Geophysical signatures of past and present hydration within a young oceanic core complex

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doi: 10.1002/2013GL058111
Author(s): Blackman, Donna K.; Slagle, Angela L.; Guerin, Gilles; Harding, Alistair
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, La Jolla, CA, United States
Other:
Lamont-Doherty Earth Observatory, United States
Volume Title: Geophysical Research Letters
Source: Geophysical Research Letters, 41(4), p.1179-1186. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0094-8276 CODEN: GPRLAJ
Note: In English. 33 refs.; illus., incl. sketch map
Summary: Borehole logging at the Atlantis Massif oceanic core complex provides new information on the relationship between the physical properties and the lithospheric hydration of a slow-spread intrusive crustal section. Integrated Ocean Drilling Program Hole U1309D penetrates 1.4 km into the footwall to an exposed detachment fault on the 1.2 Ma flank of the mid-Atlantic Ridge, 30°N. Downhole variations in seismic velocity and resistivity show a strong correspondence to the degree of alteration, a recorder of past seawater circulation. Average velocity and resistivity are lower, and alteration is more pervasive above a fault around 750 m. Deeper, these properties have higher values except in heavily altered ultramafic zones that are several tens of meters thick. Present circulation inferred from temperature mimics this pattern: advective cooling persists above 750 m, but below, conductive cooling dominates except for small excursions within the ultramafic zones. These alteration-related physical property signatures are probably a characteristic of gabbroic cores at oceanic core complexes. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; 20 Geophysics, Applied; Alteration; Atlantic Ocean; Atlantis Massif; Cenozoic; Crust; Downhole methods; Expeditions 304/305; Geophysical methods; Geophysical surveys; Hydration; IODP Site U1309; Integrated Ocean Drilling Program; Lithosphere; Metamorphic core complexes; Mid-Atlantic Ridge; Miocene; Neogene; North Atlantic; Ocean circulation; Oceanic crust; Oceanic lithosphere; Paleo-oceanography; Paleocirculation; Quaternary; Seismic methods; Surveys; Tertiary
Coordinates: N301000 N301100 W0420600 W0420700
Record ID: 2014035156
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom