Extrusive upper crust formation at slow-spreading ridges: Fault steering of lava flows

Type Article
Date 2021-12
Language English
Author(s) Gini C.1, 3, Escartín J.ORCID2, Cannat M.ORCID3, Barreyre ThibautORCID4
Affiliation(s) 1 : Dept. of Earth Sciences, Memorial University of Newfoundland, St. John's, Canada
2 : Laboratoire de Géologie, UMR 8538, Ecole Normale Supérieure, PSL Research University, CNRS, Paris, France
3 : Université de Paris, Institut de Physique du Globe de Paris, UMR 7154, CNRS, Paris, France
4 : Centre for Deep Sea Research, University Bergen, Bergen, Norway
Source Earth And Planetary Science Letters (0012-821X) (Elsevier BV), 2021-12 , Vol. 576 , P. 117202 (11p.)
DOI 10.1016/j.epsl.2021.117202
WOS© Times Cited 1
Keyword(s) faulting, submarine volcanism, lava flows, morphology

The structure of the oceanic upper volcanic crust is less understood at slow-spreading ridges than at faster ones. Its construction is dominated by pillow lavas, reflecting lower effusion rates than those at fast spreading ridges, where sheet and lobate flows are common and flow off-axis while thickening the extrusive volcanic layer. Based on optical and high-resolution bathymetry data from the Lucky Strike segment (Mid-Atlantic Ridge), we document a mode of volcanic emplacement that likely operates at some magmatically robust slow- and ultra-slow spreading ridge segments, in the presence of strong gradients in magma supply. In these settings, sheet flows may efficiently transport melt away from magmatically robust segment centers in the along-axis direction, steered by normal faults, and exploiting along-axis topographic gradients, with limited across-axis flow. Surface lineations of sheet lava flows tend to be subparallel to fault scarps and the overall segment orientation, and show whorls, well-developed lava channels with associated levees, and surface fold structures at flow fronts. This mode of lava emplacement transitions away from the segment center to pillow-dominated seafloor near the segment ends, associated often with hummocks and axial volcanic ridges. This results in local lava emplacement due to a melt supply that is lower than at the segment center. We propose that fault-steering of lava flows along-axis, limiting off-axis transport as observed at fast-spreading systems, may be common at both slow- and ultra-slow spreading ridges with significant along-axis changes in magma supply linked to topographic gradients. As a result, the nature and properties of the extrusive volcanic layer may vary significantly along axis owing to changes in the modes of volcanic emplacement, as transitions from sheet flows to pillow lavas may impact the porosity structure and hence the seismic properties of the extrusive layer in the oceanic upper crust.

Full Text
File Pages Size Access
11 4 MB Access on demand
3 MB Access on demand
Author's final draft 62 6 MB Open access
Top of the page