Thematic Article A bathymetric overview of the Mariana forearc
... (1993) state that no active accretionary wedge exists where the average trench ®ll is less than 1 km. High-sediment-supply forearcs are characterized by thick sequences of relatively undeformed sediments derived from the arc and continent lying inboard and above deformed sediments that are scraped o ...
... (1993) state that no active accretionary wedge exists where the average trench ®ll is less than 1 km. High-sediment-supply forearcs are characterized by thick sequences of relatively undeformed sediments derived from the arc and continent lying inboard and above deformed sediments that are scraped o ...
Crustal radial anisotropy across Eastern Tibet and the Western
... curves are measured from ambient noise cross correlations between each pair of simultaneously operating stations between 8 and 44 s period for Love waves and 8 and 65 s for Rayleigh waves. As shown later, the inability to observe Love waves at longer periods implies that radial anisotropy cannot be ...
... curves are measured from ambient noise cross correlations between each pair of simultaneously operating stations between 8 and 44 s period for Love waves and 8 and 65 s for Rayleigh waves. As shown later, the inability to observe Love waves at longer periods implies that radial anisotropy cannot be ...
Adakitic Dacites Formed by Intracrustal Crystal Fractionation of
... problem; that is, a rock’s name and its definition are tied to a particular interpretation of its magmatic genesis, thereby tainting the meaning of the term adakite when it is applied to all magmas that have the requisite chemical signature, regardless of their origin. We use the rock name ‘adakite’ ...
... problem; that is, a rock’s name and its definition are tied to a particular interpretation of its magmatic genesis, thereby tainting the meaning of the term adakite when it is applied to all magmas that have the requisite chemical signature, regardless of their origin. We use the rock name ‘adakite’ ...
Fulltext - ETH E-Collection
... formed as a result of NE-dipping subduction of the Neotethys ocean beneath the European continental margin during the Late Cretaceous. This magmatic arc is associated with some of Europe’s largest porphyry Cu-Au and epithermal Cu-Au deposits. However, the ore deposits are not evenly distributed with ...
... formed as a result of NE-dipping subduction of the Neotethys ocean beneath the European continental margin during the Late Cretaceous. This magmatic arc is associated with some of Europe’s largest porphyry Cu-Au and epithermal Cu-Au deposits. However, the ore deposits are not evenly distributed with ...
Setting Based Classification
... since hydrothermal effects often play some role in most of the other types of metamorphism ...
... since hydrothermal effects often play some role in most of the other types of metamorphism ...
Mantle Convection in the Earth and Planets - U
... convection is the primary mechanism for the transport of heat from the Earth’s deep interior to its surface, it is the underlying cause of plate tectonics, formation and drift of continents, volcanism, earthquakes, and mountain building processes. It also shapes the gravitational and magnetic fields ...
... convection is the primary mechanism for the transport of heat from the Earth’s deep interior to its surface, it is the underlying cause of plate tectonics, formation and drift of continents, volcanism, earthquakes, and mountain building processes. It also shapes the gravitational and magnetic fields ...
Reprint - Frederic MOUTHEREAU
... above a viscous lower crust. In contrast, the weak sedimentary cover deforms by buckling of a thick multilayered cover. Thrust faulting associated with folding occurs in the competent layers and is responsible for most of the earthquakes. There is evidence that the role of the slab pull force in dri ...
... above a viscous lower crust. In contrast, the weak sedimentary cover deforms by buckling of a thick multilayered cover. Thrust faulting associated with folding occurs in the competent layers and is responsible for most of the earthquakes. There is evidence that the role of the slab pull force in dri ...
Dyke swarm emplacement in the Ethiopian Large Igneous Province
... to correlate the dykes with their regional tectonic setting. In this paper, we report on the ¢rst ¢eld observations of the dykes in the Tana^Belaya area, western Ethiopia, that we complement with satellite imagery. This area was selected due to excellent dyke exposure compared with most other dyke s ...
... to correlate the dykes with their regional tectonic setting. In this paper, we report on the ¢rst ¢eld observations of the dykes in the Tana^Belaya area, western Ethiopia, that we complement with satellite imagery. This area was selected due to excellent dyke exposure compared with most other dyke s ...
