scholarly journals A VELOCITY MODEL FOR BACKARC BASINS UPPER MANTLE

2016 ◽  
Vol 12 (2) ◽  
pp. 37-47
Author(s):  
V.V. Gordienko ◽  
L.Ya. Gordienko
Keyword(s):  
Upper Mantle ◽  
Velocity Model ◽  
Backarc Basins

scholarly journals Antarctic Upper Mantle Rheology

2021 ◽  
pp. M56-2020-19
Author(s):  
E. R. Ivins ◽  
W. van der Wal ◽  
D. A. Wiens ◽  
A. J. Lloyd ◽  
L. Caron
Keyword(s):  
Wave Velocity ◽  
Upper Mantle ◽  
Effective Viscosity ◽  
Seismic Velocity ◽  
Imaging Techniques ◽  
Three Dimensional ◽  
Velocity Model ◽  
Mantle Flow ◽  
S Wave ◽  
Velocity Changes

AbstractThe Antarctic mantle and lithosphere are known to have large lateral contrasts in seismic velocity and tectonic history. These contrasts suggest differences in the response time scale of mantle flow across the continent, similar to those documented between the northeastern and southwestern upper mantle of North America. Glacial isostatic adjustment and geodynamical modeling rely on independent estimates of lateral variability in effective viscosity. Recent improvements in imaging techniques and the distribution of seismic stations now allow resolution of both lateral and vertical variability of seismic velocity, making detailed inferences about lateral viscosity variations possible. Geodetic and paleo sea-level investigations of Antarctica provide quantitative ways of independently assessing the three-dimensional mantle viscosity structure. While observational and causal connections between inferred lateral viscosity variability and seismic velocity changes are qualitatively reconciled, significant improvements in the quantitative relations between effective viscosity anomalies and those imaged by P- and S-wave tomography have remained elusive. Here we describe several methods for estimating effective viscosity from S-wave velocity. We then present and compare maps of the viscosity variability beneath Antarctica based on the recent S-wave velocity model ANT-20 using three different approaches.

scholarly journals Origins of topography in the western U.S.: Mapping crustal and upper mantle density variations using a uniform seismic velocity model

2014 ◽  
Vol 119 (3) ◽  
pp. 2375-2396 ◽  
Author(s):  
Will Levandowski ◽  
Craig H. Jones ◽  
Weisen Shen ◽  
Michael H. Ritzwoller ◽  
Vera Schulte‐Pelkum
Keyword(s):  
Upper Mantle ◽  
Seismic Velocity ◽  
Velocity Model

A shear wave velocity model of the European upper mantle from automated inversion of seismic shear and surface waveforms

2012 ◽  
Vol 191 (1) ◽  
pp. 282-304 ◽  
Author(s):  
C. P. Legendre ◽  
T. Meier ◽  
S. Lebedev ◽  
W. Friederich ◽  
L. Viereck-Götte
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Upper Mantle ◽  
Velocity Model ◽  
Seismic Shear

An improved velocity model for the crust and upper mantle along the central mobile belt of the Newfoundland Appalachian orogen and its offshore extension

1998 ◽  
Vol 35 (11) ◽  
pp. 1238-1251 ◽  
Author(s):  
Deping Chian ◽  
François Marillier ◽  
Jeremy Hall ◽  
Garry Quinlan
Keyword(s):  
Upper Mantle ◽  
Lower Crust ◽  
Velocity Structure ◽  
Sedimentary Basins ◽  
Velocity Model ◽  
Mobile Belt ◽  
Wide Angle ◽  
Crust And Upper Mantle ◽  
Angle Data ◽  
Appalachian Orogen

