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Triassic-Jurassic outcrops in Provençal Domain-SE France and Upper Cretaceous Bekhme Formation in Harir-Safin anticlines-NE Iraq are extensively fractured and dolomitized along open spaces in carbonate rocks. Extensive fieldwork, enhanced petrography and geochemistry (trace, REE, major elements, 87Sr/86Sr, δ18OVPDB, δ13CVPDB), and U-Pb datings demonstrate the multi-phase generation of saddle dolomites and blocky calcites formed by the action of deep hot brine fluids, which migrated along fault zones.Petrography and geochemistry revealed three main diagenetic stages in the French Triassic (T)-Jurassic (J) studied outcrops. The first stage is characterized by crystalline replacive dolomites (D1T/ DJ) and medium-sized dolospars (D2T) precipitated in the eogenetic realm from normal seawater and meteoric fluids. The second stage with medium- to coarse-grained saddle dolomites (SD1T/J and SD2T/J) formed under shallow diagenetic realm during Early Cretaceous times, and very coarse-sized zoned and unzoned saddle dolomites (SD3T/J, SD4T/J, and SD5J, SD6J, DrJ) precipitated under deep diagenetic realm (Th between 120 °C and 278 °C) during a Late Cretaceous tectonic activity. Two types of stylolites, extensive fracturing of the carbonates, and breccia/zebra structures, were also formed as a result of the activities of two recognized sub-generations of hydrothermal fluid influxes associated to the second stages. Therefore, they are characterized by a pervasive polyphasic hydrothermal dolomitization that occurred along fractured zones with a wide range of δ18OVPDB and 87Sr/86Sr values. The transition from high (Th between 81 °C and 278 °C; av. = 207 °C) to low (Th between 44 °C and 77 °C; av. = 61 °C) fluid temperatures identifies the third stage of diagenesis. This stage produced the late calcitic cements C1T and C1J with extra-negative oxygen and carbon isotope compositions, and this is related to two different fluids during the uplifting of the studied area in Late Cretaceous-Eocene times. The Triassic dolomites mostly show depleted 87Sr/86Sr values compared to the Jurassic dolomites that have striking higher 87Sr/86Sr values with respect to the marine sea facies. The same lowered radiogenic compositions are measured in the Jurassic calcites (C1J) while the one of the Triassic calcite is higher (C1T). These are probably linked to the pulses of the seafloor hydrothermal activity that lowered the 87Sr/86Sr ratios and to an increase of the continental riverine input during Late Cretaceous and Early Cenozoic.In NE-Iraq, the Bekhme Formation along the Harir-Safin anticlines experienced extensive hot brine fluids that produced several phases of saddle dolomites (SD1, SD2, SD3) and blocky calcite cements (CI, CII). Detailed petrography and geochemical analysis showed that the saddle dolomites and blocky calcites precipitated from deep hydrothermal fluxes (83 °C - 190 °C) and from very saline fluids (up to 25 eq. wt.% NaCl; i.e. 7 times the seawater salinity) that interacted with the crystalline basement rocks during their circulation before invading the Bekhme Formation. Fluid inclusion petrography, fluorescence microscopy and microthermometry revealed two entrapment episodes of oil FIs hosted in the HT cements, i.e. early and late episodes. The early entrapment episode of FIs is linked to the fault-related fractures in the Bekhme Formation and was contemporaneous with the precipitation of the HT cements. The late entrapment episode of FIs is consistent with low saline fluids (0.18 and 2.57 eq. wt.% NaCl) formed under near-surface conditions (13 °C).Shortly after the HT emplacement, an alteration and in situ brecciation of the host limestone and HT saddle dolomites/blocky calcites by alveolar texture led to the formation of two calcrete levels in the dolomitized Bekhme Formation. Extensive fieldwork and geochemistry show repeated occurrence of 2-6 m thick pedogenic levels within the Bekhme carbonates. These levels resulted from a complex interplay between sea level fluctuations and/or tectonic events that produced multiple phases of submergence and emergence during the depositional age of the Bekhme Formation. Consequently, sea level fluctuations and tidal signals are strongly implied.The LA U-Pb dating analysis using small scale isochrones (SSI) method defines the first generation of major HT diagenesis occurring at ~73.8 Ma and predates the calcrete formation (~ 70 Ma) and postdates the early matrix dolomite (~74.8 Ma). Therefore, this diagenetic generation was emplaced in the lowermost part of the Bekhme Formation (75.1 Ma) and was synchronous with the formation of depositional age (Campanian-Early Maastrichtian). The second generation of major HT diagenesis during which a new phase of saddle dolomites/blocky calcites precipitated, spans ages between 8.6 Ma and 30.3 Ma. Within this phase minor phases of HT fluids precipitated similar products (CI = 30.3 Ma - Early Oligocene; CII = 18.7 Ma - Late Miocene; SD2/SD3 = 14.5/8.6 Ma - Late Miocene). Tectonically, the numerical age data (~ 73.8 Ma to 8.6 Ma) is in an acceptable agreement with the two major generations of orogenic folding-faulting systems during the Late Cretaceous and Tertiary interval times and caused by Arabian-Eurasian plates convergence.Samples from the lower calcrete level returned two LA U-Pb ages ~70 Ma and 3.8 Ma corresponding to two horizons within the calcrete, and strongly suggesting that the same calcrete level was twice exposed to subaerial conditions. The earlier exposure was associated with alveolar and other microbial diagenetic features such as dissolution, micritization, cementation…etc. while the second calcrete exposure is associated with laminae, pisolitic, and microstromatolite features during regional uplifting of the area within the Pliocene. In conclusion, a tectonic model is developed for Harir-Safin anticlines, combines fieldwork observations, petrography, geochemistry, and U-Pb numerical age data. The latter method brings new insight into the dating of the fractures/geodes formation and the generation of the HT fluids controlled by tectonics. