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Simon M Peacock - One of the best experts on this subject based on the ideXlab platform.
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subduction factory 1 theoretical mineralogy densities seismic wave speeds and h2o contents
Journal of Geophysical Research, 2003Co-Authors: Bradley R. Hacker, Geoffrey A Abers, Simon M PeacockAbstract:[1] We present a new compilation of physical properties of minerals relevant to subduction zones and new phase diagrams for mid-ocean ridge basalt, lherzolite, depleted lherzolite, harzburgite, and serpentinite. We use these data to calculate H2O content, density and seismic wave speeds of subduction zone rocks. These calculations provide a new basis for evaluating the subduction factory, including (1) the presence of hydrous phases and the distribution of H2O within a subduction zone; (2) the densification of the subducting slab and resultant effects on measured gravity and slab shape; and (3) the variations in seismic wave speeds resulting from thermal and metamorphic processes at depth. In considering specific examples, we find that for ocean basins worldwide the lower oceanic crust is partially hydrated (<1.3 wt % H2O), and the uppermost mantle ranges from unhydrated to � 20% serpentinized (� 2.4 wt % H2O). Anhydrous eclogite cannot be distinguished from harzburgite on the basis of wave speeds, but its � 6% greater density may render it detectable through gravity measurements. Subducted hydrous crust in cold slabs can persist to several gigapascals at seismic velocities that are several percent slower than the surrounding mantle. Seismic velocities and VP/VS ratios indicate that mantle wedges locally reach 60–80% hydration. INDEX TERMS: 3040 Marine Geology and Geophysics: Plate tectonics (8150, 8155, 8157, 8158); 3660 Mineralogy and Petrology: Metamorphic petrology; 3919 Mineral Physics: Equations of state; 5199 Physical Properties of Rocks: General or miscellaneous; 8123 Tectonophysics: Dynamics, seismotectonics; KEYWORDS: subduction, seismic velocities, mineral physics, H2O
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subduction factory 1 theoretical mineralogy densities seismic wave speeds and h 2 o contents
Journal of Geophysical Research, 2003Co-Authors: Bradley R. Hacker, Geoffrey A Abers, Simon M PeacockAbstract:[1] We present a new compilation of physical properties of minerals relevant to subduction zones and new phase diagrams for mid-ocean ridge basalt, lherzolite, depleted lherzolite, harzburgite, and serpentinite. We use these data to calculate H2O content, density and seismic wave speeds of subduction zone rocks. These calculations provide a new basis for evaluating the subduction factory, including (1) the presence of hydrous phases and the distribution of H2O within a subduction zone; (2) the densification of the subducting slab and resultant effects on measured gravity and slab shape; and (3) the variations in seismic wave speeds resulting from thermal and metamorphic processes at depth. In considering specific examples, we find that for ocean basins worldwide the lower oceanic crust is partially hydrated (<1.3 wt % H2O), and the uppermost mantle ranges from unhydrated to � 20% serpentinized (� 2.4 wt % H2O). Anhydrous eclogite cannot be distinguished from harzburgite on the basis of wave speeds, but its � 6% greater density may render it detectable through gravity measurements. Subducted hydrous crust in cold slabs can persist to several gigapascals at seismic velocities that are several percent slower than the surrounding mantle. Seismic velocities and VP/VS ratios indicate that mantle wedges locally reach 60–80% hydration. INDEX TERMS: 3040 Marine Geology and Geophysics: Plate tectonics (8150, 8155, 8157, 8158); 3660 Mineralogy and Petrology: Metamorphic petrology; 3919 Mineral Physics: Equations of state; 5199 Physical Properties of Rocks: General or miscellaneous; 8123 Tectonophysics: Dynamics, seismotectonics; KEYWORDS: subduction, seismic velocities, mineral physics, H2O
Bradley R. Hacker - One of the best experts on this subject based on the ideXlab platform.
