Magmatic and tectonic extension at the Chile Ridge : evidence for mantle controls on ridge segmentation
Howell, Samuel M.
Ito, Garrett T.
Behn, Mark D.
Escartin, Javier E.
MetadataShow full item record
KeywordChile Ridge; Active upwelling; Abyssal hill evolution; Faulting and magmatism; Ridge morphology
We use data from an extensive multibeam bathymetry survey of the Chile Ridge to study tectonomagmatic processes at the ridge axis. Specifically, we investigate how abyssal hills evolve from axial faults, how variations in magmatic extension influence morphology and faulting along the spreading axis, and how these variations correlate with ridge segmentation. The bathymetry data are used to estimate the fraction of plate separation accommodated by normal faulting, and the remaining fraction of extension, M, is attributed primarily to magmatic accretion. Results show that M ranges from 0.85 to 0.96, systematically increasing from first-order and second-order ridge segment offsets toward segment centers as the depth of ridge axis shoals relative to the flanking highs of the axial valley. Fault spacing, however, does not correlate with ridge geometry, morphology, or M along the Chile Ridge, which suggests the observed increase in tectonic strain toward segment ends is achieved through increased slip on approximately equally spaced faults. Variations in M along the segments follow variations in petrologic indicators of mantle melt fraction, both showing a preferred length scale of 50 ± 20 km that persists even along much longer ridge segments. In comparison, mean M and axial relief fail to show significant correlations with distance offsetting the segments. These two findings suggest a form of magmatic segmentation that is partially decoupled from the geometry of the plate boundary. We hypothesize this magmatic segmentation arises from cells of buoyantly upwelling mantle that influence tectonic segmentation from the mantle, up.
Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 17 (2016): 2354–2373, doi:10.1002/2016GC006380.
Showing items related by title, author, creator and subject.
Stratus 15 fifteenth setting of the Stratus Ocean Reference Station cruise on board RV Cabo de Hornos June 15 – 29, 2016 Valparaiso, Chile – Valparaiso, Chile Bigorre, Sebastien P.; Weller, Robert A.; Lord, Jeffrey; Hasbrouck, Emerson; Pietro, Benjamin; Gazale, Dario Torres; Jiménez, Ignacio Burgos (Woods Hole Oceanographic Institution, 2016-10)The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide ongoing climate-quality records of surface meteorology, air-sea fluxes of heat, freshwater, and ...
Post-seismic viscoelastic deformation and stress transfer after the 1960 M9.5 Valdivia, Chile earthquake : effects on the 2010 M8.8 Maule, Chile earthquake Ding, Min; Lin, Jian (Oxford University Press, 2014-03-04)After the 1960 M9.5 Valdivia, Chile earthquake, three types of geodetic observations were made during four time periods at nearby locations. These post-seismic observations were previously explained by post-seismic afterslip ...
Stratus 13 thirteenth setting of the Stratus Ocean Reference Station cruise on board RV Ron Brown February 25 - March 15, 2014 Valparaiso, Chile - Arica, Chile Bigorre, Sebastien P.; Weller, Robert A.; Lord, Jeffrey; Galbraith, Nancy R.; Whelan, Sean P.; Coleman, James; Contreras, Marcela Pas; Aguilera, Cristobal (Woods Hole Oceanographic Institution, 2014-07)The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide ongoing climate-quality records of surface meteorology, air-sea fluxes of heat, freshwater, and ...