Possible density segregation of subducted oceanic
... thickness of the serpentinite layer evolves with time due to progressive warming of the slab's interior (numbers mark Myr since subduction). (B) Effective viscosity of the subducted slab and surrounding mantle as a function of time, following temperatures estimated in panel A. We used known non-Newt ...
... thickness of the serpentinite layer evolves with time due to progressive warming of the slab's interior (numbers mark Myr since subduction). (B) Effective viscosity of the subducted slab and surrounding mantle as a function of time, following temperatures estimated in panel A. We used known non-Newt ...
Uppermost mantle structure of the North China Craton: Constraints
... The uppermost mantle is the key area for exchange of heat flux and material convection between the crust and lithospheric mantle. Spatial variations of lithospheric thinning and dynamic processes in the North China Craton could inevitably induce the velocity heterogeneity in the uppermost mantle. In ...
... The uppermost mantle is the key area for exchange of heat flux and material convection between the crust and lithospheric mantle. Spatial variations of lithospheric thinning and dynamic processes in the North China Craton could inevitably induce the velocity heterogeneity in the uppermost mantle. In ...
Primary magmas and mantle temperatures
... 1200°C-1250°C. This global, first-order similarity led to the concept of a generalized mantle potential temperature (Tp) with Tp ≈ 1280°C (McKenzie & Bickle, 1988). The crust and lithosphere are interpreted as a thin boundary layer over the asthenosphere, which is inferred to have a potential temper ...
... 1200°C-1250°C. This global, first-order similarity led to the concept of a generalized mantle potential temperature (Tp) with Tp ≈ 1280°C (McKenzie & Bickle, 1988). The crust and lithosphere are interpreted as a thin boundary layer over the asthenosphere, which is inferred to have a potential temper ...
Physics of the Earth and Planetary Interiors Bulldozing the core
... WWSSN short-period data appeared to possess the best SNR for the PKIKP phase and its precursors. Generally, amplitudes of PKIKP precursors increase with epicentral distance. The observed difference in precursor amplitude between the two groups of earthquakes, however, does not seem to result from a ...
... WWSSN short-period data appeared to possess the best SNR for the PKIKP phase and its precursors. Generally, amplitudes of PKIKP precursors increase with epicentral distance. The observed difference in precursor amplitude between the two groups of earthquakes, however, does not seem to result from a ...
A normalised seawater strontium isotope curve: possible
... likely depressed during much of the Precambrian relative to today (Lenton and Watson, 2004). The flux of Sr derived from carbonate dissolution seems therefore likely to have dominated over that from silicate weathering for as long as carbonate platforms have been abundant on Earth, i.e. since the ea ...
... likely depressed during much of the Precambrian relative to today (Lenton and Watson, 2004). The flux of Sr derived from carbonate dissolution seems therefore likely to have dominated over that from silicate weathering for as long as carbonate platforms have been abundant on Earth, i.e. since the ea ...
Origin of the concentrated deformation zone in the Japanese Islands... accumulation process of intraplate earthquakes
... A concentrated deformation zone along the Japan Sea coast (NKTZ: Niigata-Kobe Tectonic Zone) has been detected by dense GPS arrays (GEONET by Geographical Survey Institute), as shown in Fig. 1 (Sagiya et al., 2000). The observed horizontal displacement rates in NKTZ were fitted, quantitatively, by 3 ...
... A concentrated deformation zone along the Japan Sea coast (NKTZ: Niigata-Kobe Tectonic Zone) has been detected by dense GPS arrays (GEONET by Geographical Survey Institute), as shown in Fig. 1 (Sagiya et al., 2000). The observed horizontal displacement rates in NKTZ were fitted, quantitatively, by 3 ...
