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(a) Paleoenvironmental map of the Transdanubian Range during the Early Triassic (b) Arrangement of the environments in SW-NE cross section during Early Triassic, (c) Arrangement of the environments in SW-NE cross-section during the Middle Triassic. Green arrows show the migration pathway of the dolomitizing fluids. (d) Schematic model for the dolomitization and other diagenetic processes that affected the Lower Triassic mixed lithotypes. (1) Diagenetic events in the dolomite, dolomitic limestone and limestone lithotypes (LT1, LT4, LT5). (2) Diagenetic events in the sandstone lithotype (LT3) These numbers correspond to those on figures (b) and (c). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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The Lower Triassic succession of the Transdanubian Range in Hungary comprises limestones, dolomite, marl, sandstones and siltstones, deposited in tidal flat, lagoon and ooid shoal environments on the marginal ramp of the western Neotethys. Seven cores were chosen for petrographic and stable isotope investigations aiming to reconstruct the paragenet...
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... Additionally, micro-stylolites with oxides in grainstone and wackestone likely served as fluid conductors during the diagenesis and compaction as documented by several authors (e.g. Vandeginste & John 2013;Gyori et al. 2020;Gomez-Rivas et al. 2022). The microfenestra fabric may also have formed during these processes. ...
... Dolomitization probably occurred in FZ 8 (Wilson 1975), associated with the platform interior and corresponding to SMF 19 or 23 (Flügel 2010). This environment, probably enriched in Mg, facilitated dolomite transformation or replacement of calcareous components during the early diagenesis in a shallow basin deposition (e.g., Gyori et al. 2020). The presence of species of the genus Diplognathodus in bed CC54-11 which corresponds to MF3, indicates a quiet to moderately water-energy environment, likely in a restricted platform interior as Sweet (1988) reported. ...
The biostratigraphic analysis of the Paleozoic sedimentary successions in Mexico is crucial for understanding their age, depositional setting, and paleogeographic implications. This study examined conodonts and microfacies of calcareous strata within the Del Monte Formation of the Tamatán Group in northeastern Mexico.
Field observations have led to the identification of three units within the Del Monte Formation: Unit 1, characterized by calcareous sandstone, bioclastic limestone, shale, occasional conglomerate, and dolomitized beds; Unit 2, consisting of conglomerate and/or breccia associated with debris flows; and Unit 3 including turbiditic sandstone and shale.
Conodonts were only recognized in Unit 1, with such genera as Idiognathoides, Neognathodus, Idiognathodus and less frequently, Streptognathodus, Adetognathus, and Diplognathodus. The faunal associations include Idiognathoides cf. Id. corrugatus Harris & Hollingsworth, 1933, Idiognathoides sulcatus sulcatus Higgins & Bouckaert, 1968, Idiognathoides convexus (Ellison & Graves, 1941), Idiognathoides asiaticus Nigmadganov & Nemyrovskaya, 1992, Neognathodus cf. N. atokaensis Grayson, 1984, Neognathodus aff. bothrops Merrill, 1972, Neognathodus nataliae Alekseev & Gerelzezeg, 2001 (in Alekseev & Goreva 2001), Streptognathodus parvus Dunn, 1966, Idiognathodus incurvus Dunn, 1966, and Idiognathodus aff. delicatus Gunnell, 1931, suggesting Morrowan and Atokan (Pennsylvanian) ages for the dolomitic limestone and grainstone beds.
Five types of microfacies (MF) and several marine facies zone (FZ) have been detected: MF1-bioclastic grainstone and MF2-wackestone deposited at the platform margin (FZ 6 and FZ 7), MF3-dolomitized wackestone representing an inner restricted platform (FZ 8), MF4-mudstone from a deeper water zone (FZ 4), and MF5-siliciclastic beds with bioclasts indicating a high-energy barrier associated with a platform margin (FZ 6). The findings confirm a shallow to deep platform and imply a connection among Mexican peri-Gondwanan basins, including the Tamatán
Basin, indicating similarities in sedimentary facies and/or depositional environments linked to the Rheic Ocean during the Early to Middle Pennsylvanian.
... 2 Mixed siliciclastic−carbonate sequences formed in various depositional settings are common in both marine and lacustrine environments. 2,3 Fine-grained sediments are those rocks with grain sizes smaller than 0.0625 mm. 4 The fine-grained terrigenous and carbonate components in the mixed sediments record abundant information about sediment dynamics and the environment. 5 In addition, fine-grained sediments are enriched in organic carbon. ...
