Provenance, Stratigraphic Architecture, and Hydrogeologic Influence of Turbidites on the Mid-Ocean Ridge Flank of Northwestern Cascadia Basin, Pacific Ocean

2005 ◽  
Vol 75 (1) ◽  
pp. 149-164 ◽  
Author(s):  
M. B. Underwood ◽  
K. D. Hoke ◽  
A. T. Fisher ◽  
E. E. Davis ◽  
E. Giambalvo ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Stratigraphic Architecture ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Ridge Flank

scholarly journals Mixing-Driven Mean Flows and Submesoscale Eddies over Mid-Ocean Ridge Flanks and Fracture Zone Canyons

2020 ◽  
Vol 50 (1) ◽  
pp. 175-195 ◽  
Author(s):  
Xiaozhou Ruan ◽  
Jörn Callies
Keyword(s):  
Numerical Experiments ◽  
Water Mass ◽  
Mixing Layers ◽  
Global Ocean ◽  
Mid Ocean Ridge ◽  
Mixing Rates ◽  
Ocean Ridge ◽  
Ridge Flank ◽  
Abyssal Mixing ◽  
Water Mass Transformation

AbstractTo close the abyssal overturning circulation, dense bottom water has to become lighter by mixing with lighter water above. This diapycnal mixing is strongly enhanced over rough topography in abyssal mixing layers, which span the bottom few hundred meters of the water column. In particular, mixing rates are enhanced over mid-ocean ridge systems, which extend for thousands of kilometers in the global ocean and are thought to be key contributors to the required abyssal water mass transformation. To examine how stratification and thus diabatic transformation is maintained in such abyssal mixing layers, this study explores the circulation driven by bottom-intensified mixing over mid-ocean ridge flanks and within ridge-flank canyons. Idealized numerical experiments show that stratification over the ridge flanks is maintained by submesoscale baroclinic eddies and that stratification within ridge-flank canyons is maintained by mixing-driven mean flows. These restratification processes affect how strong a diabatic buoyancy flux into the abyss can be maintained, and they are essential for maintaining the dipole in water mass transformation that has emerged as the hallmark of a diabatic circulation driven by bottom-intensified mixing.

Magnetostratigraphic effects and artifacts of an inverse redox zonation in bottom-up oxygenated East Pacific mid-ocean ridge flank sediments

2021 ◽  
Author(s):  
Adrian Höfken ◽  
Tilo von Dobeneck ◽  
Sabine Kasten
Keyword(s):  
Pore Water ◽  
Planetary Science ◽  
Ex Situ ◽  
Sediment Geochemistry ◽  
Magnetic Minerals ◽  
Diagenetic Alteration ◽  
Mid Ocean Ridge ◽  
Redox Zonation ◽  
Ocean Ridge ◽  
Ridge Flank

<p><span>Shipborne ex-situ oxygen measurements in mid-ocean ridge flank sediment cores from the eastern low-latitude North Pacific (Clarion-Clipperton Zone) revealed a downward increase of pore-water oxygen above the sediment-crust interface (Mewes et al., 2016, Kuhn et al., 2017). This inverse redox zonation is caused by an upward diffusion of oxygen (and other solutes) from fluids circulating through the underlying 20 Mio. Year old and still cooling ocean crust. In consequence, these sediments experience a cyclic change in redox-conditions from oxic seafloor conditions at the top through mostly suboxic conditions throughout the sediment column back to oxygen-rich pore water in the last few sediment meters above the rock basement. </span></p><p><span>We studied paleomagnetic records and bulk magnetic properties of three gravity cores from such settings that were collected during </span><span><em>RV Sonne</em></span><span> expedition SO-240 in 2015 and obtained high-quality magnetostratigraphic records covering the past 3.2 Ma. The generally very good preservation and interpretability of our reversal and RPI records, however, conflicts with a well-defined, but irregular ‘ghost event’ of normal polarity within the upper Gilbert reversed C2Ar section. This magnetic polarity and intensity artifact cannot be explained by sediment tectonics, but coincides with the present depth of the lower suboxic-to-oxic redox boundary. Although chemical overprinting could be considered as an obvious explanation of such findings, bulk magnetic analyses (FORCs, thermomagnetics) infer no diagenetic alteration of the magnetic minerals. Over the entire paleomagnetic record, bacterial magnetite appears to be the predominant NRM carrier. We therefore introduce a novel conceptual model of secondary biogenic magnetite formation at crustal depth, hypothesizing that microaerophilic magnetotactic bacteria live and biomineralize not only in the shallow subsurface, but also near the deep oxygen above the sediment-crust interface.</span></p><p> </p><p><span>References </span></p><p><span>Mewes, K., Mogollón, J.M., Picard, A., Rühlemann, C., Eisenhauer, A., Kuhn, T., Ziebis, W., Kasten, S., 2016. Diffusive transfer of oxygen from seamount basaltic crust into overlying sediments: An example from the Clarion-Clipperton Fracture Zone. Earth and Planetary Science Letters 433, 215-225.</span></p><p><span>Kuhn, T., Versteegh, G.J.M., Villinger, H., Dohrmann, I., Heller, C., Koschinsky, A., Kaul, N., Ritter, S., Wegorzewski, A.V., Kasten, S., 2017. Widespread seawater circulation in 18-22 Ma oceanic crust: Impact on heat flow and sediment geochemistry. Geology 45, 799-802.</span></p><p> </p><p> </p><p> </p>

