42. Rifting and the Volcanic-Tectonic Evolution of the Izu
... modern-style volcanic arc developed by the Oligocene, along which intense tholeiitic and calc-alkaline volcanism continued until 29 (Mariana) and 27 Ma (Izu-Bonin). The Eocene-Oligocene arc massif was stretched during protracted Oligocene rifting, creating sags and half graben in the forearc and bac ...
... modern-style volcanic arc developed by the Oligocene, along which intense tholeiitic and calc-alkaline volcanism continued until 29 (Mariana) and 27 Ma (Izu-Bonin). The Eocene-Oligocene arc massif was stretched during protracted Oligocene rifting, creating sags and half graben in the forearc and bac ...
Generation of new continental crust by sublithospheric silicic
... 1. Introduction The Earth's continents are mostly composed of igneous and meta-igneous rocks that on average yield an andesite composition with SiO2 = 60.6 wt.% and MgO = 4.7 wt.%. (Taylor and McLennan, 1985; Rudnick and Gao, 2003). New estimates (Hacker et al., 2011), based on physical properties o ...
... 1. Introduction The Earth's continents are mostly composed of igneous and meta-igneous rocks that on average yield an andesite composition with SiO2 = 60.6 wt.% and MgO = 4.7 wt.%. (Taylor and McLennan, 1985; Rudnick and Gao, 2003). New estimates (Hacker et al., 2011), based on physical properties o ...
Journal of Asian Earth Sciences 20 2002
... older orogenic belts. They preserve a record of major changes in tectonics, including subduction polarity reversals, elimination of volcanic arcs, changing plate boundaries and extension within an overall contractional setting. Rapid tectonic changes have occurred within periods of less than 5 Ma. M ...
... older orogenic belts. They preserve a record of major changes in tectonics, including subduction polarity reversals, elimination of volcanic arcs, changing plate boundaries and extension within an overall contractional setting. Rapid tectonic changes have occurred within periods of less than 5 Ma. M ...
Thermal structure of the shallow upper mantle beneath Italy and
... correspond to the preferred Vs-depth distributions, derived from the nonlinear tomographic inversion, following the optimization procedure described by Boyadzhiev et al. (2008). 2. Calculation of mantle temperatures from seismic wave velocities 2.1. The heterogeneous composition of the Italian mantl ...
... correspond to the preferred Vs-depth distributions, derived from the nonlinear tomographic inversion, following the optimization procedure described by Boyadzhiev et al. (2008). 2. Calculation of mantle temperatures from seismic wave velocities 2.1. The heterogeneous composition of the Italian mantl ...
Cenozoic geological and plate tectonic evolution of SE Asia and the
... older orogenic belts. They preserve a record of major changes in tectonics, including subduction polarity reversals, elimination of volcanic arcs, changing plate boundaries and extension within an overall contractional setting. Rapid tectonic changes have occurred within periods of less than 5 Ma. M ...
... older orogenic belts. They preserve a record of major changes in tectonics, including subduction polarity reversals, elimination of volcanic arcs, changing plate boundaries and extension within an overall contractional setting. Rapid tectonic changes have occurred within periods of less than 5 Ma. M ...
Geology
... Showa-machi 3173-25, Kanazawa-ku, Yokohama, Japan Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Natsushima 2-15, Yokosuka, Japan ...
... Showa-machi 3173-25, Kanazawa-ku, Yokohama, Japan Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Natsushima 2-15, Yokosuka, Japan ...
Niu, Y., Generation and evolution of basaltic magmas
... felsic (i.e., higher SiO2) or less mafic (i.e., lower FeO and MgO, and lower MgO/FeO ratio) than the source rock. In other words, basaltic melts result from partial melting of mantle peridotites; partial melting of basaltic rocks (basalts, diabases, gabbros etc.) cannot produce basaltic melts, but m ...
... felsic (i.e., higher SiO2) or less mafic (i.e., lower FeO and MgO, and lower MgO/FeO ratio) than the source rock. In other words, basaltic melts result from partial melting of mantle peridotites; partial melting of basaltic rocks (basalts, diabases, gabbros etc.) cannot produce basaltic melts, but m ...
Mantle Melting Beneath Mid-Ocean Ridges The Harvard community
... the solidus at greater depths, leading to a larger melting regime, greater extents of melting, and thicker crust than that produced by cold mantle. The numbers on the bottom diagrams correspond to the pressures where melting stops for the numbered flow lines on the upper diagrams. ...
... the solidus at greater depths, leading to a larger melting regime, greater extents of melting, and thicker crust than that produced by cold mantle. The numbers on the bottom diagrams correspond to the pressures where melting stops for the numbered flow lines on the upper diagrams. ...
