Hotspots and Melting Anomalies - Earth and Environmental Sciences
... An intriguing, yet enigmatic form of age-progressive volcanism is represented by the PukaPuka and Sojourn Ridges, which extend NW away from the East Pacific Rise. With respect to its geographic trend and duration, the Puka-Puka Ridge resembles some of the other volcano chains the region, such as the ...
... An intriguing, yet enigmatic form of age-progressive volcanism is represented by the PukaPuka and Sojourn Ridges, which extend NW away from the East Pacific Rise. With respect to its geographic trend and duration, the Puka-Puka Ridge resembles some of the other volcano chains the region, such as the ...
the Zero Paradox Noble Gas Mantle
... layered model of the mantle in which a shallow well mixed, volatile poor and depleted reservoir supplies mid ocean ridge volcanism. In this model plumes feed intraplate volcanism from the deep mantle and sample a more volatile rich and less depleted portion of the mantle. The boundary between these ...
... layered model of the mantle in which a shallow well mixed, volatile poor and depleted reservoir supplies mid ocean ridge volcanism. In this model plumes feed intraplate volcanism from the deep mantle and sample a more volatile rich and less depleted portion of the mantle. The boundary between these ...
Earth`s heterogeneous mantle: A product of convection
... Ubiquitous heterogeneity in the Earth's mantle has been documented by numerous chemical and isotopic analyses of oceanic basalts. Despite the ever-increasing amount of data, the way in which compositional heterogeneity is manifest in the Earth's mantle, as well as the processes leading to mantle het ...
... Ubiquitous heterogeneity in the Earth's mantle has been documented by numerous chemical and isotopic analyses of oceanic basalts. Despite the ever-increasing amount of data, the way in which compositional heterogeneity is manifest in the Earth's mantle, as well as the processes leading to mantle het ...
physical, chemical, and chronological characteristics of
... Figure 3. Cross section showing the P wave velocity variation in the upper mantle of southern Africa [James et al., 2001]. The cross section runs from SW to NE beginning in Cape Town (B) and extending into central Zimbabwe (B0). The light blue band at the top shows vertically exaggerated surface top ...
... Figure 3. Cross section showing the P wave velocity variation in the upper mantle of southern Africa [James et al., 2001]. The cross section runs from SW to NE beginning in Cape Town (B) and extending into central Zimbabwe (B0). The light blue band at the top shows vertically exaggerated surface top ...
Mantle Mixing - Earth and Environmental Sciences
... Observations of the geochemical diversity of mid oceanic ridge and ocean island basalts have traditionally been attributed to the existence of large scale mantle heterogeneity. In particular the layered convection model has provided an important conceptual basis for discussing the chemical evolution ...
... Observations of the geochemical diversity of mid oceanic ridge and ocean island basalts have traditionally been attributed to the existence of large scale mantle heterogeneity. In particular the layered convection model has provided an important conceptual basis for discussing the chemical evolution ...
Crustal thickness anomalies in the North Atlantic Ocean Tingting Wang
... (Figure 1e) from the 5 min global database of Divins [2009]. In most of the North Atlantic away from continental margins the sediment thickness is less than 1 km. Thicker sediments occur primarily along the continental margins and can exceed 10 km on the older margins. When comparing sediment thickn ...
... (Figure 1e) from the 5 min global database of Divins [2009]. In most of the North Atlantic away from continental margins the sediment thickness is less than 1 km. Thicker sediments occur primarily along the continental margins and can exceed 10 km on the older margins. When comparing sediment thickn ...
The life cycle of suprasubduction zone ophiolites
... 1985]. I will focus here on those ophiolites thought to be associated with forearc rifting. These constitute most of the major ophiolite occurrences of the world, including those that are commonly used as structural analogues for oceanic crust. One of the most robust tectonic models for SSZ ophiolit ...
... 1985]. I will focus here on those ophiolites thought to be associated with forearc rifting. These constitute most of the major ophiolite occurrences of the world, including those that are commonly used as structural analogues for oceanic crust. One of the most robust tectonic models for SSZ ophiolit ...
Shervais, J.W., 2001, Birth, Death, and Resurrection: The Life Cycle
... 1985]. I will focus here on those ophiolites thought to be associated with forearc rifting. These constitute most of the major ophiolite occurrences of the world, including those that are commonly used as structural analogues for oceanic crust. One of the most robust tectonic models for SSZ ophiolit ...
... 1985]. I will focus here on those ophiolites thought to be associated with forearc rifting. These constitute most of the major ophiolite occurrences of the world, including those that are commonly used as structural analogues for oceanic crust. One of the most robust tectonic models for SSZ ophiolit ...