Thermal Structure and Metamorphic Evolution of Subducting Slabs
... then to perovskite + magnesiowustite at 670 km depth [e.g., Kirby et al., 1996a]. These solidsolid reactions increase the density of the subducting slab. A number of studies [e.g., Green and Burnley, 1989; Kirby et al., 1991; 1996a] suggest that deep-focus earthquakes (>300 km depth) may be caused b ...
... then to perovskite + magnesiowustite at 670 km depth [e.g., Kirby et al., 1996a]. These solidsolid reactions increase the density of the subducting slab. A number of studies [e.g., Green and Burnley, 1989; Kirby et al., 1991; 1996a] suggest that deep-focus earthquakes (>300 km depth) may be caused b ...
The stability of arc lower crust: Insights from the Talkeetna Arc
... Talkeetna section were likely denser than the underlying mantle, while the remaining gabbronorites are neutrally or slightly positively buoyant. In addition, we show that arc lower crustal rock compositions that are denser than the underlying mantle generally have P-wave velocities > 7.4 km/s. Becau ...
... Talkeetna section were likely denser than the underlying mantle, while the remaining gabbronorites are neutrally or slightly positively buoyant. In addition, we show that arc lower crustal rock compositions that are denser than the underlying mantle generally have P-wave velocities > 7.4 km/s. Becau ...
Mechanical (de-)coupling of the lithosphere in the Valencia Trough
... The rift basin started to open during Late Oligocene over an inverted Mesozoic basin that was subjected to non-deposition and erosion during most of the Paleogene [33]. It appears that the opening was not synchronous all over the basin [34], but that rifting commenced earlier in the northeast (Late ...
... The rift basin started to open during Late Oligocene over an inverted Mesozoic basin that was subjected to non-deposition and erosion during most of the Paleogene [33]. It appears that the opening was not synchronous all over the basin [34], but that rifting commenced earlier in the northeast (Late ...
Yin and yang of continental crust creation and destruction by plate
... Mature continental crust is compositionally layered and can be subdivided into upper continental crust (∼20 km thick) of approximately granodioritic composition and lower, mafic crust (∼20 km thick), separated by a Conrad discontinuity that is well to weakly formed (Christensen and Mooney 1995; Rudn ...
... Mature continental crust is compositionally layered and can be subdivided into upper continental crust (∼20 km thick) of approximately granodioritic composition and lower, mafic crust (∼20 km thick), separated by a Conrad discontinuity that is well to weakly formed (Christensen and Mooney 1995; Rudn ...
Batholith tectonics: Formation and deformation of ghost stratigraphy
... marbles with distinctive Sr and C isotopic signatures indicate deposition during Neoproterozoic time (Trønnes, 1994; Trønnes and Sundvoll, 1995; Sandøy, 2003; see Melezhik et al., 2005, for discussion of the methodology). Ultramafic rocks are characteristic of the Middle Nappe, but greenschist to lo ...
... marbles with distinctive Sr and C isotopic signatures indicate deposition during Neoproterozoic time (Trønnes, 1994; Trønnes and Sundvoll, 1995; Sandøy, 2003; see Melezhik et al., 2005, for discussion of the methodology). Ultramafic rocks are characteristic of the Middle Nappe, but greenschist to lo ...
Evolution of Metamorphic Belts - CiteSeerX
... group. As an example of the low-pressure intermediate group, the metamorphic terrain in the north-eastern Grampian Highlands (Aberdeenshire and Banffshire) of Scotland may be cited. In this area, andalusite and cordierite occur in pelitic metamorphic rocks, just as in the andalusite-sillimanite type ...
... group. As an example of the low-pressure intermediate group, the metamorphic terrain in the north-eastern Grampian Highlands (Aberdeenshire and Banffshire) of Scotland may be cited. In this area, andalusite and cordierite occur in pelitic metamorphic rocks, just as in the andalusite-sillimanite type ...
tectonics - GeoKniga
... with depth. The data reveal that there are specific depths inside the Earth at which velocity abruptly changes and waves bend—these depths are called seismic discontinuities (Figure 14.3a and b). Seismic discontinuities divide the Earth’s interior into distinct shells; within a shell, seismic wave v ...