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Research on dolomitic limestones and dolomites from selected localities of the Barrandian, stratigraphically related to the Scyphocrinites Horizon near the Silurian-Devonian boundary, showed the occurrence of two distinct types of dolomite - diagenetic and epigenetic - differing in petrography and genesis. The diagenetic dolomite is quantitatively predominant. It is finely to moderately coarsely grained with crystal size from 20 μm to 450 μm. Crystals of this dolomite form mostly xenotopic and hypidiotopic textures (occasionally even idiotopic). This type of dolomite formed at low temperature and depth by recrystallization of a carbonate mud during early diagenesis, or during subsequent deeper burial. It is also possible that it originated from recrystallization of previously formed syngenetic dolomite. Fine texture of the diagenetic dolomite is a proof of fast dolomitization and of formation of numerous crystallization centers. Very fine-grained variant of dolomite was also detected (forming aphanotopic texture, size of crystals below 0,002 mm). The epigenetic dolomite, also known as baroque or saddle dolomite, is less common than the former one. It forms white, milky-turbid or clear crystals of large dimensions (0.8 - 3.1 mm). The shapes of these crystals are conspicuous, variously twisted,...

The purpose of this thesis is to establish possible changes in the CI/Br ratio of ancient oceans over the past 2 x 10 9 years. Variations in the Cl/Br ratio of carbonate rocks are used to indicate these changes. A secondary objective of this thesis is to determine the distribution patterns of F in limestones and dolomites. Variations in the F content of dolomites are shown to be related to environment of deposition and can be used to establish tho genesis of dolomite. The contents of the thesis include; 1) a comprehensive review of the pertinent literature, 2) a discussion of the evolution of the Cl/Br ratio of the ocean. 3) application of F in paleoenvironmental reconstruction, and 4) suggestions for further research. / Thesis / Doctor of Philosophy (PhD)

Thirty cores from the Late Jurassic uppermost Jubaila, Arab-D reservoir and Arab-D anhydrite in Hawiyah (Ghawar) and Harmaliyah fields, eastern Saudi Arabia were studied to document the detailed facies stacking and high resolution sequence stratigraphy. The Jubaila-Arab-D interval is a shallowing upward succession of two composite sequences, in which the Arab-D reservoir and overlying anhydrite have up to twelve higher frequency sequences. Both fields are strikingly similar in terms of facies, parasequences, and vertical stacking of facies. The direction of the progrodaion is east and northeast and that is supported by northeast thickening of the Arab-D reservoir and by the stromatoporoid and Cladocoropsis facies progrodation. This suggests that the Arab-D reservoirs in both fields may represent part of a single carbonate ramp with subtle syndepositional highs. The scarcity of exposure surfaces with caliche in the Arab-D reflects the relatively high subsidence rate (~6 cm/k.y.) relative to the small sea level oscillations that formed the succession coupled with the long term shallowing trend up through the section. Dolomites from the Arab-D reservoir zones 1 to 4, in both fields were studied to better understand their origin. The dolomites are dominantly fabric destructive medium to coarse grained types, and much less common fabric retentive finer grained dolomites in the uppermost Arab-D reservoir. The δ¹³C values are rock buffered while the δ¹⁸O values have been greatly shifted toward negative values relative to unaltered early dolomite, and dolomite crystal rims generally have lighter δ¹⁸O values than cores. The dolomites were initiated at different times during shallowing phases on the Arab-D platform, with the bulk of the fabric destructive dolomites forming under near normal salinities, while the fabric preserving dolomites formed as a result of dolomitizing aragonitic sediments from more evaporated waters. With increasing burial and increasing temperature, the early dolomites re-equilibrated with the increasingly warm basinal brines resulting in replacement of cores, and dolomite cementation by rim overgrowth. Progressive plugging of higher dolomites earlier, caused some of these to retain slightly heavier δ¹⁸O values and marine seawater Sr isotope values while those that remained permeable developed very light δ¹⁸O values and more radiogenic Sr values, shifting them toward the field of late stage baroque dolomite. / Ph. D.

