Poisson`s ratio in the lower mantle beneath Alaska: Evidence for
... [4] There are, at least, two major difficulties with seismological studies of compositional heterogeneity that rely on wave speed ratios. First, without absolute values the trade-off between temperature and compositional effects cannot be resolved, so that the interpretation in terms of the origin o ...
... [4] There are, at least, two major difficulties with seismological studies of compositional heterogeneity that rely on wave speed ratios. First, without absolute values the trade-off between temperature and compositional effects cannot be resolved, so that the interpretation in terms of the origin o ...
Geologic Structures
... The atmosphere is a mixture of gases, mostly nitrogen and oxygen (Fig. 1–4). It is held to the Earth by gravity and thins rapidly with altitude. Ninety-nine percent is concentrated within 30 kilometers of the Earth’s surface, but a few traces remain even 10,000 kilometers above the surface. A brief ...
... The atmosphere is a mixture of gases, mostly nitrogen and oxygen (Fig. 1–4). It is held to the Earth by gravity and thins rapidly with altitude. Ninety-nine percent is concentrated within 30 kilometers of the Earth’s surface, but a few traces remain even 10,000 kilometers above the surface. A brief ...
workshop report
... that, once formed, felsic middle crust may be almost unsubductable, and represent permanent additions to continental crust. Studies of Hf and O isotopes and U/Pb ages of tens of thousands of zircons have led to nuanced studies of continuous crustal creation and periodic preservation during most of E ...
... that, once formed, felsic middle crust may be almost unsubductable, and represent permanent additions to continental crust. Studies of Hf and O isotopes and U/Pb ages of tens of thousands of zircons have led to nuanced studies of continuous crustal creation and periodic preservation during most of E ...
7.08 Mantle Downwellings and the Fate of Subducting Slabs
... studies (e.g., Isacks and Molnar, 1971), most slab thermal structure models assume no deformation of the downgoing slab. There is a continuing effort to document and understand changes in petrology along arcs as well, and in many cases these changes cannot be correlated with the traditional paramete ...
... studies (e.g., Isacks and Molnar, 1971), most slab thermal structure models assume no deformation of the downgoing slab. There is a continuing effort to document and understand changes in petrology along arcs as well, and in many cases these changes cannot be correlated with the traditional paramete ...
Deep structure of the Baikal rift zone revealed by joint inversion of
... [6] Previous studies in the Baikal rift zone have led to contrasting interpretations regarding its deep structure and the driving mechanisms. In their teleseismic study, Gao et al. [1994] proceed to a downward projection, assuming that the delay times arise from the geometry of the lithosphereasthen ...
... [6] Previous studies in the Baikal rift zone have led to contrasting interpretations regarding its deep structure and the driving mechanisms. In their teleseismic study, Gao et al. [1994] proceed to a downward projection, assuming that the delay times arise from the geometry of the lithosphereasthen ...
Magma Genesis and Mantle Dynamics at the Harrat Ash
... microprobe at the Institut für Geowissenschaften, Universität Kiel, using standard wavelength-dispersive techniques. The instrument was operated at an accelerating voltage of 15 kV and a beam current of 15 nA. The beam diameter during calibration and measurement was set at 5 µm for glasses and felds ...
... microprobe at the Institut für Geowissenschaften, Universität Kiel, using standard wavelength-dispersive techniques. The instrument was operated at an accelerating voltage of 15 kV and a beam current of 15 nA. The beam diameter during calibration and measurement was set at 5 µm for glasses and felds ...
Igneous Environments
... What Processes Are Involved in the Formation of Igneous Rocks? Igneous rocks form by melting at depth, usually followed by movement of magma toward the surface, and then solidification of the magma into igneous rock. With such a history, igneous systems are best described from the bottom up. Begin wi ...
... What Processes Are Involved in the Formation of Igneous Rocks? Igneous rocks form by melting at depth, usually followed by movement of magma toward the surface, and then solidification of the magma into igneous rock. With such a history, igneous systems are best described from the bottom up. Begin wi ...
The Role of Plate Tectonic-Climate Coupling and Exposed Land
... Plate tectonics plays a vital role in the operation of the long-term carbon cycle. Plate tectonics drives volcanism at ridges and arcs, the major sources of atmospheric CO2 , and facilitates silicate weathering, the primary sink of atmospheric CO2 , by providing a continuous supply of fresh, weather ...
... Plate tectonics plays a vital role in the operation of the long-term carbon cycle. Plate tectonics drives volcanism at ridges and arcs, the major sources of atmospheric CO2 , and facilitates silicate weathering, the primary sink of atmospheric CO2 , by providing a continuous supply of fresh, weather ...
