V- Diamond Deposits in Kimberlites and Lamproites
... Depth of generation: 100 – 300 km. Require areas of thick continental crust, and a source of C. Some C recycled by subduction of crustal material as indicated by 13C measurements; note different signatures for eclogitic vs. peridotitic diamonds. Some diamonds in alkali basalts, ophiolites a ...
... Depth of generation: 100 – 300 km. Require areas of thick continental crust, and a source of C. Some C recycled by subduction of crustal material as indicated by 13C measurements; note different signatures for eclogitic vs. peridotitic diamonds. Some diamonds in alkali basalts, ophiolites a ...
Course Outline - School of Geosciences
... Subduction zones are often viewed as giant factories in which oceanic lithospheres, and to a lesser extent older continental crusts and water-saturated sediments, are recycled back into the mantle, whereas new continental crust is created. Geothermal fields, volcanoes, ore deposits, earthquakes, mou ...
... Subduction zones are often viewed as giant factories in which oceanic lithospheres, and to a lesser extent older continental crusts and water-saturated sediments, are recycled back into the mantle, whereas new continental crust is created. Geothermal fields, volcanoes, ore deposits, earthquakes, mou ...
Insights into the structure of the upper mantle beneath the Murray
... good signal-to-noise ratios were recorded, allowing 3085 relative arrival time residuals to be picked with high accuracy. These arrival time residuals are mapped as 3D perturbations in P-wave velocity with respect to the ak135 global reference model using teleseismic tomography. The resulting images ...
... good signal-to-noise ratios were recorded, allowing 3085 relative arrival time residuals to be picked with high accuracy. These arrival time residuals are mapped as 3D perturbations in P-wave velocity with respect to the ak135 global reference model using teleseismic tomography. The resulting images ...
Physics of the Earth and Planetary Interiors Supercontinent
... 2. Supercontinent cycles and supercontinent–superplume coupling 2.1. What are superplumes? Mantle plumes are thought to result from thermal boundary layer instabilities at the base of the mantle (Morgan, 1971; Griffiths and Campbell, 1990). Mantle plumes were first proposed to account for hotspot vo ...
... 2. Supercontinent cycles and supercontinent–superplume coupling 2.1. What are superplumes? Mantle plumes are thought to result from thermal boundary layer instabilities at the base of the mantle (Morgan, 1971; Griffiths and Campbell, 1990). Mantle plumes were first proposed to account for hotspot vo ...
Plate Boundaries - WWWeb Course Listings
... Part III: Overview of plate tectonics Go to the Earth Systems Laboratory and open the following WWW site: http://geosci.sfsu.edu/courses/geol103/labs/labs.html and open The Seafloor exercise. Computer Part 1: The Seafloor and Plate Boundaries Bathymetric Features on the Seafloor Figure 1. The map be ...
... Part III: Overview of plate tectonics Go to the Earth Systems Laboratory and open the following WWW site: http://geosci.sfsu.edu/courses/geol103/labs/labs.html and open The Seafloor exercise. Computer Part 1: The Seafloor and Plate Boundaries Bathymetric Features on the Seafloor Figure 1. The map be ...
Plate Tectonics
... • Conduction – the transfer of heat within a material or between materials that are touching – Ex: spoon in a pot of hot soup In conduction, the heated particles of a substance transfer heat through contact with other particles in the substance. ...
... • Conduction – the transfer of heat within a material or between materials that are touching – Ex: spoon in a pot of hot soup In conduction, the heated particles of a substance transfer heat through contact with other particles in the substance. ...
STRUCTURE OF THE MOON BY SEISMIC DATA
... 1976 for the same travel-time curves. In right fig. shows the velocity distribution of P- and S-waves in the crust and mantle of the Moon, obtained Goins et al. in 1981. A comparison of these velocity curves shows that the variation of velocities with depth in both figures differ slightly, but in ri ...
... 1976 for the same travel-time curves. In right fig. shows the velocity distribution of P- and S-waves in the crust and mantle of the Moon, obtained Goins et al. in 1981. A comparison of these velocity curves shows that the variation of velocities with depth in both figures differ slightly, but in ri ...