The present thesis provides assessment potential of the Mořina - Východ deposit (Velká Amerika) as a raw material reserves for the Kozolupy - Čeřinka deposit. The reason for this work is limited lifetime of the Kozolupy - Čeřinka deposit (approx. 11-14 years) that does not allow fulfilling the requirement to ensure the production of limestone for flue gas desulphurization for ČEZ until 2035. Objective of this work is to summarize all the existing knowledge of the deposit and define the expected technological parameters of raw materials and consider the possibility of its use as a raw material for flue gas desulphurization. Special attention was paid to dolomitization of the limestone, namely to its extent and nature, because elevated Mg content lowers the quality of the limestone ore. Finally, ore reserve calculations and mining intentions are presented. On the basis of microscopic research two types of dolomite were distinguish: diagenetic and epigenetic. Diagenetic dolomite originated at shallow burial together with recrystallization of limestone slurry at temperatures up to 50 řC. Homogenization temperatures of primary fluid inclusions in epigenetic dolomite lay in the range 76-92 řC (sample A9) and 63-88 řC (sample A25).The trapping temperature of these inclusions was probably only slightly...

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The Late Triassic platform carbonates of the Transdanubian Range, Hungary were part of a passive margin platform at the southwestern end of the Triassic Tethys now occurs in a single fault-bounded terrain. The Hungarian platform is made up of meter-scale, precessional (~20 k.y.) carbonate cycles. It contains a lower unit, the Main Dolomite Formation (600-1500m thick), which is totally dolomitized. It is overlain by the Transitional Unit (150-400m thick). The overlying Dachstein Limestone is up to 800m thick. The platform is a cyclic succession of subtidal carbonate, laminated tidal flat limestone or dolomitic caps, and reddish or greenish paleosols or reworked paleosols. The Triassic was a time of global greenhouse conditions and Milankovitch climate forcing has been well documented from lakes and off-shelf facies. The Triassic Hungarian carbonate platform records an imperfect Milankovitch eustatic signal. They lack the bundling of 5 precessional cycles into 100 k.y. eccentricity cycles or 20 cycles/400 k.y. bundle. This is interpreted to be due to many missed beats evidenced by caliches and paleosols, and thick amalgamated subtidal carbonates. These result from precessional sea-level fluctuations either not flooding the platform, or flooding it too deeply to allow shallowing up to sea-level in one precessional beat. Spectral analysis of the Hungarian carbonates was used to compare the amplitude spectra of different time series including lithology, gamma ray, self potential and neutron density. The spectra based on lithology were compared to synthetic spectra generated by computer from platforms subjected differing Milankovitch signals. Most dolomitization of the Hungarian carbonates occurred early in tidal flat settinfs during each high frequency cycle. Intertidal-supratidal dolomites are fine grained, Fe²⁺ and Mn²⁺ rich and slightly enriched in δ¹⁸O compared marine calcite cement, and formed from weakly to moderately reducing marine waters. Subtidal dolomites are slightly coarser grained, low in Fe²⁺ and Mn²⁺ and have heaviest d¹⁸O signatures, indicating more evaporative oxidizing brines beneath flats. Repeated emergence stabilized the dolomites to low Sr²⁺ and Na⁺ types similar to Cenozoic dolomites. Later, coarse-grained dolomites with very low Mn²⁺ Fe²⁺ and light δ¹⁸O signatures were formed along the platform margin by thermally driven, warm oxidizing marine water associated with Jurassic rifting of the Pennini Ocean (Neo-Tethys). The overall vertical distribution of early dolomite on the platform does not reflect long term ecstasy. Instead the regional stratigraphic trends in climatically sensitive sediments, as well as stable isotopes, suggest that intense dolomitization of the lower platform reflects a semi-arid, hot subtropical setting and megamonsoonal climate. Global cooling and increased humidity toward the latest Triassic and Early Jurassic, inhibited pervasive early dolomitization, leaving the upper platform little dolomitized. / Ph. D.

