Geological and geophysical investigation of the Mid‐Cayman Spreading Centre: seismic velocity measurements and implications for the constitution of layer 3

J. A. Karson, P. J. Fox

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Summary. In this paper we present laboratory measurements of compressional and shear wave velocities of a diverse suite of gabbroic rocks collected from the walls of the Mid‐Cayman Spreading Centre with DSRV Alvin. The degree of deformation and alteration affecting these gabbros is quite variable, and we believe that they are typical of plutonic rocks emplaced at shallow levels (upper portion of seismic layer 3 and shallower) of the oceanic crust. The compositional and textural variations are reflected in the wide range of laboratory velocities which span most of the range of seismic velocities reported for oceanic and ophiolite rock samples including basalts, gabbros, ultramafics, and their altered derivatives. Based upon the laboratory velocities and the geological setting of the Mid‐Cayman gabbros, it is argued that no unique lithology, except anhydrous peridotite, can be unequivocally identified in the oceanic lithosphere from seismic velocity data alone. Furthermore, these data allow for the possibility of considerable lithologic heterogeneity within portions of the oceanic crust at the scale of a few centimetres to a few hundred metres. Such heterogeneities would go unrecognized because seismic refraction studies mask these variations resulting in a picture of apparent uniformity.

Original languageEnglish (US)
Pages (from-to)389-411
Number of pages23
JournalGeophysical Journal of the Royal Astronomical Society
Volume85
Issue number2
DOIs
StatePublished - Apr 1986
Externally publishedYes

Keywords

  • compressional wave velocities
  • gabbroic rocks
  • oceanic crust
  • ophiolites
  • seismic refraction
  • seismic velocities

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Fingerprint Dive into the research topics of 'Geological and geophysical investigation of the Mid‐Cayman Spreading Centre: seismic velocity measurements and implications for the constitution of layer 3'. Together they form a unique fingerprint.

  • Cite this