Rio Grande Rift in Southern New Mexico, West Texas, and Northern Chihuahua
- Robert E. Riecker
Published Online: 21 MAR 2013
Copyright © 1979 by the American Geophysical Union.
Rio Grande Rift: Tectonics and Magmatism
How to Cite
Seager, W. R. and Morgan, P. (1979) Rio Grande Rift in Southern New Mexico, West Texas, and Northern Chihuahua, in Rio Grande Rift: Tectonics and Magmatism (ed R. E. Riecker), American Geophysical Union, Washington, D. C.. doi: 10.1029/SP014p0087
- Published Online: 21 MAR 2013
- Published Print: 1 JAN 1979
Print ISBN: 9780875902142
Online ISBN: 9781118664988
- Deep thermal structure;
- Geologic and geophysical data;
- Resistivity and conductivity models;
- Rift basalts and magma genesis;
- Rio grande rift;
- Tectono-magmatic evolution;
- Thermal conditions;
Relative to adjacent more stable areas the Rio Grande rift is a tectonically active, thermally anomalous structure distinguished throughout its length by the combination of high heat flow, recently active volcanoes, exceptionally deep basins and late Quaternary faulting. These features are interpreted to be shallow manifestations of an asthenosphere upwarp, thinned crust containing dike swarms, and an associated thermal regime beneath the rift, an hypothesis consistent with a variety of geophysical data from the southern as well as the northern portions of the rift. The shallow features can also be used (collectively) to trace the Rio Grande rift into far west Texas and northern Chihuahua, where the rift appears to end as a distinct thermotectonic system.
The southern Rio Grande rift has taken about 26 to 28 m.y. to evolve to its present state. Alkali olivine basalts first appear in the southern rift about 13 m.y. ago, and these may mark a time when, after 13 to 15 m.y. of extension, the crust became critically stretched, thus allowing partial melting in the upper mantle bulge beneath. An apparent increase, and perhaps peaking of basaltic magmatism in the last 5 m.y. probably was triggered by the accelerated rate of thinning of the crust associated with the culmination of rifting 3 to 8 m.y. ago. Xenolith studies show that these basalts came from the 50 to 70 km depth range in the upper mantle. The culmination of rifting resulted in thin-skinned styles of faulting in regions of exceptionally high heat flow and rapid extension while more widely spaced horst and graben structure developed elsewhere. Rates of faulting appear to have declined in the last 2 to 3 m.y.