22_Lectures_PPT
... • Plates move away from one another • As plates move apart, asthenosphere rises and partially melts to form lava —New crust is formed as lava fills in the gaps between plates ...
... • Plates move away from one another • As plates move apart, asthenosphere rises and partially melts to form lava —New crust is formed as lava fills in the gaps between plates ...
Intracratonic asthenosphere upwelling and lithosphere rejuvenation
... anhydrous spinel lherzolites. Major and trace element analyses on bulk rocks and constituent mineral phases show that the primary compositions are widely overprinted by metasomatic processes. Trace element modelling of the metasomatised clinopyroxenes allows the inference that the metasomatic agents ...
... anhydrous spinel lherzolites. Major and trace element analyses on bulk rocks and constituent mineral phases show that the primary compositions are widely overprinted by metasomatic processes. Trace element modelling of the metasomatised clinopyroxenes allows the inference that the metasomatic agents ...
Mantle Meltıng Beneath Mıd-Ocean rıdges
... the solidus at greater depths, leading to a larger melting regime, greater extents of melting, and thicker crust than that produced by cold mantle. The numbers on the bottom diagrams correspond to the pressures where melting stops for the numbered flow lines on the upper diagrams. ...
... the solidus at greater depths, leading to a larger melting regime, greater extents of melting, and thicker crust than that produced by cold mantle. The numbers on the bottom diagrams correspond to the pressures where melting stops for the numbered flow lines on the upper diagrams. ...
Mantle-driven deformation of orogenic zones and clutch tectonics
... mantle and a more mobile, fluid-like asthenospheric mantle (Brace & Kohlstedt 1980). Modifications to these rheological estimates have been made, such as the recognition of the importance of micas in upper crustal deformation (Imber et al. 2001) or the effect of water in the mantle rheology (Kohlste ...
... mantle and a more mobile, fluid-like asthenospheric mantle (Brace & Kohlstedt 1980). Modifications to these rheological estimates have been made, such as the recognition of the importance of micas in upper crustal deformation (Imber et al. 2001) or the effect of water in the mantle rheology (Kohlste ...
Contents and Preface
... the continental lithosphere, affected by a much longer geological evolution and characterized by significant heterogeneity in both its crustal and mantle components. By now, the lithosphere is probably the best studied part of the plate-tectonics system. Seismic tomography has led to the realization ...
... the continental lithosphere, affected by a much longer geological evolution and characterized by significant heterogeneity in both its crustal and mantle components. By now, the lithosphere is probably the best studied part of the plate-tectonics system. Seismic tomography has led to the realization ...
SCIENCE CHINA Magmatism during continental collision
... accretionary orogen is referred as the oceanic circumPacific subduction systems, including the Cordillera-Andes active continental margin accretionary belt and the trencharc-basin system in the west part of the Pacific Ocean. The accretionary mechanism is characterized by oceanic subduction (B-type) ...
... accretionary orogen is referred as the oceanic circumPacific subduction systems, including the Cordillera-Andes active continental margin accretionary belt and the trencharc-basin system in the west part of the Pacific Ocean. The accretionary mechanism is characterized by oceanic subduction (B-type) ...
The Lithosphere-Asthenosphere Boundary
... over more conductive asthenosphere. The lack of variation in the thickness of this layer (despite significant differences in plate age and cooling across the study region), coupled with anisotropy in asthenospheric conductivity, was interpreted as evidence that the mantle lithosphere corresponds to t ...
... over more conductive asthenosphere. The lack of variation in the thickness of this layer (despite significant differences in plate age and cooling across the study region), coupled with anisotropy in asthenospheric conductivity, was interpreted as evidence that the mantle lithosphere corresponds to t ...
A model for the layered upper mantle
... the experimentally determined high melting temperatures of (Mg,Fe)SiO 3 perovskite (Zerr and Boehler, 1993) would prohibit convection in the lower mantle unless the melting temperatures are decreased by volatiles. Any estimate of the rheological properties of the Earth, for example from a postglacia ...
... the experimentally determined high melting temperatures of (Mg,Fe)SiO 3 perovskite (Zerr and Boehler, 1993) would prohibit convection in the lower mantle unless the melting temperatures are decreased by volatiles. Any estimate of the rheological properties of the Earth, for example from a postglacia ...
Earth Science Ch. 4 Practice Test
... Samples collected by the Glomar Challenger showed that the youngest rocks on the ocean floor are found in the center of ____________________. ...
... Samples collected by the Glomar Challenger showed that the youngest rocks on the ocean floor are found in the center of ____________________. ...
Geodynamic models of Cordilleran orogens
... Two distinct modes of gravitational foundering are: (1) RayleighTaylor–type (RT) instability (“drip”; Fig. 1B), possibly induced by lithospheric shortening combined with magmatic extraction at deep levels under the arcs (e.g., Houseman et al., 1981; Houseman and Molnar, 1997; Molnar et al., 1998) an ...
