorphic and granitic rocks in the Tibetan Plateau. Kaolinite has primarily been released by chemical erosion of the K-feldspar rich bed rocks in the middle part of the Mekong Basin. However, smectite has been basically derived by chemical weathering of the parent basaltic rock in the middle to lower reaches of the Mekong Basin.
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Kemp, S. J., R. J. Merriman, and J. E. Bouch. "Clay mineral reaction progress – the maturity and burial history of the Lias Group of England and Wales." Clay Minerals 40, no. 1 (March 2005): 43–61. http://dx.doi.org/10.1180/0009855054010154.
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AbstractThe clay mineral assemblages and microtextures of a suite of mudrocks from the Lias Group of England and Wales indicate important regional differences in burial history.Samples from the northern Cleveland Basin are characterized by illite-smectite (I-S, 90% illite) and little carbonate whilst samples from the southern Worcester and Wessex basins contain less mature discrete smectite and are often calcite- and dolomite-rich. Lias Group rocks have been buried to 4 km in the Cleveland Basin but to <2 km in the Worcester and Wessex basins. Burial in the Cleveland Basin is deeper than previously estimated and does not need a local heating event. Illite- smectite (80% illite) detected in samples from the East Midlands Shelf suggests burial to 3 km, again deeper than previous estimates for this region.
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Anderson, Melissa O., Mark D. Hannington, Timothy F. McConachy, John W. Jamieson, Maria Anders, Henning Wienkenjohann, Harald Strauss, Thor Hansteen, and Sven Petersen. "Mineralization and Alteration of a Modern Seafloor Massive Sulfide Deposit Hosted in Mafic Volcaniclastic Rocks." Economic Geology 114, no. 5 (August 1, 2019): 857–96. http://dx.doi.org/10.5382/econgeo.4666.
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Abstract Tinakula is the first seafloor massive sulfide deposit described in the Jean Charcot troughs and is the first such deposit described in the Solomon Islands—on land or the seabed. The deposit is hosted by mafic (basaltic-andesitic) volcaniclastic rocks within a series of cinder cones along a single eruptive fissure. Extensive mapping and sampling by remotely operated vehicle, together with shallow drilling, provide insights into deposit geology and especially hydrothermal processes operating in the shallow subsurface. On the seafloor, mostly inactive chimneys and mounds cover an area of ~77,000 m2 and are partially buried by volcaniclastic sand. Mineralization is characterized by abundant barite- and sulfide-rich chimneys that formed by low-temperature (<250°C) venting over ~5,600 years. Barite-rich samples have high SiO2, Pb, and Hg contents; the sulfide chimneys are dominated by low-Fe sphalerite and are high in Cd, Ge, Sb, and Ag. Few high-temperature chimneys, including zoned chalcopyrite-sphalerite samples and rare massive chalcopyrite, are rich in As, Mo, In, and Au (up to 9.26 ppm), locally as visible gold. Below the seafloor, the mineralization includes buried intervals of sulfide-rich talus with disseminated sulfides in volcaniclastic rocks consisting mainly of lapillistone with minor tuffaceous beds and autobreccias. The volcaniclastic rocks are intensely altered and variably cemented by anhydrite with crosscutting sulfate (± minor sulfide) veins. Fluid inclusions in anhydrite and sphalerite from the footwall (to 19.3 m below seafloor; m b.s.f.) have trapping temperatures of up to 298°C with salinities close to, but slightly higher than, that of seawater (2.8–4.5 wt % NaCl equiv). These temperatures are 10° to 20°C lower than the minimum temperature of boiling at this depth (1,070–1,204 m below sea level; m b.s.l.), suggesting that the highest-temperature fluids boiled below the seafloor. The alteration is distributed in broadly conformable zones, expressed in order of increasing depth and temperature as (1) montmorillonite/nontronite, (2) nontronite + corrensite, (3) illite/smectite + pyrite, (4) illite/smectite + chamosite, and (5) chamosite + corrensite. Zones of argillic alteration are distinguished from chloritic alteration by large positive mass changes in K2O (enriched in illite/smectite), MgO (enriched in chamosite and corrensite), and Fe2O3 (enriched in pyrite associated with illite/smectite alteration). The δ18O and δD values of clay minerals confirm increasing temperature with depth, from 124° to 256°C, and interaction with seawater-dominated hydrothermal fluids at high water/rock ratios. Leaching of the volcanic host rocks and thermochemical reduction of seawater sulfate are the primary sources of sulfur, with δ34S values of sulfides, from –0.8 to 3.4‰, and those of sulfate minerals close to seawater sulfate, from 19.3 to 22.5‰. The mineralization and alteration at Tinakula are typical of a class of ancient massive sulfide deposits hosted mainly by permeable volcaniclastic rocks with broad, semiconformable alteration zones. Processes by which these deposits form have never been documented in modern seafloor massive sulfide systems, because they mostly develop below the seafloor. Our study shows how hydrothermal fluids can become focused within permeable rocks by progressive, low-temperature fluid circulation, leading to a large area (>150,000 m2) of alteration with reduced permeability close to the seafloor. In our model, overpressuring and fracturing of the sulfate- and clay-cemented volcaniclastic rocks produced the pathways for higher-temperature fluids to reach the seafloor, present now as sulfate-sulfide veins within the footwall. In the geologic record, the sulfate (anhydrite) is not preserved, leaving a broad zone of intense alteration with disseminated and stringer sulfides typical of this class of deposits.
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Velde, B., and C. Renac. "Smectite to illite conversion and K-Ar ages." Clay Minerals 31, no. 1 (March 1996): 25–32. http://dx.doi.org/10.1180/claymin.1996.031.1.02.
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AbstractInterpretation of K-Ar determinations of the apparent age of crystallization of diagenetic potassic layer silicates should take into account the current ideas concerning the smectite to illite conversion of clay minerals. These minerals are the major K-bearing neogenic phases in sedimentary rocks and, therefore, it is important to keep in mind their origin and the pathway of their evolution. Another important contributor to K and Ar content are detrital minerals which are not considered in detail in this paper. The radiogenic Ar retained by diagenetic illitic clay minerals (illite and illite-smectite interstratified minerals with a low smectite content) will be a function of: (1) the amount Ar lost through the destruction of mixed-layer and small grained illitic material dissolved to produce new, larger, illite-rich crystals; and (2) the amount of Ar produced and retained in the growing, stable illite mineral grains. Hence the K/Ar ratios in diagenetic illites depend on several variables. In samples where the detrital contribution is small, when the illite growth reaction is rapid, i. e. occurring over a short period of time, the accumulated radiogenic Ar can be used to date the geologic event which caused this crystal growth. However, if the process occurs over a significant period of time, as is usually the case in shales, the age deduced by radiogenic Ar content will indicate the changes in mineralogy and grain-sizes of the different participating phases. These changes will be the result of time and temperature variables of the sedimentation and burial of the samples studied. The radiogenic Ar accumulated will reflect a sequence of mineral changes over a period of time.
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Hillier, S., M. J. Wilson, and R. J. Merriman. "Clay mineralogy of the Old Red Sandstone and Devonian sedimentary rocks of Wales, Scotland and England." Clay Minerals 41, no. 1 (March 2006): 433–71. http://dx.doi.org/10.1180/0009855064110203.
