Lithospheric discontinuities beneath the U.S. Midcontinent – signatures of Proterozoic terrane accretion and failed rifting

Chen Chen, Hersh Gilbert, Karen M. Fischer, Christopher L. Andronicos, Gary L. Pavlis, Michael W. Hamburger, Stephen Marshak, Timothy H Larson, Xiaotao Yang

Research output: Contribution to journalArticle

Abstract

Seismic discontinuities between the Moho and the inferred lithosphere–asthenosphere boundary (LAB) are known as mid-lithospheric discontinuities (MLDs) and have been ascribed to a variety of phenomena that are critical to understanding lithospheric growth and evolution. In this study, we used S-to-P converted waves recorded by the USArray Transportable Array and the OIINK (Ozarks–Illinois–Indiana–Kentucky) Flexible Array to investigate lithospheric structure beneath the central U.S. This region, a portion of North America's cratonic platform, provides an opportunity to explore how terrane accretion, cratonization, and subsequent rifting may have influenced lithospheric structure. The 3D common conversion point (CCP) volume produced by stacking back-projected Sp receiver functions reveals a general absence of negative converted phases at the depths of the LAB across much of the central U.S. This observation suggests a gradual velocity decrease between the lithosphere and asthenosphere. Within the lithosphere, the CCP stacks display negative arrivals at depths between 65 km and 125 km. We interpret these as MLDs resulting from the top of a layer of crystallized melts (sill-like igneous intrusions) or otherwise chemically modified lithosphere that is enriched in water and/or hydrous minerals. Chemical modification in this manner would cause a weak layer in the lithosphere that marks the MLDs. The depth and amplitude of negative MLD phases vary significantly both within and between the physiographic provinces of the midcontinent. Double, or overlapping, MLDs can be seen along Precambrian terrane boundaries and appear to result from stacked or imbricated lithospheric blocks. A prominent negative Sp phase can be clearly identified at 80 km depth within the Reelfoot Rift. This arrival aligns with the top of a zone of low shear-wave velocities, which suggests that it marks an unusually shallow seismic LAB for the midcontinent. This boundary would correspond to the top of a region of mechanically and chemically rejuvenated mantle that was likely emplaced during late Precambrian/early Cambrian rifting. These observations suggest that the lithospheric structure beneath the Reelfoot Rift may be an example of a global phenomenon in which MLDs act as weak zones that facilitate the removal of cratonic lithosphere that lies beneath.

Original languageEnglish (US)
Pages (from-to)223-235
Number of pages13
JournalEarth and Planetary Science Letters
Volume481
DOIs
StatePublished - Jan 1 2018

Fingerprint

rifting
terrane
Proterozoic
discontinuity
accretion
signatures
lithosphere
Shear waves
Chemical modification
lithospheric structure
Minerals
Water
arrivals
Precambrian
hydrous mineral
asthenosphere
Moho
intrusion
P waves
stacking

Keywords

  • Reelfoot Rift
  • Sp receiver function
  • U.S. Midcontinent
  • lithosphere–asthenosphere boundary
  • mid-lithospheric discontinuity
  • terrane accretion

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Lithospheric discontinuities beneath the U.S. Midcontinent – signatures of Proterozoic terrane accretion and failed rifting. / Chen, Chen; Gilbert, Hersh; Fischer, Karen M.; Andronicos, Christopher L.; Pavlis, Gary L.; Hamburger, Michael W.; Marshak, Stephen; Larson, Timothy H; Yang, Xiaotao.

In: Earth and Planetary Science Letters, Vol. 481, 01.01.2018, p. 223-235.

Research output: Contribution to journalArticle

Chen, Chen ; Gilbert, Hersh ; Fischer, Karen M. ; Andronicos, Christopher L. ; Pavlis, Gary L. ; Hamburger, Michael W. ; Marshak, Stephen ; Larson, Timothy H ; Yang, Xiaotao. / Lithospheric discontinuities beneath the U.S. Midcontinent – signatures of Proterozoic terrane accretion and failed rifting. In: Earth and Planetary Science Letters. 2018 ; Vol. 481. pp. 223-235.
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AU - Pavlis, Gary L.

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AU - Larson, Timothy H

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