... Two distinct modes of gravitational foundering are: (1) RayleighTaylor–type (RT) instability (“drip”; Fig. 1B), possibly induced by lithospheric shortening combined with magmatic extraction at deep levels under the arcs (e.g., Houseman et al., 1981; Houseman and Molnar, 1997; Molnar et al., 1998) an ...
Serpentinite - Elements Magazine
... from host serpentinite, provides a geochemical test of this model by showing a peak frequency at Mg# = 97 (Evans et al. 2012, Fig. 14). Lizardite compositions have a similarly placed frequency maximum (Mg# = 96–97), but in contrast to chrysotile the histogram has a broad tail extending to an Mg# of ...
... from host serpentinite, provides a geochemical test of this model by showing a peak frequency at Mg# = 97 (Evans et al. 2012, Fig. 14). Lizardite compositions have a similarly placed frequency maximum (Mg# = 96–97), but in contrast to chrysotile the histogram has a broad tail extending to an Mg# of ...
Crustal collapse, mantle upwelling, and Cenozoic extension in the
... Although eruption of mafic magma is rare, significant mantle upwelling seems necessaryto provide heat for the extensive crustal anatexis [Hildreth, 1981] and sourcematerials for some of the silicic tuff [Grunder, 1995; Johnson, 1991]. The relationship between extensional tectonics and volcanism is c ...
... Although eruption of mafic magma is rare, significant mantle upwelling seems necessaryto provide heat for the extensive crustal anatexis [Hildreth, 1981] and sourcematerials for some of the silicic tuff [Grunder, 1995; Johnson, 1991]. The relationship between extensional tectonics and volcanism is c ...
Topography and geoid due to lithospheric mass anomalies
... important observations. First, the oceanic floor everywhere follows the same topography versus age relationship, indicating that the long-wavelength topography of deep origin over the ocean basins has a small amplitude. If the flattening of the sea-floor topography at age larger than 100 Ma is assoc ...
... important observations. First, the oceanic floor everywhere follows the same topography versus age relationship, indicating that the long-wavelength topography of deep origin over the ocean basins has a small amplitude. If the flattening of the sea-floor topography at age larger than 100 Ma is assoc ...
california state university, northridge rayleigh wave tomography
... direction today. This Pacific–North American deformation zone began contracting in width during Pliocene time, but clockwise rotation progresses today (Luyendyk, 1991). However, it is not clear whether the WTR continues offshore to the south or west across the coastline, or how far offshore rotation ...
... direction today. This Pacific–North American deformation zone began contracting in width during Pliocene time, but clockwise rotation progresses today (Luyendyk, 1991). However, it is not clear whether the WTR continues offshore to the south or west across the coastline, or how far offshore rotation ...
Crustal structure and evolution of the Mariana intra
... crustal, and lower-crustal layers in the northern Izu arc are 496 km3/km, 732 km3/km, 963 km3/km, and 2455 km3/km, and their proportions are 11%, 16%, 21%, and 53%, respectively (Table 1). It might be expected that the proportions of the three arcs would be roughly similar; however, the proportion o ...
... crustal, and lower-crustal layers in the northern Izu arc are 496 km3/km, 732 km3/km, 963 km3/km, and 2455 km3/km, and their proportions are 11%, 16%, 21%, and 53%, respectively (Table 1). It might be expected that the proportions of the three arcs would be roughly similar; however, the proportion o ...
Geology - Archean Environment: The habitat of early life.
... Proterozoic and Phanerozoic, where the data are abundant, and between the preNeoproterozoic, where UHP metamorphism does not occur, and Neoproterozoic and younger belts, where UHP metamorphism is common. These observations are inconsistent with a progressively degraded record with increasing age. Ho ...
... Proterozoic and Phanerozoic, where the data are abundant, and between the preNeoproterozoic, where UHP metamorphism does not occur, and Neoproterozoic and younger belts, where UHP metamorphism is common. These observations are inconsistent with a progressively degraded record with increasing age. Ho ...
Oceanic trench
The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor. Oceanic trenches are a distinctive morphological feature of convergent plate boundaries, along which lithospheric plates move towards each other at rates that vary from a few mm to over ten cm per year. A trench marks the position at which the flexed, subducting slab begins to descend beneath another lithospheric slab. Trenches are generally parallel to a volcanic island arc, and about 200 km (120 mi) from a volcanic arc. Oceanic trenches typically extend 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic floor. The greatest ocean depth to be sounded is in the Challenger Deep of the Mariana Trench, at a depth of 11,034 m (36,201 ft) below sea level. Oceanic lithosphere moves into trenches at a global rate of about 3 km2/yr.