Upper mantle tomographic Vp and Vs, images of the Rocky Mountains in Wyoming, Colorado and New Mexico

evidence for a thick heterogeneous chemical lithosphere

Huaiyu Yuan, Ken Dueker

Research output: Chapter in Book/Report/Conference proceedingChapter

21 Citations (Scopus)

Abstract

Upper mantle tomographic body wave images from the CD-ROM deployment reveal two major lithospheric anomalies across two primary structural boundaries in the southern Roclq Mountains: a ~200 km deep high velocity north-dipping "Cheyenne slab" beneath the Archean-Proterozoic Cheyenne belt, and a 100 km deep low velocity "Jemez body" beneath the Proterozoic-Proterozoic Jemez suture. The Cheyenne slab is most likely a slab fragment accreted against the Archean Wyoming during the Proterozoic arc collision processes. This interpretation suggests that the ancient slab's thermal signature has been diffused away and non-thermal explanations for the high velocity slab are required. Tomographic modeling of possible chemical and anisotropic velocity variations associated with the slab shows that our isotropic velocity images can be explained via non-thermal models. In addition, the de-correlation of the Pand S-velocity images and tlie CD-ROM shear-wave splitting modeling are consistent with a dipping slab. The Jemez body plausibly results from the combination of lowsolidus materials in the suture lithosphere and the late Cenozoic regional heating of the lithosphere. The 100 km deep lithospheric layering and the uniform shear-wave splitting measurements support our contention that the Jemez body is a lithospheric anomaly. A third low velocity structure extends beneath the middle RIO Grande Rift to 300 km depth. This asnomaly may manifest a thermal upwelling that could increase heat flow into the lithosphere. Our results suggest that lithospheric heterogeneities related to fossil accretionary processes have been preserved in the Precambrian sutures, and are preferentially affecting the subsequent tectonism in this region.

Original languageEnglish
Title of host publicationThe Rocky Mountain Region
Subtitle of host publicationan evolving lithosphere: tectonics, geochemistry, and geophysics
EditorsKarl E. Kalstrom, G. Randy Keller
Place of PublicationWashington, D.C.
PublisherAmerican Geophysical Union
Pages329-345
Number of pages17
ISBN (Electronic)9781118666326
ISBN (Print)0875904181, 9780875904191
DOIs
Publication statusPublished - 2005
Externally publishedYes

Publication series

NameGeophysical Monograph Series
PublisherAmerican Geophysical Union
Volume154
ISSN (Print)0065-8448

Keywords

  • Core-mantle boundary
  • Geology, Structural-Rocky Mountains
  • Geophysics-Rocky Mountains
  • Orogeny-Rocky Mountains

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    Yuan, H., & Dueker, K. (2005). Upper mantle tomographic Vp and Vs, images of the Rocky Mountains in Wyoming, Colorado and New Mexico: evidence for a thick heterogeneous chemical lithosphere. In K. E. Kalstrom, & G. R. Keller (Eds.), The Rocky Mountain Region: an evolving lithosphere: tectonics, geochemistry, and geophysics (pp. 329-345). (Geophysical Monograph Series; Vol. 154). Washington, D.C.: American Geophysical Union. https://doi.org/10.1029/154GM25