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2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 47-43
Presentation Time: 9:00 AM-5:30 PM

PALEOMAGNETIC, ANISOTROPY OF MAGNETIC SUSCEPTIBILITY, AND GEOCHRONOLOGIC DATA FROM THE BUENA VISTA INTRUSION, NORTH-CENTRAL NEW MEXICO


CASTILLO, Geno1, PETRONIS, Michael2, LINDLINE, Jennifer3, ZEBROWSKI, J.P.4, MCCARTHY, William5, LEMEN, Daren1 and MCINTOSH, William6, (1)Environmental Geology, Natural Resource Management Department, New Mexico Highlands University, Las Vegas, NM 87701, (2)Environmental Geology, Natural Resource Managment, New Mexico Highlands University, PO Box 9000, Las Vegas, NM 87701, (3)Natural Resources Management Department, New Mexico Highlands University, P.O. Box 9000, Las Vegas, NM 87701, (4)Natural Resources Management, New Mexico Highlands University, Box 9000, Las Vegas, NM 87701, (5)Irvine Building, University of St Andrews, North Street, St Andrews, KY16 9AL, Fife,, Irvine Building, University of St Andrews, North Street, St Andrews, KY16 9AL, Fife,, Irvine Building, University of St Andrews, North Street, St Andrews, KY16 9AL, Fife,, St Andrews,, Scotland, (6)New Mexico Bureau of Geology and Mineral Resources, New Mexico Tech, 801 Leroy Place, Socorro, NM 87801, mspetro@nmhu.edu

The Buena Vista intrusion outcrops on the eastern side of the Sangre de Cristo Mountains near the transition between the Rocky Mountains and the Great Plains. Along the five kilometer strike of the intrusion, at least (?) three compositionally distinct phases occur. These include a marginal augite porphyritic basalt, a main-phase hornblende gabbro, and a central plagioclase-rich (tourmaline anorthosite) phase. This region has historically been viewed as an amagmatic region during the mid-Miocene with intrusive and extrusive magmatism occurring during the latest Miocene to Pleistocene. Four of the five new 40Ar/39Ar age determinations, however, yield generally well-defined plateau or isochron ages that range in age from 14.71 Ma to 14.20 Ma placing igneous emplacement in the mid-Miocene. In order to assess the emplacement mode, and along-strike variation in emplacement style and/or deformation, we conducted detailed rock magnetic, paleomagnetic, and anisotropy of magnetic susceptibility studies. The primary magnetic phase is a cubic, Fe-Ti oxide phase (titanomagnetite) of a pseudosingle domain to multi-domain grain size with low to moderate Ti substitution. Paleomagnetic data from thirteen of the eighteen sites yield dominantly a single component reverse polarity magnetization that is clockwise discordant to the mid-Miocene expected direction. AMS data from fifteen of eighteen sites yield remarkably consistent results along strike, characterized by well-defined oblate susceptibility ellipsoids with magnetic foliation planes that strike parallel to the trend of the dike and K1 magnetic lineations that trend south-southwest with a low plunge (< 30°). We postulate that the region east of the Sangre de Cristo range, at this latitude, experienced a modest amount of clockwise vertical axis rotation and that magma emplacement occurred via flow sub-horizontally from the north-northeast to the south-southwest. The Buena Vista intrusion is part of the until now, a previously unrecognized suite of igneous intrusions emplaced during the middle Miocene. We informally define this region as the Las Vegas Igneous Province.

Session No. 47--Booth# 465

Tectonics/Tectonophysics (Posters)
Sunday, 1 November 2015: 9:00 AM-5:30 PM
Exhibit Hall (Baltimore Convention Center)
Geological Society of America Abstracts with Programs. Vol. 47, No. 7, p.159
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