Journal cover Journal topic
Solid Earth An interactive open-access journal of the European Geosciences Union

Journal metrics

  • IF value: 3.495 IF 3.495
  • IF 5-year<br/> value: 3.386 IF 5-year
    3.386
  • CiteScore<br/> value: 3.70 CiteScore
    3.70
  • SNIP value: 0.783 SNIP 0.783
  • SJR value: 1.039 SJR 1.039
  • IPP value: 1.987 IPP 1.987
  • h5-index value: 20 h5-index 20
https://doi.org/10.5194/se-2017-45
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
11 May 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Solid Earth (SE) and is expected to appear here in due course.
Constraints on the rheology of lower crust in a strike-slip plate boundary: Evidence from the San Quintin xenoliths, Baja California, Mexico
Thomas van der Werf1, Vasileios Chatzaras1,2, Leo M. Kriegsman1,3, Andreas Kronenberg4, Basil Tikoff2, and Martyn R. Drury1 1Department of Earth Sciences, Utrecht University, Utrecht, Netherlands
2Department of Geoscience, University of Wisconsin - Madison, Madison, Wisconsin, USA
3Department of Research & Education, Naturalis Biodiversity Center, Leiden, Netherlands
4De partment of Geology and Geophysics, Texas A&M University, College Station, Texas, USA
Abstract. The rheology of lower crust and its time-dependent behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of mafic granulite and lherzolite xenoliths from the Holocene San Quintin volcanic field, of northern Baja California, Mexico. The San Quintin volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. Combining microstructural observations, geothermometry and phase equilibria modeling we constrain that crystal-plastic deformation took place at temperatures of 750–900 °C and pressures of 400–580 MPa, corresponding to 15–22 km depth. A hot crustal geothermal gradient of 40 °C/km is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is dry. Microstructural evidence suggests that the mafic granulite and peridotite xenoliths were dominantly deforming by processes transitional between dislocation creep and diffusion creep. Recrystallized grain size paleopiezometry yields similar differential stresses in both the uppermost lower crust and upper mantle. Using dry-plagioclase and dry-olivine flow laws we demonstrate that the viscosity of the lower crust and upper mantle is low (2.2 × 1018 – 1.4 × 1020 Pa s). Comparing the viscosity structure of the lithosphere constrained from the San Quintin xenoliths with results from post-seismic relaxation studies from western US, we suggest that lower crust is stronger during transient deformation (e.g., post-seismic relaxation period) while the upper mantle is stronger during long-term deformation (e.g., interseismic period).

Citation: van der Werf, T., Chatzaras, V., M. Kriegsman, L., Kronenberg, A., Tikoff, B., and R. Drury, M.: Constraints on the rheology of lower crust in a strike-slip plate boundary: Evidence from the San Quintin xenoliths, Baja California, Mexico, Solid Earth Discuss., https://doi.org/10.5194/se-2017-45, in review, 2017.
Thomas van der Werf et al.
Thomas van der Werf et al.

Viewed

Total article views: 578 (including HTML, PDF, and XML)

HTML PDF XML Total Supplement BibTeX EndNote
488 76 14 578 26 2 10

Views and downloads (calculated since 11 May 2017)

Cumulative views and downloads (calculated since 11 May 2017)

Viewed (geographical distribution)

Total article views: 578 (including HTML, PDF, and XML)

Thereof 572 with geography defined and 6 with unknown origin.

Country # Views %
  • 1

Saved

Discussed

Latest update: 16 Dec 2017
Publications Copernicus
Download
Short summary
The behavior of Earth’s deep crust affects seismicity in tectonic plate boundaries where two plates slide past each other. We studied rocks from the deep crust and shallow mantle beneath Baja California, Mexico, transferred to the surface through volcanoes. These rocks provide unique constraints on the deformation processes in the Pacific-Baja California plate boundary, and show that lithosphere is hot, weak, and its strength as a function of depth changes over time during the earthquake cycle.
The behavior of Earth’s deep crust affects seismicity in tectonic plate boundaries where two...
Share