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Wyświetlanie 1-6 z 6
Tytuł:
Constraints on the nature and evolution of the volcanic fields of the Andahua Group, Central Volcanic Zone, southern Peru
Autorzy:
Gałaś, Andrzej
Németh, Károly
Lewińska, Paulina
Powiązania:
https://bibliotekanauki.pl/articles/2201223.pdf
Data publikacji:
2022
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
monogenetic volcanoes
small lava dome
petrological modelling
Andes
Opis:
The Andahua Group is a distinct cluster of typically monogenetic volcanoes located in the northernmost part of the Central Volcanic Zone in the Andes, characterized by small-volume lava domes and scoria cones. Seven volcanic clusters have been distinguished. Using satellite imagery, geological mapping, and fieldwork, we found a total of 103 lava domes, 43 scoria cones, and 3 small composite volcanoes. Most of the lava domes are monogenetic but 9 were formed by multiple eruptions. Petrogenetic models have been developed for the magma evolution of the Andahua Group. They show local crustal influence on the magmas generated, and possible controls on the magma pathway to the surface, and potential segregation. Local compositional variation of the crustal rocks is inferred to have a strong influence on the magma that ascends through the thick continental crust. Assimilation and contamination by deeply seated granitoids of the Arequipa and Paracas massifs are also inferred to play a role in the final magmatic products. Future activity with gas emissions from the Andahua Group volcanoes may cause hazardous conditions for tourists.
Źródło:
Geological Quarterly; 2022, 66, 3; art. no. 25
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oxygen and sulphur isotopes of gypsum from the Mogilno Salt Dome cap-rock (Central Poland)
Autorzy:
Jaworska, J. K
Wilkosz, P.
Powiązania:
https://bibliotekanauki.pl/articles/2059001.pdf
Data publikacji:
2012
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
gypsum
oxygen isotopes
sulphur isotopes
cap-rock
Mogilno Salt Dome
Opis:
The stable-isotope compositions of oxygen and sulphur from 30 gypsum samples obtained from three drill cores of the Mogilno Salt Dome cap-rock have been analysed; the Mogilno Salt Dome itself is composed of Zechstein evaporites. d344 184242418344182418181818218218218218182
Źródło:
Geological Quarterly; 2012, 56, 2; 249-260
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An oxygen and sulfur isotopic study of gypsumfrom the Wapno Salt Dome cap-rock (Poland)
Autorzy:
Jaworska, J.
Powiązania:
https://bibliotekanauki.pl/articles/2059040.pdf
Data publikacji:
2010
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Wapno Salt Dome
cap-rock
gypsum
oxygen and sulfur isotopes
Opis:
The stable isotope compositions of oxygen and sulfur from gypsum samples derived from borehole cores of the Wapno Salt Domecap-rock have been determined. The d18O values were measured (for both the SO4 and the H2O) in bulk samples of gypsum(CaSO4 2H2O) and in its dehydrated equivalents (CaSO4). The SO4 is enriched in the heavy oxygen isotope, which unequivocally indicates the Zechstein sea as the place of origin of the sulfate. The variable δ18O values of the H2O (water of crystallization) indicate different conditions (and stages) of diagenetic processes of these samples, primarily recrystallization (hydration) episodes. Two groups ofgypsum were distinguished: (1) a group in which the δ18O values of H2O range between -9.0 and -10.2‰ (interpreted as gypsum in equilibrium with recent or subrecent meteoric water), (2) a group in which the d18O values of the H2O were less than -10.2‰ (this gypsum hasrecrystallized in the presence of water enriched in the light isotopes of oxygen). In addition, in one single analysis the δ18O value of the H>sub>2O amounts to -5.6‰ (gypsum with mixed isotopic composition).
Źródło:
Geological Quarterly; 2010, 54, 1; 25-32
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase transitions in the borate minerals from the Kłodawa Salt Dome (Central Poland) as the indicators of the temperature processes in salt diapirs
Autorzy:
Wachowiak, J.
Toboła, T.
Powiązania:
https://bibliotekanauki.pl/articles/2060065.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
boracite
congolite
phase transitions
temperature study
Zechstein
salt dome
Kłodawa
Polska
Opis:
The diapiric structures of the Polish Lowlands are tectonically deeply seated down to the autochthonous Zechstein strata at a depth of ca. 6 km. In the process of deep burial and halokinetic diapirism, the salt rocks were subjected to diagenetic and metamorphic transformations, with the temperature being an essential factor. Considering the thermal gradient, a temperature of up to ca. 200°C can be achieved in the salt dome within a depth range from several hundred metres to 6 km, which may lead to transformations of the majority of salt minerals. Phase transitions of two borate minerals – boracite and congolite from the Kłodawa salt dome – provide evidence for higher temperatures in the salt dome rocks. The authigenic euhedral crystals of those borate minerals display their external habitus in ambient temperature in the form of regular symmetry (F43c – pseudo-regular polyhedrons), whereas their internal structure is lower: orthorhombic (Pca21) for boracite and rhombohedral (R3C) for congolite. The heating and cooling of boracite and congolite crystals show reversible phase transition. At a temperature of ca. 270°C, boracite crystals change their symmetry: orthorhombic ↔ cubic. In the case of congolite three reversible phase transitions within a temperature range of 50–339°C can be observed: rhombohedral ↔ monoclinic ↔ orthorhombic ↔ cubic symmetry. Those phase transitions, confirmed experimentally in our study, clearly document at least local occurrences of temperatures exceeding 339°C in the Kłodawa salt dome.