scholarly journals Germanium in mid-ocean ridge flank hydrothermal fluids

2008 ◽  
Vol 9 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. Geoffrey Wheat ◽  
James McManus
Keyword(s):  
Hydrothermal Fluids ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Ridge Flank

Mid-ocean-ridge basalt of Indian type in the northwest Pacific Ocean basin

2009 ◽  
Vol 2 (4) ◽  
pp. 286-289 ◽  
Author(s):  
Susanne M. Straub ◽  
Steven L. Goldstein ◽  
Cornelia Class ◽  
Angelika Schmidt
Keyword(s):  
Pacific Ocean ◽  
Ocean Basin ◽  
Northwest Pacific ◽  
Northwest Pacific Ocean ◽  
Ridge Basalt ◽  
Mid Ocean Ridge ◽  
The Northwest Pacific Ocean ◽  
Ocean Ridge

scholarly journals Oceanic phosphorus imbalance: Magnitude of the mid-ocean ridge flank hydrothermal sink

2003 ◽  
Vol 30 (17) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. Geoffrey Wheat ◽  
James McManus ◽  
Michael J. Mottl ◽  
Emily Giambalvo
Keyword(s):  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Ridge Flank

The subduction influence on ocean ridge basalts and its significance

2021 ◽  
Author(s):  
Alexandra Yang Yang ◽  
Charles Langmuir ◽  
Yue Cai ◽  
Steven Goldstein ◽  
Peter Michael ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Upper Mantle ◽  
The Arctic ◽  
Plate Tectonic ◽  
Gakkel Ridge ◽  
The Pacific ◽  
Mid Ocean Ridge ◽  
The Pacific Ocean ◽  
Back Arc ◽  
Ocean Ridge

Abstract The plate tectonic cycle produces chemically distinct mid-ocean ridge basalts (MORB) and arc volcanics, with the latter enriched in fluid-mobile elements and depleted in Nb owing to fluxes from the subducted slab. Basalts from back-arc basins (BABB), with intermediate compositions, show that the subduction flux can escape the arc. Hence it is puzzling why arc signatures have rarely been recognized in MORB. Here we report the first MORB samples with distinct arc signatures, akin to BABB, from the Arctic Gakkel Ridge. A new high precision dataset for 576 Gakkel samples suggests a pervasive subduction influence. This influence can also be identified in Atlantic and Indian MORB with a “BABB filter”, but is nearly absent in Pacific MORB. This global distribution reflects the control of a “subduction shield” that has surrounded the Pacific Ocean for 180Myr. Statistics suggest that a flux equivalent to ~ 13% of output at arcs is incorporated into the convecting upper mantle.

scholarly journals Novel microbial assemblages inhabiting crustal fluids within mid-ocean ridge flank subsurface basalt

2016 ◽  
Vol 10 (8) ◽  
pp. 2033-2047 ◽  
Author(s):  
Sean P Jungbluth ◽  
Robert M Bowers ◽  
Huei-Ting Lin ◽  
James P Cowen ◽  
Michael S Rappé
Keyword(s):  
Crustal Fluids ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Ridge Flank
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