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AbstractThe Devonian sedimentary rocks of the UK are made up of a continental red bed facies, the Old Red Sandstone (ORS), and sediments of a marine origin. The latter are confined to southwest England whereas the ORS occurs much more extensively, particularly in South Wales, the West Midlands, Northern England, the Midland Valley of Scotland and the Orcadian basin. The ORS also occurs extensively offshore where it contains important hydrocarbon reservoirs. Highly variable suites of clay mineral assemblages are characteristic of the ORS. In the West Midlands and Monmouthshire, the Downton Group is characterized by illitic, smectitic, and mixed-layer illite-smectite minerals. A tuff bed (Townsend Tuff) also contains expansible minerals but when the bed is traced westwards it is found that the clay mineralogy changes progressively to an illite-chlorite assemblage, suggesting the influence of diagenetic or metamorphic change. It is not known, however, whether such a transformation is typical of the Downton Group as a whole. The overlying Ditton Group in its eastern outcrops contains a high-spacing mineral identified as tosudite, together with regularly interstratified illite-smectite and well crystallized kaolinite. Further west this assemblage gives way to illite and chlorite, with the latter being trioctahedral or dioctahedral, while in Dyfed the Ditton Group may contain smectite and poorly crystallized kaolinite in addition to illite and chlorite. The geographical distribution of clay minerals in the Ditton Group may also be accounted for by progressive diagenetic to low-grade metamorphic reactions, although it is necessary to postulate retrogressive diagenesis to account for the smectite and kaolinite that occur in the Dyfed samples. The clay mineralogy of the overlying Brecon Group and the Upper ORS also consists of mixtures of illite and chlorite in the west and central parts of the region. No data are available for the Brecon Group in the eastern parts of the outcrop but the Upper ORS from around Monmouth and Portishead contains assemblages rich in kaolinite and mixed-layer illite-smectite with only minor amounts of chlorite. The distribution of clay minerals in the Upper ORS is again suggestive of a progressive westerly increase in the influence of diagenetic alteration, although the influence of provenance cannot be discounted.In Scotland the clay mineralogy of the Lower ORS in the Midland valley is characterized by a variety of interstratified minerals, including regularly interstratified trioctahedral chlorite-vermiculite, a tosudite mineral similar to that described from South Wales and illite-smectite, as well as occasional illite, chlorite and smectite. The oldest Stonehaven Group is kaolinitic but in the younger groups kaolinite is either completely absent or present in only minor amounts. It is clear that detrital inputs, particularly from associated volcanic rocks, have contributed to the clay minerals found in these rocks, although the contribution could be indirect with diagenetic clay minerals forming from volcanic detritus after deposition. Diagenetic alteration may also be important, particularly with respect to the origin of the tosudite mineral. The Middle ORS lacustrine sediments of the Orcadian Basin of Scotland are characterized by mixtures of trioctahedral chlorite and dioctahedral illite, with interstratified chlorite-smectite, illite-smectite, kaolinite and occasional reports of minor montmorillonite. The most recent interpretations of the origins of the clay minerals in these rocks emphasize the role of progressive diagenetic and low-grade metamorphic reactions, based on correlations of clay mineral assemblages and parameters such as illite crystallinity with organic maturation data. This interpretation argues that the illite-smectite in the shales is derived largely from a precursor detrital smectite. However, the finding of two populations of morphologically and structurally distinct illite-smectite particles in the Middle and Upper ORS sandstones suggests a more complex picture involving different diagenetic episodes. In addition, the likelihood of a smectitic-rich detrital input to the ORS may also be a point of debate. The clay mineralogy of the North Sea offshore is also described briefly, in addition to the marine Devonian in southwest England. The latter is characterized by chlorite and illite assemblages of low-grade metamorphic origin, although smectite and kaolinite are also found occasionally in these rocks. The offshore ORS, however, contains a variety of clay minerals, including an assemblage similar to that found in the Lower ORS south of the Highland Boundary Fault and notably contains a tosudite-like mineral.
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Bauluz Lazaro, B., M. J. Mayayo Burillo, C. Fernandez-Nieto, and J. M. Gonzalez Lopez. "Mineralogy and geochemistry of Devonian detrital rocks from the Iberian Range (Spain)." Clay Minerals 30, no. 4 (December 1995): 381–94. http://dx.doi.org/10.1180/claymin.1995.030.4.10.
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AbstractTwo profiles in Devonian marine deposits have been studied, consisting of pelites, subgreywackes, greywackes and quartzites. Quartz and clay minerals are major components and feldspar and calcite are minor ones. Phyllosilicates in the fine fractions are kaolinite and illite; kaolinite has a high degree of ordering; illite is predominantly of a 1Md polytype, with low Na content and poor crystallinity and has a phengitic composition in greywackes, whereas in pelites it is muscovitic in composition. Both phyllosilicates may be inherited from a source area with intensive weathering processes, although illite may also be a diagenetic phase. These mineral characteristics indicate that the Devonian rocks did not reach the anchizone boundary in their post-depositional evolution.The chemical composition of pelites and subgreywackes reveals a high degree of chemical maturity. Chondrite-normalized REE patterns indicate a higher degree of weathering of these Devonian sediments than of Post-Archaean Australian Shales (PAAS), possibly as a consequence of sedimentary recycling processes. The REE patterns of the Devonian rocks in addition to the high Th/Sc, La/Sc and Th/Co ratios suggest a felsic composition of the primitive source area, probably a K-rich granite.
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Drief, A., and F. Nieto. "Chemical composition of smectites formed in clastic sediments. Implications for the smectite-illite transformation." Clay Minerals 35, no. 4 (September 2000): 665–78. http://dx.doi.org/10.1180/000985500547124.
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AbstractAnalytical electron microscopy of representative smectites from soils and sediments revealed that K was present in significant proportions. It was the major interlayer cation in soils from pelitic rocks, continental and marine sediments, independent of their diagenetic grade. Sodium was predominant only in soils from basic rock. Fluvial sediments contained smectites with both kinds of interlayer compositions. The octahedral composition of each sample ranged widely, covering various fields of dioctahedral smectites. The most important trend was the substitution of Al by Fe and Mg; the chemistry of each smectite particle was determined by the parent mineral from which it formed. The real interlayer composition has important implications for the diagenetic smectite–illite transformation. When considering a typical K content, the smectite–illite reaction, with chlorite and quartz as subproducts, needs only 0.21 K atoms. For more K-rich compositions, a reaction is possible without an external supply of K.
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Andrews, Julian E. "Jurassic clay mineral assemblages and their post-depositional alteration: upper Great Estuarine Group, Scotland." Geological Magazine 124, no. 3 (May 1987): 261–71. http://dx.doi.org/10.1017/s0016756800016289.
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AbstractClay minerals from Middle Jurassic lagoonal mudrocks, siltstones and silty fine-grained sandstones of the upper Great Estuarine Group (Bathonian) are divided into four assemblages. Assemblage 1, the most common assemblage, is rich in mixed-layer illite–smectite with attendant illite and kaolinite. Assemblage 2 is dominated by smectitic clay. These assemblages are indicative of primary Jurassic deposition. Illite and kaolinite were probably derived from the weathering of older rocks and soils in the basin hinterland and were deposited in the lagoons as river-borne detritus. The majority of smectite and mixed-layer illite–smectite is interpreted as the argillization product of Jurassic volcanic dust, also deposited in the lagoons by rivers. Near major Tertiary igneous intrusions these depositional clay mineral assemblages have been altered. Assemblage 3 contains smectite-poor mixed-layer illite–smectite, whilst Assemblage 4 contains no smectitic clay at all. Destruction of smectite interlayers occurred at relatively shallow burial depths (< 2500 m) due to enhanced geothermal gradients and local convective hot-water circulation cells associated with the major Tertiary igneous intrusions.
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Glaas, Carole, Patricia Patrier, Jeanne Vidal, Daniel Beaufort, and Albert Genter. "Clay Mineralogy: A Signature of Granitic Geothermal Reservoirs of the Central Upper Rhine Graben." Minerals 11, no. 5 (April 30, 2021): 479. http://dx.doi.org/10.3390/min11050479.
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Clay minerals are the signature of hydrothermal alterations related to fluid circulation in volcanic and crystalline rocks. In the French part of the Upper Rhine Graben, in the deep-seated granites, illitic minerals (illite and I/S mixed layers (ml)) are typical products of the structurally-controlled argillic alteration in the Paleozoic granitic basement. In the new Illkirch geothermal well, GIL-1, drill-cuttings were studied with various petrographic methods to determine the characteristics of illite in paleo- and present-permeable zones, and to compare the alteration mineralogy with that of geothermal Soultz-sous-Forêts and Rittershoffen sites. Alteration petrography, crystal structure as well as the chemical composition of the illitic minerals and the altered bulk rocks were performed all along the well. This complete characterization, combined with geophysical logs and structural results, highlighted that the illitic minerals at Illkirch, Soultz-sous-Forêts, and Rittershoffen are composed of illite and illite-rich illite-smectite mixed layers (I/S ml) (<10% smectite). Two mineralogical assemblages were distinguished: chlorite + illite resulting from the propylitic alteration after the emplacement of the granitic basement under temperatures higher than 350 °C, and illite + I/S ml + carbonates + quartz resulting from the argillic alteration due to fluid circulation in the fractures at temperatures between 130 and 160 °C. Fracture zones are characterized by the occurrence of illitic minerals (illite and I/S ml), and specifically, by higher quantities of I/S ml in present-day permeable zones than in paleo-permeable zones. A conceptual model of the fracture zones at the interface between the overlying sedimentary rocks and the granitic basement is proposed. The present-day permeability distribution is controlled by the fault and fracture network, which consists of sealed zones and unsealed zones. Fluid convection in the URG implies paleo and present fluids circulating in both fractured sedimentary and crystalline reservoirs. Such circulations develop illitic minerals that could be considered as exploration guides for future geothermal sites in the URG. At Illkirch, the repartition of the present-permeable fracture zones (KFZs) in the GIL-1 well indicates that the moderately argillically altered granite distally situated from the Eschau fault is more permeable than the intensely argillically altered granite close to the Eschau fault.
