- ERA - University of Alberta
... lithosphere; crustal flow in a lower-crust channel can cause the surface to invert to become a topographic high. Magmatism caused by lithosphere removal depends on the removal style and the initial thermal structure of lithosphere. During a Rayleigh-Taylor instability (drip), three types of magmas a ...
... lithosphere; crustal flow in a lower-crust channel can cause the surface to invert to become a topographic high. Magmatism caused by lithosphere removal depends on the removal style and the initial thermal structure of lithosphere. During a Rayleigh-Taylor instability (drip), three types of magmas a ...
The nature of the crust beneath the Afar triple junction: Evidence
... plateau (∼40 km) and southeastern plateau (∼35 km). The western plateau shows VP/VS ranging between 1.7–1.9, suggesting a mafic altered crust, likely associated with Cenozoic flood basalts, or current magmatism. The southeastern plateau shows VP/VS more typical of silicic continental crust (∼1.78). ...
... plateau (∼40 km) and southeastern plateau (∼35 km). The western plateau shows VP/VS ranging between 1.7–1.9, suggesting a mafic altered crust, likely associated with Cenozoic flood basalts, or current magmatism. The southeastern plateau shows VP/VS more typical of silicic continental crust (∼1.78). ...
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 ...
Subduction erosion modes: Comparing finite
... have been estimated in the central Andes due to subduction erosion (Kukowski and Oncken, 2006). Elsewhere, higher rates of ca. 10 km Ma− 1 have been associated with topographic asperities on the lower plate (e.g. Clift et al., 2003). Possible mechanisms for this mode of subduction erosion include du ...
... have been estimated in the central Andes due to subduction erosion (Kukowski and Oncken, 2006). Elsewhere, higher rates of ca. 10 km Ma− 1 have been associated with topographic asperities on the lower plate (e.g. Clift et al., 2003). Possible mechanisms for this mode of subduction erosion include du ...
High-Mg# andesitic lavas of the Shisheisky Complex, Northern
... et al. 2002; Kelemen et al. 2003b; Conder 2005). Despite the basic differences between the two models for high-Mg# andesite genesis described earlier, both interpretations imply that high-Mg# andesites are a primary arc magma type that is generated below the crust–mantle boundary under hydrous condi ...
... et al. 2002; Kelemen et al. 2003b; Conder 2005). Despite the basic differences between the two models for high-Mg# andesite genesis described earlier, both interpretations imply that high-Mg# andesites are a primary arc magma type that is generated below the crust–mantle boundary under hydrous condi ...
1 Imaging the transition from flat to normal subduction: Variations in
... km depth based on the offset between the slab anomaly north of the ridge and the location of the ...
... km depth based on the offset between the slab anomaly north of the ridge and the location of the ...
Volatile Cycling of H2O, CO2, F, and Cl in the HIMU Mantle: A New
... Kogiso et al., 1997; Salters and White, 1998; Schiano et al., 2001; Lassiter et al., 2003; Stracke et al., 2003; Stroncik and Haase, 2004; Nishio et al., 2005; Chan et al., 2009; Parai et al., 2009; John et al., 2010; Hanyu et al., 2011; Kawabata et al., 2011; Salters et al., 2011; Krienitz et al., ...
... Kogiso et al., 1997; Salters and White, 1998; Schiano et al., 2001; Lassiter et al., 2003; Stracke et al., 2003; Stroncik and Haase, 2004; Nishio et al., 2005; Chan et al., 2009; Parai et al., 2009; John et al., 2010; Hanyu et al., 2011; Kawabata et al., 2011; Salters et al., 2011; Krienitz et al., ...
The stability of arc lower crust: Insights from the Talkeetna Arc
... -4were not able to compare the density structure of the Talkeetna and Kohistan sections to modern volcanic arcs. In this study, we combine field observations, thermodynamic modeling, and seismic data to constrain the conditions of igneous crystallization in arc lower crust and to determine whether ...
... -4were not able to compare the density structure of the Talkeetna and Kohistan sections to modern volcanic arcs. In this study, we combine field observations, thermodynamic modeling, and seismic data to constrain the conditions of igneous crystallization in arc lower crust and to determine whether ...
Global geochemical variation of mid-ocean ridge basalts - UiO
... (Hofmann, 1997). Such lithosphere contains a sizeable proportion of basaltic ocean crust and minor amounts of pelagic sediments, which have sampled the average upper continental crust. The subducted material is variably processed by fluid extraction in the Benioff zones, where large-ion lithophile e ...
... (Hofmann, 1997). Such lithosphere contains a sizeable proportion of basaltic ocean crust and minor amounts of pelagic sediments, which have sampled the average upper continental crust. The subducted material is variably processed by fluid extraction in the Benioff zones, where large-ion lithophile e ...
Lower Continental Crust. - UCSB Earth Science
... (1990) assembled a database of rock compositions from Archean and post-Archean terrains recrystallized at >0.6 GPa. Huang et al. (2013) updated this database and added a compilation of amphibolite-facies samples. We augmented their granulite data with additional analyses from the literature, and her ...
... (1990) assembled a database of rock compositions from Archean and post-Archean terrains recrystallized at >0.6 GPa. Huang et al. (2013) updated this database and added a compilation of amphibolite-facies samples. We augmented their granulite data with additional analyses from the literature, and her ...
Geochemistry of mafic rocks and melt inclusions and their
... ment of large massive sulfide deposits. On the other hand, slow spreading ridges (e.g. MAR-Middle Atlantic Ridge), which are characterized by relatively weak magmatism, generally lack steady-state magma chambers for their relatively low mantle temperature (Niu and O’hara, 2008), and consequently hav ...
... ment of large massive sulfide deposits. On the other hand, slow spreading ridges (e.g. MAR-Middle Atlantic Ridge), which are characterized by relatively weak magmatism, generally lack steady-state magma chambers for their relatively low mantle temperature (Niu and O’hara, 2008), and consequently hav ...
Geophysical Journal International - E
... understand the mechanisms that produced extension and westward motion of the Alboran domain, simultaneously with NW–SE compression driven by Africa–Europe plates convergence. We perform a P-wave receiver function analysis in which we analyse new data recorded at 83 permanent and temporary seismic br ...
... understand the mechanisms that produced extension and westward motion of the Alboran domain, simultaneously with NW–SE compression driven by Africa–Europe plates convergence. We perform a P-wave receiver function analysis in which we analyse new data recorded at 83 permanent and temporary seismic br ...
1 Bathymetry of the Pacific Plate and its Implications for Thermal
... regions are shown in Figure 3a, 3b, 3c, and 3d, respectively. There are two important features in the results for the Pacific plate as a whole. First, the topography stops deepening with age at ~70 Ma (i.e., topographic “flattening”). Second, the standard deviations are non-uniform and are much lar ...
... regions are shown in Figure 3a, 3b, 3c, and 3d, respectively. There are two important features in the results for the Pacific plate as a whole. First, the topography stops deepening with age at ~70 Ma (i.e., topographic “flattening”). Second, the standard deviations are non-uniform and are much lar ...
Kerguelen Hotspot Magma Output since 130 Ma
... mantle plume paradigm, one involving multiple plume sources, and another consisting of a single, but dismembered plume source. ...
... mantle plume paradigm, one involving multiple plume sources, and another consisting of a single, but dismembered plume source. ...
Oxygen-isotope and trace element constraints on the origins of silica
... values are consistent with the melts having been in oxygen isotope exchange equilibrium with average mantle peridotite at temperatures of 875°C. We suggest the d 18O values of Batan inclusions, as well as their major and trace element compositions, can be explained if they are low-degree melts (or ...
... values are consistent with the melts having been in oxygen isotope exchange equilibrium with average mantle peridotite at temperatures of 875°C. We suggest the d 18O values of Batan inclusions, as well as their major and trace element compositions, can be explained if they are low-degree melts (or ...
Reconstructing the Alps–Carpathians–Dinarides as a key to
... delimits the southernmost units in the Alps affected by penetrative Cenozoic deformation (Schmid et al. 1989). Adria’s motion relative to Europe is represented in all maps by a vector connecting past locations of Ivrea. We emphasize that this vector is only an approximation of the true motion of Adr ...
... delimits the southernmost units in the Alps affected by penetrative Cenozoic deformation (Schmid et al. 1989). Adria’s motion relative to Europe is represented in all maps by a vector connecting past locations of Ivrea. We emphasize that this vector is only an approximation of the true motion of Adr ...
nature and composition of the continental crust
... increase progressively with depth. There is large variation in average P wave velocity of the lower crust between different type sections, but in^general, lower crustal velocities are high (>6.9 km s"1) and average middle crustal velocities range between 6.3 and 6.7 km s"1. Heat-producing elements d ...
... increase progressively with depth. There is large variation in average P wave velocity of the lower crust between different type sections, but in^general, lower crustal velocities are high (>6.9 km s"1) and average middle crustal velocities range between 6.3 and 6.7 km s"1. Heat-producing elements d ...
Melting of the Uppermost Metasomatized Asthenosphere Triggered
... Major and trace element and Sr^Nd^Pb isotope data for wholerocks and major element data for minerals within basalt samples from the Chugaryeong volcano, an intra-plate back-arc volcanic centre in the central part of the Korean Peninsula, are used to address the process of magma genesis in the deep b ...
