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EN
Large-scale shale gas prospecting in the Polish part of the East European Platform did not discover large reserves of this resources. The article presents new research indicating that one of the reasons for the lack of shale gas relates to the thermal history of the Lower Palaeozoic rocks. Illite-smectite palaeothermometry was used to reconstruct the history of the platform and determine the maximum temperatures to which these rocks were subjected. The age of illitisation was also constrained using the K-Ar method. This method allowed precise dating of the maximum age of thermal transformations due to the deposition of numerous pyroclastic horizons (K-bentonite) throughout the entire geological profile from the Cambrian to the Silurian. Isotopic dating was made on over 53 samples of Lower Palaeozoic bentonites and low-grade metamorphic clays. These results were supplemented by analysis of the degree of thermal (smectite to illite) transformation in the profiles of 37 deep boreholes. 11 zones could be distinguished with different tectonic histories within the Polish part of the East European Platform edge. Maximum heating occurred in this region at about 320–340 Ma, corresponding to the Early Carboniferous or the turn of the Early and Late Carboniferous, phase A of the Variscan orogeny, known as the Sudetian phase. In the southern part of study area, the maximum of thermodiagenesis is slightly younger – 270–290 Ma, which responds to the Early Permian, the Asturian phase, the last phase of the Variscan orogeny. This means that the generation of hydrocarbons occurred before significant Mesozoic exhumation of the Polish part of the East European Platform, which led to the escape of a considerable amount of the gas generated. The study also presents the results of an interlaboratory comparison of illite age dating using the K-Ar and Ar-Ar methods. The comparison was conducted to find out what realistic error should be considered when interpreting geological K-Ar dating results.
EN
Thermal maturity modelling was carried out in over sixty wells along the SW margin of the East European Craton (EEC). The burial and thermal history modelling of the EEC, using thermochronological data, allowed the construction of burial history maps showing its geological development in the Phanerozoic. These results have proved that the Ordovician and Silurian source rocks occurring at the SW margin of the EEC reached a maximum palaeotemperature in the Palaeozoic, mainly during Devonian-Carboniferous time and at the latest during the Silurian in the most westerly part of this margin, along the Teisseyre-Tornquist Zone. In Mesozoic and Cainozoic time, the Ordovician and Silurian strata generally were subjected to cooling or to very minor heating, certainly below the Variscan level. The maximum burial and maximum temperature of the Ediacaran-Lower Palaeozoic strata were reached during the Early Carboniferous in the Baltic Basin and during the Late Carboniferous in the Lublin area, and even in the Early Permian in the SE corner of the Lublin Basin. Thus, the main period of maturation of organic matter and hydrocarbon generation in the Ordovician and Silurian source rocks was in the Late Palaeozoic (mainly Devonian-Carboniferous) and in the westernmost zone along the Teisseyre-Tornquist line at the end of the Silurian.
PL
Przeprowadzono datowania za pomocą metody trakowej i helowej dla apatytów z utworów karbońskich w Górnośląskim Zagłębiu Węglowym w celu określenia ram czasowych procesów uwęglenia. Pomierzone centralne wieki trakowe apatytów mieszczą się w przedziale od 259±11 (późny perm) do 103±6 milionów lat (wczesna kreda), a średnia długość traków waha się od 11,7±0,2 do 13,7±0,1 μm. Wszystkie wieki trakowe są młodsze od wieku stratygraficznego analizowanych próbek, wskazując znaczne zaawansowanie procesów diagenetycznych. Próbki z zachodniej i środkowej części GZW mają wieki trakowe od późnego permu do środkowego/późnego triasu (259±11 do 214±10 mln lat). Jednomodalne rozkłady długości traków i ich średnie wartości wskazują na pojedyncze, względnie szybkie zdarzenie postwaryscyjskiego wychładzania do temperatury poniżej 60°C, co jest zgodne ze znaczną erozją postinwersyjną utworów górnokarbońskich po fazie asturyjskiej. W pozostałej części mezozoiku następowało wolniejsze wychładzanie. Próbki ze wschodniej i NE części GZW mają wieki trakowe od późnego triasu do wczesnej kredy (210±10 do 103±6 milionów lat). Charakteryzuje je względnie krótsza średnia długość traków i wyższe odchylenia standardowe, a także w przypadku części próbek bimodalny i/lub mieszany charakter rozkładów długości. Jest to razem wskazówką bardziej złożonej historii termicznej, z długim okresem przebywania w PAZ i możliwym drugim zdarzeniem termicznym. Wieki helowe apatytów w całym basenie są wczesnokredowe (144,1±11 do 108,1±8milionów lat), wskazując raczej na wolne postwaryscyjskie wychładzanie lub możliwe mezozoiczne podgrzanie karbonu do temperatury nie większej niż 60–70°C, które spowodowało częściową dyfuzję helu i odmłodzenie wieków helowych, ale równocześnie nie spowodowało znaczącego zabliźniania traków na większości obszaru GZW. Jedynie w NE części GZW podgrzanie mezozoiczne mogło być nieco wyższe, do temperatury 70–85°C, powodując odmłodzenie wieków trakowych, zwłaszcza przy długim okresie przebywania w PAZ. Mezozoiczny impuls termiczny był przypuszczalnie spowodowany cyrkulacją gorących roztworów związaną z procesami ekstensji. Powyższe zakresy temperatur i czas ich występowania świadczą, że uwęglenie materii organicznej w GZW nastąpiło zasadniczo z końcem okresu karbońskiego.