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Bailey, Lydia R., Jason Kirk, Sidney R. Hemming, Robert W. Krantz, and Peter W. Reiners. "Eocene fault-controlled fluid flow and mineralization in the Paradox Basin, United States." Geology 50, no. 3 (November 22, 2021): 326–30. http://dx.doi.org/10.1130/g49466.1.
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Abstract Sedimentary rocks of the Paradox Basin of the Colorado Plateau (southwestern USA) record widespread manifestations of paleo–fluid flow and fluid-rock reactions including Cu, U-V, and Fe-Mn mineral deposits, Si and Ca metasomatism, hydrocarbon accumulations, and bleached sandstones. Many of these are spatially associated with faults. Here we show evidence for a widespread phase of fault-related fluid migration and mineralization at 41–48 Ma in the Paradox Basin. We measured K-Ar dates of multiple size fractions of clay-rich fault gouge, yielding statistically overlapping dates of authigenic (1Md) illite for the Salt Valley (47.0 ± 3.0 Ma), Kane Springs (47.7 ± 3.8 Ma), Cliffdweller (43.4 ± 4.6 Ma), Courthouse (41.9 ± 2.3 Ma), Lisbon Valley (45.3 ± 0.9 Ma), and GTO (48.1 ± 2.6 Ma) faults. The latter two have an illite Rb-Sr isochron age of 50.9 ± 3.5 Ma, and fault-adjacent bornite has a Re-Os isochron age of 47.5 ± 1.5 Ma. Authigenic illite from a paleo–oil reservoir near the Courthouse fault formed from the interaction of reduced fluids with oxidized red-bed sandstones at 41.1 ± 2.5 Ma. The Moab and Keystone faults have older authigenic illite ages of 59.1 ± 5.7 Ma and 65.2 ± 1.0 Ma, respectively. Our results show a close temporal relationship between fault gouge formation, red-bed bleaching, and Cu mineralization during an enigmatic time interval, raising questions about drivers of Eocene fluid flow.
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Ju, Jinfeng, Quansheng Li, and Jialin Xu. "Experimental Study on the Self-Healing Behavior of Fractured Rocks Induced by Water-CO2-Rock Interactions in the Shendong Coalfield." Geofluids 2020 (October 8, 2020): 1–14. http://dx.doi.org/10.1155/2020/8863898.
Full textAbstract:
This study experimentally investigated the self-healing behavior, referring to the naturally occurring water permeability decrease, of fractured rocks exposed to water-CO2-rock interaction (WCRI). The experiment was conducted on prefractured specimens of three rock types typical of the Shendong coalfield: coarse-grained sandrock, fine-grained sandrock, and sandy mudrock. During the experiment, which ran for nearly 15 months, all three specimens exhibited decreasing permeabilities. The coarse- and fine-grained sandrock specimens exhibited smooth decreases in permeability, with approximately parallel permeability time curves, whereas that of the sandy mudrock specimen decreased rapidly during the initial stage and slowly during later stages. The sandrock specimens were rich in feldspars, which were dissolved and/or corroded and involved in ionic exchange reactions with CO2 and groundwater, thereby generating secondary minerals (such as kaolinite, quartz, and sericite) or CaSO4 sediments. These derivative matters adhered to the fracture surface, thereby gradually repairing fractures and decreasing the water permeability of the fractured rocks. In comparison, the sandy mudrock had a high content of clay minerals, and the water-rock interaction caused rapid expansions of illite, mixed illite-smectite, and other clay minerals, thereby narrowing the fractures and causing the rapid permeability decrease during the initial stage. In later stages, the derivative matters generated by the dissolution and/or corrosion of feldspars and other aluminum silicate minerals in the mudrock filled and sealed the fractures, causing the slow permeability decreases during the later stages, as in the sandrock specimens. Neutral and basic groundwater conditions facilitated better self-healing of fractured mudrocks rich in clay minerals, whereas acidic groundwater conditions and the presence of CO2 facilitated better self-healing of fractured sandrocks. Thus, this study’s results are of significant value to aquifer restoration efforts in the Shendong coalfield and other ecologically vulnerable mining areas.
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Dudek, Teresa. "Clay minerals as palaeoenvironmental indicators in the Bathonian (Middle Jurassic) ore-bearing clays from Gnaszyn, Kraków-Silesia Homocline." Acta Geologica Polonica 62, no. 3 (December 28, 2012): 297–305. http://dx.doi.org/10.2478/v10263-012-0016-9.
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ABSTRACT Dudek, T. 2012. Clay minerals as palaeoenvironmental indicators in the Bathonian (Middle Jurassic) ore-bearing clays from Gnaszyn, Kraków-Silesia Homocline. Acta Geologica Polonica, 62 (3), 297-305. Warszawa. This paper reports the results of X-ray diffraction quantitative mineralogical studies of the clay-rich Middle Jurassic sedimentary rocks from Gnaszyn, central Poland and their palaeoenvironmental interpretation. The palaeoenvironmental interpretation is aided by the fact that the sediments have not been significantly altered by diagenesis. The mineral composition is uniform throughout the succession: quartz, K-feldspar, plagioclase, calcite, gypsum, anhydrite, pyrite, illite, kaolinite, chlorite, and glauconite. The clay assemblage is dominated by illite, which alone accounts for about 20 wt% of the total mineral content. Kaolinite amounts usually <10 wt% and chlorite and glauconite occur in subordinate quantities. The clay mineral assemblage is largely of detrital origin and indicates rather cool and/or dry climatic conditions favouring mechanical erosion of the source rocks.
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Henry, C., J. Y. Boisson, A. Bouchet, and A. Meunier. "Thermally induced mineral and chemical transformations in calcareous mudstones around a basaltic dyke (Perthus Pass, southern Massif Central, France). Possible implications as a natural analogue of nuclear waste disposal." Clay Minerals 42, no. 2 (June 2007): 213–31. http://dx.doi.org/10.1180/claymin.2007.042.2.07.
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AbstractA mixed-layer illite-smectite, illite-rich calcareous mudstone intruded by a basaltic dyke at the Perthus Pass (southern Massif Central, France) allows us to study the transformation of clays subjected to a brief thermal gradient. X-ray diffraction, scanning electron microscopy, electron microprobe and atomic absorption spectroscopy analyses were performed on samples at variable distances from the mudstone-dyke contacts.A roughly similar evolution is seen on both sides of the dyke: quartz, calcite, kaolinite and illite disappear; Ca-silicates, albite and saponite-beidellite form, late meteoric halloysite crystallizes in open fractures.Chemical and mineralogical transformations are related to heat diffusion from the dyke. Theoretical calculations highlight the influence of the dyke orientation. The mineralogical reactions observed in rocks are similar to those observed in experimental conditions. The formation of new swelling phases with a high retention capacity linked to a short duration, large-temperature increase, should constitute a positive process for Repository Performance Assessment.
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Martín, Domingo, Patricia Aparicio, Susana García, and María Mercedes Maroto-Valer. "Mixed-Layer Illite-Smectite Illitization under Supercritical CO2 Conditions." Applied Sciences 12, no. 22 (November 11, 2022): 11477. http://dx.doi.org/10.3390/app122211477.
