The thermochemical structure and evolution of Earth`s mantle
... possibly causing partial melting and making it di¯ cult for su¯ cient heat to leave the core to drive the geodynamo. Most seismic tomographic models (e.g. Grand et al . 1997; Masters et al. 2000) suggest that slabs reach the core{mantle boundary (CMB) in many areas. The boundary of such a layer has ...
... possibly causing partial melting and making it di¯ cult for su¯ cient heat to leave the core to drive the geodynamo. Most seismic tomographic models (e.g. Grand et al . 1997; Masters et al. 2000) suggest that slabs reach the core{mantle boundary (CMB) in many areas. The boundary of such a layer has ...
Recycled crust in the Galápagos Plume source at 70 Ma
... as well as affecting the thermodynamic cooling of Earth. Furthermore, when compared with a primitive mantle reference, typical OIB trace element signatures show positive high field strength element (e.g., Nb and Ta) anomalies, suggesting a subducted slab reservoir in the mantle (McDonough, 1991; Rudn ...
... as well as affecting the thermodynamic cooling of Earth. Furthermore, when compared with a primitive mantle reference, typical OIB trace element signatures show positive high field strength element (e.g., Nb and Ta) anomalies, suggesting a subducted slab reservoir in the mantle (McDonough, 1991; Rudn ...
Printer-friendly Version - Solid Earth Discussions
... of 4–24 km. The P wave velocity in the uppermost mantle is 7.9–8.2 km s . The ratio of P wave velocity to S wave velocity varies typically from 1.67–1.70 in the upper crust to 1.77–1.80 in the lower crust. In the upper mantle the ratio is about 1.73 (e.g. Guggisberg, 1986; Grad and Luosto, 1987; Luo ...
... of 4–24 km. The P wave velocity in the uppermost mantle is 7.9–8.2 km s . The ratio of P wave velocity to S wave velocity varies typically from 1.67–1.70 in the upper crust to 1.77–1.80 in the lower crust. In the upper mantle the ratio is about 1.73 (e.g. Guggisberg, 1986; Grad and Luosto, 1987; Luo ...
The westward drift of the lithosphere
... upper-mantle geochemistry, and a thermally and phase change–driven negative buoyancy. However, the mineralogical constraints of the upper mantle are quite weak, and focal mechanisms indicate that slabs undergo downdip compression beneath depths of 350 km, if not shallower in many subduction zones (I ...
... upper-mantle geochemistry, and a thermally and phase change–driven negative buoyancy. However, the mineralogical constraints of the upper mantle are quite weak, and focal mechanisms indicate that slabs undergo downdip compression beneath depths of 350 km, if not shallower in many subduction zones (I ...
Seismic structure of Cocos and Malpelo Volcanic Ridges and
... improve the signal-to-noise ratio. [10] The Pg phase is clearly observed in all the record sections. The pattern of this phase is similar in most of the instruments from the three lines, though some strong lateral variations related with prominent bathymetric features are also observed. At near offs ...
... improve the signal-to-noise ratio. [10] The Pg phase is clearly observed in all the record sections. The pattern of this phase is similar in most of the instruments from the three lines, though some strong lateral variations related with prominent bathymetric features are also observed. At near offs ...
Crustal structure of northern and southern Tibet from surface wave
... can be caused by event mislocations and origin time errors. Assuming the quoted errors for the epicentral coordinates and origin time of the CMT solution (references in Table 1), the resulting error for the group velocity would be 1%, i.e., about 0.03 km/s, smaller than the scatter of group velocit ...
... can be caused by event mislocations and origin time errors. Assuming the quoted errors for the epicentral coordinates and origin time of the CMT solution (references in Table 1), the resulting error for the group velocity would be 1%, i.e., about 0.03 km/s, smaller than the scatter of group velocit ...
Extinct spreading center in the Labrador Sea
... Oceanography)were deployedat locations(Figure 2) along shotpoints, and rangesfrom a positionon the referencegrid lines R1 (five OBSs) and R2 (eight OBSs). The spacing to the shot points. A detailed discussion and listing of between OBSs was approximately 20 km at the extinct uncertaintiesin OBS and ...
... Oceanography)were deployedat locations(Figure 2) along shotpoints, and rangesfrom a positionon the referencegrid lines R1 (five OBSs) and R2 (eight OBSs). The spacing to the shot points. A detailed discussion and listing of between OBSs was approximately 20 km at the extinct uncertaintiesin OBS and ...
Subduction-related intermediate-depth and deep seismicity in Italy
... to about 170 km (e.g., Bally et al., 1986). As a consequence, after a period of oceanic lithosphere subduction, about 170 km of continental lithosphere were subducted under the Northern Apennines. The continental nature of the subducting Adriatic plate is confirmed by geochemical and petrological st ...