Źródło:
Geological Quarterly; 2014, 58, 3; 543--554
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Monazite Th-U-total Pb geochronology and P-T thermodynamic modelling in a revision of the HP-HT metamorphic record in granulites from Stary Gierałtów (NE Orlica-Śnieżnik Dome, SW Poland)
Autorzy:
Budzyń, B.
Jastrzębski, M.
Kozub-Budzyń, G. A.
Konečný, P.
Powiązania:
https://bibliotekanauki.pl/articles/2060006.pdf
Data publikacji:
2015
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
monazite
Th-U-total Pb dating
thermodynamic modelling
granulite
Orlica-Śnieżnik Dome
Bohemian Massif
Opis:
Thermodynamic modelling and monazite Th-U-total Pb dating via electron microprobe were used to improve the pressure, temperature and timing constraints of the HP-HT metamorphic record in granulites from Stary Gierałtów (NE Orlica-Śnieżnik Dome (OSD), SW Poland). The thermodynamic calculations constrained the P-T conditions to 20-22 kbar and ca. 920ºC in the felsic to intermediate granulites and 20-22 kbar and ca. 970ºC in the mafic granulite. These conditions are considered to closely represent the peak temperatures experienced by these rocks. In the intermediate granulite, the matrix monazite and monazite inclusions in garnet and allanite yielded an age of 349±2.5 Ma. An HP-HT metamorphic event with temperature conditions exceeding 900ºC, which are greater than the closure temperatures of most geochronometers, must have disturbed and completely reset the isotopic systems, including the Th-U-Pb system in the monazite. Consequently, this resetting prevented us from constraining the age of potential earlier metamorphic events or the igneous protolith. The 349±2.5 Ma age reflects the timing of the late-stage HP-HT event and cooling below 900ºC related to the initial exhumation of the granulites. A comparison of the new P-T-t constraints with previous data from the NE Orlica-Śnieżnik Dome indicates that the activation of the channels that exhumed the HP rocks to mid-crustal depths most likely initiated at ca. 350 Ma, and all the metamorphic rocks in the OSD likely shared a common Variscan evolution after ca. 340 Ma.
Źródło:
Geological Quarterly; 2015, 59, 4; 700--717
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Monazite stability and the maintenance of Th-U-total Pb ages during post-magmatic processes in granitoids and host metasedimentary rocks: A case study from the Sudetes (SW Poland)
Autorzy:
Budzyń, B.
Jastrzębski, M.
Powiązania:
https://bibliotekanauki.pl/articles/2060191.pdf
Data publikacji:
2016
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
monazite stability
Th-U-total Pb dating
Jawornik granitoids
Kłodzko–Złoty Stok Pluton
Orlica-Śnieżnik Dome
Bohemian Massif
Opis:
The stability and maintenance of the age record of monazite during post-magmatic processes were studied in granitic and host metasedimentary rocks from the Sudetes (SW Poland). Unaltered monazite in the Kłodzko–Złoty Stok granitoid provided a Th-U-total Pb age of 329 ± 5 Ma, which was related to the late stage of pluton emplacement. In contrast, monazite in the Jawornik granitoid remained unaltered or was partially replaced by secondary phases, including (1) allanite, epidote and, occasionally, apatite; (2) cheralite, allanite and a mixture of clays, Fe oxides and possible unknown rare earth element (REE) phases; and (3) K-feldspar and cheralite with subsequent formation of titanite. Different alteration products on the thin section scale indicate the local character of the post-magmatic processes affecting monazite induced by alkali-rich fluids. The altered and unaltered monazite grains both yielded a Th-U-total Pb age of 343 ± 4 Ma. The Th-U-total Pb ages of the monazite in the accompanying metasedimentary rocks thermally affected by intruding magmas were also constrained. In the paragneiss in contact with the Jawornik granitoid, the unaltered monazite and monazite partially replaced by allanite yielded an age of 344 ± 5 Ma. The monazite from the mica schist, farther from the contact with the granitoids, exhibited an age of 336 ± 4.5 Ma. The 344–336 Ma ages exhibited a record of monazite (re)growth during prolonged Variscan metamorphism. The predominant early Viséan ages constrain the timing of the development of the Złoty Stok Skrzynka Shear Zone and the emplacement of the Jawornik granitoid intrusion. The age results, which are consistent with previous geochronology, indicate that the partial alteration of the monazite did not affect the internal domains or the maintenance of the monazite ages. Thus, this study reveals that monazite geochronology can provide meaningful data in crystalline rocks affected by fluid-induced post-magmatic processes.
Źródło:
Geological Quarterly; 2016, 60, 1; 106--123
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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