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The long-term safe storage of CO2 in geological reservoirs requires the understanding of the impact of CO2 on clay-rich sealing cap rocks. The reactivity of the mixed layer of illite-smectite was investigated to determine the reaction pathways under conditions of supercritical CO2 (scCO2) conditions in the context of geological CO2 storage. A common clay (blue marl from the Guadalquivir Tertiary basin, southern Spain) was tested under brine scCO2 conditions (100 bar and 35 °C) for 120 and 240 h. The clay sample (blue marl) contains calcite, quartz, illite, smectite, and the corresponding mixed-layer and kaolinite. X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and inductively coupled plasma optical emission spectroscopy (ICP-OES) analyses were performed. The illitization of mixed-layer illite-smectite was observed by XRD and confirmed by a variation in the content of different elements (K, Mg, Na, Ca, and Fe) of the transformation, as well as an increase in the specific surface (SSA) of the clay (36.1 to 38.1 m2/g by N2, 14.5 to 15.4 m2/g by CO2 adsorption). Furthermore, these reactions lead to mineral dissolution and secondary mineral formation along the CO2–water–clay intercalations of the source rock were responsible for a change in porosity (7.8 to 7.0 nm pore size). The implications of illitisation, mineral destruction, and precipitation processes on CO2 storage and clay layer integrity should be explored before deciding on a geological storage location.
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Liang, Fei, Jun Niu, Adrian Linsel, Matthias Hinderer, Dirk Scheuvens, and Rainer Petschick. "Rock alteration at the post-Variscan nonconformity: implications for Carboniferous–Permian surface weathering versus burial diagenesis and paleoclimate evaluation." Solid Earth 12, no. 5 (May 25, 2021): 1165–84. http://dx.doi.org/10.5194/se-12-1165-2021.
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Abstract. A nonconformity refers to a hiatal surface located between metamorphic or igneous rocks and overlying sedimentary or volcanic rocks. These surfaces are key features with respect to understanding the relations among climate, lithosphere and tectonic movements during ancient times. In this study, the petrological, mineralogical and geochemical characteristics of Variscan basement rock as well as its overlying Permian volcano-sedimentary succession from a drill core in the Sprendlinger Horst, Germany, are analyzed by means of polarization microscopy, and environmental scanning electron microscope, X-Ray diffraction, X-ray fluorescence and inductively coupled plasma mass spectrometry analyses. In the gabbroic diorite of the basement, the intensity of micro- and macro-fractures increases towards the top, indicating an intense physical weathering. The overlying Permian volcanic rock is a basaltic andesite that shows less intense physical weathering compared with the gabbroic diorite. In both segments, secondary minerals are dominated by illite and a mixed-layer phase of illite and smectite (I–S). The corrected chemical index of alteration (CIA) and the plagioclase index of alteration (PIA) indicate an intermediate to unweathered degree in the gabbroic diorite and an extreme to unweathered degree in the basaltic andesite. The τ values for both basaltic andesite and gabbroic diorite indicate an abnormal enrichment of K, Rb and Cs that cannot be observed in the overlying Permian sedimentary rocks. Accompanying minerals such as adularia suggest subsequent overprint by (K-rich) fluids during burial diagenesis which promoted the conversion from smectite to illite. The overall order of element depletion in both basaltic andesite and gabbroic diorite during the weathering process is as follows: large-ion lithophile elements (LILEs) > rare earth elements (REEs) > high-field-strength elements (HFSEs). Concerning the REEs, heavy rare earth elements (HREEs) are less depleted than light rare earth elements (LREEs). Our study shows that features of supergene physical and chemical paleo-weathering are well conserved at the post-Variscan nonconformity despite hypogene alteration. Both can be distinguished by characteristic minerals and geochemical indices. Based on these results, a new workflow to eliminate distractions for paleoclimate evaluation and evolution is developed.
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Galan, E., M. I. Carretero, and J. C. Fernandez-Caliani. "Effects of acid mine drainage on clay minerals suspended in the Tinto River (Río Tinto, Spain). An experimental approach." Clay Minerals 34, no. 1 (March 1999): 99–108. http://dx.doi.org/10.1180/000985599546118.
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AbstractThe Tinto river is one of the most polluted stream environments in the world, as a result of both acid mine drainage and natural acid rock drainage. Two representative samples from the phyllosilicate-rich rocks exposed in the drainage basin (Palaeozoic chlorite-bearing slates and Miocene smectite-rich marls) were treated with acid river water (pH = 2.2) for different times to constrain the effects of extreme hydrogeochemical conditions on clay mineral stability. Illite and kaolinite did not show appreciable variations in their crystal chemistry parameters upon treatment. Chlorite underwent an incipient chemical degradation evidenced by the progressive loss of Fe in octahedral positions coupled with a shortening of the b unit-cell parameter, although no weathering products of chlorite were observed. Smectite and calcite were rapidly and fully dissolved thus neutralizing the water acidity, and subsequently Fe and Al oxy-hydroxides and opaline silica precipitated from the aqueous solution, together with a neoformed amorphous silicate phase largely enriched in Al and Mg.
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Vernik, Lev. "Hydrocarbon‐generation‐induced microcracking of source rocks." GEOPHYSICS 59, no. 4 (April 1994): 555–63. http://dx.doi.org/10.1190/1.1443616.
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Laboratory measurements of ultrasonic velocity and anisotropy in kerogen‐rich black shales of varying maturity suggest that extensive, bedding‐parallel microcracks exist in situ in most mature source rocks undergoing the major stage of hydrocarbon generation and migration. Given the normal faulting regime with the vertical stress being the maximum principal stress typical of most sedimentary basins, this microcrack alignment cannot be accounted for using simplified fracture mechanics concepts. This subhorizontal microcrack alignment is consistent with (1) a model of local principal stress rotation and deviatoric stress reduction within an overpressured formation undergoing hydrocarbon generation, and with (2) a strong mechanical strength anisotropy of kerogen‐rich shales caused by bedding‐parallel alignment of kerogen microlayers. Microcracks originate within kerogen or at kerogen‐illite interfaces when pore pressure exceeds the bedding‐normal total stress by only a few MPa due to the extremely low‐fracture toughness of organic matter. P‐wave and, especially, S‐wave anisotropy of the most mature black shales, measured as a function of confining pressure, indicate the effective closure pressure of these microcracks in the range from 10 to 25 MPa. Estimates of pore pressure cycles in the matrix of the active hydrocarbon‐generating/expelling part of the source rock formation show that microcracks can be maintained open over the sequence of these cycles and hence be detectable via high‐resolution in‐situ sonic/seismic studies.
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Whittaker, S. G., T. K. Kyser, and W. G. E. Caldwell. "Lithic geochemistry of the Claggett marine cyclothem in south-central Saskatchewan." Canadian Journal of Earth Sciences 25, no. 10 (October 1, 1988): 1554–63. http://dx.doi.org/10.1139/e88-148.
Full textAbstract:
Sediments of the Lea Park Formation in south-central Saskatchewan were deposited in the Claggett sea during the Late Cretaceous (Campanian) Claggett marine cycle. Rocks of the Lea Park Formation have remained virtually unaffected by diagenetic alteration; hence, variations in mineralogical and chemical compositions result primarily from changes in the source of detritus. Quartz, feldspar, discrete illite, kaolinite, and chlorite were derived from weathering of the western highlands, whereas illite–smectite (I–S), the dominant clay phase, originated from volcanic ash. Changes in the proportions of these minerals suggest a large-scale volcanic episode during deposition of the Lea Park sediments, an episode that affected not only the detritus delivered to the seaway but also the chemical and isotopic compositions of the sea water itself. δ13C values of organic matter increase with little change in the quantity of organic carbon preserved through both the transgressive and regressive phases of the Claggett cyclothem, unlike other cyclothems in which δ13C values generally decrease through the regressive phase. The increase in δ13C values in the Claggett cyclothem suggests a partial contribution from volcanic emanations to the 13C/12C ratio of the sea. Dissolution of Mg-rich volcanic debris from a major volcanic episode resulted in anomalously high Mg/Ca ratios in the sea and in the shells of molluscs living in the sea at that time. Rocks containing the shells with anomalously high Mg/Ca ratios are not themselves unusually Mg rich, but a general increase in Mg/SiO2 ratios in the rocks points to an increase in volcanic influx. The similarity between the mineralogical composition of the Lea Park Formation in Canada and that of the coeval lower part of the Pierre Shale in the United States indicates that volcanic ash was an important detrital source for both formations.