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subduction factory 1 theoretical mineralogy densities seismic wave speeds and h2o contents
Journal of Geophysical Research, 2003Co-Authors: Bradley R. Hacker, Geoffrey A Abers, Simon M PeacockAbstract:[1] We present a new compilation of physical properties of minerals relevant to subduction zones and new phase diagrams for mid-ocean ridge basalt, lherzolite, depleted lherzolite, harzburgite, and serpentinite. We use these data to calculate H2O content, density and seismic wave speeds of subduction zone rocks. These calculations provide a new basis for evaluating the subduction factory, including (1) the presence of hydrous phases and the distribution of H2O within a subduction zone; (2) the densification of the subducting slab and resultant effects on measured gravity and slab shape; and (3) the variations in seismic wave speeds resulting from thermal and metamorphic processes at depth. In considering specific examples, we find that for ocean basins worldwide the lower oceanic crust is partially hydrated (<1.3 wt % H2O), and the uppermost mantle ranges from unhydrated to � 20% serpentinized (� 2.4 wt % H2O). Anhydrous eclogite cannot be distinguished from harzburgite on the basis of wave speeds, but its � 6% greater density may render it detectable through gravity measurements. Subducted hydrous crust in cold slabs can persist to several gigapascals at seismic velocities that are several percent slower than the surrounding mantle. Seismic velocities and VP/VS ratios indicate that mantle wedges locally reach 60–80% hydration. INDEX TERMS: 3040 Marine Geology and Geophysics: Plate tectonics (8150, 8155, 8157, 8158); 3660 Mineralogy and Petrology: Metamorphic petrology; 3919 Mineral Physics: Equations of state; 5199 Physical Properties of Rocks: General or miscellaneous; 8123 Tectonophysics: Dynamics, seismotectonics; KEYWORDS: subduction, seismic velocities, mineral physics, H2O
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subduction factory 1 theoretical mineralogy densities seismic wave speeds and h 2 o contents
Journal of Geophysical Research, 2003Co-Authors: Bradley R. Hacker, Geoffrey A Abers, Simon M PeacockAbstract:[1] We present a new compilation of physical properties of minerals relevant to subduction zones and new phase diagrams for mid-ocean ridge basalt, lherzolite, depleted lherzolite, harzburgite, and serpentinite. We use these data to calculate H2O content, density and seismic wave speeds of subduction zone rocks. These calculations provide a new basis for evaluating the subduction factory, including (1) the presence of hydrous phases and the distribution of H2O within a subduction zone; (2) the densification of the subducting slab and resultant effects on measured gravity and slab shape; and (3) the variations in seismic wave speeds resulting from thermal and metamorphic processes at depth. In considering specific examples, we find that for ocean basins worldwide the lower oceanic crust is partially hydrated (<1.3 wt % H2O), and the uppermost mantle ranges from unhydrated to � 20% serpentinized (� 2.4 wt % H2O). Anhydrous eclogite cannot be distinguished from harzburgite on the basis of wave speeds, but its � 6% greater density may render it detectable through gravity measurements. Subducted hydrous crust in cold slabs can persist to several gigapascals at seismic velocities that are several percent slower than the surrounding mantle. Seismic velocities and VP/VS ratios indicate that mantle wedges locally reach 60–80% hydration. INDEX TERMS: 3040 Marine Geology and Geophysics: Plate tectonics (8150, 8155, 8157, 8158); 3660 Mineralogy and Petrology: Metamorphic petrology; 3919 Mineral Physics: Equations of state; 5199 Physical Properties of Rocks: General or miscellaneous; 8123 Tectonophysics: Dynamics, seismotectonics; KEYWORDS: subduction, seismic velocities, mineral physics, H2O
Jose A Jimenez - One of the best experts on this subject based on the ideXlab platform.
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comment on wave climate sediment supply and the depth of the sand mud transition a global survey by d a george and p s hill Marine Geology 254 2008 121 128
Marine Geology, 2009Co-Authors: Jorge Guillen, Jose A JimenezAbstract:Abstract An extensive dataset of sediment grain size and wave conditions in the Ebro Delta (NW Mediterranean) is used to verify the local scale applicability of the work of George and Hill (George, D.A., Hill, P.S., 2008. Wave climate, sediment supply and the depth of the sand–mud transition: a global survey. Mar. Geol., 254, 121–128) on the definition of the sand–mud transition (SMT). The proposal of using either a mean grain size of 63 μm or a mud content of 25% to define the presence of the sand–mud transition was locally verified (96% well-classified of a total of 382 samples). However, determining the depth of the sand–mud transition ( h SMT ) based only on the wave height shows several practical and conceptual inconsistencies that could be partially solved by including the wave period into the equation. On the Ebro Delta shelf, the use of the across-shelf distribution of skin friction accurately predicts the h SMT .
