IODP Expedition 340T; Borehole logging at Atlantis Massif oceanic core complex

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doi: 10.2204/iodp.sd.15.04.2013
Author(s): Blackman, Donna; Slagle, Angela; Harding, Alistair; Guerin, Gilles; McCaig, Andrew
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, La Jolla, CA, United States
Other:
Lamont-Doherty Earth Observatory, United States
University of Leeds, United Kingdom
Volume Title: Scientific Drilling
Source: Scientific Drilling, Vol.15, p.31-35. Publisher: Integrated Ocean Drilling Program Management International, Sapporo; Washington, DC, International. ISSN: 1816-8957
Note: In English. 25 refs.; illus., incl. sketch map
Summary: Integrated Ocean Drilling Program (IODP) Expedition 340T returned to the 1.4-km-deep Hole U1309D at Atlantis Massif to carry out borehole logging including vertical seismic profiling (VSP). Seismic, resistivity, and temperature logs were obtained throughout the geologic section in the footwall of this oceanic core complex. Reliable downhole temperature measurements throughout and the first seismic coverage of the 800-1400 meters below seafloor (mbsf) portion of the section were obtained. Distinct changes in velocity, resistivity, and magnetic susceptibility characterize the boundaries of altered, olivine-rich troctolite intervals within the otherwise dominantly gabbroic sequence. Some narrow fault zones also are associated with downhole resistivity or velocity excursions. Small deviations in temperature were measured in borehole fluid adjacent to known faults at 750 mbsf and 1100 mbsf. This suggests that flow of seawater remains active along these zones of faulting and rock alteration. Vertical seismic profile station coverage at zero offset now extends the full length of the hole, including the uppermost 150 mbsf, where detachment processes are expected to have left their strongest imprint. Analysis of wallrock properties, together with alteration and structural characteristics of the cores from Site U1309, highlights the likely interplay between lithology, structure, lithospheric hydration, and core complex evolution
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 05 Petrology, Igneous and Metamorphic; Atlantic Ocean; Atlantis Massif; Body waves; Boreholes; Cores; Crust; Elastic waves; Expedition 340T; Expeditions 304/305; IODP Site U1309; Igneous rocks; Integrated Ocean Drilling Program; Magnetic properties; Magnetic susceptibility; Metamorphic core complexes; Mid-Atlantic Ridge; North Atlantic; Oceanic crust; P-waves; Paleomagnetism; Plutonic rocks; Resistivity; Seismic waves; Velocity; Well logs
Coordinates: N301000 N301100 W0420600 W0420700
Record ID: 2013047787
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute.