Trace element and isotope geochemistry of gabbro
... enrichment which reflect relatively high amphibole amounts. The samples with the highest mg# have a marked positive Eu anomaly, which is coupled with spikes at Sr and Ba in the chondrite-normalized patterns of incompatible elements. The gabbroderived granulites with the lowest mg# are characterized ...
... enrichment which reflect relatively high amphibole amounts. The samples with the highest mg# have a marked positive Eu anomaly, which is coupled with spikes at Sr and Ba in the chondrite-normalized patterns of incompatible elements. The gabbroderived granulites with the lowest mg# are characterized ...
Geology, 39
... The Nunatak eclogites occur in the Tasiusarsuaq terrane, central NAC, an area dominated by Late Archean TTG gneisses (Fig. 1A). Our eclogite Pb-Pb secondary isochron of 2.70 ± 0.29 Ga (Fig. 2C) overlaps the main peak in crustal growth of the central NAC between 2.9 and 2.7 Ga (Nutman et al., 2004; N ...
... The Nunatak eclogites occur in the Tasiusarsuaq terrane, central NAC, an area dominated by Late Archean TTG gneisses (Fig. 1A). Our eclogite Pb-Pb secondary isochron of 2.70 ± 0.29 Ga (Fig. 2C) overlaps the main peak in crustal growth of the central NAC between 2.9 and 2.7 Ga (Nutman et al., 2004; N ...
Deep structure of the northeastern Japan arc
... Recent seismic tomography studies in the northeastern Japan arc have provided new information that shows that water supplied by dehydration of the subducting slab reaches the upper crust via the mantle wedge, entrained in an upwelling flow in the mantle that travels nearly parallel to the slab as a ...
... Recent seismic tomography studies in the northeastern Japan arc have provided new information that shows that water supplied by dehydration of the subducting slab reaches the upper crust via the mantle wedge, entrained in an upwelling flow in the mantle that travels nearly parallel to the slab as a ...
Molnar, P., and C. N. Garzione (2007), Bounds on the viscosity coefficient of continental lithosphere
... before it was removed, is consistent with laboratory experiments on the flow of olivine or eclogite at temperatures that are reasonable for the Altiplano at the time when dense material was removed. [3] We carry out an analysis similar to that of Molnar and Jones [2004], who discussed the average vi ...
... before it was removed, is consistent with laboratory experiments on the flow of olivine or eclogite at temperatures that are reasonable for the Altiplano at the time when dense material was removed. [3] We carry out an analysis similar to that of Molnar and Jones [2004], who discussed the average vi ...
Mantle instability beneath the Sierra Nevada Mountains in California
... We hypothesize that the cold geotherm of the surface was caused by the inverse geothermal gradient associated with Farallon plate subduction until 30 Ma [21, 22]. This protects the chemistry of the region sampled by the deep xenoliths by the advection of cold material below the Sierra. By the time s ...
... We hypothesize that the cold geotherm of the surface was caused by the inverse geothermal gradient associated with Farallon plate subduction until 30 Ma [21, 22]. This protects the chemistry of the region sampled by the deep xenoliths by the advection of cold material below the Sierra. By the time s ...
Poisson`s ratio in the lower mantle beneath Alaska: Evidence for
... addition, there is both evidence for [Revenaugh and Meyer, 1997; Garnero and Helmberger, 1998] and against [Castle and van der Hilst, 2000; Persh et al., 2001] an ultralowvelocity zone at the CMB directly beneath and to the south of Aleutians. [6] Following Robertson and Woodhouse [1996], Kennett et ...
... addition, there is both evidence for [Revenaugh and Meyer, 1997; Garnero and Helmberger, 1998] and against [Castle and van der Hilst, 2000; Persh et al., 2001] an ultralowvelocity zone at the CMB directly beneath and to the south of Aleutians. [6] Following Robertson and Woodhouse [1996], Kennett et ...
and S-wave delay times at Eurasian seismic
... better focus is a possible problem in the time history of NRI during the period 1980–1984. The same analysis for station CHG changes the grand median of the azimuthal sector medians from −0.10 to −0.84 s and reduces the spread from 0.89 to 0.57 s and for station CMAR changes the grand median from −0 ...
... better focus is a possible problem in the time history of NRI during the period 1980–1984. The same analysis for station CHG changes the grand median of the azimuthal sector medians from −0.10 to −0.84 s and reduces the spread from 0.89 to 0.57 s and for station CMAR changes the grand median from −0 ...
