Browsing by Subject "thermodynamic modeling"

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Charakterystyka petrologiczna wybranych skał formacji Isbjørnhamna, SW Spitsbergen
(Data obrony: 2016-06-30) Figura, Paulina
Wydział Geologii, Geofizyki i Ochrony Środowiska
Grupa Isbjørnhamna jest jedną z najstarszych i najmocniej przeobrażonych formacji skalnych w południowo-zachodniej prowincji Svalbardu. Budują ją metasedymenty przeobrażone w warunkach facji amfibolitowej. W niniejszej pracy analizie petrologicznej poddano metapelity formacji Revdalen, Grupy Isbjørnhamna oraz oszacowano warunki metamorfizmu stosując klasyczną geotermobarometrię oraz modelowanie termodynamiczne. Dokładne odtworzenie ścieżki P-T tych utworów pomoże w określeniu ich egzotycznego do dziś pochodzenia oraz korelacji z kaledonitami terranu Pearya na wyspie Ellesmere w Kanadzie.
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Metamorphic evolution of the Seve Nappe Complex in the Scandinavian Caledonides of west-central Sweden
(Data obrony: 2012-09-12) Klonowska, Iwona
Wydział Geologii, Geofizyki i Ochrony Środowiska
The Seve Nappe Complex in the Caledonides of western Jämtland (Sweden) is composed of high grade metamorphic rocks, mainly amphibolite facies metasediments and granulite facies gneisses, locally migmatized, with rare eclogites and peridotites. Within ?reskutan Nappe of west-central Jämtland (studied area), kyanite-bearing leucogranulites are found. Conventional geothermobarometry and thermodynamic modeling were utilized to constrain metamorphic conditions. Phg (Si apfu), Grt-Phg, Grt-Phg-Ky-Qtz geothermobarometers and modeled phase equilibria for high pressure assemblages (garnet, phengite) in NCKFMMnASH system indicate peak pressure conditions of 24-32 kbar at temperature of ~700°C. The decompression stage together with partial melting is inferred from GASP barometer, ternary feldspar modeling, kyanite-sillimanite transition, assemblages of biotite-plagioclase and melt occurrence (phase diagrams). Decompression to pressures of ~5kbar is simultaneous with increase of temperature to ~800-820°C and partial melting initiated by micas, what was followed by cooling and crystallization of melt. Geothermobarometry and modeling approach connected with field work observations and microtextures analysis show the innovative conception of ?reskutan’s Nappe HP and HT history. It enabled getting a more complete picture of the SNC evolution during Caledonies orogeny formation.
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New evidence for high pressure metamorphism in the Caledonian basement of south-west Svalbard
(Data obrony: 2013-07-25) Kośmińska, Karolina
Wydział Geologii, Geofizyki i Ochrony Środowiska
Recent fieldwork in western part of Nordenskiold Land (W-Svalbard) has established the presence of blueschists. They are strongly retrogressed and the original progressive and peak HP assemblages are vastly replaced by later, lower pressure assemblages. The P-T conditions were estimated using the phase equilibrium modeling in the NCKFMMnASHTO system. P-T estimates indicate peak pressure conditions of c. 20 kbar and 480 oC. Blueschists from Nordenskiold Land indicate a geothermal gradient of 7 oC/km, which provides evidence for a unique cold subduction event in Paleozoic. These results are in agreement with the P-T estimates for the HP unit known from Oskar II Land (Motalafjella region). New evidence for blueschist facies metamorphism in Nordenskiold Land suggests that the extent of the HP-LT metamorphism on Svalbard is larger than previously supposed.