GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 39-21
Presentation Time: 9:00 AM-5:30 PM


LAURICELLA, Sindy, Natural Resources Management Department, New Mexico Highlands University, P.O. Box 9000, Las Vegas, NM 87701, PETRONIS, Michael, Environmental Geology Program, Natural Resources Management Department, New Mexico Highlands University, P.O. Box 9000, Las Vegas, NM 87701, RAPPRICH, Vladislav, Czech Geological Survey, Klárov 3, Prague, 118 21 Praha 1, Czech Republic, VALENTA, Jan, Institute of Rock Structure and Mechanics, Academy of Sciences of the Czech Republic, V Holesovickach 41, 182 09 Praha 8, Prague, Czech Republic and LINDLINE, Jennifer, Environmental Geology Program, Natural Resource Management Department, New Mexico Highlands University, PO Box 9000, Las Vegas, NM 87701

The Krasny Vrch maar diatreme is located within the northeast - southwest trending Eger Rift in northern Bohemia, Czech Republic. The Eger Rift is part of an intercontinental rift within the larger European Cenozoic Rift System. Magmatism within the rift is dominated by lithospheric melts that yield silica undersaturated olivine-nepheline basalt. Krasny Vrch (17.2 Ma, K-Ar) outcrops along the northwestern most part of the Eger Rift. It is well-exposed in a quarry that reveals the inner skeleton of the volcano. The quarry was opened in the mid-1960’s and mined for Tertiary basalts, kaolinite, bentonite, and uranium. Exposed along the 500 m quarry walls are basanite dikes, lava flows, sills, welded and non-welded pyroclastic material, and phreatomagmatic lapilli tuffs. Here we report paleomagnetic, rock magnetic, and anisotropy of magnetic susceptibility (AMS) data from forty-two sampling sites. To date, twenty AMS sites from paired margins of the dikes indicate primary magma flow directions to the SW-NE. Preliminary paleomagnetic data yield stable remanence directions at the site level with a high degree of dispersion between sites in the diatreme. Rock magnetic data are consistent with moderate to high Ti- titanomagnetite of a restricted grain size. Our preliminary interpretation of the data is that the diatreme did not experience a single pulse of magmatism leading to a lone phreatomagmatic eruption. We argue that the system remained active with secondary intrusions deforming the sub-volcanic roots of the system following the initial phreatomagmatic eruption.