Preliminary Anisotropy of Magnetic Susceptibility and Paleomagnetic Data from Mafic Dikes in the Chili Quadrangle, Rio Arriba County, New Mexico
Abstract
Migration of magma at shallow levels of the crust is a fundamental process that has bearing on the construction of volcanoes, associated hazards in active volcanic terranes, and igneous mass redistribution in near surface environments. This study examines a suite of Miocene mafic dikes in the Española Basin, north-central NM. The problems addressed by this research involves: 1) collect paleomagnetic data from the dikes to discern components of vertical-axis rotation across structural blocks, between separate dikes, and along strike within individual dikes, and 2) obtain anisotropy of magnetic susceptibility (AMS) data, thin section, and field observations, to infer magma flow within each dike and document any variation in magma flow patterns within the swarm. We plan to test the following hypotheses: 1) the mafic dikes experienced some degree of vertical axis rotation associated with rifting and/or intrusion of younger dikes 2) the magma flow pattern within the dikes reflects lateral emplacement with flow directed away from the magma ascent location. Low-field susceptibility versus temperature experiments yield a spectrum of results reflecting thermomagnetic behavior typical of intermediate composition titanomagnetite while others exhibit a more complex behavior with the presence of two or more magnetic phases. Curie point estimates range from ~ 100°C to 575°C indicating a range of moderate to low Ti- titanomagnetite compositions as well as some evidence of a Fe-sulfide phase, possibly pyrrhotite. AMS fabric data reveal a combination of both prolate and oblate susceptibility ellipsoids. At several sites, the fabrics are oblate from the paired dike margins and reveal a unique magma flow direction. Susceptibility values are high and consistent with a ferromagnetic phase providing encouraging evidence that the remanence is likely a primary thermoremanent magnetization and geologically stable. Paleomagnetic analysis is underway and should help further constrain the emplacement of the dikes and tectonic evolution of the study area.Additional paleomagnetic data will aide in constraining the tectonic and thermal history of the dikes and provide insight into the regional deformation of the area. AMS data should document the direction of magma flow within each intrusion allowing us to deduce the source region of the magma body.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMGP23A1038T
- Keywords:
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- 1518 GEOMAGNETISM AND PALEOMAGNETISM / Magnetic fabrics and anisotropy;
- 1527 GEOMAGNETISM AND PALEOMAGNETISM / Paleomagnetism applied to geologic processes;
- 8400 VOLCANOLOGY;
- 8486 VOLCANOLOGY / Field relationships