The lacustrine shale of the Middle Permian Lucaogou Formation in the Jimusar Sag is the principal prospective unconventional target in the Junggar Basin. The effect of petroleum generation and retention on nanopore structure change during thermal maturity in lacustrine shale is still unclear. In this study, two laminated and two massive shale samples from the Permian Lucaogou Formation were selected to study this change by closed hydrous pyrolysis. The pyrolysis temperatures were 295, 320, 345, 370, and 400 °C, which cover from the mature to the post-mature stage. Total organic carbon (TOC), Rock-Eval, and low-pressure N2 adsorption tests on pyrolyzed shale samples before and after extractable organic matter (EOM) extraction were conducted systematically. The results indicate that (1) the petroleum generation on nanopore structure change is in stages. The peak nanopore volume expanding stage is the late oil window (R o = 0.9-1.35%). At the post-mature stage (R o > 1.35%), the mesopore volume decreased and the majority of the nanopore space is from macropores. (2) The presence of EOM decreased both mesopores and macropores in the peak oil window. (3) The organic-rich laminated shale generated more macropores than massive shale with increasing thermal maturity. The results of this study shed light on the dynamic effect of laminae fabric, petroleum generation, and retention on shale nanopore structure change across the oil window.
... Esteban et al. [26] mentioned the influence of hydrothermal action, Machel et al. [27] hypothesized that dolomites were dissolved by sulfate during hydrocarbon impregnation, and Poros et al. [22] not only induced the above theories but also established a new model of dolomite sanding caused by freeze-thaw process when studying Triassic dolomites in Hungary. Orsolya et al. [28] investigated Triassic dolomites in Hungary, selected seven rock-cores for stable isotope analysis, and for identifying the relationship between dolomitization and hydrothermal dissolution. Giuseppe et al. [29] studied the dissolution of dolomite by macro methods (via pH-stat system and mixed flow reactor) and micro-characterization methods (via atomic force and transmission electron microscopy). ...
The No. 2 conduit of the Xiaopu Tunnel in the Yuxi section of central Yunnan’s water diversion project is taken as the research object, starting from the geological conditions along with the characteristics, formation mechanism and evolutionary model of dolomite sanding. This paper discusses the engineering problems of the project’s tunnels with dolomite sanding in the water-rich section, and its corresponding engineering reinforcement plan. It was found that in the tunnel section with normal level of dolomite sanding, there was no water seepage, where measures such as advanced small conduit, mechanical excavation, short grubbing and strong support could all be adopted for safe passage. Even in the water seepage section of the weak dolomite sanding tunnel, the surrounding rock was found in close interlock with strong self-stability. The excavation and support were implemented according to the category of normal surrounding rock. In the water-rich sections with strong and intense dolomite sanding, gushing of water and sand were quite frequent, with developed fissures, broken rock masses and rich waters. During the engineering operation, phosphoric acid and sodium silicate slurry in addition to urea formaldehyde resin and oxalic acid slurry plus Malisan and liquid catalyst slurry were first prepared for water plugging. Then, pure water slurry was used for surrounding rock reinforcement, which exerted an excellent effect. This method can provide reference for reinforcing tunnels of sandy dolomite in other areas of projects.
... There is a general agreement that the reflux model is capable of producing thick dolomite covers (Adams and Rhodes, 1960;Machel, 2004;Jasionowski et al., 2014;Adams et al., 2018;Sorento et al., 2018;Zhu et al., 2018;Lukoczki et al., 2019;Győri et al., 2020). In the studied case, it seems that dolomite originated chiefly from the combination of a downward seepage of heavy brines and burial processes acting at relatively low temperatures (see Jasionowski et al., 2014 and Fig. 15). ...
Reefs may be formed in the middle parts of sedimentary basins and grow on tectonically uplifted substrate blocks. In this paper, the strata of the Central European reef system of the Upper Permian Zechstein Limestone (Ca1) formation located in West Poland are evaluated. The formation has produced natural gas since the early nineties of the past century. The reefs grew on an uplifted horst built of Carboniferous rocks, known as the Wolsztyn Ridge. As individual sub-blocks originally showed diversified altitudes, four zones suspected to
represent initial sedimentation conditions are distinguished: (1) basin zone, located close to the margins of the WR; (2) lower reef zone; (3) transitional zone and (4) the upper reef zone. Clear diagenetic differences between particular zones are observed. The basin zone strata are characterized by a strongly recrystallized mosaic of dolomite but show a limited extent of anhydrite cementation. The lower reef zone rocks, covered by thick Zechstein evaporites have been dolomitized and anhydritized most intensively, probably by means of the downward seepage of heavy brines, as suggested by the stable isotope data. It is assumed that the process was focused on the calm-water facies due to their low primary porosity and permeability. This mechanism was also probably responsible for the dolomitization of Ca1 strata in the remaining zones, where lower δ18O values in dolomite reflect some temperature increase on the final isotopic signature of rocks. Transitional zone carbonates appear to be almost purely calcitic with only a minor dolomite admixture. They contain various types of calcite cement, including marine and meteoric-phreatic phases, reflecting an intermediate position of the substrate and optimal reef growth conditions. Marine phases are also commonly recognized in the upper reef zone. Owing to a significant elevation of the substrate in this zone, the corresponding strata might have experienced some impact of karstification, presumably taking place well before the deposition of the Zechstein evaporites. It is concluded that the morphology of the substrate in tectonically-influenced areas strongly controls the reef diagenesis, and thus can affect the distribution of hydrocarbon accumulations.