Subduction of oceanic lithosphere
... and serpentinites (B). These fluids rise into the overlying mantle to form hydrous phases in mantle peridotite (C). Amphiboles are shown forming here, but it could also be another hydrous mineral. Metasomatized mantle descends with the subducted slab. At the maximum depth of stability for amphibole ...
... and serpentinites (B). These fluids rise into the overlying mantle to form hydrous phases in mantle peridotite (C). Amphiboles are shown forming here, but it could also be another hydrous mineral. Metasomatized mantle descends with the subducted slab. At the maximum depth of stability for amphibole ...
1 Four-D Investigation of Subduction Initiation (SI
... massive sheet flows in the upper 400 m. Boninitic dikes and lavas occur as the youngest igneous products within the EMO (Fig. 1b). Cpx porphyroclast-bearing harzburgites occur in the lower parts of the upper mantle units, whereas harzburgites and dunites are more abundant in structurally higher part ...
... massive sheet flows in the upper 400 m. Boninitic dikes and lavas occur as the youngest igneous products within the EMO (Fig. 1b). Cpx porphyroclast-bearing harzburgites occur in the lower parts of the upper mantle units, whereas harzburgites and dunites are more abundant in structurally higher part ...
2014072 - Geological Society of America
... aspect ratio of the scattering media is varied. Modelling shows that the coda decay is relatively insensitive to the shape of scatter (supplementary figure DR2). A single LVL and other scattering models, such as scattering in the mantle wedge or over riding crust cannot account for the observed exte ...
... aspect ratio of the scattering media is varied. Modelling shows that the coda decay is relatively insensitive to the shape of scatter (supplementary figure DR2). A single LVL and other scattering models, such as scattering in the mantle wedge or over riding crust cannot account for the observed exte ...
Lecture 2
... The structure and distribution of sediments can be understood based on the geomorphology of the ocean floor. These sediments are important because they tell us about the geochemistry of the ocean floor. Also they can be used to reconstruct ocean circulation of the past and improve our understanding ...
... The structure and distribution of sediments can be understood based on the geomorphology of the ocean floor. These sediments are important because they tell us about the geochemistry of the ocean floor. Also they can be used to reconstruct ocean circulation of the past and improve our understanding ...
1 Final Exam, Earth 50 Fall 2006
... 2. Eruptions of andesitic and rhyolitic lavas tend to be much more explosive than those of basaltic lavas. What factors are responsible for this difference in eruptive style? The more silica rich lavas are more viscous than basalt preventing slow degassing. Rhyolitic and andesitic melts also have mo ...
... 2. Eruptions of andesitic and rhyolitic lavas tend to be much more explosive than those of basaltic lavas. What factors are responsible for this difference in eruptive style? The more silica rich lavas are more viscous than basalt preventing slow degassing. Rhyolitic and andesitic melts also have mo ...
mid-ocean ridge
... • Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor. They are among the Earth's flattest and smoothest regions and the least explored. • Abyssal plains result from the blanketing of an originally uneven surface of oceanic crust by fine-grained sediments, mainly clay ...
... • Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor. They are among the Earth's flattest and smoothest regions and the least explored. • Abyssal plains result from the blanketing of an originally uneven surface of oceanic crust by fine-grained sediments, mainly clay ...
A three-dimensional model of seismic velocities beneath northern
... In the last two decades, structural information about the deep interior of the earth in local, regional and global scale has been drawn extensively from travel-time tomography experiments. Depending on the kind of station network used, two- or three-dimensional (2- or 3-D) models of the pand S-wave ...
... In the last two decades, structural information about the deep interior of the earth in local, regional and global scale has been drawn extensively from travel-time tomography experiments. Depending on the kind of station network used, two- or three-dimensional (2- or 3-D) models of the pand S-wave ...
Hyperextended continental margins—Knowns and
... et al., 2010), but this can be difficult to identify from velocity structure alone: P-wave to S-wave velocity ratios (Vp/Vs) can be used as a lithology indicator, but at a Vp range of 7.0–7.5 km/s there is significant overlap with gabbroic rocks (“underplate”), and other potential sub-crustal bodies ...
