Mantle earthquakes in recently thinned Neoproterozoic lithosphere: Harrat Lunayyir, Saudi Arabia

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Authors

Alexander Robert Blanchette , Simon L Klemperer, Walter D Mooney, Hani M Zahran

Abstract

We use earthquake geothermometry, measured heat flow, and structural constraints from P-wave receiver functions to model the thermal evolution of the lithosphere beneath Harrat Lunayyir. We suggest that the lithosphere thinned to its present 60-km thickness in a second stage of lithospheric thinning at 15–12 Ma following initial Red Sea extension at ~27 Ma. Harrat Lunayyir is an active volcanic field located in the Arabian Shield > 150 km east of the Red Sea rift axis. In the lithospheric mantle beneath Harrat Lunayyir we locate 64 high-frequency earthquakes at depths of 42–48 km, all with mL ≤ 2.5. These brittle-failure earthquakes must have nucleated at relatively low temperatures, based upon global maximum nucleation depths and temperature-dependent-deformation experimental results. Therefore, the mantle earthquakes show that the upper-mantle lithosphere is not in thermal equilibrium with the shallow (60 km) underlying asthenosphere. Our thermal modeling indicates that the lithosphere beneath Harrat Lunayyir thinned to its current 60-km thickness at 12 ± 2 Ma, as constrained by thermal modeling of: (1) surface heat-flow; (2) the depth to the mid-crustal brittle-ductile transition, and (3) the depth to the upper-mantle brittle-ductile transition.

DOI

https://doi.org/10.31223/X54S43

Subjects

Geophysics and Seismology, Tectonics and Structure

Keywords

Saudi Arabia, Red Sea Rifting, cratonic rejuvenation, lithosphere-asthenosphere boundary

Dates

Published: 2020-11-20 08:26

Last Updated: 2020-11-20 16:25

License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
None

Data Availability (Reason not available):
Data is available upon request from the Saudi Geological Survey (SGS).

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