MANTLE MIXING - Earth and Environmental Sciences
... extent of MORB melting. An estimate of 20% partial melting at mid-oceanic ridges gives a MORB source mantle He concentration of 1.3 × 109 atoms 3He/g. O’Nions & Oxburgh (1983) noted that the rate of outgassing of the associated radiogenic 4He was similar to the amount produced in the MORB-source abo ...
... extent of MORB melting. An estimate of 20% partial melting at mid-oceanic ridges gives a MORB source mantle He concentration of 1.3 × 109 atoms 3He/g. O’Nions & Oxburgh (1983) noted that the rate of outgassing of the associated radiogenic 4He was similar to the amount produced in the MORB-source abo ...
Mantle mixing - Earth and Environmental Sciences
... Convective flows provide a mechanism for stirring and mixing of heterogeneities. The principle components of this process are stretching, folding, breakup, and diffusion (Ottino, 1989). Stretching and folding are illustrated in Figure 1. Stretching occurs in the presence of velocity gradients (such ...
... Convective flows provide a mechanism for stirring and mixing of heterogeneities. The principle components of this process are stretching, folding, breakup, and diffusion (Ottino, 1989). Stretching and folding are illustrated in Figure 1. Stretching occurs in the presence of velocity gradients (such ...
ž / Evidence from mantle xenoliths for relatively thin -100
... Garnet peridotite xenoliths in the Quaternary Pali-Aike alkali olivine basalts of southernmost South America are samples of the deeper portion of continental lithosphere formed by accretion along the western margin of Gondwanaland during the Phanerozoic. Core compositions of minerals in garnet perid ...
... Garnet peridotite xenoliths in the Quaternary Pali-Aike alkali olivine basalts of southernmost South America are samples of the deeper portion of continental lithosphere formed by accretion along the western margin of Gondwanaland during the Phanerozoic. Core compositions of minerals in garnet perid ...
KENT C. CONDIE
... The parental theory of plate tectonics, seafloor spreading, states that new lithosphere is formed at ocean ridges and moves away from ridge axes with a motion like that of a conveyor belt as new lithosphere fills in the resulting crack or rift. The mosaic of plates, which range from 50 to over 200 k ...
... The parental theory of plate tectonics, seafloor spreading, states that new lithosphere is formed at ocean ridges and moves away from ridge axes with a motion like that of a conveyor belt as new lithosphere fills in the resulting crack or rift. The mosaic of plates, which range from 50 to over 200 k ...
Plate Tectonics Jeopardy
... dense so it floats to the top, where it cools and contracts, making it sink. 100 pts. ...
... dense so it floats to the top, where it cools and contracts, making it sink. 100 pts. ...
Oxygen-isotope and trace element constraints on the origins of silica
... dacitic) hydrous melt inclusions that were likely trapped when these rocks were within the upper mantle wedge underlying the arc. These melt inclusions have been previously interpreted to be slab-derived melts. We tested this hypothesis by analyzing the oxygen isotope compositions of these inclusion ...
... dacitic) hydrous melt inclusions that were likely trapped when these rocks were within the upper mantle wedge underlying the arc. These melt inclusions have been previously interpreted to be slab-derived melts. We tested this hypothesis by analyzing the oxygen isotope compositions of these inclusion ...
Numerical models, geochemistry and the zero-paradox noble
... depleted reservoir supplies mid-ocean-ridge volcanism. In this model, plumes feed intraplate volcanism from the deep mantle and sample a more volatile-rich and less depleted portion of the mantle. The boundary between these reservoirs has often been assumed to be at a depth of 670 km, where either a ...
... depleted reservoir supplies mid-ocean-ridge volcanism. In this model, plumes feed intraplate volcanism from the deep mantle and sample a more volatile-rich and less depleted portion of the mantle. The boundary between these reservoirs has often been assumed to be at a depth of 670 km, where either a ...
Hawaii, Boundary Layers and Ambient
... controlled by processes and materials entirely in the upper boundary layer (5220 km depth) of the mantle rather than by deep-seated thermal instabilities. The upper boundary layer (BL) of the mantle is fertile enough, hot enough and variable enough to provide the observed range of temperatures and c ...
... controlled by processes and materials entirely in the upper boundary layer (5220 km depth) of the mantle rather than by deep-seated thermal instabilities. The upper boundary layer (BL) of the mantle is fertile enough, hot enough and variable enough to provide the observed range of temperatures and c ...
Phase Transitions and Mineralogy of the Upper Mantle
... xenoliths incorporated in volcanic rocks erupted on the Earth’s surface. Such mantle xenoliths are common in certain alkali-rich mafic magmas and kimberlites. Field evidence suggests that the upper mantle is peridotitic in composition, although significant heterogeneities are clearly recognized. Fro ...