Garnet: Common Mineral, Uncommonly Useful
... The dark red crystals that frequently adorn common and to its applications in society. Wood, Kiseeva, and Matzen begin with a discussion of the largest reservoir mica schists are garnet (FIG. 1A). The purple-red hue that of garnet in the planet—the mantle—where the mineral sometimes decorates the cr ...
... The dark red crystals that frequently adorn common and to its applications in society. Wood, Kiseeva, and Matzen begin with a discussion of the largest reservoir mica schists are garnet (FIG. 1A). The purple-red hue that of garnet in the planet—the mantle—where the mineral sometimes decorates the cr ...
alleghanian plutonism in the eastern blue ridge
... the Alleghanian plutonism. Regardless, this research does not attempt to identify melting mechanisms but rather whether or not it was subduction driven. Continental arc Although the origin of Alleghanian plutonism is widely accepted as crustal melting, synand post-collisional mechanisms do not expla ...
... the Alleghanian plutonism. Regardless, this research does not attempt to identify melting mechanisms but rather whether or not it was subduction driven. Continental arc Although the origin of Alleghanian plutonism is widely accepted as crustal melting, synand post-collisional mechanisms do not expla ...
Tourmaline Isotopes: No Element Left Behind
... these rocks does not significantly fractionate B isotopes, as demonstrated by Kasemann et al. (2000). These authors also showed that tourmaline from metamorphic rocks and granites in the same crustal section have overlapping B isotope compositions, consistent with their estimate for the average cont ...
... these rocks does not significantly fractionate B isotopes, as demonstrated by Kasemann et al. (2000). These authors also showed that tourmaline from metamorphic rocks and granites in the same crustal section have overlapping B isotope compositions, consistent with their estimate for the average cont ...
An Investigation of the carbonatites of the Kaapvaal Craton and their
... used to constrain an extensional setting for related occurrences. In order to give context in which to consider this hypothesis, the formation of carbonatites is reviewed. This work favours the direct mantle melting model as it is most relevant and consistent with observations of Kaapvaal Craton car ...
... used to constrain an extensional setting for related occurrences. In order to give context in which to consider this hypothesis, the formation of carbonatites is reviewed. This work favours the direct mantle melting model as it is most relevant and consistent with observations of Kaapvaal Craton car ...
Mapping the Moho with seismic surface waves: A review, resolution
... period and indicative of the increase of elastic velocities with depth. He also inferred different crustal thicknesses for Eurasia, America and the Atlantic and Pacific Oceans. Testing crustal thicknesses of 30, 60 and 120 km, he estimated the crustal thickness for Eurasia to be around 50 km. This wa ...
... period and indicative of the increase of elastic velocities with depth. He also inferred different crustal thicknesses for Eurasia, America and the Atlantic and Pacific Oceans. Testing crustal thicknesses of 30, 60 and 120 km, he estimated the crustal thickness for Eurasia to be around 50 km. This wa ...
CHAPTER 5 Mafic-ultramafic complexes
... environment for ophiolite formation is in marginal extension basins in arcs (either back arc, or forearc) or as part of the magmatic arc itself (Leitch, 1984). As a consequence there has been a shift from the early interpretation of ophiolites as on-land analogues of the crust and upper mantle forme ...
... environment for ophiolite formation is in marginal extension basins in arcs (either back arc, or forearc) or as part of the magmatic arc itself (Leitch, 1984). As a consequence there has been a shift from the early interpretation of ophiolites as on-land analogues of the crust and upper mantle forme ...
An olivine-free mantle source of Hawaiian shield
... generated in equilibrium with this mineral. Here, however, we show that the unusually high nickel and silicon contents of most parental Hawaiian magmas are inconsistent with a deep olivine-bearing source, because this mineral together with pyroxene buffers both nickel and silicon at lower levels. Th ...
... generated in equilibrium with this mineral. Here, however, we show that the unusually high nickel and silicon contents of most parental Hawaiian magmas are inconsistent with a deep olivine-bearing source, because this mineral together with pyroxene buffers both nickel and silicon at lower levels. Th ...
An olivine-free mantle source of Hawaiian shield basalts
... generated in equilibrium with this mineral. Here, however, we show that the unusually high nickel and silicon contents of most parental Hawaiian magmas are inconsistent with a deep olivine-bearing source, because this mineral together with pyroxene buffers both nickel and silicon at lower levels. Th ...
... generated in equilibrium with this mineral. Here, however, we show that the unusually high nickel and silicon contents of most parental Hawaiian magmas are inconsistent with a deep olivine-bearing source, because this mineral together with pyroxene buffers both nickel and silicon at lower levels. Th ...
Peridotite and Metabasic Rocks of the Marianské Lázně
... version (Fig. 3) is useful for illustrating the presence of fault slices of MLC lithologies in the Teplá Crystalline Unit southeast of the MLC s.s. In the northwest, the MLC is thrust over the Kladská Unit (Figs. 2 & 3), which consists of metasediments and metavolcanics (schists and amphibolites) of ...
... version (Fig. 3) is useful for illustrating the presence of fault slices of MLC lithologies in the Teplá Crystalline Unit southeast of the MLC s.s. In the northwest, the MLC is thrust over the Kladská Unit (Figs. 2 & 3), which consists of metasediments and metavolcanics (schists and amphibolites) of ...
Temporal variation in relative zircon abundance throughout Earth
... content has increased, while average M-value has decreased. These changes are a consequence of secular mantle cooling, where lower average mantle melting extent has led to increased average concentrations of incompatible elements such as Zr (Keller and Schoene, 2012), and generally lower M values du ...
... content has increased, while average M-value has decreased. These changes are a consequence of secular mantle cooling, where lower average mantle melting extent has led to increased average concentrations of incompatible elements such as Zr (Keller and Schoene, 2012), and generally lower M values du ...
u series disequilibria: insights into mantle melting and
... rocks are both expected and usually observed to have (234U/238U) = 1, then 238U can essentially be treated as the parent of 230Th. It is important to remember that for all these U series nuclide pairs both the parent and daughter nuclides are unstable and will undergo radioactive decay at different ...
... rocks are both expected and usually observed to have (234U/238U) = 1, then 238U can essentially be treated as the parent of 230Th. It is important to remember that for all these U series nuclide pairs both the parent and daughter nuclides are unstable and will undergo radioactive decay at different ...
Christiansen, EH, and Keith, JD, 1996, Trace
... decompression, the amount of fluxing volatiles introduced, or the proportions of hydrous minerals for dehydration melting. Regarding this latter point, a crustal protolith with abundant hydrous minerals may produce a magma with low incompatible element concentrations because a larger proportion of t ...
... decompression, the amount of fluxing volatiles introduced, or the proportions of hydrous minerals for dehydration melting. Regarding this latter point, a crustal protolith with abundant hydrous minerals may produce a magma with low incompatible element concentrations because a larger proportion of t ...
thermal state of continental and oceanic lithosphere
... redistribution of heat in young seafloor due to hydrothermal circulation of seawater through the oceanic lithosphere. Chapter 5 computes a number of plate-cooling models, which explore the importance of physical complexities and the addition of a crustal layer not commonly included in these models. ...
... redistribution of heat in young seafloor due to hydrothermal circulation of seawater through the oceanic lithosphere. Chapter 5 computes a number of plate-cooling models, which explore the importance of physical complexities and the addition of a crustal layer not commonly included in these models. ...
Melt migration beneath mid-ocean ridges
... suggests that the accumulated strain associated with passive mantle £ow beneath the spreading centre results in an anisotropic permeability, so that melt can be e¡ectively focused within the neovolcanic zone even in a lower-viscosity upper mantle. The magnitude of the permeability enhancement has ye ...
... suggests that the accumulated strain associated with passive mantle £ow beneath the spreading centre results in an anisotropic permeability, so that melt can be e¡ectively focused within the neovolcanic zone even in a lower-viscosity upper mantle. The magnitude of the permeability enhancement has ye ...
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.