... La dolomitisation en condition hydrothermale est souvent observée dans des cas de dolomitisation généralement limitée autour de failles et fractures, et quelquefois massive (e.g. Beckert et al., 2016;Biehl et al., 2016;Brigaud et al., 2009;Cantrell et al., 2004;Chen et al., 2004;Di Cuia et al., 2011;Elias Bahnan et al., 2020;Győri et al., 2020;Hollis et al., 2017;Navarro-Ciurana et al., 2016;Paganoni et al., 2016;Ramkumar et al., 2019). ...
... La majorité des dolomitisations massives décrites semble être essentiellement contrôlée par l'environnement de dépôt sédimentaire et climatique (e.g. Bajestani et al., 2016;Cantrell et al., 2004;Franchi, 2018;Gabellone et al., 2014;Győri et al., 2020;Lukoczki et al., 2018;Rustichelli et al., 2017;Syah et al., 2019). L'hydrothermalisme associé à la circulation de fluides le long de failles ou de fractures contribue également à la mise en place de volumes de dolomie importants (e.g. ...
... La dolomitisation hydrothermale, régulièrement associée aux gîtes métallifères de type Mississippian Valley Type (MVT) concentre une grande partie de ces récentes études (e.g. Biehl et al., 2016;Győri et al., 2020;Haeri-Ardakani et al., 2013b;Hollis et al., 2017;Incerpi et al., 2020aIncerpi et al., , 2020bIriarte et al., 2012;Lopez-Horgue et al., 2010;Motte et al., in revision.;Renard et al., 2018;Salardon et al., 2017). ...
The Western Pyrenean Jurassic carbonate platform, cropping out on the northerwestern Pyrenees foreland, is a remarkable laboratory for the characterization of dolomitization. With a geodynamic evolution at the interface between margin and chain, as well as the presence of the whole carbonate system at the outcrop, the study of this zone allows to apprehend the crucial parameters of the dolomitization and thus to determine which geodynamic and sedimentary contexts are suitable. The combination of field observations, petrographic, elemental, isotopic and microthermometric analyses on fluid inclusions coupled with carbonate U-Pb dating allowed to determine the dolomitization conditions of different localities of this carbonate system cropping out in the Chaïnons béarnais and the Basque Country.
In the Mano (Tithonian) and Meillon (Batho-Callovo-Oxfordian) Formations of the Mail Arrouy (reference outcrop) in the Chaînons Béarnais, dolomitization occurred in several stages, spanning the Neocomian (pre-rift) to the Albian (syn-rift, associated with crustal hyper-thinning and mantle exhumation, accompanied by active salt tectonics). Both units were first massively dolomitized in near-surface to shallow burial conditions during Berriasian- Valanginian, likely triggered by the influx of marine-derived waters. Between the Barremian and the Albian, the Lower Cretaceous rifting caused the upward influx of hot fluids, associated with partial to complete recrystallization of the initial dolomites. Subsequent dolomites precipitated in both formations during the Albian, from distinct hot fluids (T > 160°C ; with evaporite-derived water in the Meillon and clay water in the Mano) as vein- and pore-filling cements. Finally, a last episode of dolomite cementation occurred only in the vicinity of faults and volcanic intrusions during the Albian, from hydrothermal water recording the mixing of mantle-, crustal- and evaporites-derived waters and the highest temperatures in both formations (T > 250°C). Subsequent quartz and calcite cement precipitation record a temperature decrease in a post-rift to inversion context (post-Cenomanian).
Southward (Layens anticline), dolomitization was only partial with the presence of isolated dolomitic bodies in the Meillon Formation. The upwelling of hot fluids during the rifting induced a partial recrystallization of this outcrop, located on the necking zone of the rift basin. Dedolomitization was also strongly present, induced by an extended emersion period, until the rifting, causing an influx of meteoric water synchronous with this episode of hydrothermalism.
In the Basque Country, the dolomitic Meillon and Mano Formations lateraly pass to the distal formations of Microfilament limestones and Hosta marls. In these compact and marl-rich formations, only a few traces of dolomite are present as vein fillings. Calcite was ubiquitous during the Albian, and partially to completely replaced the dolomites initially in place. Thus, the distal zone of this carbonate system was also affected by dolomitization, during the Cretaceous rifting, probably caused by the upwelling of hot fluids.
