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Direct geological evidence for oceanic detachment faulting; the Mid-Atlantic Ridge, 15 degrees 45'N

C. J. MacLeod, J. Escartin, D. Banerji, G. J. Banks, M. Gleeson, D. H. B. Irving, R. M. Lilly, A. M. McCaig, Y. Niu, S. Allerton and D. K. Smith
Direct geological evidence for oceanic detachment faulting; the Mid-Atlantic Ridge, 15 degrees 45'N
Geology (Boulder) (October 2002) 30 (10): 879-882

Abstract

From a detailed survey and sampling study of corrugated massifs north of the Fifteen-Twenty Fracture Zone on the Mid-Atlantic Ridge, we demonstrate that their surfaces are low-angle detachment fault planes, as proposed but not previously verified. Spreading-direction-parallel striations on the massifs occur at wavelengths from kilometers to centimeters. Oriented drill-core samples from the striated surfaces are dominated by fault rocks with low-angle shear planes and highly deformed greenschist facies assemblages that include talc, chlorite, tremolite, and serpentine. Deformation was very localized and occurred in the brittle regime; no evidence is seen for ductile deformation of the footwall. Synkinematic emplacement of diabase dikes into the fault zone from an immediately subjacent gabbro pluton implies that the detachment must have been active as a low-angle fault surface at very shallow levels directly beneath the ridge axis. Strain localization occurred in response to the weakening of a range of hydrous secondary minerals at a very early stage and was highly efficient.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 30
Serial Issue: 10
Title: Direct geological evidence for oceanic detachment faulting; the Mid-Atlantic Ridge, 15 degrees 45'N
Affiliation: Cardiff University, Department of Earth Sciences, Cardiff, United Kingdom
Pages: 879-882
Published: 200210
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 29
Accession Number: 2002-075303
Categories: Solid-earth geophysicsApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Inst. Phys. Globe de Paris, Contrib. No. 1833
Illustration Description: illus. incl. sketch map
N15°40'00" - N15°54'00", W47°10'00" - W46°49'60"
Secondary Affiliation: Institut de Physique du Globe, FRA, FranceUniversity of Houston, USA, United StatesOpen University, GBR, United KingdomUniversity of Leeds, GBR, United KingdomHalliburton, GBR, United KingdomWoods Hole Oceanographic Institution, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200223
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