... to about 170 km (e.g., Bally et al., 1986). As a consequence, after a period of oceanic lithosphere subduction, about 170 km of continental lithosphere were subducted under the Northern Apennines. The continental nature of the subducting Adriatic plate is confirmed by geochemical and petrological st ...
Magnetotelluric Studies at the San Andreas Fault Zone: Implications
... (Hickman et al. 2004), and a range of geological, geochemical, and geophysical exploration and monitoring programs have tremendously increased our knowledge about physical and chemical processes within and surrounding the fault zone, making the SAF the best studied fault zone on Earth. However, fund ...
... (Hickman et al. 2004), and a range of geological, geochemical, and geophysical exploration and monitoring programs have tremendously increased our knowledge about physical and chemical processes within and surrounding the fault zone, making the SAF the best studied fault zone on Earth. However, fund ...
Inclusions in Sublithospheric Diamonds
... recognition of inclusions in diamonds from the deep asthenosphere and transition zone would be fairly straightforward and could be based on phase identification (X-ray diffraction, Raman spectroscopy). In fact, exhumation converts these high-pressure minerals to lower-pressure phases or assemblages. ...
... recognition of inclusions in diamonds from the deep asthenosphere and transition zone would be fairly straightforward and could be based on phase identification (X-ray diffraction, Raman spectroscopy). In fact, exhumation converts these high-pressure minerals to lower-pressure phases or assemblages. ...
Shear zones in the Proterozoic lithosphere of the
... for the Hales, if applicable generally in continental regions, would validate the slab-accretion model for the formation of continental lithosphere (e.g. Abbott, 1992), as it would imply that buoyant trapping of shallow-subducting slabs by the retardation of the gabbro-to-eclogite phase transition ( ...
... for the Hales, if applicable generally in continental regions, would validate the slab-accretion model for the formation of continental lithosphere (e.g. Abbott, 1992), as it would imply that buoyant trapping of shallow-subducting slabs by the retardation of the gabbro-to-eclogite phase transition ( ...
Petrological interpretation of deep crustal intrusive bodies beneath
... or above the Moho, e.g., Hawaii, the Marquesas, and La Reunion. However, at other hotspot provinces such as the Galapagos, Nazca Ridge, and Louisville the lower crust is intruded by large volumes of gabbroic (mafic) rocks (Vp ~ 6.8–7.5 km/s). Ultramafic primary melts formed beneath mature oceanic lith ...
... or above the Moho, e.g., Hawaii, the Marquesas, and La Reunion. However, at other hotspot provinces such as the Galapagos, Nazca Ridge, and Louisville the lower crust is intruded by large volumes of gabbroic (mafic) rocks (Vp ~ 6.8–7.5 km/s). Ultramafic primary melts formed beneath mature oceanic lith ...
Imaging the lithosphere‐asthenosphere boundary
... conductive cooling models, this relatively simple realization of the tectonic plates is not completely understood. Old (>70 Ma) ocean depths are shallower than predicted. Furthermore, precise imaging of the lower boundary of the oceanic lithosphere has proven challenging. Here we directly map the de ...
... conductive cooling models, this relatively simple realization of the tectonic plates is not completely understood. Old (>70 Ma) ocean depths are shallower than predicted. Furthermore, precise imaging of the lower boundary of the oceanic lithosphere has proven challenging. Here we directly map the de ...
Properties of iron at the Earth`s core conditions
... ionized under pressure. Experimental geophysics is now capable of observing any phase change that would transform a silicate into a metallic conductor at core pressures. Phase changes in silicate exist at high pressure, but the density change is small compared to that required for the mantle-core bo ...
... ionized under pressure. Experimental geophysics is now capable of observing any phase change that would transform a silicate into a metallic conductor at core pressures. Phase changes in silicate exist at high pressure, but the density change is small compared to that required for the mantle-core bo ...
Magnetotellurics
Magnetotellurics (MT) is an electromagnetic geophysical method for inferring the earth's subsurface electrical conductivity from measurements of natural geomagnetic and geoelectric field variation at the Earth's surface. Investigation depth ranges from 300m below ground by recording higher frequencies down to 10,000m or deeper with long-period soundings. Developed in the USSR and France during the 1950s, MT is now an international academic discipline and is used in exploration surveys around the world. Commercial uses include hydrocarbon (oil and gas) exploration, geothermal exploration, mining exploration, as well as hydrocarbon and groundwater monitoring. Research applications include experimentation to further develop the MT technique, long-period deep crustal exploration, and earthquake precursor prediction research.