The dolomitization of the West Pyrenean platform was primarily controlled by the sedimentary and climatic depositional environment allowing the influx of seawater generating early massive dolomitization. Cretaceous rifting inducing thermal anomalies, combined with the presence of a significant salt layer and salt tectonics represent the second control, inducing massive recrystallization and dolomitic cementations throughout the basin. The stratigraphic architecture of the carbonate system also conditions the distribution of the dolomite with the presence of traces of cement in the distal environment as opposed to the abundance of dolomite observed in the more internal environment. Thus, the distribution of dolomite on carbonate platform on salt-rich hyperthinned passive margin depends essentially on the correlation between the sedimentology of the carbonate system and the paleogeography of the margin.
In the Middle Anisian, extensional tectonic movements led to the development of isolated carbonate platforms in the area of the southwestern part of the Transdanubian Range. The platforms are made up of meter-scale peritidal–lagoonal cycles bounded by subaerial exposure surfaces. One of the platform successions (Tagyon Platform) consists predominantly of limestone that contains partially and completely dolomitized intervals, whereas the other one (Kádárta Platform) is completely dolomitized. Drowning of the platforms took place in the latest Pelsonian to the early Illyrian interval when submarine highs came into existence and then condensed pelagic carbonate successions with volcanic tuff interbeds were deposited on the top of the drowned platforms from the late Illyrian up to the late Ladinian. The comparative study of dolomitization of the coeval platforms, affected by different diagenetic histories, is discussed in the current paper. Traces of probably microbially-mediated early dolomitization were preserved in the slightly dolomitized successions of the Tagyon Platform. This might also have been present in the successions of the Kádárta Platform, but was overprinted by geothermal dolomitization along the basinward platform margin and by pervasive reflux dolomitization in the internal parts of the platform. The Carnian evolution of the two submarine highs was different, and this may have significantly influenced the grade of the shallow to deeper burial dolomitization.
The late-Permian succession of the Upper-Indus Basin is represented by carbonate dominated Zaluch Group, which consists of Amb, Wargal and Chhidru Formations. These formations accumulated on the southwestern shelf of the Paleo-Tethys Ocean, north of hydrocarbon-producing Permian strata of the Arabian Peninsula. The reservoir properties of mixed clastic-carbonate Chhidru Formation are evaluated based on Petrography, Scanning Electron Microscopy (SEM), Energy Dispersive X-rays-Spectroscopy (EDX) and X-ray Diffraction (XRD) techniques. The diagenetic features, ranging from marine (isopachous fibrous calcite, micrite), through meteoric (blocky calcite-I, neomorphism and dissolution) to burial (poikilotopic cement, blocky calcite-II-III, fractures, fracture-filling and stylolites) are recognized. Major porosity types included fracture and moldic, while inter-and intra-particle porosities also existed. The visual porosity from 1.5–7.14% with an average of 5.15% was recognized. The sandstone facies (CMF-4) had the highest average porosity of 10.7%, while siliciclastic grainstone microfacies (CMF-3) showed average porosity of 5.3%. The siliciclastic mudstone microfacies (CMF-1) and siliciclastic wacke-packestone microfacies (CMF-2) showed the lowest porosity of 4.8% and 5.0%, respectively. Diagenetic processes like cementation, neomorphism, stylolitization and compaction have reduced the primary porosities. However, processes of dissolution and fracturing have produced secondary porosity. On average, the Chhidru Formation in Nammal Gorge (Salt Range) showed promising and at Gula Khel Gorge (Trans-Indus) lowest porosity.
During the Miocene, when the Zhujiang Formation was deposited, the eastern part of the Pearl River Mouth Basin, northern South China Sea, underwent intense mixed siliciclastic and carbonate sedimentation, particularly on the platform of the marginal ramp of the Dongsha Rise, northeastern margin of the South China Sea. Cores and well logs from industrial boreholes were collected and systematically investigated to reveal the sedimentary-petrographic characteristics of the mixed deposits and their formative processes. Four lithotypes were differentiated in the deposits, that is, (1) sandstone, (2) dolomitic sandstone and calcitic sandstone, (3) sandy dolomite and sandy limestone, and (4) dolomite, bioclastic limestone, and micrite limestone, which were formed by three major types of mixing processes: punctuated, facies, and in situ mixing processes. The porosity and permeability of the mixed deposits indicated that the siliciclastic component of the mixed deposits that experienced punctuated mixing formed the most high-quality hydrocarbon reservoirs. Exploration revealed that the lithologic reserves in the study area were mainly developed in mixed sedimentation areas. Our results suggest that the mixed sedimentation area, particularly with pure sandstone sedimentation or bioclastic sandstone, that underwent compaction or structural fracture activities, may be the next preference for lithologic exploration.