... xenoliths incorporated in volcanic rocks erupted on the Earth’s surface. Such mantle xenoliths are common in certain alkali-rich mafic magmas and kimberlites. Field evidence suggests that the upper mantle is peridotitic in composition, although significant heterogeneities are clearly recognized. Fro ...
PDF (Chapter 11. Evolution of the Mantle)
... parental picrites, except for K,O (Green and others, 1979). Melting of eclogites, of course, also gives basaltic composition melts, so the above argument, at best, is permissive rather than persuasive. Melting of eclogites would have to be very extensive, and melt-crystal segregation would occur bef ...
... parental picrites, except for K,O (Green and others, 1979). Melting of eclogites, of course, also gives basaltic composition melts, so the above argument, at best, is permissive rather than persuasive. Melting of eclogites would have to be very extensive, and melt-crystal segregation would occur bef ...
Karson, J.A., and Lawrence, R.M., 1997. Tectonic setting of
... in structural geometry of adjacent segments require that these regions contain oblique-slip or strike-slip fault zones that permit different normal fault geometries and/or rates of tectonic extension in adjacent segments. These are similar to "accommodation zones" or "transfer zones" found in contin ...
... in structural geometry of adjacent segments require that these regions contain oblique-slip or strike-slip fault zones that permit different normal fault geometries and/or rates of tectonic extension in adjacent segments. These are similar to "accommodation zones" or "transfer zones" found in contin ...
Plume mantle source heterogeneity through time: Insights from the
... unit, lava flows locally grade to tuff breccias, occasionally with chert and picrite clasts, probably resulting from explosive volcanism caused by the contact between magma, water and sediments. The presence of these breccias on top of the lava pile suggests that eruptions may have occurred in shall ...
... unit, lava flows locally grade to tuff breccias, occasionally with chert and picrite clasts, probably resulting from explosive volcanism caused by the contact between magma, water and sediments. The presence of these breccias on top of the lava pile suggests that eruptions may have occurred in shall ...
High-Mg# andesitic lavas of the Shisheisky Complex, Northern
... SiO2) combined with the location of the volcanic field above the edge of the subducting Pacific Plate support a genetic model that involves melting of eclogite or pyroxenite at or near the surface of the subducting plate, followed by interaction of that melt with hotter peridotite in the over-lying ...
... SiO2) combined with the location of the volcanic field above the edge of the subducting Pacific Plate support a genetic model that involves melting of eclogite or pyroxenite at or near the surface of the subducting plate, followed by interaction of that melt with hotter peridotite in the over-lying ...
Geophysical-petrological model of the crust and upper mantle in the
... The India-Eurasia collision zone consists of a large amalgamation of crustal and lithospheric domains, accreted each other throughout time. The India peninsula is formed by an ancient continental crust (the Precambrian Indian shield), which is itself a collage of cratonic blocks and mobile belts ass ...
... The India-Eurasia collision zone consists of a large amalgamation of crustal and lithospheric domains, accreted each other throughout time. The India peninsula is formed by an ancient continental crust (the Precambrian Indian shield), which is itself a collage of cratonic blocks and mobile belts ass ...
Lithosphere delamination in continental collisional orogens: A
... We used a large-scale model domain (4000 × 400 km) to study the dynamics of continental collision and lithosphere delamination. Using a nonuniform rectangular numerical grid, we represent the collision zone with a 1 × 1 km high resolution while using a 5 × 1 km for the rest of the model domain. A de ...
... We used a large-scale model domain (4000 × 400 km) to study the dynamics of continental collision and lithosphere delamination. Using a nonuniform rectangular numerical grid, we represent the collision zone with a 1 × 1 km high resolution while using a 5 × 1 km for the rest of the model domain. A de ...
Roberts et al., 2013, Basin Modeling
... The gravity inversion methodology and workflow is summarized in Figure 1a (adapted from Alvey 2010). Key to the success of the gravity inversion method are two geological corrections, made in order to account for the highly attenuated nature of the continental crust at rifted margins. The two correc ...
... The gravity inversion methodology and workflow is summarized in Figure 1a (adapted from Alvey 2010). Key to the success of the gravity inversion method are two geological corrections, made in order to account for the highly attenuated nature of the continental crust at rifted margins. The two correc ...
Crustal geophysical research helps constrain the nature of mantle
... crust. Regardless of crustal thickness variations, the ratio of Layer 2 thickness versus total crustal thickness is quite uniform (around 25 %), indicating that Layer 3 accommodates most of the crustal overthickening (Mutter and Mutter, 1993), and the mean Layer 3 velocity is similar to that of norm ...
... crust. Regardless of crustal thickness variations, the ratio of Layer 2 thickness versus total crustal thickness is quite uniform (around 25 %), indicating that Layer 3 accommodates most of the crustal overthickening (Mutter and Mutter, 1993), and the mean Layer 3 velocity is similar to that of norm ...
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.