... with depth. The data reveal that there are specific depths inside the Earth at which velocity abruptly changes and waves bend—these depths are called seismic discontinuities (Figure 14.3a and b). Seismic discontinuities divide the Earth’s interior into distinct shells; within a shell, seismic wave v ...
Geochemistry of the granitoid plutons of the Brookville terrane, Saint
... White, 1996). The older (ca. 635-600 Ma) group of volcanic and sedimentary rocks (Broad River Group) is regionally metamorphosed (greenschistlacies). The associated plutonic units (ca. 625-615 Ma) are calc-alkaline and were emplaced during continental margin subduction (Barr and White, 1988). The yo ...
... White, 1996). The older (ca. 635-600 Ma) group of volcanic and sedimentary rocks (Broad River Group) is regionally metamorphosed (greenschistlacies). The associated plutonic units (ca. 625-615 Ma) are calc-alkaline and were emplaced during continental margin subduction (Barr and White, 1988). The yo ...
Behavior of subducting sediments beneath an arc under a high
... However, chert, shale and banded iron formations are common in the Archean Greenstone belt (Windley, 1995), indicating that the sediment subduction had already occurred at the Archean time. If this is the case, sediment melting within a slab is also a likely consequence of subduction when steep geot ...
... However, chert, shale and banded iron formations are common in the Archean Greenstone belt (Windley, 1995), indicating that the sediment subduction had already occurred at the Archean time. If this is the case, sediment melting within a slab is also a likely consequence of subduction when steep geot ...
Workshop on the Rio Grande Rift
... allow us to interpret paleotectonics (late Cenozoic) of the rift. Concepts and models developed by Bull (Univ. of Arizona) would be applicable at scales of 1: 100,000 to 1:500,000. The resultant analysis will help block out both temporal and areal variations in tectonism, both uplift and extension 1 ...
... allow us to interpret paleotectonics (late Cenozoic) of the rift. Concepts and models developed by Bull (Univ. of Arizona) would be applicable at scales of 1: 100,000 to 1:500,000. The resultant analysis will help block out both temporal and areal variations in tectonism, both uplift and extension 1 ...
The origin of Mount St. Helens andesites
... We have subdivided MSH basalts and andesites into six groups mainly on the basis of SiO2 contents and FeO*/MgO ratios (Table 2 and Fig. 2). The basaltic lavas include three variants, I-B, II-B, and III-BA, all of which were erupted during the Castle Creek period. Group I-B includes samples of the 'c ...
... We have subdivided MSH basalts and andesites into six groups mainly on the basis of SiO2 contents and FeO*/MgO ratios (Table 2 and Fig. 2). The basaltic lavas include three variants, I-B, II-B, and III-BA, all of which were erupted during the Castle Creek period. Group I-B includes samples of the 'c ...
ax2009ag.aw
... of mappable landscape features that represent the mapping criteria and that provide consistency in stratification; and 4) development of map units based upon the array of these mappable features or mapping differentia within the survey area. Survey objectives were defined by the Forest Plan revision ...
... of mappable landscape features that represent the mapping criteria and that provide consistency in stratification; and 4) development of map units based upon the array of these mappable features or mapping differentia within the survey area. Survey objectives were defined by the Forest Plan revision ...
Some Thermal Constraints on Crustal
... during the early stages of fractionation may be particularly important. In other cases the degree of assimilation seems to increase during the differentiation history (e.g. Mantovani & Hawkesworth, 1990; Kagami et al., 1991). The thermal aspects of the interaction of magmas with their host rocks will ...
... during the early stages of fractionation may be particularly important. In other cases the degree of assimilation seems to increase during the differentiation history (e.g. Mantovani & Hawkesworth, 1990; Kagami et al., 1991). The thermal aspects of the interaction of magmas with their host rocks will ...