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Tsirambides, A., I. K. Georgiadis, A. A. Papadopoulos, A. A. Ziafetis, and A. N. Giouri. "MINERALOGICAL AND GEOCHEMICAL STUDY OF NEOGENE RED BEDS FROM MOUDANIA AND POTIDEA, CHALKIDIKI (MACEDONIA, GREECE)." Bulletin of the Geological Society of Greece 40, no. 2 (January 1, 2007): 1022. http://dx.doi.org/10.12681/bgsg.16784.
Full textAbstract:
The Neogene red beds from Moudania and Potidea (Chalkidiki) are studied in order to find the conditions under which they were formed. They are incoherent coarse grained sands, with poorly sorted grains. Angular to sub-angular rock fragments derived from the adjacent parent rocL· are very common. The red beds are texturally and mineralogically immature. Most of the samples are gravel sands. The extended presence of sand size grains (>0.063 mm) in the samples suggests high intensity of weathering of the parent rocks and rapid transportation and deposition of the weathered materials close to the source area. The detrital minerals present in the whole samples in decreasing abundance are quartz, feldspars (plagioclase + orthoclase), mica (+clay minerals), pyroxene, amphibole, pyrite and halite (except two samples which are rich in calcite). In the <0.063 mm fraction quartz decreases greatly, while feldspars increase. The presence of illite, smectite (+illite/smectite), and chlorite (+vermiculite) in the <0.063 mm fraction is evident. The most likely source minerals for the formation of the studied red beds are quartz, feldspars, micas, and various Fe-Mg silicates, which are primary constituents of the Mesozoic basement igneous and metamorphic rocks predominating in the adjacent area. In the poorly drained lowland of the studied area mean annual air temperature is 16.2° C, mean annual humidity 75%, and mean annual rainfall 59.5 cm. The samples may be considered ferromagnesian and potassic sandstones. The felsic igneous provenance signature is justified for most of the samples. The climate under which these Neogene red beds were formed was warm and semiarid.
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Oo, Toe, Agung Harijoko, and Lucas Setijadji. "Origin of the Kyaukmyet Low-Sulfidation Epithermal Gold Prospect, Monywa District, Central Myanmar." Iraqi Geological Journal 54, no. 1E (May 31, 2021): 1–18. http://dx.doi.org/10.46717/igj.54.1e.1ms-2021-05-22.
Full textAbstract:
The Kyaukmyet prospect is one of the principal epithermal gold prospects in the Monywa District, Central Myanmar; its gold- and base metal-bearing quartz veins contain around 3 g/t gold. Ore minerals are mainly hosted by volcanic and volcaniclastic rocks of the Late Oligocene to Middle Miocene Magyigon Formation. The distribution of magmatic intrusions in the area is controlled by ENE-WSW trending faults; these faults are likely related to ore mineralization. Common ore minerals at the Kyaukmyet prospect include pyrite, sphalerite, galena, chalcopyrite, and electrum. They occur in mineralized crustiform-textured brecciated quartz veins and banded (colloform) and massive quartz veins. Mineralized rock is accompanied by silicification and propylitic and argillic alterations. The alteration mineral assemblages include quartz, adularia, calcite, chlorite, illite/smectite, sericite, and illite. Fluid inclusions in the quartz veins have homogenization temperatures ranging from 148 °C to 304 °C and salinities from 0.35 wt % to 2.75 wt % NaCl equiv. The quartz in the mineralized quartz veins was most likely precipitated at a depth ranges165-256 m below the paleosurface. The precipitation of gold at the Kyaukmyet prospect may have been formed by mixing large amounts of meteoric fluid with small amounts of magmatic fluid. The coexistence of liquid-rich and vapor-rich inclusions and presence of adularia and bladed calcite indicate that fluid boiling is caused the main mechanism of ore formation. The vein textures, ore mineral assemblages, alteration minerals and fluid inclusion data suggest that the Kyaukmyet prospect is a polymetallic low-sulfidation epithermal gold deposit.
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Tseni, X., E. Koutsopoulou, B. Tsikouras, and K. Hatzipanagiotou. "Investigation of the mineralogical petrographic, geochemical and physical properties of carbonate rocks from Ileia Prefecture and assesment for industrial applications." Bulletin of the Geological Society of Greece 46 (December 21, 2016): 123. http://dx.doi.org/10.12681/bgsg.10937.
Full textAbstract:
Research on carbonate rocks has been increasingly important during the last few decades, due to their numerous applications. In this paper, we examined the properties of Cretaceous carbonate rocks from the Olonos-Pindos Zone from Ileia Prefecture. The relationships between various physical properties and between petrographic features and physical properties were defined. This may lead to preliminary evaluation of carbonate rocks using microscopic investigation, which unlike the elaboration of a series of physical and mechanical properties, is a fast and inexpensive method. In addition, these properties, along with their geochemical characteristics, were used to assess the suitability of these carbonate rocks as fillers in various applications. Detailed petrographic study of the collected samples revealed the occurrence of biomicrite, intramicrite (mudstone και wackestone), biosparite (packstones and grainstones), intrasparite and rudstone. From the lower to the upper members, a decrease of the grain size of calcite is observed. X-ray diffraction study of the insoluble residue revealed the presence of quartz, chlorite, illite, smectite, and mixed layer illite-chlorite. The colour index of the investigated powdered samples is negatively influenced by the increase of organic and insoluble residue contents. The water absorption is inversely correlated with CaO content while moisture is positively correlated with insoluble residue. The grainstone and rudstone are characterized as ultra-high pure calcium limestones, except for Mg-rich crystalline dolomitic limestones. The packstones are calcium limestones of high to medium purity. Mudstones and wackestones are characterized as low calcium limestones. The results suggest that all the examined lithotypes can be used as soil conditioners and animal feed supplements; however only grainstones and rudstones are suitable for desulphurization of exhaust gasses and cement production.
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DI BENEDETTI, VERÔNICA, RUY PAULO PHILIPP, and ROBERTO SACKS DE CAMPOS. "Análise e Avaliação dos Problemas Existentes na Fachada de Arenito do Museu Júlio de Castilhos, Porto Alegre, RS." Pesquisas em Geociências 34, no. 1 (June 30, 2007): 63. http://dx.doi.org/10.22456/1807-9806.19463.
Full textAbstract:
The Júlio de Castilhos museum of Porto Alegre, formerly used as residence, was built in 1877 by a military engineer Catão Roxo. This building is one of the few examples of urban architecture from the last part of the nineteenth century. Its façade is covered by arenitic and granitic rocks quarried near the city. The covering shows the effects of weathering processes occurred during many years. Some of these were observed during a façade mapping as loss of rocky materials, discoloration, chemical deposition, desintegration and fracturing. Petrographic analyses of the arenite indicate an arcosean composition, rich in quartz, with plagioclase and alkali-feldspar (microcline) and opaque minerals in lesser amounts. The grains have a fine layer of iron oxide (hematite) clad, with a fringe of siliceous cement. The remained pores are filled by clay minerals, mainly illite. The elevated degree of compactation and diagenesis are responsible for the high coherence of the rock, allowing its use as covering rock. The petrographic features (textures and mineralogical composition) indicate that the arenites used on the façade’s museum, comes from the Botucatu Formation. The recognition of the mineral constituents and the knowledge of regional geology allow the façade’s recuperation through the replacing of unrecoverable pieces by new ones.
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Çiflikli, M., E. Çiftçi, and H. Bayhan. "Alteration of glassy volcanic rocks to Naand Ca-smectites in the Neogene basin of Manisa, western Anatolia, Turkey." Clay Minerals 48, no. 3 (June 2013): 513–27. http://dx.doi.org/10.1180/claymin.2013.048.3.08.
Full textAbstract:
AbstractAlkali- and Ca-rich smectites occur in association with Neogene lacustrine sedimentary rocks and high-K calc-alkaline volcanic rocks with compositions ranging from andesite to rhyolite in western Anatolia (Turkey). Major clay occurrences are associated predominantly with the Foça and Akçaköy ignimbrites and with the ignimbrites within the Rahmanlar pyroclastics. Experimental studies indicate that the main clay minerals present are Na- and Ca-smectite and subordinate illite, associated with silica polymorphs, trace clinoptilolite and chlorite. The authigenic minerals formed by weathering and metasomatic reactions between hot volcanic material and lake water. Smectite was produced as a result of argillic alteration of the volcanic glass and feldspars of the ignimbrites, Rahmanlar pyroclastics and reworked volcaniclastic sediments through chemical weathering and dissolution-precipitation processes and formed as authigenic phases both in terrestrial and nearby shallow lacustrine environments under prevalent humid or semi-humid climate during the Neogene.