... et al., 2010), but this can be difficult to identify from velocity structure alone: P-wave to S-wave velocity ratios (Vp/Vs) can be used as a lithology indicator, but at a Vp range of 7.0–7.5 km/s there is significant overlap with gabbroic rocks (“underplate”), and other potential sub-crustal bodies ...
Hyperextended continental margins—Knowns and
... et al., 2010), but this can be difficult to identify from velocity structure alone: P-wave to S-wave velocity ratios (Vp/Vs) can be used as a lithology indicator, but at a Vp range of 7.0–7.5 km/s there is significant overlap with gabbroic rocks (“underplate”), and other potential sub-crustal bodies ...
... et al., 2010), but this can be difficult to identify from velocity structure alone: P-wave to S-wave velocity ratios (Vp/Vs) can be used as a lithology indicator, but at a Vp range of 7.0–7.5 km/s there is significant overlap with gabbroic rocks (“underplate”), and other potential sub-crustal bodies ...
Seismic structures of the 154–160 Ma oceanic crust and uppermost... in the Northwest Pacific Basin
... just below the Moho, whose depth was well constrained by a number of clear Pm P arrivals. However, the calculated Pn travel times were shorter than the ones observed in this model, and the offsets of 30–40 km where the Pn appears as a first arrival on the observed record sections are smaller than th ...
... just below the Moho, whose depth was well constrained by a number of clear Pm P arrivals. However, the calculated Pn travel times were shorter than the ones observed in this model, and the offsets of 30–40 km where the Pn appears as a first arrival on the observed record sections are smaller than th ...
Chapter 7. Convection and Complexity
... melting causes a reduction in density, and a Rayleigh-Taylor instability can develop. Material can be lifted out of the eclogite or piclogite eclogite plus peridotite- layer by such a mechanism and extensive melting occurs during ascent to the shallower mantle . At shallow depths peridotite elevated ...
... melting causes a reduction in density, and a Rayleigh-Taylor instability can develop. Material can be lifted out of the eclogite or piclogite eclogite plus peridotite- layer by such a mechanism and extensive melting occurs during ascent to the shallower mantle . At shallow depths peridotite elevated ...
Unraveling the Tapestry of Ocean Crust
... melt can flow—in a positive feedback loop that spontaneously creates channels that focus the flow. Small channels formed in this fashion coalesce to form larger channels, in a network analogous to a river drainage system. The number and size of melt flow channels we observe in the mantle section of ...
... melt can flow—in a positive feedback loop that spontaneously creates channels that focus the flow. Small channels formed in this fashion coalesce to form larger channels, in a network analogous to a river drainage system. The number and size of melt flow channels we observe in the mantle section of ...
Delamination, Slab Break-Off, and Slab Roll-Back
... • Large sheets of material (flakes) shearing off the top of one of the colliding plates. ...
... • Large sheets of material (flakes) shearing off the top of one of the colliding plates. ...
Subsurface structure of the “petit
... and low inclination referring to results from DSDP [Larson and Lowrie, 1975]. Thus, ‘‘petit-spot’’ volcanoes must have strong magnetization contrast to the old crust, and may produce particular magnetic anomaly, if large volume of such basalts are extruded and/or intruded. However, magnetic anomaly ...
... and low inclination referring to results from DSDP [Larson and Lowrie, 1975]. Thus, ‘‘petit-spot’’ volcanoes must have strong magnetization contrast to the old crust, and may produce particular magnetic anomaly, if large volume of such basalts are extruded and/or intruded. However, magnetic anomaly ...
PDF - Geological Society of America
... mantle deformation beneath this region. The broadband seismic data used in this study were recorded during August 2007 to April 2013 employing 75 permanent stations in the eastern China. These stations are widely distributed in the southeastern part of the NCB and the northeastern part of the SCB. S ...
... mantle deformation beneath this region. The broadband seismic data used in this study were recorded during August 2007 to April 2013 employing 75 permanent stations in the eastern China. These stations are widely distributed in the southeastern part of the NCB and the northeastern part of the SCB. S ...
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.