HR: 1340h
AN: T33B-1350    [Abstracts]
TI: Photographic analysis of seafloor geologic features at the 9 N Overlapping Spreading Center, East Pacific Rise
AU: * Nunnery, A
EM: jan19@duke.edu
AF: Duke University Nicholas School of the Environment and Earth Sciences, Duke University 103 Old Chem, Durham, NC 27708, United States
AU: Klein, E
EM: ek4@duke.edu
AF: Duke University Nicholas School of the Environment and Earth Sciences, Duke University 103 Old Chem, Durham, NC 27708, United States
AU: White, S
EM: swhite@geol.sc.edu
AF: University of South Carolina Department of Geological Sciences, University of South Carolina, Columbia, SC 29208, United States
AU: Perfit, M
EM: perfit@geology.ufl.edu
AF: University of Florida Department of Geological Sciences, University of Florida Box 112120, Gainesville, FL 32611, United States
AU: Fornari, D
EM: dfornari@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Geophysics, Woods Hole, MA 02543, United States
AU: Soule, A
EM: ssoule@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Geophysics, Woods Hole, MA 02543, United States
AU: Mason, J
EM: masonjl@mailbox.sc.edu
AF: University of South Carolina Department of Geological Sciences, University of South Carolina, Columbia, SC 29208, United States
AB: In March and April 2007, a cruise to the overlapping spreading center (OSC) at 9 deg 03' N on the East Pacific Rise collected geological, geochemical, and hydrothermal activity data along both limbs of the OSC and within the overlap basin to explore linkages between the melt lenses identified by Kent et al. (2000) and surficial geological processes. Here we report preliminary results of photographic data obtained by the ROV Jason II (4 lowerings; covering ~ 20.4 km; ~7000 digital photographs; 213 hrs continuous video for each of the three video streams) and the WHOI TowCam (7 lowerings; covering 29.3 km; ~ 10,000 digital photographs). The majority of our work focused on and adjacent to the eastern (propagating) limb of the OSC. Along the east limb, lavas (including pillow/lobate and sheet/hackly flows) with the freshest and most abundant glass, least sediment cover, and most delicate ornamentation are present along the bathymetrically elevated portion of the ridge between ~9 deg 7'- 10'N. This area also includes lava lake-style collapse structures with remnant pillars, as well as the only hydrothermal vent site observed in this study (at 9 deg 8.3' N). Further south along the east limb, to 9 deg 0' N, sediment cover and tectonic features (predominantly ~N-S-trending fissures) gradually increase, only lobate flows are observed, and glassy surfaces on the lavas are less abundant. Along the southernmost portion of the east limb, the melt lens plunges and cuts east across the ridge axis fabric. Above the location of the plunging melt lens, heavily sedimented lavas are observed with no evidence of recent volcanism. Photographs collected west of the bathymetrically robust portion of the east limb, overlying the wide, off-axis melt lens, generally show volcanism older than that found on-axis at the same latitude, although some areas associated with an elevated NW-trending ridge appear younger than surrounding terrane. Our study of the west (dying) limb of the OSC extends from ~ 9 deg 3' N to 8 deg 57 ' N. In this area, only pillow/lobate flows with variably fresh glass were observed and sediment cover varied, with some areas having a light dusting while others were completely blanketed. Tectonism, in the form of ~N-S fissures and fault scarps (some with talus accumulations) were also observed along the west limb. At the southern end of our study of the west limb, an area of lightly sedimented large pillows with delicate ornamentation was observed. Thorough analysis of our photographic data, in combination with information on the geochemical characteristics of collected samples and U-series age constraints will lead to a better understanding of the magma plumbing system beneath the limbs of the OSC and its relationship to the melt lenses imaged at depth.
DE: 1032 Mid-oceanic ridge processes (3614, 8416)
DE: 3035 Midocean ridge processes
DE: 8150 Plate boundary: general (3040)
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting