Earth and Planetary Science Letters
... from a high MgO and CaO primary magma will not only have low contents of CaO, but they will also be low in SiO2. This is in contrast to observed high MgO lavas that contain both low CaO and high SiO2. Therefore, some other process is controlling the substantial ...
... from a high MgO and CaO primary magma will not only have low contents of CaO, but they will also be low in SiO2. This is in contrast to observed high MgO lavas that contain both low CaO and high SiO2. Therefore, some other process is controlling the substantial ...
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... the dikes and the magnitude of anisotropy is likely smaller than that beneath active rifts. Paleozoic rifting of the aulacogen parallels a group of ca. 1350 Ma northwest-striking dikes (Thomas, 2006) and massive synrift intrusions are required to explain the linear gravity high (Fig. 1) and the seis ...
... the dikes and the magnitude of anisotropy is likely smaller than that beneath active rifts. Paleozoic rifting of the aulacogen parallels a group of ca. 1350 Ma northwest-striking dikes (Thomas, 2006) and massive synrift intrusions are required to explain the linear gravity high (Fig. 1) and the seis ...
Tectonic controls on the distribution of large
... No significant porphyry systems are known in western Indonesia. The subducting oceanic plate in this region comprises cold Eocene crust, while the thin lithosphere of SE Asia is also relatively cold. These factors suggest that the subducting oceanic plate never had time to heat up sufficiently to si ...
... No significant porphyry systems are known in western Indonesia. The subducting oceanic plate in this region comprises cold Eocene crust, while the thin lithosphere of SE Asia is also relatively cold. These factors suggest that the subducting oceanic plate never had time to heat up sufficiently to si ...
Relations between sedimentary basins and petroleum
... geodesy, earthquakes and magnetic anomalies for past movements. The flow of the plates, its westward polarization and the greater velocity of plates at low latitudes suggest that plate tectonics is influenced by the Earth’s rotation. The concentration of the mantle also seems to support this hypothe ...
... geodesy, earthquakes and magnetic anomalies for past movements. The flow of the plates, its westward polarization and the greater velocity of plates at low latitudes suggest that plate tectonics is influenced by the Earth’s rotation. The concentration of the mantle also seems to support this hypothe ...
Lecture 40 - Cornell geology
... Edmond, 1987). The discrepancy reflects the fact that the ocean is not a simple equilibrium system, but rather a kinetically controlled open one. Since all processes operating in the ocean appear to preferentially remove 10B from the ocean, seawater is driven to an extremely 11B-rich composition. Is ...
... Edmond, 1987). The discrepancy reflects the fact that the ocean is not a simple equilibrium system, but rather a kinetically controlled open one. Since all processes operating in the ocean appear to preferentially remove 10B from the ocean, seawater is driven to an extremely 11B-rich composition. Is ...
Fluid Processes in Subduction Zones Hydrous Minerals and
... Selected Characteristics of Volcanic Arcs • Depth to underlying Benioff zone is ~100 – 200 km • Depth to underlying Benioff zone beneath volcanic ...
... Selected Characteristics of Volcanic Arcs • Depth to underlying Benioff zone is ~100 – 200 km • Depth to underlying Benioff zone beneath volcanic ...
Petrology and tectonics of Phanerozoic continent formation: From
... continent formation. We combine new trace-element data on lower crustal xenoliths from the Mesozoic Sierra Nevada Batholith with an extensive grid-based geochemical map of the Peninsular Ranges Batholith, the southern equivalent of the Sierras. Collectively, these observations give a three-dimension ...
... continent formation. We combine new trace-element data on lower crustal xenoliths from the Mesozoic Sierra Nevada Batholith with an extensive grid-based geochemical map of the Peninsular Ranges Batholith, the southern equivalent of the Sierras. Collectively, these observations give a three-dimension ...
The key role of global solid-Earth processes in
... Fig. 1 Tomographic images and inferred flow of the mantle beneath the North Atlantic, Iceland and Greenland. (A) Cross-section through P-wave velocity anomaly model P06_CSloc (Amaru, 2007; http://igitur-archive.library.uu.nl/dissertations/ 2007-0202-201924/index.htm) along the line shown in (C). (B) ...
... Fig. 1 Tomographic images and inferred flow of the mantle beneath the North Atlantic, Iceland and Greenland. (A) Cross-section through P-wave velocity anomaly model P06_CSloc (Amaru, 2007; http://igitur-archive.library.uu.nl/dissertations/ 2007-0202-201924/index.htm) along the line shown in (C). (B) ...
Proterozoic Rocks, Glacier NP
... • Geologist have rather arbitrarily placed – the Archean-Proterozoic boundary – at 2.5 billion years ago – because it marks the approximate time – of changes in the style of crustal evolution • However, we must emphasize "approximate," – because Archean-type crustal evolution ...
... • Geologist have rather arbitrarily placed – the Archean-Proterozoic boundary – at 2.5 billion years ago – because it marks the approximate time – of changes in the style of crustal evolution • However, we must emphasize "approximate," – because Archean-type crustal evolution ...
Evolution of the Indian Continental Lithosphere: Insights from
... drag during the post-130Ma drift of the Indian shield and, if true, would erase the expectations of lithospheric properties imbibed through over 3.5 Ga in the span of some 130 million years of drift. Geological contradictions to this conclusion arise from a total absence of any dynamic or magmatic m ...
... drag during the post-130Ma drift of the Indian shield and, if true, would erase the expectations of lithospheric properties imbibed through over 3.5 Ga in the span of some 130 million years of drift. Geological contradictions to this conclusion arise from a total absence of any dynamic or magmatic m ...
Plate Tectonics Teacher Assessment User Manual
... forced upward forming mountain ranges rather than being completely subducted into Earth’s interior. If two plates without continents are in contact and being pushed together, the colder/denser plate subducts beneath the other. ...
... forced upward forming mountain ranges rather than being completely subducted into Earth’s interior. If two plates without continents are in contact and being pushed together, the colder/denser plate subducts beneath the other. ...
The reflection seismic survey of project TIPTEQ—the inventory of the
... in the Coastal Cordillera. Both the schists and the homogeneous granite body are favourable for deep seismic imaging, whereas due to scattering absorption it is probably difficult to image structures below the strongly heterogeneous basement. This situation is one possible explanation for the less r ...
... in the Coastal Cordillera. Both the schists and the homogeneous granite body are favourable for deep seismic imaging, whereas due to scattering absorption it is probably difficult to image structures below the strongly heterogeneous basement. This situation is one possible explanation for the less r ...
From oceanic plateaus to allochthonous terranes: Numerical
... accretion upon the slab and overriding plate. It has been demonstrated in terms of geodynamic models, that oceanic plateaus might alter trench behaviour leading to flat subduction, slab break off, trench advance and trench retreat (van Hunen et al., 2002; Gerya et al., 2009; Mason et al., 2010). Thre ...
... accretion upon the slab and overriding plate. It has been demonstrated in terms of geodynamic models, that oceanic plateaus might alter trench behaviour leading to flat subduction, slab break off, trench advance and trench retreat (van Hunen et al., 2002; Gerya et al., 2009; Mason et al., 2010). Thre ...
38. EVIDENCE FOR DETACHMENT TECTONICS ON THE IBERIA
... capped by a 450- to 750-m-thick seismically transparent layer of prerift or pretilting sediment (Fig. 9). The basement itself exhibits velocities of 5.5 to 6 km/s, whereas within the pretilting layer the velocity values between 2.8 and 3.4 km/s are relatively low compared to approximately 4.1 km/s c ...
... capped by a 450- to 750-m-thick seismically transparent layer of prerift or pretilting sediment (Fig. 9). The basement itself exhibits velocities of 5.5 to 6 km/s, whereas within the pretilting layer the velocity values between 2.8 and 3.4 km/s are relatively low compared to approximately 4.1 km/s c ...
here - W. Steven Holbrook
... that continues 100 km behind the arc, and a subducting slab that is only 50–60 km beneath the present-day arc platform. In addition, one feature is notably absent: there is virtually no material within the arc with velocities of 6.0 ± 0.4 km/s. This finding is in marked contrast to recent results fr ...
... that continues 100 km behind the arc, and a subducting slab that is only 50–60 km beneath the present-day arc platform. In addition, one feature is notably absent: there is virtually no material within the arc with velocities of 6.0 ± 0.4 km/s. This finding is in marked contrast to recent results fr ...
Subduction of the Rivera plate beneath the Jalisco block as imaged
... Another seismic study at the northern terminus of the MAT (Brown, 2007) shows that the oceanic crust underplates the continental crust north of Bahía de Banderas at depths of 30 km to its top, at a distance of 135 km from the trench. MAGNETOTELLURIC SURVEY Magnetotelluric (MT) surveys have been exte ...
... Another seismic study at the northern terminus of the MAT (Brown, 2007) shows that the oceanic crust underplates the continental crust north of Bahía de Banderas at depths of 30 km to its top, at a distance of 135 km from the trench. MAGNETOTELLURIC SURVEY Magnetotelluric (MT) surveys have been exte ...
34 - School of Ocean and Earth Science and Technology
... produces a bimodal distribution of crustal elevation on Earth that is markedly different from that of Venus, which appears to have a uniform density probably basaltic, crust. ...
... produces a bimodal distribution of crustal elevation on Earth that is markedly different from that of Venus, which appears to have a uniform density probably basaltic, crust. ...
The origin and evolution of the Earth`s continental crust
... The composition of the Archaean upper crust as revealed in the sedimentary record stands in marked contrast to that of the post-Archaean crust (Taylor & McLennan 1995, table 3). A significant difference is shown by the REE patterns in the Archaean sedimentary rocks, which, relative to those of the p ...
... The composition of the Archaean upper crust as revealed in the sedimentary record stands in marked contrast to that of the post-Archaean crust (Taylor & McLennan 1995, table 3). A significant difference is shown by the REE patterns in the Archaean sedimentary rocks, which, relative to those of the p ...
- Wiley Online Library
... [1] Physical properties of the mantle lithosphere have a strong influence on the rifting processes and rifted structures. In particular, in context of rifting, two of these properties have been overlooked: (1) Mohr-Coulomb plasticity (localizing pressure dependent) may not be valid at mantle depths a ...
... [1] Physical properties of the mantle lithosphere have a strong influence on the rifting processes and rifted structures. In particular, in context of rifting, two of these properties have been overlooked: (1) Mohr-Coulomb plasticity (localizing pressure dependent) may not be valid at mantle depths a ...
Dipping reflector sequences in the vicinity of the continent
... of material combined with the rapid and persistent progradation of a fan or outwash deposit from the eroded 'inner high' source area could develop a profile identical to those observed through the dipping reflector sequences (Figure 6A). The nature and composition of the prominent reflector is uncer ...
... of material combined with the rapid and persistent progradation of a fan or outwash deposit from the eroded 'inner high' source area could develop a profile identical to those observed through the dipping reflector sequences (Figure 6A). The nature and composition of the prominent reflector is uncer ...
June 2006 in Valdez, Alaska
... and volcanism along the entire arc, with peak periods of activity from 38–29, 16–11, and 6–0 Ma. David Farris used structural relationships in the Kodiak portion of the Talkeetna arc to propose that the arc was exhumed following an episode of subduction erosion during which blueschist units were und ...
... and volcanism along the entire arc, with peak periods of activity from 38–29, 16–11, and 6–0 Ma. David Farris used structural relationships in the Kodiak portion of the Talkeetna arc to propose that the arc was exhumed following an episode of subduction erosion during which blueschist units were und ...
Noble Gas Constraints on Mantle Structure and Convection
... • For clinopyroxene, Ar slightly more incompatible than K • Experimental data still not good enough to show conclusively how He behaves with respect to U and Th • Time integrated ratios however provide some insights; for example high 3He/4He ratios are never associated with the most depleted isotopi ...
... • For clinopyroxene, Ar slightly more incompatible than K • Experimental data still not good enough to show conclusively how He behaves with respect to U and Th • Time integrated ratios however provide some insights; for example high 3He/4He ratios are never associated with the most depleted isotopi ...
Late-orogenic heating during exhumation: Alpine PTt trajectories
... a subduction and collision zone (Fig. 4). We use a kinematic thermomechanical model based on a model that investigated the feasibility of detachment of part of a subducted lithosphere [32]. The current model was developed to investigate the thermal implications of shallow slab detachment on the over ...
... a subduction and collision zone (Fig. 4). We use a kinematic thermomechanical model based on a model that investigated the feasibility of detachment of part of a subducted lithosphere [32]. The current model was developed to investigate the thermal implications of shallow slab detachment on the over ...
Seismic view on the svalbard passive continental margin
... Thanks to the dense system of airgun shots it was possible to model very accurately the seismic crustal structure along profiles located in the western Svalbard and Barents Sea continental passive margin. There were found sedimentary basins (probably of Cenozoic sequence) with a low seismic velocity ...
... Thanks to the dense system of airgun shots it was possible to model very accurately the seismic crustal structure along profiles located in the western Svalbard and Barents Sea continental passive margin. There were found sedimentary basins (probably of Cenozoic sequence) with a low seismic velocity ...
Supercontinent
In geology, a supercontinent is the assembly of most or all of the Earth's continental blocks or cratons to form a single large landmass. However, the definition of a supercontinent can be ambiguous. Many tectonicists such as P.F. Hoffman (1999) use the term ""supercontinent"" to mean ""a clustering of nearly all continents"". This definition leaves room for interpretation when labeling a continental body and is easier to apply to Precambrian times. Using the first definition provided here, Gondwana (aka Gondwanaland) is not considered a supercontinent, because the landmasses of Baltica, Laurentia and Siberia also existed at the same time but physically separate from each other. The landmass of Pangaea is the collective name describing all of these continental masses when they were in a close proximity to one another. This would classify Pangaea as a supercontinent. According to the definition by Rogers and Santosh (2004), a supercontinent does not exist today. Supercontinents have assembled and dispersed multiple times in the geologic past (see table). The positions of continents have been accurately determined back to the early Jurassic. However, beyond 200 Ma, continental positions are much less certain.