Dolomitos são rochas carbonáticas abundantes no registro sedimentar Pré-Cambriano, porém raras no registro Fanerozóico e sua gênese até hoje permanece como um enigma da geologia, conhecido como o \"Problema Dolomito\". As rochas sedimentares fosfáticas são amplamente estudadas por fornecerem dados importantes sobre a evolução sedimentar e condições físico-químicas e biológicas da água do mar durante a sedimentação e a diagênese, além de constituírem os maiores depósitos econômicos de fósforo do mundo. Os dolomitos e fosforitos da Formação Bocaina foram estudados com base na individualização de fácies sedimentares e petrografia, complementado com investigações geoquímicas (elementar e de isótopos de C e O), a fim de discutir os processos envolvidos na gênese destas rochas. As fácies sedimentares da Formação Bocaina, caracterizadas principalmente por grainstonesoolíticos, pisolíticos, e estromatólitos, indicam ambiente de águas rasas, límpidas e agitadas, interpretado como uma laguna, propícia à proliferação microbiana, com conexão restrita ao mar aberto. Estruturas tepeese pseudomorfos de cristais de gipsita sugerem condições evaporíticas para a bacia, com eventos de exposição subaérea dos sedimentos. Os dolomitos da Formação Bocaina são interpretados como secundários, originados da substituição de sedimentos calcíticos na eodiagênese, provavelmentedevido a elevada taxa de evaporação e refluxo das águas oceânicas. Modelos organogênicos para estes dolomitos não são descartados, devido à assinatura isotópica de C ser ligeiramente positiva (\'delta\' POT.13C IND.VPDB\' entre 0,95 e 3,15%o). A fosfogênese é interpretada como um processo eodiagenético, ocorrido em ambiente geoquímico anóxico, corroborado pelas anomalias positivas de Ce. O excesso de matéria orgânica permitiu a formação da apatita, provavelmente bioinduzida, durante eventos de subida do nível do mar, e desta forma, os fosforitos representam um marco estratigráfico para a bacia, como uma superfície condensada. Subseqüentemente, há rebaixamento do nível do mar, registrado nas fácies de fosfarenito e de conglomerado polimítico da base da Formação Tamengo, unidade que se justapõe à Formação Bocaina, marcando o fim do ambiente lagunar restrito e a instalação de uma plataforma francamente marinha. / Dolomites are carbonatic rocks abundant in the Precambrian but rarely found in the Phanerozoic sedimentary record. Their genesis has remained as a long-standing enigma in geology, often called the \"Dolomite Problem\". The phosphatic rocks, which represent the largest economic deposits of phosphorus in the world, have been studied to provide some important data about the sedimentary evolution and physical-chemical and biological condition of seawater during the sedimentation and diagenesis. The dolomites and phosphorites of the Bocaina Formation were studied based on sedimentary facies, petrography, geochemistry and carbon and oxygen isotopes investigations, to understand the process involved in the genesis of both rocks. The sedimentary facies of the Bocaina Formation are characterized by stromatolites, oolitic and pisolitic grainstones, which indicate shallow, clear and agitated water, favorable to microbial growth. The paleoenvironment was interpreted as a lagoon with restrict connection to the sea. Tepees structures and pseudomorphs of gypsum crystals suggest evaporitic condition to this basin, and also show evidences of aridity. The Bocaina Formation\'s dolomites have been interpreted as secondary, from replacement of limestones during eodiagenesis by reflux of oceanic waters. Organogenic models are also consideraded as a process to form these dolomites, based on the positive carbon isotope signature (\'delta\' POT.13 IND.CVPDB\' between 0.95 and 3.15%o). The phosphogenesis has been interpreted as eodiagenetic process occurred in anoxic geochemical environment, due to the excess oforganic matter, mediated by microbial process. The positive Ce anomalies support this interpretation. This process occurs during rising of sea level and the phosphorites represent a stratigraphic mark as a condensed surface. Subsequently, it is observed a sea level lowering, recorded in phospharenite facies and in basal polymict conglomerate of Tamengo Formation, unit which overlies the Bocaina Formation. This lowering event marks the end of the restrict lagoon environment and the installation of a marine platform.