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From deposition to caldera resurgence: pyroclastic density current dynamics as revealed by magnetic anisotropy of the Teplice rhyolite, Bohemian Massif
Vitouš, Petr ; Tomek, Filip (advisor) ; Mlčoch, Bedřich (referee)
Better understanding of pyroclastic density current (PDC) dynamics is one of the key volcanological focuses, as PDCs represent one of the most life-threatening volcanic hazards. PDCs associated with explosive collapse calderas are difficult to observe and examine directly, and thus research of internal architecture of calderas and their PDC deposits is focused on extinct and partly eroded volcano-plutonic systems. Such a case is the Late-Carboniferous Altenberg-Teplice caldera in NW Bohemian Massif, which exposes a large body of ignimbrites (deposits of the PDC) called Teplice rhyolite (an intra-caldera fill). This body is well exposed on the southern flank of the Krušné hory/Erzgebirge Mts., mainly its members: Teichweg, Lugstein-Pramenáč, Vlčí kámen-Medvědí vrch and Přední Cínovec. As these ignimbrites appear macroscopically isotropic, I employed the Anisotropy of magnetic susceptibility (AMS) in order to quantify their internal structure. A total of 1232 specimens from 63 sampling stations were analyzed for the AMS, complemented by susceptibility vs. temperature variations and petrographic observations. Obtained AMS data, carried by a mixture of paramagnetic ferrosilicates and low-Ti titanomagnetite, indicate various processes recorded in ignimbrites. The relatively oldest and moderately welded Teichweg...
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From deposition to caldera resurgence: pyroclastic density current dynamics as revealed by magnetic anisotropy of the Teplice rhyolite, Bohemian Massif
Vitouš, Petr ; Tomek, Filip (advisor) ; Mlčoch, Bedřich (referee)
Better understanding of pyroclastic density current (PDC) dynamics is one of the key volcanological focuses, as PDCs represent one of the most life-threatening volcanic hazards. PDCs associated with explosive collapse calderas are difficult to observe and examine directly, and thus research of internal architecture of calderas and their PDC deposits is focused on extinct and partly eroded volcano-plutonic systems. Such a case is the Late-Carboniferous Altenberg-Teplice caldera in NW Bohemian Massif, which exposes a large body of ignimbrites (deposits of the PDC) called Teplice rhyolite (an intra-caldera fill). This body is well exposed on the southern flank of the Krušné hory/Erzgebirge Mts., mainly its members: Teichweg, Lugstein-Pramenáč, Vlčí kámen-Medvědí vrch and Přední Cínovec. As these ignimbrites appear macroscopically isotropic, I employed the Anisotropy of magnetic susceptibility (AMS) in order to quantify their internal structure. A total of 1232 specimens from 63 sampling stations were analyzed for the AMS, complemented by susceptibility vs. temperature variations and petrographic observations. Obtained AMS data, carried by a mixture of paramagnetic ferrosilicates and low-Ti titanomagnetite, indicate various processes recorded in ignimbrites. The relatively oldest and moderately welded Teichweg...
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Record of mechanical processes during emplacement of shallow-level postcaldera intrusions: an example from Cínovec granite, Bohemian Massif
Vitouš, Petr ; Tomek, Filip (advisor) ; Trubač, Jakub (referee)
Collapse calderas are volcanic depressions created by emptying of underlying magma chamber during volcanic eruption and following fall of upper layers. After this the event is often succeeded by resurgence and magma chamber is filled with new magma, which may lead to creation of dike complexes and laccoliths. Inner structure of these resurgent magmatic bodies is defined by many processes like injection of magma, flow and deformation by local and regional stress fields. During crystallization, magma is still vulnerable to deformation, crystals may react to these deformations and orient themselves to it, and the inner structure may become overprinted. So, the creation of magmatic structures happens during final stages of emplacement and records only the last increment of deformation of magma. For studying the existence of inner structures even from macroscopically isotropic rocks, which may show the characteristics of mechanisms of creation of these rocks, I chose the anisotropy of magnetic susceptibility technique (AMS). This work is focused on the Cínovec granite in the Altenberg- Teplice caldera, Krušné hory mountains on the border between Czechia and Germany. Apart from the studied Cínovec granite this caldera is penetrated by series of other granitic bodies. The result of my study is for interpretation...
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