New modelling of wide-angle reflection-refraction data of the Canadian Lithoprobe East profile 91-1 along the central mobile belt of the Newfoundland Appalachian orogen reveals new features of the upper mantle, and establishes links in the crust and upper mantle between existing land and marine wide-angle data sets by combining onshore-offshore recordings. The revised model provides detailed velocity structure in the 30-34 km thick crust and the top 30 km of upper mantle. The lower crust is characterized by a velocity of 6.6-6.8 km/s onshore, increasing by 0.2 km/s to the northeast offshore beneath the sedimentary basins. This seaward increase in velocity may be caused by intrusion of about 4 km of basic rocks into the lower crust during the extension that formed the overlying Carboniferous basins. The Moho is found at 34 km depth onshore, rising to 30 km offshore to the northeast with a local minimum of 27 km. The data confirm the absence of deep crustal roots under the central mobile belt of Newfoundland. Our long-range (up to 450 km offset) wide-angle data define a bulk velocity of 8.1-8.3 km/s within the upper 20 km of mantle. The data also contain strong reflective phases that can be correlated with two prominent mantle reflectors. The upper reflector is found at 50 km depth under central Newfoundland, rising abruptly towards the northeast where it reaches a minimum depth of 36 km. This reflector is associated with a thin layer (1-2 km) unlikely to coincide with a discontinuity with a large cross-boundary change in velocity. The lower reflector at 55-65 km depths is much stronger, and may have similar origins to reflections observed below the Appalachians in the Canadian Maritimes which are associated with a velocity increase to 8.5 km/s. Our data are insufficient for discriminating among various interpretations for the origins of these mantle reflectors.

scholarly journals Basalt derived from highly refractory mantle sources during early Izu-Bonin-Mariana arc development

2020 ◽  
Author(s):  
He Li ◽  
Richard Arculus ◽  
Osamu Ishizuka ◽  
Rosemary Hickey-Vargas ◽  
Gene Yogodzinski ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Philippine Sea Plate ◽  
Island Arcs ◽  
Element Abundances ◽  
Mid Ocean Ridge ◽  
Mantle Sources ◽  
Backarc Basins ◽  
Mariana Arc ◽  
Ocean Ridge ◽  
Aluminous Spinel

Abstract The character of magmatism associated with the early stages of subduction zone and island arc development is unlike that of mature systems, being dominated in the Izu-Bonon-Mariana (IBM) case by low-Ti-K tholeiitic basalts and boninites. Basalts recovered by coring the basement of the Amami Sankaku Basin (ASB), located west of the oldest remnant arc of the IBM system (Kyushu-Palau Ridge; KPR), were erupted at ~49 Ma, about 3 million years after subduction inception. The chain of stratovolcanoes defined by the KPR is superimposed on this basement. The basalts were sourced from upper mantle similar to that tapped following subduction inception, and represented by forearc basalt (FAB) dated at ~52-51 Ma. The mantle sources of the ASB basalt basement were more depleted by prior melt extraction than those involved in the vast majority of mid-ocean ridge (MOR) basalt generation. The ASB basalts are low-Ti-K, aluminous spinel-olivine-plagioclase-clinopyroxene-bearing tholeiites. We show this primary mineralogy is collectively distinct compared to basalts of MOR, backarc basins of the Philippine Sea Plate, forearc, or mature island arcs. In combination with bulk compositional (major and trace element abundances plus radiogenic isotope characteristics) data for the ASB basalts, we infer the upper mantle involved was hot (~1400oC), reduced, and refractory peridotite. For a few million years following subduction initiation, a broad region of mantle upwelling accompanied by partial melting prevailed. The ASB basalts were transferred rapidly from moderate pressures (1-2 GPa), preserving a mineralogy established at sub-crustal conditions, and experienced little of recharge-mix-tap-fractionate regimes typical of MOR or mature arcs.

scholarly journals GEOPHYSICAL STUDIES AND TECTONISM OF THE HELLENIDES

2017 ◽  
Vol 43 (1) ◽  
pp. 32 ◽  
Author(s):  
J. Makris
Keyword(s):  
Upper Mantle ◽  
Aegean Sea ◽  
Velocity Model ◽  
Normal Faults ◽  
Tectonic Deformation ◽  
Flow Density ◽  
Crust And Upper Mantle ◽  
The North ◽  
Deep Seismic Soundings ◽  
Western Greece

