The Rio Grande Rift in Context of Regional Post-40 M.Y. Volcanic and Tectonics Events

  1. Robert E. Riecker
  1. Wolfgang E. Elston and
  2. Theodore J. Bornhorst

Published Online: 21 MAR 2013

DOI: 10.1029/SP014p0416

Rio Grande Rift: Tectonics and Magmatism

Rio Grande Rift: Tectonics and Magmatism

How to Cite

Elston, W. E. and Bornhorst, T. J. (1979) The Rio Grande Rift in Context of Regional Post-40 M.Y. Volcanic and Tectonics Events, in Rio Grande Rift: Tectonics and Magmatism (ed R. E. Riecker), American Geophysical Union, Washington, D. C.. doi: 10.1029/SP014p0416

Author Information

  1. Department of Geology, University of New Mexico, Albuquerque, New Mexico 87131

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1979

ISBN Information

Print ISBN: 9780875902142

Online ISBN: 9781118664988



  • Intraplate block faulting;
  • Isotherms;
  • Petrogenesis;
  • Rock chemical analyses;
  • Volcanic and tectonics


In context with other post-40 m.y. volcanic and tectonic events of southwestern North America (including regional extension, possibly by hundreds of km, and eruption of 106 km3 of calc-alkalic volcanic rocks in the Basin and Range province and Sierra Madre Occidental), formation of the Rio Grande graben system is relatively local and recent. Events in New Mexico and Colorado can be interpreted in three overlapping stages (dates indicate the minimum range of each stage) .

(1) Modified Andean arc stage, 40 to 29 m.y., with calc-alkalic volcanism.

(2) Modified back-arc extension stage, 30 to 18 m.y., with eruption of basaltic andesite and related rocks and high-silica rhyolite.

(3) Intraplate block faulting, 21 m.y. to present, volcanism basaltic and locally rhyolitic.

During calc-alkalic volcanism of stage (1) and rhyolitic volcanism of stage (2), large composite plutons were passively emplaced. Their cupolas blistered and burst, resulting in individual eruptions of as much as 103 km3 of ash-flow tuff. Modified back-arc extension made room for the plutons and also explains the present 1,000 km width of the volcanic zone, its thin crust, high heat flow and Sn-wave attenuation. Extension during stage (3) was less than in stage (2). In areas of large-scale volcanism during the preceding stages, the crust broke up into a broad zone of Basin and Range fault blocks; in regions of little or no earlier volcanism the cooler and more rigid crust broke into blocks that were larger and more distinctly defined. The Rio Grande graben system assumes the characteristics of a sharply-defined rift in northern New Mexico but merges into the broader Basin and Range province as it enters the region of mid-Tertiary volcanism south of Socorro.