A climate induced transition in the tectonic style of a terrestrial planet
... where I is the second strain-rate invariant. This formulation allows localized zones of lithospheric failure, analogs to weak plate boundaries, to form in a self-consistent manner. The failure zones allow for lithospheric recycling and mantle stirring akin to plate tectonics on present day Earth. If ...
... where I is the second strain-rate invariant. This formulation allows localized zones of lithospheric failure, analogs to weak plate boundaries, to form in a self-consistent manner. The failure zones allow for lithospheric recycling and mantle stirring akin to plate tectonics on present day Earth. If ...
Constraints on the Lithospheric Structure of Venus from Mechanical
... consequenceof unstable deformation, then the widespread occurrenceof thesestructuresprovidesdirect evidencefor the lithosphericstructureof this planet on a globalscale. In this study, we investigate the stability of the Venus lithospherein extensionand compression.The purposeis to assessthe conditio ...
... consequenceof unstable deformation, then the widespread occurrenceof thesestructuresprovidesdirect evidencefor the lithosphericstructureof this planet on a globalscale. In this study, we investigate the stability of the Venus lithospherein extensionand compression.The purposeis to assessthe conditio ...
Chemical Composition of Continental Crust and the Primitive Mantle
... continental crust. The average value of 3.8 for Th/U ratios at the surface of continental crust yields 2.8 ppm as the U content of the source area. Furthermore, the average value of 1.0 104 for K/U ratios gives 2.8% by weight as the K content of the source. Based on this method, Taylor and McLenna ...
... continental crust. The average value of 3.8 for Th/U ratios at the surface of continental crust yields 2.8 ppm as the U content of the source area. Furthermore, the average value of 1.0 104 for K/U ratios gives 2.8% by weight as the K content of the source. Based on this method, Taylor and McLenna ...
Thermal Structure and Metamorphic Evolution of Subducting Slabs
... Uyeda, 1975]. Subduction zones are regions of intense earthquake activity, explosive volcanism, and complex mass transfer between the crust, mantle, hydrosphere, and atmosphere. In this contribution, I focus on the thermal, petrologic, and seismological processes that occur in subducting slabs. The ...
... Uyeda, 1975]. Subduction zones are regions of intense earthquake activity, explosive volcanism, and complex mass transfer between the crust, mantle, hydrosphere, and atmosphere. In this contribution, I focus on the thermal, petrologic, and seismological processes that occur in subducting slabs. The ...
Continental rifting as a function of lithosphere mantle strength
... forces — i.e. softening the lithosphere during extension by the thinning of brittle layers and general heating. Narrow rifts occur when the total force change on rifting is negative, so that the ongoing thinning is kept in the same narrow region. On the contrary, wide rifts occur when the total forc ...
... forces — i.e. softening the lithosphere during extension by the thinning of brittle layers and general heating. Narrow rifts occur when the total force change on rifting is negative, so that the ongoing thinning is kept in the same narrow region. On the contrary, wide rifts occur when the total forc ...
Chapter 1- INTRODUCTION 1.1. Mantle Rocks This study is
... transformations as upper mantle olivine changes first into spinel and then into perovskite structured high-pressure polymorphs. Finally, the crust is a compositionally distinct layer overlying the mantle that concentrates preferentially the incompatible elements derived by partial melting of the man ...
... transformations as upper mantle olivine changes first into spinel and then into perovskite structured high-pressure polymorphs. Finally, the crust is a compositionally distinct layer overlying the mantle that concentrates preferentially the incompatible elements derived by partial melting of the man ...
An analysis of young ocean depth, gravity and global residual
... Since then, a number of physical explanations have been put forward for this flattening. These include (1) the addition of heat from convective instability underneath the rigid mechanical boundary layer (Parsons & McKenzie 1978); (2) radioactive heating in the upper part of the mantle (Forsyth 1977) ...
... Since then, a number of physical explanations have been put forward for this flattening. These include (1) the addition of heat from convective instability underneath the rigid mechanical boundary layer (Parsons & McKenzie 1978); (2) radioactive heating in the upper part of the mantle (Forsyth 1977) ...
Document
... In short, the driving forces advocated at the moment can be divided into three categories based on the relationship to the movement: mantle dynamics related, gravity related (mostly secondary forces), and Earth rotation related. ...
