New Mexico Geological Society Annual Spring Meeting — Abstracts

Volcanism in the Intra-Sudetic Basin occurred in the Carboniferous and culminated in the Permian with caldera forming eruptions along the present-day Czech-Polish border. Volcanism was followed by the emplacement of trachyandesite intrusions that outcrop sparsely in the region. The apparent intrusive geometry includes laccoliths and sills emplaced along an accurate belt that rings the remains of an ignimbrite caldera that erupted the Góry Suche Rhyolitic Tuffs (GSRT). The GSRT outcrop within a NW-SE trending belt that is 50 km long and up to 10 km wide. It is estimated to have an eruption volume in the hundreds of cubic kilometers, similar to that of the northern New Mexico Bandelier Tuff ignimbrites which are the result of a super volcano eruption from one of Earth's largest and youngest calderas, the Valles Caldera. The exposed floor and ceiling of several GSRT intrusive bodies reveal that they are a single laccolith while others occur as stacked sills, and/or inclined sills crosscutting the intrusive rocks. The intrusions are dominated by coherent cores with thin envelopes of intrusive breccias and peperites along the margins. The host rocks along the contacts are strongly tilted and folded, with fold amplitudes ranging from decimeters to meters in length. The sedimentary host rocks adjacent to trachyandesites are variably recrystallized and locally silicified but lack signs of contact metamorphism. Our research aims to better understand the complex geometries and emplacement dynamics of trachyandesite intrusions exposed at two active quarries, Gardzien and Tlumaczów, and two partly flooded quarries, Swierki and Gluszyca, along the Polish-Czech border. The rock types at the four locations are similar and may indicate that the intrusions at the four quarries are connected at depth. These field sites provide a unique opportunity for the National Science Foundation supported International Research Experience for Student 2024 team to further our studies. The goals of this research are to better understand the magma plumbing system and igneous geometry. Preliminary anisotropy of magnetic susceptibility (AMS) data indicate that most of the sampled sites yield an oblate magnetic fabric. The inferred magma flow directions reveal a complex flow pattern throughout the quarry. AMS data from outcrops located near the floor and roof of the intrusion yield oblate magnetic fabrics that parallel the contacts. Prolate susceptibility ellipsoids are rare. Preliminary rock magnetic experiments suggest that the magnetic fabric is composed of multidomain grains of low-Ti titanomagnetite compositions, some evidence of maghemite, and another magnetic mineral phase potentially an iron-sulfide phase. Paleomagnetic data yield a high coercivity, characteristic remanent magnetization carried by titanohematite, that plots near the expected late Paleozoic direction, and a secondary component of magnetization, carried by titanomagnetite. The active quarries at Gardzien and Tlumaczów provide three-dimensional exposure of trachyandesite intrusive geometries and contact relationships. The ongoing exploration will offer additional insight into the nature of Permian igneous activity associated with the Góry Suche caldera eruption and emplacement of the post-caldera trachyandesite intrusions specifically and catastrophic caldera-forming eruptions in general.