Formation and stability of magmatic segments in the Main Ethiopian
... whereby the magmatic segments are oriented sub-orthogonal to the spreading direction (Géli et al., 1994; Dauteuil and Brun, 1996). These magmatic segments are the loci of magma injections and extensional deformation (Géli et al., 1994). Magmatic injections appear to play an important role in maintai ...
... whereby the magmatic segments are oriented sub-orthogonal to the spreading direction (Géli et al., 1994; Dauteuil and Brun, 1996). These magmatic segments are the loci of magma injections and extensional deformation (Géli et al., 1994). Magmatic injections appear to play an important role in maintai ...
State of lithosphere beneath Tien Shan from petrology and electrical
... [1] The shortening of Tien Shan and the evolution of its lithosphere have been evaluated from P‐T geothermobarometry of xenoliths and from comparison of their electrical conductivity with conductivities obtained from the inversion of magnetotelluric (MT) data. Spinel lherzolite and granulite xenolit ...
... [1] The shortening of Tien Shan and the evolution of its lithosphere have been evaluated from P‐T geothermobarometry of xenoliths and from comparison of their electrical conductivity with conductivities obtained from the inversion of magnetotelluric (MT) data. Spinel lherzolite and granulite xenolit ...
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... sections should have deformed the accretionary prism or other parts of the crust in the shallow part of the subduction zone hanging wall (e.g., Taira, 2001). The first signs of this collision should define when the NE Philippine Sea plate began to be subducted beneath SW Japan. Understanding migrati ...
... sections should have deformed the accretionary prism or other parts of the crust in the shallow part of the subduction zone hanging wall (e.g., Taira, 2001). The first signs of this collision should define when the NE Philippine Sea plate began to be subducted beneath SW Japan. Understanding migrati ...
`emplacement` of an ophiolite?
... Ophiolites have long been recognized as on-land fragments of fossil oceanic lithosphere, which becomes an ophiolite when incorporated into continental margins through a complex process known as 'emplacement'. A fundamental problem of ophiolite emplacement is how dense oceanic crust becomes emplaced ...
... Ophiolites have long been recognized as on-land fragments of fossil oceanic lithosphere, which becomes an ophiolite when incorporated into continental margins through a complex process known as 'emplacement'. A fundamental problem of ophiolite emplacement is how dense oceanic crust becomes emplaced ...
Spatial, temporal and geochemical evolution of
... and Sr–Nd isotopic compositions, indicating common mantle melt sources and magmatic evolutionary trends. The isotopic signatures and trace element characteristics of these granitoids indicate that both lithospheric and asthenospheric mantle melts appear to have contributed to source region of the RM ...
... and Sr–Nd isotopic compositions, indicating common mantle melt sources and magmatic evolutionary trends. The isotopic signatures and trace element characteristics of these granitoids indicate that both lithospheric and asthenospheric mantle melts appear to have contributed to source region of the RM ...
Chapter 17 Basins in arc-continent collisions
... upper plate driven by basal tectonic erosion (Fig. 17.2; von Huene and Scholl, 1991; Underwood and Moore, 1995; Underwood et al., 2003). Forearc basins form on the upper plate between the arc and the outer-arc high (trench-slope break; Dickinson, 1995). Intra-arc basins form among volcanic edifices ...
... upper plate driven by basal tectonic erosion (Fig. 17.2; von Huene and Scholl, 1991; Underwood and Moore, 1995; Underwood et al., 2003). Forearc basins form on the upper plate between the arc and the outer-arc high (trench-slope break; Dickinson, 1995). Intra-arc basins form among volcanic edifices ...
Geol.Soc Australia Spec Publ.22 2003
... the margin west of the Tasman Line underwent substantial extension and rifting, with major microcontinents breaking away in the Early Palaeozoic and the Permo-Carboniferous (Metcalfe 1996, 1998) (Figure 3). The thick, relatively undeformed Palaeozoic section in mainland Irian Jaya is consistent with ...
... the margin west of the Tasman Line underwent substantial extension and rifting, with major microcontinents breaking away in the Early Palaeozoic and the Permo-Carboniferous (Metcalfe 1996, 1998) (Figure 3). The thick, relatively undeformed Palaeozoic section in mainland Irian Jaya is consistent with ...
The volcanic–plutonic connection as a stage for
... view that volcanic provinces are underlain by shallow and deep plutons in the crustal record. 2.1.4. Crystal-rich volcanic units: remobilized plutons? In long-lived calc-alkaline volcanic provinces, large, crystal-rich, ash-flow sheets with probable kinship to granodioritic batholiths (and upper cru ...