EN
The apatite fission track and helium dating were used to provide a temporal framework for the coal rank data in the Upper Silesia Coal Basin. Measured apatite fission–track (AFT) central ages from sandstones and tonsteins in the USCB range from 259±11 (Permian) to 103±6 Ma (Early Cretaceous), with mean track lengths ranging from 11.7±0.2 to 13.7±0.1 μm. All AFT ages are younger than sample stratigraphic ages, indicating substantial post–depositional annealing. Samples from the western and central part of the USCB yield AFT ages of Permian to Late Triassic (259±11 to 214±10 Ma). Mean track lengths and unimodal track length distributions of these samples are indicative of a single relatively rapid Variscan cooling event to below 60°C consistent with erosion during the Asturian inversion of the basin. This was followed by slower cooling during the Mesozoic. The samples from the eastern and NE part of the USCB have AFT ages from Late Triassic to Early Cretaceous (210±10 Ma to 103±6 Ma). The relatively shorter mean track length and higher standard deviation, combined with a bimodal and/or mixed fission track length distribution in some samples, is indicative of amore complex thermal history with possibly a thermal event separated by a prolonged period in the PAZ. Apatite helium ages of samples from across the basin range from 144.1±11 to 108.1±8Ma (Early Cretaceous) indicating rather slow, post–Variscan inversion cooling or the possible mid–Mesozoic re–heating where temperatures reached only to 60–70°C. It was high enough for partial He loss from the apatite but not enough to anneal fission tracks in the most areas of the USCB. Only in the NE part of the USCB Mid–Mezozoic re-heating could be able to increase temperature to ~70–85°C causing partially resetting AFT (particularly during long stay in PAZ). Mid–Mesozoic re–heating would be caused by a hot fluid circulation related to extensional tectonic development. The timing and temperature range from thermochronological analysis imply that major coalification processes occurred in the latest Carboniferous period.
EN
In the present study, the thermal history of the Late Carboniferous (Stephanian) coal-bearing sediments of the Sabero Coalfield has been reconstructed in order to elucidate coal rank. The Sabero Coalfield is located in a small intramontane coal-bearing basin along the Sabero-Gordón fault zone, one of the major E-W trending strike-slip fault systems of the southern part of the Cantabrian Zone (NW Spain). The total thickness of the Stephanian succession is in excess of 2,000 m, and is composed of siliclastic rocks and intercalated coal seams with tonsteins. Mean vitrinite reflectance values in the Stephanian rocks in the Sabero Coalfield are in the range from 0.61 to 3.14% Rr, but most values are in the range from 0.8 to 1.5% Rr (based on 84 samples). Average vitrinite reflectance gradient is high (0.73% Rr/km), which suggests high value of average paleogeothermal gradient (52°C/km). The maximum paleotemperatures calculated from vitrinite reflectance values for the Stephanian rocks range between 89°C (top of the Stephanian) and 195°C (bottom of the Stephanian). Coalification of the organic matter in the Stephanian rocks was achieved in the Early Permian, and was most likely related to several almost simultaneous related to magmatic and hydrothermal activity during high subsidence period in the pull-apart basin. The primary, burial-related maturity pattern, was probably slightly overprinted by fluid migration event, which is supposed to have occurred in Early Permian time.