Luis Miguel Caceres - One of the best experts on this subject based on the ideXlab platform.
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comment on formation of chenier plain of the donana marshland sw spain observations and geomorphic model by a rodriguez ramirez and c m yanez camacho Marine Geology 254 2008 187 196
Marine Geology, 2010Co-Authors: Joaquin Rodriguezvidal, Francisco Ruiz, Luis Miguel CaceresAbstract:Abstract The application of the regional Marine 14 C reservoir effect (Δ R ) to obtain an accurate calibration of conventional Marine shell 14 C dates requires prior research concerning the oceanographic conditions and the Δ R of that region. Rodriguez-Ramirez and Yanez-Camacho [A. Rodriguez-Ramirez, C.M. Yanez-Camacho, Formation of chenier plain of the Donana marshland (SW Spain): Observations and geomorphic model, Marine Geology 254 (2008) 187–196] and afterwards A. Rodriguez-Ramirez, J.A. Morales, J. Borrego and E.G. San Miguel in a reply [A. Rodriguez-Ramirez, J.A. Morales, J. Borrego, E.G. San Miguel, Reply to the comment on “Formation of chenier plain of the Donana marshland (SW Spain): Observations and geomorphic model” by A. Rodriguez-Ramirez and C.M. Yanez-Camacho [Marine Geology 254 (2008) 187–196], Marine Geology 263 (2009) 123–125] to the comment by J. Rodriguez-Vidal, F. Ruiz and L.M. Caceres on the paper mentioned above [J. Rodriguez-Vidal, F. Ruiz, L. M. Caceres, Comment on “Formation of chenier plain of the Donana marshland (SW Spain): Observations and geomorphic model” by A. Rodriguez-Ramirez, C.M. Yanez-Camacho [Marine Geology 254 (2008) 187–196], Marine Geology 263 (2009) 120–122] use, in both cases, not only incorrect Δ R values for the calibration of 14 C dates obtained from shell samples collected from the east coast of the Gulf of Cadiz, but they also confuse the Δ R concept with that of R ( t ), the 14 C reservoir age. Because the misunderstanding of these concepts by these authors and, in the first case, also their failure to take into account the Δ R values obtained by us (and already published) from the east coast of Gulf of Cadiz, all the calibrated dates presented either in the first paper or in the reply cannot be accepted. Here I present a new calibrated dataset using accurate Δ R values and I recommend that the conclusions obtained by Rodriguez-Ramirez and their collaborators be revised, as J. Rodriguez-Vidal, F. Ruiz and L.M. Caceres proposed in their comment.
Paul S Hill - One of the best experts on this subject based on the ideXlab platform.
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reply to the comment on wave climate sediment supply and the depth of the sand mud transition a global survey by d a george and p s hill Marine Geology 254 2008 121 128
Marine Geology, 2009Co-Authors: Douglas A George, Paul S HillAbstract:Abstract An analysis of concepts presented by George and Hill [George, D.A., Hill, P.S., 2008. Wave climate, sediment supply and the depth of the sand–mud transition: A global survey. Marine Geology, 254, 121–128.] regarding the depth of the sand–mud transition ( h SMT ) was performed by Guillen and Jimenez [Jorge Guillen and Jose A. Jimenez, Comment on “Wave climate, sediment supply and the depth of the sand–mud transition: A global survey” by D.A. George and P.S. Hill [Marine Geology 254 (2008) 121–128], Marine Geology, in press]. We are pleased that our proposed definition of the h SMT was confirmed to be appropriate. We are encouraged that the authors agree that wave period and wave height should both be used to determine h SMT as we demonstrated in our Eq. (1), which calculates the bed shear stress at h SMT . More in-depth research should focus on characterizing the role of sediment supply in determining h SMT .