... Major and trace element and Sr^Nd^Pb isotope data for wholerocks and major element data for minerals within basalt samples from the Chugaryeong volcano, an intra-plate back-arc volcanic centre in the central part of the Korean Peninsula, are used to address the process of magma genesis in the deep b ...
Weakening of the subduction interface and its effects on surface
... Cascadia and Nankai, to be discussed in section 5.1. ETS may be rare in cold-slab subduction zones. (b) Surface heat flow (solid curve). Heat flow patterns for cold-slab subduction zones are similar, except that values near the trench and further seaward are much lower. Models that do not include ma ...
... Cascadia and Nankai, to be discussed in section 5.1. ETS may be rare in cold-slab subduction zones. (b) Surface heat flow (solid curve). Heat flow patterns for cold-slab subduction zones are similar, except that values near the trench and further seaward are much lower. Models that do not include ma ...
The Upper Mantle Geoid: Implications for Continental Structure and
... (degree/order up to 2159) is shown in Figure 1a. This geoid is the height of the geoid above/below the chosen reference ellipsoid, so the polar flattening and equatorial bulge (ellipticity) of the geoid doesn’t show in (Figure 1a) because this field is the difference between a (near) ellipsoidal ge ...
... (degree/order up to 2159) is shown in Figure 1a. This geoid is the height of the geoid above/below the chosen reference ellipsoid, so the polar flattening and equatorial bulge (ellipticity) of the geoid doesn’t show in (Figure 1a) because this field is the difference between a (near) ellipsoidal ge ...
Mantle structure and tectonic history of SE Asia
... Seismic travel-time tomography of the mantle under SE Asia reveals patterns of subduction-related seismic Pwave velocity anomalies that are of great value in helping to understand the region's tectonic development. We discuss tomography and tectonic interpretations of an area centred on Indonesia an ...
... Seismic travel-time tomography of the mantle under SE Asia reveals patterns of subduction-related seismic Pwave velocity anomalies that are of great value in helping to understand the region's tectonic development. We discuss tomography and tectonic interpretations of an area centred on Indonesia an ...
3 Factors controlling the crustal density structure - diss.fu
... absorb significant amounts of water via the formation of amphiboles, strongly reducing their density with respect to the dry granulites formed by garnet-pyroxene assemblages. This fact, plus the density reduction generated by the retention of some volume percent of melt, suggests that MASH zones und ...
... absorb significant amounts of water via the formation of amphiboles, strongly reducing their density with respect to the dry granulites formed by garnet-pyroxene assemblages. This fact, plus the density reduction generated by the retention of some volume percent of melt, suggests that MASH zones und ...
Leseane_okstate_0664M_13248
... 1. Digital Elevation Models (DEMs) extracted from the Global 30 Arc Second Elevation Data (GTOPO30, 1 km spatial resolution) showing the different parts of the Southwestern Branch of the East African Rift System. A=Afar. MER=Main Ethiopian Rift. R. Rhino graben. AL=Albertine graben. TA=Tarkana rift. ...
... 1. Digital Elevation Models (DEMs) extracted from the Global 30 Arc Second Elevation Data (GTOPO30, 1 km spatial resolution) showing the different parts of the Southwestern Branch of the East African Rift System. A=Afar. MER=Main Ethiopian Rift. R. Rhino graben. AL=Albertine graben. TA=Tarkana rift. ...
Ancient recycled mantle lithosphere in the Hawaiian plume: Osmium
... composition of the plume has always been inferred from the compositions of the erupted lavas. It has been suggested that recycled (i.e. previously subducted) basaltic oceanic crust (with or without sediments) is part of this plume and responsible for the enriched isotopic compositions of the Hawaiia ...
... composition of the plume has always been inferred from the compositions of the erupted lavas. It has been suggested that recycled (i.e. previously subducted) basaltic oceanic crust (with or without sediments) is part of this plume and responsible for the enriched isotopic compositions of the Hawaiia ...
Composition of the Oceanic Crust - DukeSpace
... in the Hess Deep (Karson et al., 2002). A 20–60-m-thick transition zone typically separates the eruptive layer from the underlying sheeted dike complex, which forms as magma freezes in dikes, typically 0.5–2 m wide, that feed the eruptions that form the overlying extrusive layer. The sheeted dike co ...
... in the Hess Deep (Karson et al., 2002). A 20–60-m-thick transition zone typically separates the eruptive layer from the underlying sheeted dike complex, which forms as magma freezes in dikes, typically 0.5–2 m wide, that feed the eruptions that form the overlying extrusive layer. The sheeted dike co ...
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.