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Środoń, J., N. Clauer, W. Huff, T. Dudek, and M. Banaś. "K-Ar dating of the Lower Palaeozoic K-bentonites from the Baltic Basin and the Baltic Shield: implications for the role of temperature and time in the illitization of smectite." Clay Minerals 44, no. 3 (September 2009): 361–87. http://dx.doi.org/10.1180/claymin.2009.044.3.361.
Full textAbstract:
AbstractMixed-layer illite-smectite samples from the Ordovician and Silurian K-bentonites of the Baltic Basin and the Baltic Shield (Norway, Sweden, Denmark, Poland and Estonia) were dated by K-Ar on several grain fractions and were studied by X-ray diffraction (XRD), both on oriented and random preparations, in order to reveal the conditions of smectite illitization in the area. Authigenic K-feldspar was also dated. The geographic pattern of the degree of illitization (% smectite in illite-smectite measured by XRD) is consistent with other indicators of palaeotemperatures (acritarchs, conodont alteration index, vitrinite reflectance, apatite fission track ages). It reveals the highest maximum palaeotemperatures (up to at least 200ºC) along the Norwegian and the German-Polish branches of the Caledonides and the lowest palaeotemperatures (120ºC) in the central part of the studied area. The distribution of K-Ar ages is not well correlated with this pattern, revealing a zone of older ages (Lower Devonian-Lower Carboniferous) between Denmark and Estonia, and areas of younger ages (Upper Devonian to Carboniferous/Permian boundary) to the north and south of this zone. The zone of older ages is interpreted as the result of illitization induced by a thermal event in front of the Caledonian orogenic belt (migration of hot metamorphic fluids?). The areas of younger ages are considered as representing deep burial illitization under a thick Silurian-Carboniferous sedimentary cover, perhaps augmented by a tectonic load. The K-Ar dates invalidate the hypothesis of a long-lasting low-temperature illitization as the mechanism of formation of the Estonian Palaeozoic illite-smectite. The ammonium content of illite-smectite from the Baltic K-bentonites reflects the proximity of organic-rich source rocks that underwent thermal alteration at the time of illite crystallization.
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Kropáč, Kamil, Daniel Šimíček, Tomáš Lehotský, and Jaroslav Kapusta. "Petrografická charakteristika spodnokarbonských ryolitových tufitů z vrtů v lomu Výkleky (moravické souvrství, kulmská pánev Nízkého Jeseníku)." Bulletin Mineralogie Petrologie 28, no. 2 (2020): 331–38. http://dx.doi.org/10.46861/bmp.28.331.
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Two layers of volcanoclastic rock with thickness 40 and 210 cm were identified in core-samples, obtained by exploration drilling in the Výkleky quarry which was established in Lower Carboniferous sediments of the Moravice Formation (Moravo-Silesian Culm basin in the Nízký Jeseník Mts.). The volcanoclastics are represented by tuffaceous sandstones to tuffaceous conglomerates. These tuffites consist of a mixture of pyroclastic and epiclastic material, mainly fragments of strongly carbonatised porphyritic rhyolite, less of quartz shards, argillitised feldspars (K-feldspar and albitised plagioclase), chloritised biotite leaflets and muscovite. Lithic and mineral fragments are surrounded by lutitic matrix. Volcanic glass was completely replaced by mixture of quartz, alkali feldspars, chlorite and “clay micas” (phengitic illite-muscovite). Chemical composition of albite from rhyolite fragments and tuffite matrix is similar (An01 - 04), chlorite chemically corresponds to chamosite (XMg = 0.39 - 0.47; Si = 2.72 - 3.08 apfu). Pyrite and carbonates (calcite and side-rite to Mg-rich siderite) often fills cracks in the rock. Studied volcanoclastic rocks represent products of extrabasinal Lower Carboniferous terrestrial explosive volcanism whose activity probably culminated during the sedimentation of the Moravice Formation.
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Liu, Xiaodong, Pinghui Liu, Chaocheng Dai, Shuai Liu, Juzhi Deng, Weimin Zhang, and Zheng Yu. "Site screening of clay formations in NW China as host rocks for a high-level radioactive waste disposal repository." Geological Society, London, Special Publications 482, no. 1 (2019): 93–99. http://dx.doi.org/10.1144/sp482.17.
Full textAbstract:
AbstractDeep geological disposal of high-level radioactive waste (HLW) in a repository with a system of engineered and natural barriers has been recognized as an appropriate disposal concept by Chinese authorities since 2003, and both crystalline rocks and argillaceous rocks are considered as the candidate host rocks for HLW disposal repository. The 1:200 000 regional survey indicated that there are potential clay formations in Mesozoic–Cenozoic sedimentary basins in NW China. Five candidate areas have been suggested with potential clay formations including the Tamusu and Suhongtu areas with upper K1 Bayingebi clay formations in the east Bayingebi Basin, in the Inner Mongolia Autonomous Region. On the basis of a detailed ground geological, hydrological and geophysical surveys, two test boreholes drilled to a depth of 800 m in the Tamusu area revealed that there are three lacustrine-facies clay formations (K1b2-3, K1b2-2 and K1b2-1). The thickness of the K1b2-3 and K1b2-2 clay formations is about 300–600 m with sandstone and siltstone interbeds, while the thickness of the K1b2-1 homogeneous clay formation is more than 200 m with the depth of 450 m below the surface. The spatial extension of the clay formations could meet the fundamental criteria to ensure the long-term safety of the repository. Initial mineralogical studies on core samples indicated that the mineral assemblage is dominated by analcite, kaolinite, illite and dolomite. The homogeneous argillaceous rocks rich in analcite in Tamusu area could be a new type of host rock for a HLW disposal repository.
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Środoń, J., J. Szulc, A. Anczkiewicz, K. Jewuła, M. Banaś, and L. Marynowski. "Weathering, sedimentary and diagenetic controls of mineral and geochemical characteristics of the vertebrate-bearing Silesian Keuper." Clay Minerals 49, no. 4 (September 2014): 569–94. http://dx.doi.org/10.1180/claymin.2014.049.4.07.
Full textAbstract:
AbstractMudstones and claystones from the southern marginal area of the European Upper Triassic, midcontinental Keuper basin (Silesia, southern Poland) were investigated using XRD, organic and inorganic geochemistry, SEM, K-Ar of illite-smectite, AFT, and stable isotopes of O and C in carbonates in order to unravel the consequent phases of the geological history of these rocks, known for abundant fossils of land vertebrates, and in particular to evaluate the diagenetic overprint on the mineral composition. The detected and quantified mineral assemblage consists of quartz, calcite, dolomite, Ca-dolomite, illite, mixed-layer illite-smectite, and kaolinite as major components, plus feldspars, hematite, pyrite, chlorite, anatase, siderite, goethite as minor components. Palygorskite, gypsum, jarosite and apatite were identified in places.The K-Ar dates document a post-sedimentary thermal event, 164 Ma or younger, which resulted in partial illitization of smectite and kaolinite. The maximum palaeotemperatures were estimated from illite-smectite as ∼125°C. Apatite fission track data support this conclusion, indicating a 200–160 Ma age range of the maximum temperatures close to 120°C, followed by a prolonged period of elevated temperatures. These conclusions agree well with the available data on the Mesozoic thermal event, which yielded Pb-Zn deposits in the area. Organic maturity indicators suggest the maximum palaeotemperatures <110°C.Palygorskite was identified as authigenic by crystal morphology (TEM), and calcite by its accumulation in soil layers and by its isotopic composition evolving with time, in accordance with the sedimentary and/or climatic changes. Dolomite isotopic composition indicates more saline (concentrated) waters. Palygorskite signals a rapid local change of sedimentary conditions, correlated with algal blooms. This assemblage of authigenic minerals indicates an arid climate and the location at the transition from a distal alluvial fan to mudflat.Fe-rich smectite, kaolinite, and hematite were products of chemical weathering on the surrounding lands and are therefore mostly detrital components of the investigated rocks. Kaolinite crystal morphology and ordering indicates a short transport distance. Hematite also crystallizedin situ, in the soil horizons. A large variation in kaolinite/2:1 minerals ratio reflects hydraulic sorting, except of the Rhaetian, where it probably signals a climatic change, i.e. a shift in the weathering pattern towards kaolinite, correlated with the disappearance of hematite. Quartz, 2M1illite, and minor feldspars and Mg-chlorite were interpreted as detrital minerals. The documented sedimentation pattern indicates that in more central parts of the Keuper playa system, where an intense authigenesis of the trioctahedral clays (chlorite, swelling chlorite, corrensite, sepiolite) took place, illite and smectite were the dominant detrital clay minerals.Cr/Nb and Cr/Ti ratios were found as the best chemostratigraphic tools, allowing for the correlation of all investigated profiles. A stable decrease of these ratios up the investigated sedimentary sequence is interpreted as reflecting changes in the provenance pattern from more basic to more acidic rocks.