... view that volcanic provinces are underlain by shallow and deep plutons in the crustal record. 2.1.4. Crystal-rich volcanic units: remobilized plutons? In long-lived calc-alkaline volcanic provinces, large, crystal-rich, ash-flow sheets with probable kinship to granodioritic batholiths (and upper cru ...
Papers presented to the conference on Plateau Uplift, Mode and
... The Parana Lava Plateau forms a major portion of the Serra do Mar of southern Brasil. From the northern part of Rio Grande do Sul state, the eastern edge of the lava plateau and its continuation in the older crystalline rocks of the Serra do Mar of the Ponta Grossa Arch (state of Parana) and northea ...
... The Parana Lava Plateau forms a major portion of the Serra do Mar of southern Brasil. From the northern part of Rio Grande do Sul state, the eastern edge of the lava plateau and its continuation in the older crystalline rocks of the Serra do Mar of the Ponta Grossa Arch (state of Parana) and northea ...
Convection in a partially molten metasedimentary crust? Insights
... Our models are set with constant temperature at the surface (20 °C) and with heat flux at the base to get an initial thermal gradient of 25 °C/km. We simulate gabbroic intrusion by imposing a temperature of 1200 °C between 25 and 29 km depth. Subsequently the gabbro cools as it loses heat upward, bu ...
... Our models are set with constant temperature at the surface (20 °C) and with heat flux at the base to get an initial thermal gradient of 25 °C/km. We simulate gabbroic intrusion by imposing a temperature of 1200 °C between 25 and 29 km depth. Subsequently the gabbro cools as it loses heat upward, bu ...
The Central Asia collision zone: numerical present-day kinematics
... It is composed by the Zagros orogen in the western sector and the Himalaya-Tibetan orogen in the eastern sector, which are the results of the subduction of the Tethys oceanic lithosphere towards the NNE and the subsequent collisions between Arabia and India plates with the Eurasia plate during the C ...
... It is composed by the Zagros orogen in the western sector and the Himalaya-Tibetan orogen in the eastern sector, which are the results of the subduction of the Tethys oceanic lithosphere towards the NNE and the subsequent collisions between Arabia and India plates with the Eurasia plate during the C ...
A long in situ section of the lower ocean crust: results of ODP Leg
... and 95 km south of the SW Indian Ridge axis. At the time of accretion, however, it was only about 15 km from the active transform fault as there was subsequent transtensional extension across the transform due to a spreading direction change [6]. The top of Atlantis Bank, where the hole is located, ...
... and 95 km south of the SW Indian Ridge axis. At the time of accretion, however, it was only about 15 km from the active transform fault as there was subsequent transtensional extension across the transform due to a spreading direction change [6]. The top of Atlantis Bank, where the hole is located, ...
Occurrences of disseminated sulphides from
... analyses revealed that the megamullion represents an inner-corner, prominent elongated domal high with typical ridge-parallel corrugations (Kamesh Raju et al. 2012). The megamullion rises from the 4,700 m deep rift axis to a depth of 2,300 m over a distance of about 9 km, with an inward-facing slope ...
... analyses revealed that the megamullion represents an inner-corner, prominent elongated domal high with typical ridge-parallel corrugations (Kamesh Raju et al. 2012). The megamullion rises from the 4,700 m deep rift axis to a depth of 2,300 m over a distance of about 9 km, with an inward-facing slope ...
Plate tectonics
Plate tectonics (from the Late Latin tectonicus, from the Greek: τεκτονικός ""pertaining to building"") is a scientific theory that describes the large-scale motion of Earth's lithosphere. This theoretical model builds on the concept of continental drift which was developed during the first few decades of the 20th century. The geoscientific community accepted the theory after the concepts of seafloor spreading were later developed in the late 1950s and early 1960s.The lithosphere, which is the rigid outermost shell of a planet (on Earth, the crust and upper mantle), is broken up into tectonic plates. On Earth, there are seven or eight major plates (depending on how they are defined) and many minor plates. Where plates meet, their relative motion determines the type of boundary; convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The lateral relative movement of the plates typically varies from zero to 100 mm annually.Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle; the material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading. In this way, the total surface of the globe remains the same. This prediction of plate tectonics is also referred to as the conveyor belt principle. Earlier theories (that still have some supporters) propose gradual shrinking (contraction) or gradual expansion of the globe.Tectonic plates are able to move because the Earth's lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the spreading ridge (due to variations in topography and density of the crust, which result in differences in gravitational forces) and drag, with downward suction, at the subduction zones. Another explanation lies in the different forces generated by the rotation of the globe and the tidal forces of the Sun and Moon. The relative importance of each of these factors and their relationship to each other is unclear, and still the subject of much debate.