HR: 1340h
AN: T33D-0592    [Abstracts]
TI: ALVIN Magnetometer Investigations of Pito Deep, Easter Microplate
AU: * Hey, R N
EM: hey@soest.hawaii.edu
AF: HIGP/SOEST, Univ. of Hawaii, 2525 Correa Rd, Honolulu, HI 96822 United States
AU: Gee, J S
EM: jsgee@ucsd.edu
AF: GRD/SIO, UCSD, La Jolla, CA 92092 United States
AB: The ALVIN magnetometer was used successfully on all 12 submersible dives during our 2005 expedition to collect "vertical" magnetic profiles of the exposed Pito Deep crustal section. We used Maurice Tivey's techniques to correct the data for sub heading, using the most appropriate submersible spin data from each dive. Preliminary analysis of the 6 Area B dives, centered near 22.95 S, 111.9 W in rifted 3.3 Ma crust, shows that the top of the interpreted dike/lava transition zone is almost always at or near a significant magnetic low. This is true whether the transition zone is broad (hundreds of meters) or narrow (tens of meters). This is similar to the pattern observed by Tivey at the Blanco transform fault scarp, where he modelled similar magnetic lows as defining the base of the highly magnetic extrusive pillow lava section, underlain by a non-magnetic transition zone and weakly magnetic dike section. If our magnetic lows can be used to define this contact, it occurs at very systematic depths in Area B (2700-2730 m on all but one dive, 2750-2780 m on the other). The Area A (22.9 S, 112.05 W, 3.1 Ma) magnetic pattern is less systematic, consistent with divers' observations of more faulting in that area, but several of the dives there also show magnetic lows near the lava/dike transition zone boundary, which is several hundred meters deeper than in Area B. Our preliminary results suggest that at least in Area B the dikes contribute significantly to the seafloor magnetic pattern, more consistent with the Hess Deep and Endeavor Deep interpretations than the Blanco or Hole 504B interpretations, suggesting a possible dependence on spreading rate.
DE: 1594 Instruments and techniques
DE: 3005 Marine magnetics and paleomagnetics (1550)
DE: 3035 Midocean ridge processes
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
SC: Tectonophysics [T]
MN: Fall Meeting 2005