PL
W celu rekonstrukcji historii uwęglenia w niecce wałbrzyskiej wykonano modelowania termicznej dojrzałości substancji organicznej zawartej w utworach karbońskich za pomocą programu PetroMod. Uzyskane wyniki modelowań utworów karbońskich niecki wałbrzyskiej wskazują że utwory te osiągnęły maksymalne wartości paleotemperatur (wynoszące od 83 do 270 °C) w Stefanie i/lub wczesnym permie. W skali regionalnej utwory karbońskie nie były już później poddane tak wysokim temperaturom. Obliczony paleostrumień cieplny dla wybranych profili niecki wałbrzyskiej waha się od 120 mW\m2 do 147 mW\m2. Powyższa wielkość jest ponad dwukrotnie większa od współczesnej średniej wartości strumienia cieplnego w tym basenie. Powyższe wysokie temperatury doprowadziły do uwęglenia pokładów węgli utworach górnokarbońskich. Uwęglenie nastąpiło w efekcie znacznej subsydencji osadów górnokarbońskich przy wysokim strumieniu cieplnym zdeterminowanym rozwojem intruzji magmowych, chociaż ich bezpośredni wpływ (metamorfizm kontaktowy) odgrywał znikomą rolę w skali regionalnej.
EN
In order to reconstruct thermal history of the coal-bearing Carboniferous strata in the Wałbrzych Coal Basin numerical modeling of thermal maturity has been performed by PetroMod software. Paleoheat flow of 120-147 mW/m2 was calculated for the time of maximum burial (Late Carboniferous to Early Permian). Maximum paleotemperatures of the Carboniferous rocks ranged between 83 (top of the Carboniferous) and 270 °C (bottom of the Carboniferous). Based on this modeling it can be shown that coalification of organic matter contained in Carboniferous rocks was achieved in the Latest Carboniferous to the Early Permian times. It was likely caused both high heat flow related to magmatic activity and high subsidence rate in this basin.
EN
In order to reconstruct thermal history of the Upper Carboniferous (Stephanian) strata in the Sabero Coal-field (NW Spain) numerical modeling of thermal maturity has been performed by Fobos software. Paleoheat flow of 102 m W/m2 was calculated for the time of maximum burial (Late Carboniferous to Early Permian) and a total overburden of 2400m. According to this model, maximum paleotemperatures for the Stephanian rocks ranged between 105 (top of the Perla Formation) and 200 °C (bottom of the Alejico Formation). Based on this modeling it can be shown that coalification of organic matter contained in Stephanian rocks was achieved in Early Permian. It was likely related to several processes such as magmatic activity, high subsidence rate in a pull-apart basin.
PL
W celu rekonstrukcji ewolucji paleotermicznej utworów górnokarbońskich (stefańskich) Zagłębia Węglowego Sabero (NW Hiszpania) przeprowadzono jednowymiarowe modelowania numeryczne dojrzałości termicznej za pomocą programu Fobos. Obliczony paleostrumień cieplny w okresie maksymalnego pogrążenia utworów górnokarbońskich (na przełomie karbonu i permu) wynosił 102 m W/m2, a całkowita wielkość erozji nadkładu wynosiła około 2400 metrów. Maksymalne paleotemperatury osiągnięte przez utwory górnokarbońskie wynosiły od 105°C (w stropie formacji Perlą) do około 200°C (w spągu formacji Alejico). Uwęglenie materii organicznej w utworach górnokarbońskich basenu Sabero nastąpiło w najwyższym karbonie oraz we wczesnym permie. Było ono związane z jednej strony z waryscyjską aktywności magmatyczną, a z drugiej strony z wysokim tempem subsydencji w basenie typu pull-apart.
EN
This paper presents an attempt to combine analysis of diagenetic processes affecting Carboniferous sediments in the SE Poland (Mazowsze and northern part of Lublin region) to their burial and thermal history. For this reason results of petrographic study, analysis of paleotemperatures from fluid inclusion and K/Ar dating of diagenetic fibrous illite were confronted with 1–D maturity modelling calibrated with vitrinite reflectance data (VRo). The main diagenetic processes of the Carboniferous sediments are compaction and cementation especially by: quartz, kaolinite and carbonates (siderite, dolomite, Fe–dolomite, ankerite, Fe–calcite). Fluid inclusions in quartz rims indicate representative temperatures of its growth in a range of 60 oC to 150 oC. Homogenisation temperatures of inclusions from Fe–dolomite and ankerite cement indicate its growth in temperatures ranging between 60–129 oC. Both mentioned above cements are followed in the succession by diagenetic illite; for Mazowsze region its K/Ar dates range from 205,4 ±4,2 Ma (late–most Triassic—early–most Jurassic) to 167,3 ±3,3 Ma (Bathonian). These measurements were indirectly used as thermochronological data for modelling. In the Mazowsze region thermal modelling based on VRo profiles does not reveal any palaeothermal events. This is due to the fact that the recent burial is not significantly different from the Late Cretaceous maximum one. However incorporation of palaeotemperatures from fluid inclusion analysis together with results of dating of diagenetic illite into thermal history modelling clearly shows presence of Early to Middle Jurassic thermal event. Similar process was independently revealed from maturity modelling for the southern part of Kujawy segment of the Polish Basin (Poprawa et al., 2002), i.e. directly to the NW of analysed area. This event correlates with tectonic phase, expressed by acceleration of subsidence and development of a system of extensional or transtensional faults. It is concluded that the mechanism of heat transport could be related to tectonically induced migration of hot fluids from deeper part of the Palaeozoic sedimentary cover. In the northern part of Lublin region and in the Mazowsze region the Variscan thermal history did not result with depth–depended VRo profiles. Instead sub-vertical or inverted maturity profiles are observed. According to model of Żywiecki (2003) this could be explained by migration of hot fluids from Kock zone, being a site of Carboniferous magmatic activity. Conducted research shows that integration of analysis of inorganic diagenetic processes and maturity modelling allows for more precise reconstruction of thermal history. Therefore this has also potential in calibration of hydrocarbon generation/expulsion modelling.
EN
The Łysogóry Block (ŁB) exposed in the northern Holy Cross Mts. (HCMts.) reveals subsidence and thermal development consistent with the pattern observed in adjoining East European Craton (EEC) areas. This evidence, in addition to previously reported similarities in sedimentation and deep crustal structure, contradicts the Pożaryski's hypothesis that the Łysogóry Block represents a terrane within the Caledonian orogen. This area is here interpreted as the part of a Late Silurian foredeep basin which developed on the Baltica margin in response to terminal phases of collision with Eastern Avalonia. The development of the continuous Late Silurian foredeep basin along the EEC margin from the Peri-Tornquist Basin in the north-west to the present northern HCMts. implies that the North German-Polish Caledonides orogen had its NE continuation near the present Holy Cross area. The southern HCMts. comprise the northern margin of the Małopolska Massif (MM). The Ordovician-Silurian subsidence development of this area, its thermal history and crustal structure point to a stable cratonic setting. Existing similarities in sedimentary succession (mostly Ordovician and Lower Silurian) as well as clearly Baltic palaeobiogeographic affinities indicate a close spatial connection between the MM and Baltica during the analysed time interval. The juxtaposition of the MM against the ŁB area can be explained assuming that the MM is a part of Baltica detached from its margin due to right-lateral strike-slip after late Ludlow and before Emsian time.
PL
Zastosowanie modelowań numerycznych do rekonstrukcji procesów generowania węglowodorów pozwala na integrację danych geologicznych, geochemicznych i geofizycznych. Ma to na celu przede wszystkim jak najbardziej wiarygodne odtwarzanie przebiegu procesów generowania węglowodorów, aby możliwie precyzyjnie oceniać potencjał naftowy skał macierzystych danego basenu sedymentacyjnego. Modelowania te obejmują modelowanie subsydencji, pogrążania i kompakcji osadów, przepływu energii cieplnej i ewolucji termicznej oraz generowania węglowodorów. Pozwalają one obliczyć stopień i czas dojrzewania (przeobrażenia) materii organicznej, a w efekcie końcowym ilość i skład wygenerowanych węglowodorów oraz określić czas kiedy miało to miejsce.
EN
Integrated numerical modelling of petroleum generation allows to reconstruct reliable hydrocarbons generation processes. Consequently, it allows to estimate petroleum potential of source rocks in the sedimentary basins. These modelling consist of modelling of subsidence, burial and compaction of sediments, energy transport, thermal history and hydrocarbons generation.
EN
The TTI modelling demonstrated that the autochthonous Miocene strata located in the outer Miocene basin of the Carpathian Foredeep, north of the present edge of the Carpathian overthrust have generated only the microbial gas. In the part of the Miocene basin covered recently by the Carpathian overthrust the low-temperature thermogenic gases were generated down to 7,000 of meters depth. Finally, in the hypothetical zone of the Lower Miocene molasse located recently at depth interval 7,500-11,000 meters only the high-temperature thermogenic gases could be formed. Alternatively, at the site of the Lower Miocene molasse the depression filled with Upper Carboniferous coal-bearing formation may occur. Therefore, at depth beneath 7,500 meters, i.e. beneath the Carpathian overthrust the gas deposits can be expected. The maximum yield of the microbial methane generation within the autochthonous Miocene calculated for depth interval 900 to 1,500 meters is about 5 cubic meters per cubic meter of source rock. It is possible that the generation process of microbial methane still continues. Accumulation of microbial methane within the autochthonous Miocene strata was facilitated by high sedimentation rate and rhythmic and cyclic deposition of clays and sands.
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