The Taos Plateau Volcanic Field, Northern Rio Grande Rift, New Mexico
- Robert E. Riecker
Published Online: 21 MAR 2013
Copyright © 1979 by the American Geophysical Union.
Rio Grande Rift: Tectonics and Magmatism
How to Cite
Lipman, P. W. and Mehnert, H. H. (1979) The Taos Plateau Volcanic Field, Northern Rio Grande Rift, New Mexico, in Rio Grande Rift: Tectonics and Magmatism (ed R. E. Riecker), American Geophysical Union, Washington, D. C.. doi: 10.1029/SP014p0289
- Published Online: 21 MAR 2013
- Published Print: 1 JAN 1979
Print ISBN: 9780875902142
Online ISBN: 9781118664988
- Olivine andesite;
- Pre-rift and early-rift rocks;
- Silicic alkalic basalt;
- Taos plateau volcanics;
- Volcanic rocks;
- Xenocrystic basaltic andesite (XBA)
Recent mapping, major- and minor-element chemistry, and K-Ar dating indicate that the Taos Plateau, a previously undescribed volcanic field covering more than 1,500 km 2 along the Rio Grande rift in northern New Mexico, contains a compositionally diverse upper Cenozoic suite ranging from tholeiitic basalt to silicic rhyolite. Most of the suite, constituting one of the largest and compositionally most variable volcanic fields along the Rio Grande rift, was erupted between about 4.5 and 2.0 m.y. ago. Younger and older basaltic rocks occur adjacent to the Taos Plateau on each side of the rift, and early-rift and pre-rift volcanic rocks also occur adjacent to and beneath the Taos Plateau.
Despite their location in a well-developed extensional rift setting, all the Taos Plateau rocks were erupted from central volcanoes, 35 of which have thus far been identified. An imperfect concentric pattern, about 50 km across, characterizes the distribution of the larger volcanoes: tholeiitic shields occur in the center of the volcanic field, rhyodacitic volcanoes are farthest out, and andesites occur at intermediate positions. Two smaller silicic lava domes occur in the central part of the volcanic field.
A preliminary model for the patterns of distribution and composition of the volcanic rocks involves generation of the tholeiitic magmas by relatively large degrees of partial melting at relatively shallow depth within an upward bulge of lithospheric mantle beneath the Rio Grande rift. The andesitic and rhyodacitic rocks would represent respectively smaller proportions of melting in mantle or mafic lower crust adjacent to the main basaltic thermal anomaly. Only for the volumetrically minor rhyolite and quartz latite does low-pressure fractional crystallization appear significant. This melting event appears to have been localized at the intersection between the rift and the Springerville-Raton volcanic zone, which became activated along much of its length about 4 m.y. ago.