By constraining gravity modelling by Deep Seismic Soundings (DSS) and the Bouguer gravity field of Greece a 3-D density-velocity model of the crust and upper mantle was developed. It was shown that in the north Aegean Trough and the Thermaikos Basins the sediments exceed 7 km in thickness. The basins along the western Hellenides and the coastal regions of western Greece are filled with sediments of up to 10 km thickness, including the Prepulia and Alpine metamorphic limestones. The thickest sedimentary series however, were mapped offshore southwest and southeast of Crete and are of the order of 12 to 14 km. The crust along western Greece and the Peloponnese ranges between 42 and 32 km thickness while the Aegean region is floored by a stretched continental crust varying between 24 to 26 km in the north and eastern parts and thins to only 16 km at the central Cretan Sea. The upper mantle below the Aegean Sea is occupied by a lithothermal system of low density (3.25 gr/cm³) and Vp velocity (7.7 km/s), which is associated with the subducted Ionian lithosphere below the Aegean Sea. Isostasy is generally maintained at crustal and subcrustal levels except for the compressional domain of western Greece and the transition between the Mediterranean Ridge and the continental backstop. The isotherms computed from the Heat Flow density data and the density model showed a significant uplift of the temperature field below the Aegean domain. The 400°C isotherm is encountered at less than 10 Km depth. Tectonic deformation is controlled by dextral wrench faulting in the Aegean domain, while western Greece is dominated by compression and crustal shortening. Strike-slip and normal faults accommodate the western Hellenic thrusts and the westwards sliding of the Alpine napes, using the Triassic evaporates as lubricants.

scholarly journals VELOCITY MODEL OF THE UPPER MANTLE OF THE FLANKING PLATEAUS OF MID-OCEANIC RIDGES

2020 ◽  
Vol 16 (4) ◽  
pp. 19-31
Author(s):  
V.V. GORDIENKO ◽  
L.Ya. GORDIENKO
Keyword(s):  
Travel Time ◽  
Upper Mantle ◽  
Seismic Waves ◽  
Bottom Topography ◽  
Velocity Model ◽  
Transfer Scheme ◽  
Transition Zones ◽  
Velocity Section ◽  
Ocean Ridges ◽  
Using Data

A new element is included in the study of velocity sections of the upper mantle of regions of continents, oceans, and transition zones with different endogenous regimes (according to the advection-polymorphic hypothesis — APH). This is the flanking plateaus (FP) of the mid-ocean ridges (MOR). It is assumed that these regions underwent the process of oceanization in the Mesozoic along with other parts of the oceans. In the Neogene MORs were formed. Significant parts of the basins were engulfed in modern activation, including magmatism. Between these parts of the oceans, relatively narrow strips (200—300 km wide) have survived, which some authors refer to as flanking plateaus. They are located at the edges of the MOR. FP did not experience young activization. This is indicated by the features of the bottom topography, magnetic, gravitational and thermal fields, and a velocity section of the upper horizons of the mantle. An element of checking the nature of the FP can be the construction of a velocity section of the mantle beneath these regions. According to the APH, it should differ from the neighboring ones by the increased velocity of seismic waves in the upper about 200 km. The experimental data for such work turned out to be extremely small. It was possible to build only one travel-time, using data on the southern part of the Atlantic Ocean. Insignificant information was also attracted on the southern part of the East Pacific Rise and the Mid-Indian Ridge. The travel-time corresponds to the velocity section, which completely coincides with the forecast. The latter was calculated according to the heat and mass transfer scheme in the APH version and the thermal model of the mantle. The velocity section of the FP mantle does not contain indications of a partial melting layer. Consequently, there should be no manifestations of young magmatism in FP. Verification showed that in most of the studied fragments of MOR this is true.

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