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X-ray computed tomography (CT) is one of the most accurate methods used in the analysis of drill cores, providing a non-invasive method of studying rocks and imaging their internal structure. Discussed technique gives the possibility to reproduce the CT image in various directions, without the necessity of mechanical interference in the rock material, resulting in the core destruction. Carbonate rocks are a specific group of rocks, very difficult to interpret due to a high variability of a number of parameters, such as: lithology, mineral composition, biogenic structures content, porosity, permeability, and others. The method of X-ray computed tomography (CT) can be very helpful in the analysis of various carbonate rocks features. Application of the X-ray computed tomography before dividing the core into archive and so-called ‘working’ parts can be very useful for the core documentation and archiving. The tomographic examination, carried out in appropriate time, allows to preserve a complete image of the core. X-ray computed tomography data can be used for various analyses and interpretations, including geophysical logs and borehole imaging. Continuous profiles of some parameters (such as density or porosity) along the studied core intervals also can be calculated from the tomographic image.
Paleomagnetic and petrological analyses were performed on Devonian carbonate rocks from the Kielce region (Janczyce 1 borehole, Dule, Łagowica escarpment, Budy Quarry) in the Holy Cross Mts. Rock samples were selected from localities with different degree of thermal alteration, diversified lithology and stratigraphy. Investigated carbonates, excluding those from the Budy Quarry, revealed traces of the Early Permian remagnetization related to magnetite. The intensity of the Late Variscan remagnetization is linked to rocks affected by the second stage of dolomitization with increased thermal maturity in the northern part of the Kielce region. The magnetic signal is probably related to rocks’self-cooling, fixed as a result of the latest Carboniferous to Early Permian uplift.
Rare-earth elements (REE) were determined for the Upper Jurassic limestone and dolomites from the following outcrops: Góra OEw. Anny, Kostrze Quarry, Księża Góra, and Skały Twardowskiego. REE patterns are similar for all the investigated samples. Dolomites and limestone are enriched in light REE, they exhibit positive La anomalies, and negative Ce and Eu anomalies. Negative Ce and Eu anomalies are typical for oxidizing environments during dolomitization processes. Distinct enrichment in light REE comparing to heavy REE indi-cates that the sea water was not the only component of dolomitization fluids.
Content available remote Dedolomityzacja w górnojurajskich skałach węglanowych z okolic Krakowa
The Upper Jurassic limestones in the vicinity of Cracow underwent extensive dedolomitization process. Petrographic and cathodoluminescent analyses of carbonates in four test areas confirm the dedolomitization as have been developed with various intensity. The alteration of dolomite into calcite occurs as centripetal and centrifugal dedolomitization. Both processes lead finally to a complete disintegration of the dolomite crystals; calcite pseudomorphs after dolorhombs are the end products. These calcite pseudomorphs are abundant in limestones of St. Anna Mt. and in the Kostrze quarry, but are scarce in the Twardowski Cliffs area and in the outcrop of Księża Mt., which indicates a less advanced and slower dedolomitization process in the latter two areas. Most probably the initiation of dedolomitization started from the moment when a carbonate bank emerged from the sea water (Vierek, 2003); temperature of mixing fluids decreased considerably, whereas Ca 2+/Mg+- ratio in the same fluids increased.
Content available remote Przejawy procesów metasomatycznych w wapieniach górnej jury z okolic Krakowa
Przedmiotem badań są procesy dolomityzacji, którym lokalnie uległy wapienie górnojurajskie z okolic Krakowa. Badania prowadzono w czterech odsłonięciach: na Górze Św. Anny, w Kamieniołomie Kostrze, na Księżej Górze oraz w Skałach Twardowskiego. Celem badań była próba określenia czasu i warunków powstania dolomitów oraz wyjanienie mechanizmu dolomityzacji i charakteru wywołujących ją roztworów. W oparciu o cechy geochemiczno-petrograficzne sugeruje się powstanie badanych dolomitów w strefie mieszania wód morskich i meteorycznych (model Dorag), w srodowisku utleniającym, w warunkach płytkiego pogrzebania, z roztworów o względniepodwyższonej temperaturze, około 60o C. Czas tworzenia dolomitów zamyka się w przedziale najwyższa jura–kreda. W toku badań stwierdzono przejawy procesów rekrystalizacji, dedolomityzacji i sylifikacji.
The zones of dolomitization within the Upper Jurassic limestones were studied in four outcrops: Góra Św. Anny, Kos trze Quarry, Księża Góra, and Skaty Twardowskiego. The study aimed to determine the time and the environment of dolomitization as well as to explain the mechanism of dolomitization and character of fluids. Petrografie studies and geochemical analyses proved that the origin of dolomites can be related to mixing zone of sea- and meteoric waters (mixed-water dolomitization model), under oxidizing and shallow burial conditions. Dolomitizingfluids reveal temperatures about 60°C. The results point to the age of dolomitization between the uppermost Jurassic and Cretaceous. Processes ofrecrystallization, dedolomitization and silicification have been identified.
The paper presents the results of petrographic investigations (included macro- and microscopic observations, X-ray and differential thermoanalyses) of the Upper Jurassic carbonate rocks from about 20 boreholes from the region on the east from Tarnów. The research shows that dolomitized carbonate rocks arc products of the dolomitization of fragmented earlier and partially redeposited limestone fragments. The effect of more intensive dolomitization of limestones is formation in some of levels porous structures, which allows to acknowledge them as reservoir levels for hydrocarbons.
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