Problems and challenges in detection of pre-Mesozoic maar volcanoes: example from the Principálek Volcano in the Permian Krkonoše Piedmont Basin

0434481 - ÚSMH 2015 RIV CZ eng J - Článek v odborném periodiku
Valenta, Jan - Rapprich, V. - Stárková, M. - Skácelová, Z. - Fojtíková, Lucia - Staněk, František - Balek, Jan
Problems and challenges in detection of pre-Mesozoic maar volcanoes: example from the Principálek Volcano in the Permian Krkonoše Piedmont Basin.
Journal of Geosciences. Roč. 59, č. 3 (2014), s. 169-181. ISSN 1802-6222. E-ISSN 1803-1943
Institucionální podpora: RVO:67985891
Klíčová slova: diatreme * geophysics * volcanology * Permian * Krkonoše Piedmont Basin
Kód oboru RIV: DB - Geologie a mineralogie
Impakt faktor: 1.405, rok: 2014
http://www.jgeosci.org/detail/jgeosci.170

The Permian pyroclastic deposits on the Principálek Hill SW of Vrchlabí (Czech Republic) were investigated by means of geological mapping and geophysics. The pyroclastic rocks are exposed in several small coherent outcrops, yet many interpretations are based on debris. The preserved textures enable reconstruction of eruptive styles. The volcanism started with phreatomagmatic eruptions documented by the fine-grained tuff with accretionary lapilli at the base. Subsequently, the activity changed to phreato-Strombolian/Surtseyan producing lapilli-tuffs and lapillistones. These events were followed by a Strombolian phase as evidenced by ill-sorted scoriaceous tuff-breccias with volcanic bombs. The uppermost unit consists of welded lava agglutinates and basaltic lavas suggesting a Hawaiian style of eruption. One of the basaltic feeder necks is exposed in a small abandoned quarry. Geophysical surveys were carried out over the extent of pyroclastic deposits. These included gravimetry, magnetometry, and DC resistivity tomography. The magnetic data indicate the occurrence of basaltic dykes in the central part of the pyroclastic deposits. The DC tomography confirms the presence of dykes, enables estimation of the pyroclastic deposits thickness, and provides evidence for the size and position of the maar-diatreme. Gravity data yield an insignificant low associated with the diatreme, which is likely a product of low rock-density contrast between the diatreme and country rocks. We argue that this is due to short time gap between sedimentation and volcanic activity and also related to conjoint burial and diagenetic history of the diatreme and the surrounding country rocks.
Trvalý link: http://hdl.handle.net/11104/0238517