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Uvarova, Yulia, Alexey Yurikov, Marina Pervukhina, Maxim Lebedev, Valeriya Shulakova, Ben Clennell, and David Dewhurst. "Microstructural characterisation of organic-rich shale before and after pyrolysis." APPEA Journal 54, no. 1 (2014): 249. http://dx.doi.org/10.1071/aj13025.
Full textAbstract:
Organic-rich shales, traditionally considered as source rocks, have recently become an ambitious goal for the oil and gas industry as important unconventional reservoirs. Understanding of the initiation and development of fractures in organic-rich shales is crucially important as fractures could drastically increase the permeability of these otherwise low-permeable rocks. Fracturing can be induced by rapid decomposition of organic matter caused by either natural heating, such as emplacement of magmatic bodies into sedimentary basins, or thermal methods used for enhanced oil recovery. In this work the authors study fracture initiation and development caused by dry pyrolysis of Kimmeridge shale, which is characterised with a high total organic carbon content of more than 20%. X-ray diffraction (XRD) analysis exhibits high carbonate (both calcite and dolomite) and low clay (illite) content. Field emission gun scanning electron microscopy (FEG-SEM) shows that kerogen is presented either as a load-bearing matrix or as a filling of the primary porosity with pores being of micron size. Cylindrical samples of the Kimmeridge shale are heated up to temperatures in the range of 330–430°C. High-resolution X-ray microtomographic (micro-CT) images are obtained. The microtomographic images are processed using AVIZO (Visualization Sciences Group) to identify and statistically characterise large kerogen-filled pores and pre-existing and initiated cracks. The relationship between the total area of fractures and the temperature experienced by the sample has been obtained. Total organic carbon content is determined for samples subjected to heating experiments. This approach enables a quantitative analysis of fracture initiation and development in organic-rich shales during heating.
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Trindade, M. J., F. Rocha, M. I. Dias, and M. I. Prudêncio. "Mineralogy and grain-size distribution of clay-rich rock units of the Algarve Basin (South Portugal)." Clay Minerals 48, no. 1 (March 2013): 59–83. http://dx.doi.org/10.1180/claymin.2013.048.1.04.
Full textAbstract:
AbstractA detailed survey of the most clay-rich rock units of the Meso-Cenozoic geological section exposed in the Algarve Basin (South Portugal) was performed and data were analysed for the grain-size distribution and mineralogy (whole rock and clay fraction), aimed at a compositional study of the clay-rich sediments and their depositional environment. Granulometry was obtained using wet sieving and laser diffraction by attenuation of X-rays, and the mineralogical study was carried out by X-ray diffraction.Most clay-rich rock units of the Algarve are classified as silty clays and clayey silts, and only a minority is coarser. The mineralogical study enabled us to define two main types of clays: (1) noncalcareous clays, consisting largely of quartz and clay minerals, with goethite as the typical Fe-rich phase (sediments of Carboniferous, Neogene and Quaternary age and Cretaceous siliciclastic clays); and (2) calcareous clays, which can be calcite-rich clays (Middle and Upper Jurassic) or dolomiterich clays (Triassic and Lower Jurassic), the latter typically containing hematite as an accessory phase. Plagioclase, K-feldspar, and Ti-oxides are often accessory phases, whereas ankerite, anhydrite, gypsum and opal are rare.In the clay fraction illite generally predominates, resulting probably from weathering of preexisting rocks, as well as the less frequent Fe-chlorite, pointing to incipient chemical alteration under semi-arid climatic conditions. Kaolinite occurs in diverse proportions, being especially abundant in Cretaceous and Cenozoic units; it is mainly related to chemical weathering in continental environments under humid conditions. As the Atlantic Ocean opened during Triassic and the continental environment evolved to a shallow-marine environment with evaporitic conditions, smectite became more expressive, being sometimes accompanied by other Mg-rich phases (chlorite, sepiolite, corrensite and palygorskite). Especially during the Cenozoic the proportion of different phases in the clay mineral association of the sediments reflects the control of tectonic movements and fluctuations in sea level during their deposition.
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Blaise, Bertrand. "Clay-Mineral Assemblages from Late Quaternary Deposits on Vancouver Island, Southwestern British Columbia, Canada." Quaternary Research 31, no. 1 (January 1989): 41–56. http://dx.doi.org/10.1016/0033-5894(89)90084-7.
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AbstractOn Vancouver Island, the Dashwood Drift, Cowichan Head Formation, Quadra Sand, and Vashon Drift were deposited during late Pleistocene glacial and interstadial periods and show large variations in clay-mineral contents partly related to changing climatic conditions. Glacial deposits are characterized by iron-rich chlorite, illite (both well crystallized), and smectite with a morphology reflecting rapid derivation from volcanic rocks. The clay mineralogy of nonglacial deposits is more complex, and is marked by the presence of vermiculite, kaolinite, halloysite, and irregular mixed-layer minerals. Nonglacial clay minerals are poorly preserved and show a higher state of alteration due to pedogenesis. Large variations in nonglacial deposits compared to glacial deposits are also due to secondary factors such as selective sorting, soil and rock source variations, differences in sedimentary environment, and diagenesis. These secondary factors do not seem to obliterate significantly the climatic imprint on the clay minerals. These studies also permit the recognition of glacially reworked sediments, the determination of relationships between two units in the same section, and the establishment of the conditions of clay-mineral formation.
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Yang, C., and R. Hesse. "Clay minerals as indicators of diagenetic and anchimetamorphic grade in an overthrust belt, External Domain of southern Canadian Appalachians." Clay Minerals 26, no. 2 (June 1991): 211–31. http://dx.doi.org/10.1180/claymin.1991.026.2.06.
Full textAbstract:
AbstractLower Palaeozoic shales and slates in the External Domain of the southern Canadian Appalachians are composed predominantly of illite and chlorite with minor occurrences of I-S mixed-layer minerals (restricted to samples with illite crystallinity, IC > 0·62°Δ2Θ) and paragonite (restricted to samples with IC < 0·42°Δ2Θ). Inverted diagenesis has occurred in the NW part of the Chaudière Nappe, indicating pre-orogenic deep burial diagenesis at the original depositional site, whereas to the SE, the diagenetic pattern was affected by synorogenic heating. Within the east-dipping thrust-fold belt and the St Lawrence Lowlands, increasing grade towards the S suggests a gradual southward increase in post-tectonic burial depth. Narrow (3–5 km) thermal haloes around the Cretaceous Monteregian intrusions show limited effects on the country rocks.The percentage of 2M1 mica polytypes and bo increase with decreasing IC. Chlorite crystallinity (CC) increases with increasing IC. Good correlations between IC, %2M1, CC and bo of micas indicate that these parameters are reliable monitors of high-grade diagenesis and low-grade metamorphism in clay-rich sedimentary rocks. IC and CC improve with increasing grain size, illustrating the effect of grain size on IC and CC. Organic material affects IC more strongly in strata with lower permeability than in those with higher permeability. In the diagenetic zone, glycolation does not uniformly produce a narrowing of the 10 Å illite peak, but may also broaden it by up to 15%, probably due to the presence of Kalkberg-type mixed-layers.
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FU, XIUGEN, JIAN WANG, XINGLEI FENG, WENBIN CHEN, DONG WANG, CHUNYAN SONG, and SHENGQIANG ZENG. "Mineralogical composition of and trace-element accumulation in lower Toarcian anoxic sediments: a case study from the Bilong Co. oil shale, eastern Tethys." Geological Magazine 153, no. 4 (November 4, 2015): 618–34. http://dx.doi.org/10.1017/s0016756815000758.
