HR: 1340h
AN: T33B-1360    [Abstracts]
TI: Tectonic and Magmatic Modification of Ocean Crustal Bulk Physical Properties: A Global Perspective
AU: * Kuenzel, N A
EM: nakuenze@coastal.edu
AF: Coastal Carolina University, Marine Science, Conway, SC 29526, United States
AU: Gilbert, L A
EM: lgilbert@williams.edu
AF: Williams College, Williams-Mystic 75 Greenmanville Ave., Mystic, CT 06355, United States
AB: We compiled crustal physical property data such as porosity, density, and velocity from several decades of ocean drilling to compare normal ocean crust with crust influenced by fracture zones, hotspots, hydrothermal alteration, and other magmatic or tectonic influences. Cores and holes from IODP Expeditions and ODP and DSDP Legs that have penetrated 100 m or more into basement have been divided into the following geologic settings: a) normal crust, b) tectonic windows, c) off-axis seamounts, d) mid-ocean ridge seamounts e) off-axis plateaus and f) areas of arc volcanism. This study aims not only to provide a more global perspective of the ocean crust with respect to factors such as geologic setting, age, and rock type from many seafloor holes globally that have yet to be compared, but also to focus more specifically on how normal crustal properties compare with those of crust which has interacted with other tectonic and magmatic zones. Preliminary analyses of the different geologic settings with respect to their average physical properties without regard for differences in rock type, depth, age, or composition show some interesting trends. Although the average crustal velocity is highest in normal oceanic crust, we find no significant difference between normal crust and any other setting. All the settings exhibit variability in the upper 200 m of crust, but below 200 m the velocity of normal oceanic crust never drops below 4 km/s. The average porosity of normal crust is similar to that of tectonic windows, but much lower than the average of any of the other geologic settings. We find that the average bulk density is again highest in normal oceanic crust and similar to the average of tectonic windows, but normal crust is not significantly different from the other settings. Average grain density is also highest in normal crust. The present data suggest a comprehensive model of both normal crust and crust that has been influenced by tectonic and magmatic processes. Using physical properties and the identifying the controlling factors such as hydrothermal alteration, mechanical collapse, and faulting, we can synthesize the global datasets provided by ocean drilling during the last four decades.
DE: 3035 Midocean ridge processes
DE: 3036 Ocean drilling
DE: 3039 Oceanic transform and fracture zone processes
DE: 7220 Oceanic crust
DE: 7245 Mid-ocean ridges
SC: Tectonophysics [T]
MN: 2007 Fall Meeting