HR: 1340h
AN: T33D-0590    [Abstracts]
TI: Digital Image Mosaics of the Oceanic Crust Exposed at the Pito Deep: Mesoscopic Perspectives on Structure and Deformation.
AU: * Hurst, S D
EM: shurst@uiuc.edu
AF: University of Illinois, Depatment of Geology 1301 W Green St, Urbana, IL 61801 United States
AU: Kolak, M
EM: mkolak@uiuc.edu
AF: University of Illinois, Depatment of Geology 1301 W Green St, Urbana, IL 61801 United States
AU: Bowles, M
EM: marshall.bowles@duke.edu
AF: Duke University, Division of Earth & Ocean Sciences 103 Old Chemistry Building, Durham, NC 27708 United States
AB: Recent investigations at the Pito Deep collected on the order of 80,000 electronic still images of rock outcrop in the upper oceanic crust formed at the ultra-fast spreading EPR. Using Alvin and Jason II during 9 long (>2km) Jason II transects and 12 Alvin dives, the images cover an area of > 200,000 meters squared. Jason II was equipped with a high dynamic range electronic still camera that provides a medium resolution image of the ocean floor at a distance of 5 to 15 meters from the ROV. The subsequent processing and mosaicking of the images provides an synoptic view of the outcrop while retaining small details (<1 cm). Several sites in massive diabase, sheeted dikes and extrusive lavas were selected for saturation imaging where up to a 100 m horizontal by 100 m vertical area was mapped with approximately 40% overlap in each direction. The composite mosaic image from these large contiguous sites provide a context for some of the detailed sampling in and around the sites, showing dike thickness variations, vein and fracture densities and the location and orientation of local faults and hydrothermal veins. The mosaic sites in the sheeted dike section verify the consistent steep (70(°) to 80(°)) "outward" (to the SW, away from the EPR axis) dip of the dikes. Dike thicknesses were predominately 0.5 to 1 meter across, with a substantial subset of thin (10 to 20 cm) dikes typically between adjacent thicker dikes. Areas of diabase, with no clear sheeted structure, form tall cliffs with widely spaced fractures and joints similar to coarse gabbro outcrop. Along some transects on the walls of Pito Deep, the "massive" diabase appears at the base of the observed section and has a relatively sudden transition into sheeted dikes. The thick diabase section, the consistently, steeply dipping sheeted dikes over large lateral areas, and lack of dikes observed in the extrusive section is substantially different from observations at the Hess Deep Rift and may be due to differences in spreading rate.
DE: 3035 Midocean ridge processes
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 3080 Submergence instruments: ROV, AUV, submersibles
DE: 8025 Mesoscopic fabrics
DE: 8040 Remote sensing
SC: Tectonophysics [T]
MN: Fall Meeting 2005