Skip to main content

Research Repository

Advanced Search

Controls on the Thermomechanical Evolution of Hyperextended Lithosphere at Magma-Poor Rifted Margins: The Example of Espirito Santo and the Kwanza Basins

Controls on the Thermomechanical Evolution of Hyperextended Lithosphere at Magma-Poor Rifted Margins: The Example of Espirito Santo and the Kwanza Basins Thumbnail


Abstract

High-quality, long offset seismic data from many distal rifted margins show evidence for hyper-extended, <10-km-thick crust. Direct observation of such domains is challenging as they lie, at great water depth, buried beneath thick sedimentary sequences and formed by rock-assemblages that are hydrated and geophysically indistinguishable. Only a few drill holes have penetrated basement at ultradistal rifted margins. These observations, together with outcrops of preserved analogs exposed in collisional orogens, suggest that the complex interaction of detachment faults rooted in a subhorizontal shear zone in the hyperextended crust or, in the serpentinized mantle controls the formation of the ocean continent transition. While depth-dependent thinning controls the early phases of rifting conforming to classical rift models, we still have a superficial understanding of how normal faults and subhorizontal shear zones form and evolve during rifting and lithospheric breakup. Here we develop a rheological parameterization to simulate the formation of, and slip-on, large offset normal faults rooted in growing brittle to ductile shear zones. The evolution of these structures leads to the creation of a hyperextended crust and eventually exhumed serpentinized mantle. We also propose a simplified formulation to simulate magmatic underplating and seafloor spreading. The resulting numerical models provide a self-consistent picture for the evolution of magma-poor rifted margins from initiation of rifting to seafloor spreading. The model results are compared with first-order observations of the Kwanza and Espirito Santo conjugate margins in the South Atlantic as well as of magma-poor margins globally.

Acceptance Date Sep 11, 2019
Publication Date Oct 31, 2019
Publicly Available Date Mar 28, 2024
Journal Geochemistry Geophysics Geosystems
Print ISSN 1525-2027
Publisher Wiley Open Access
Pages 5148 - 5176
DOI https://doi.org/10.1029/2019GC008580
Keywords rifting; margins; hyperextension; detachment faults; numerical modeling; South Atlantic
Publisher URL https://doi.org/10.1029/2019GC008580

Files




Downloadable Citations