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AbstractThe sediments of organic-rich oil shales in the Bilong Co. area can be correlated with those of the early Toarcian anoxic black-shale events in Europe. The Bilong Co. sediments are rich in trace elements Se, Mo, Cd, As and Ni, and, to a lesser extent, Li, F, V, Co, Cu, Cs, Hg and Bi, in comparison to the upper continental crust. Thirty-two oil shale samples were collected from the Bilong Co. oil shale to evaluate the controlling factors of trace-element enrichment in the lower Toarcian anoxic sediments. Minerals identified in the Bilong Co. oil shale include calcite, quartz, illite, feldspar and dolomite, and trace amounts of siderite, magnesite, halite, haematite, zeolite, amphibole, gypsum, anhydrite, apatite, pyrite, sphalerite, barite and mixed-layer illite/smectite. Mineralogical and geochemical data show that seawater and hydrothermal activities are the dominant influences on the mineralogical composition and elevated trace-element concentrations in the oil shale. The clay minerals, quartz and feldspar in the Bilong Co. oil shale were derived from the Nadi Kangri volcanic rocks. Input of sediment from this source may have led to enrichment of trace elements Li, Cr and Cs in the oil shale. Carbonate minerals and nodular- and framboidal-pyrite are authigenic phases formed from seawater. The enrichment of V, Co, Ni, Cu, Mo, As, Se, Bi and U in the oil shale was owing to marine influence. Barite, sphalerite and fracture-filling pyrites were derived from hydrothermal solutions. High concentrations of F, Zn and Cd were probably derived from hydrothermal fluids.
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Potter, Eric G., Colter J. Kelly, William J. Davis, Guoxiang Chi, Shao-Yong Jiang, Morteza Rabiei, and Brian J. McEwan. "Fluid sources in basement-hosted unconformity–uranium ore systems: tourmaline chemistry and boron isotopes from the Patterson Lake corridor deposits, Canada." Geochemistry: Exploration, Environment, Analysis 22, no. 1 (December 1, 2021): geochem2021–037. http://dx.doi.org/10.1144/geochem2021-037.
Full textAbstract:
The Patterson Lake corridor is a new uranium district located on the southwestern margin of the Athabasca Basin. Known resources extend almost 1 km below the unconformity in graphite- and sulfide-bearing shear zones within highly altered metamorphic rocks. Despite different host rocks and greater depths below the unconformity, alteration assemblages (chlorite, illite, kaolinite, tourmaline and hematite), ore grades and textures are typical of unconformity-related deposits. This alteration includes at least three generations of Mg-rich tourmaline (magnesio-foitite). The boron isotopic composition of magnesio-foitite varies with generation: the earliest generation, which is only observed in shallow samples from the Triple R deposit (Tur 1), contain the heaviest isotopic signature (δ11B ≈ 19–26‰), whereas subsequent generations (Tur 2 and Tur 3) yield lighter and more homogeneous isotopic signatures (δ11B ≈ 17.5–19.9‰). These results are consistent with precipitation from low-temperature, NaCl- and CaCl2-rich brine(s) derived from an isotopically heavy boron source (e.g. evaporated seawater) that interacted with tourmaline and silicates in the basement rocks and/or fluids derived from depth (with low δ11B values). The lower δ11B values in paragenetically later magnesio-foitite reflect greater contributions of basement-derived boron over time, whereas minor compositional variations reflect local metal sources (e.g. Cr, V, Ti) and evolving fluid chemistry (decreasing Na and Ca, increasing Mg) over time. The δ11B and chemical variation in magnesio-foitite over time reinforce the strong interactions with basement rocks in these systems while supporting incursion of basinal brines well below the unconformity contact.Supplementary material: Complete analytical dataset including reference materials are available at https://doi.org/10.6084/m9.figshare.c.5727555Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways
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Pialy, P., C. Nkoumbou, F. Villiéras, A. Razafitianamaharavo, O. Barres, M. Pelletier, G. Ollivier, et al. "Characterization for industrial applications of clays from Lembo deposit, Mount Bana (Cameroon)." Clay Minerals 43, no. 3 (September 2008): 415–35. http://dx.doi.org/10.1180/claymin.2008.043.3.07.
Full textAbstract:
AbstractThe Lembo clay deposit occurs on orthogneiss, but it also comprises clays with litho-relicts of volcanic rocks. In this study, ten samples from two sites were investigated. The mineralogical compositions consisted of kaolinite + halloysite + illite + quartz + hematite + anatase ± rutile ± orthoclase ± sanidine ± magnetite ± maghemite ± goethite ± Ba-Al-Fe-phosphates ± carbonates ± sulphates. Kaolinite-halloysite and quartz are the prevailing minerals. Some volcanicderived clays contain Fe-rich kaolinite-halloysite (9.6–14.1 wt.% Fe2O3). The chemical compositions, colours and specific surface area (SSA) measurements reveal two groups of clays: one with a positive whiteness index (IB), small SSA and small Fe content, and the other showing a large SSA, negative IB and relatively large Fe contents. The compositions of the first group are close to those of clays from the Mayouom deposit (Cameroon), and from some European commercial kaolins used in ceramics. Relatively Fe-rich clay materials may conform to most formulations of earthen bricks. As a whole, the Lembo clay deposit comprises various compositions of kaolinitic clays, which may yield the opportunity for extensive application in ceramics.
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Weibel, Rikke, and Nynke Keulen. "Diagenesis influencing the porosity of Upper Jurassic reservoir sandstones, Danish North Sea." Geological Survey of Denmark and Greenland (GEUS) Bulletin 15 (July 10, 2008): 9–12. http://dx.doi.org/10.34194/geusb.v15.5031.
Full textAbstract:
Upper Jurassic quartz-rich sandstones in the North Sea Basin are important reservoir rocks for oil and gas, and one of the latest discoveries of oil in the Danish sector was made in the area of the Hejre wells that penetrated such sediments (Fig. 1). The reservoir properties of sandstones are strongly influenced by diagenetic alteration, i.e. the mineralogical changes that take place during burial of the sediments. The diagenetic features depend on the source area, depositional setting, facies architecture and burial history of the sediment. The major diagenetic features influencing porosity in Upper Jurassic reservoir sandstones are feldspar dissolution and precipitation, preci-pitation of illite, calcite and quartz, and quartz stylolite formation. With regard to the Upper Jurassic sandstones in the Danish sector of the North Sea, the important question is: how can porosity be preserved in sediments buried at depths of more than 5 km? The Hejre-2 well penetrated the Upper Jurassic sediments (Fig. 2) before reaching pre-Upper Jurassic volcaniclastic conglomerates. The diagenetic features were studied in thin sections of core samples with traditional petrographic techniques using transmitted light microscopy supplemented by scanning electron microscopy (SEM) of rock chips and thin sections.
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Mullineux, S., RSJ Sparks, MD Murphy, C. MacNiocaill, D. Barfod, J. Njorka, and JC Schumacher. "Columnar-jointed bentonite below a Doleritic Sill, Tideswell Dale, Derbyshire, UK: formation during prograde contact metamorphism." Geological Magazine 157, no. 7 (February 12, 2020): 1181–98. http://dx.doi.org/10.1017/s0016756819001535.
Full textAbstract:
AbstractColumnar-jointed tuffs (bentonites) are located below the Lower Carboniferous Tideswell Dale Sill, Derbyshire, in an abandoned quarry. There are three zones of prismatic joints, columnar joints (∼60 cm thick and mean column width of 4.1 cm) and massive, conchoidally fractured rock sequentially from the dolerite contact downwards. The rocks are very fine-grained (1–10 µm) and consist mainly of sanidine, interlayered illite/smectite, and hematite, with minor quartz, apatite, montmorillonite, anatase and detrital minerals. High K2O and Fe2O3, low Na2O and low MgO are interpreted as due to alteration of felsic volcanic ash. The bentonite was contact-metamorphosed by the sill to temperatures of c. 300 °C. The progression of fracture geometries, thermal considerations and application of theories of column formation indicate that columns formed downwards away from the sill, due to prograde contact metamorphism of the originally clay-rich bentonite. The formation of columnar fracture networks by shrinkage due to igneous heating may have implications for the effectiveness of bentonite as a barrier for disposal of high-level radioactive waste. Regional dimensions include documenting widespread felsic explosive volcanism and inferring a Triassic oxidation event from palaeomagnetic data.