... In short, the driving forces advocated at the moment can be divided into three categories based on the relationship to the movement: mantle dynamics related, gravity related (mostly secondary forces), and Earth rotation related. ...
PDF - Wiley Online Library
... and thus also on the asthenospheric viscosity, come primarily from observations of glacial rebound [see Mitrovica et al., 2007, for a review]. They inform us about the rates at which regions such as Fennoscandia, Canada, and Antarctica rise in response to melting of thousand-kilometer-wide ice sheet ...
... and thus also on the asthenospheric viscosity, come primarily from observations of glacial rebound [see Mitrovica et al., 2007, for a review]. They inform us about the rates at which regions such as Fennoscandia, Canada, and Antarctica rise in response to melting of thousand-kilometer-wide ice sheet ...
Upper mantle and lithospheric heterogeneities in central
... Helffrich & Wood 2001; Lebedev et al. 2002, 2003). The transformation of the olivine component has a major impact on the seismic velocities observed. Olivine is transformed to a spinel structure at a depth of about 410 km and finally breaks down to perovskite and magnesiowüstite at about 660 km (e. ...
... Helffrich & Wood 2001; Lebedev et al. 2002, 2003). The transformation of the olivine component has a major impact on the seismic velocities observed. Olivine is transformed to a spinel structure at a depth of about 410 km and finally breaks down to perovskite and magnesiowüstite at about 660 km (e. ...
Mantle flow in regions of complex tectonics: Insights from Indonesia
... [10] The oldest and most prominent subduction ...
... [10] The oldest and most prominent subduction ...
On the detectability of 3-D postperovskite distribution in Dв€і by
... tect deep mantle structures. Geomagnetic storms, excited by the Sun, and manifested in the magnetosphere by energizing of the equatorial ring current, represent such a signal. It is capable of inducing secondary electric currents in the deepest regions of the Earth, including the core (Velímský and ...
... tect deep mantle structures. Geomagnetic storms, excited by the Sun, and manifested in the magnetosphere by energizing of the equatorial ring current, represent such a signal. It is capable of inducing secondary electric currents in the deepest regions of the Earth, including the core (Velímský and ...
Seismic Data Interpretation 2
... This course introduces students to seismic signals and seismic noise and their interpretations. Course Objectives By the end of the course the students should be able to: 1. Distinguish between seismic signals and seismic noise. 2. Acquire and process signals by different methods. 3. Interpret seism ...
... This course introduces students to seismic signals and seismic noise and their interpretations. Course Objectives By the end of the course the students should be able to: 1. Distinguish between seismic signals and seismic noise. 2. Acquire and process signals by different methods. 3. Interpret seism ...
GEOL_2_mid_term_I
... A) Kings Sandstone is older than 85 million yrs. B) Kings Sandstone is younger than 30 million yrs. C) We cannot tell how old Kings Sandstone is. D) Kings Sandstone is older than 30 million yrs. (45) 1 pt. The half-life of carbon-14 is about 6000 years. Assume that a sample of charcoal formed by bur ...
... A) Kings Sandstone is older than 85 million yrs. B) Kings Sandstone is younger than 30 million yrs. C) We cannot tell how old Kings Sandstone is. D) Kings Sandstone is older than 30 million yrs. (45) 1 pt. The half-life of carbon-14 is about 6000 years. Assume that a sample of charcoal formed by bur ...
Mantle plume
A mantle plume is a mechanism proposed in 1971 to explain volcanic regions of the earth that were not thought to be explicable by the then-new theory of plate tectonics. Some such volcanic regions lie far from tectonic plate boundaries, for example, Hawaii. Others represent unusually large-volume volcanism, whether on plate boundaries, e.g. Iceland, or basalt floods such as the Deccan or Siberian traps.A mantle plume is posited to exist where hot rock nucleates at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust. The currently active volcanic centers are known as ""hot spots"". In particular, the concept that mantle plumes are fixed relative to one another, and anchored at the core-mantle boundary, was thought to provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some such hot spots, such as the Hawaiian–Emperor seamount chain.The hypothesis of mantle plumes from depth is not universally accepted as explaining all such volcanism. It has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes and pulsing plumes. Another hypothesis for unusual volcanic regions is the ""Plate model"". This proposes shallower, passive leakage of magma from the mantle onto the Earth's surface where extension of the lithosphere permits it, attributing most volcanism to plate tectonic processes, with volcanoes far from plate boundaries resulting from intraplate extension.