A. Mills, T. Calon and C. Peddle - Department of Natural Resources
... Thin- to medium-bedded, siliceous sandstone and mudstone of the CPG were examined, in detail, at a roadside outcrop along Highway 230 (Figures 1 and 3A). At Station 15AM131, poles to bedding planes define a π girdle with an F1 fold axis that plunges very gently to the southwest (Figure 3B). Cleavage ...
... Thin- to medium-bedded, siliceous sandstone and mudstone of the CPG were examined, in detail, at a roadside outcrop along Highway 230 (Figures 1 and 3A). At Station 15AM131, poles to bedding planes define a π girdle with an F1 fold axis that plunges very gently to the southwest (Figure 3B). Cleavage ...
The continent marginal crust characteristic of nothern South China
... differences between these models are different extension mechanical and igneous activity. The previous studies suggest the north and south margins of the SCS was an asymmetric conjugated pair and the north part can be classified as non-volcanic margin (Yan et al., 2001). No matter which model, the f ...
... differences between these models are different extension mechanical and igneous activity. The previous studies suggest the north and south margins of the SCS was an asymmetric conjugated pair and the north part can be classified as non-volcanic margin (Yan et al., 2001). No matter which model, the f ...
On the relationship between the Bushveld Complex and its felsic
... lavas have been subdivided into the Dullstroom, Damwal, Kwaggasnek, and Schrikkloof formations (SACS 1980). Some of the ferroan lavas may have been generated by fractional crystallization of the Bushveld mafic magmas (VanTongeren et al. 2010, see below). Understanding the roof of the Bushveld Comple ...
... lavas have been subdivided into the Dullstroom, Damwal, Kwaggasnek, and Schrikkloof formations (SACS 1980). Some of the ferroan lavas may have been generated by fractional crystallization of the Bushveld mafic magmas (VanTongeren et al. 2010, see below). Understanding the roof of the Bushveld Comple ...
Unconventional Isotopes and Approaches
... Came et al. (2007) applied clumped isotope geothermometry to carbon and oxygen isotopes of Silurian brachiopods from Anticosti Island, Canada and Carboniferous (Pennsylvanian) molluscs from Oklahoma (both of these localities were tropical at the time). Some samples were diagenically altered, yieldin ...
... Came et al. (2007) applied clumped isotope geothermometry to carbon and oxygen isotopes of Silurian brachiopods from Anticosti Island, Canada and Carboniferous (Pennsylvanian) molluscs from Oklahoma (both of these localities were tropical at the time). Some samples were diagenically altered, yieldin ...
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 ...
Nazca slab retreat versus compressional deformation in the central
... careful and critical examination of the few localities where folding and faulting is reported during intracordilleran sedimentation, suggests that each example of progressive compressional &formations may correspond to a detailed record of one of the gencralixed compressional events. The deformation ...
... careful and critical examination of the few localities where folding and faulting is reported during intracordilleran sedimentation, suggests that each example of progressive compressional &formations may correspond to a detailed record of one of the gencralixed compressional events. The deformation ...
Baltic Shield
The Baltic Shield (sometimes referred to as the Fennoscandian Shield) is located in Fennoscandia (Norway, Sweden and Finland), northwest Russia and under the Baltic Sea. The Baltic Shield is defined as the exposed Precambrian northwest segment of the East European Craton. It is composed mostly of Archean and Proterozoic gneisses and greenstones which have undergone numerous deformations through tectonic activity (see Geology of Fennoscandia map [1]). The Baltic Shield contains the oldest rocks of the European continent. The lithospheric thickness is about 200-300 km. During the Pleistocene epoch, great continental ice sheets scoured and depressed the shield's surface, leaving a thin covering of glacial material and innumerable lakes and streams. The Baltic Shield is still rebounding today following the melting of the thick glaciers during the Quaternary Period.