Four- and five-phase peridotites from a continental rift system: evidence for upper mantle uplift and cooling at the Ross Sea margin (Antarctica)

1992 ◽  
Vol 111 (1) ◽  
pp. 24-36 ◽  
Author(s):  
J. Zipfel ◽  
G. W�rner
Keyword(s):  
Upper Mantle ◽  
Ross Sea ◽  
Continental Rift ◽  
Rift System

Geochemistry of Siluro-Devonian Tobique volcanic belt in northern and central New Brunswick (Canada): tectonic implications

1989 ◽  
Vol 26 (6) ◽  
pp. 1282-1296 ◽  
Author(s):  
J. Dostal ◽  
R. A. Wilson ◽  
J. D. Keppie
Keyword(s):  
New Brunswick ◽  
Mantle Source ◽  
Upper Mantle ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Continental Rift ◽  
Basaltic Rocks ◽  
Incompatible Elements ◽  
Tectonic Implications

Siluro-Devonian volcanic rocks of the northwestern mainland Appalachians are found mainly in the Tobique belt of New Brunswick where they consist predominantly of bimodal mafic–felsic suites erupted in a continental-rift environment. The axis of the Tobique rift trends north-northeast – south-southwest, obliquely to the regional northeast–southwest trend of the Appalachians. These geometric relationships are interpreted as being the result of rifting in a sinistral shear regime produced during emplacement of the Avalon terrene. The basaltic rocks are continental tholeiites and transitional basalts derived from a heterogeneous upper-mantle source that was enriched in incompatible elements relative to the primordial mantle. The mantle source was probably affected by the subduction processes.

P and S velocity structure of the upper mantle beneath the Transantarctic Mountains, East Antarctic craton, and Ross Sea from travel time tomography

2006 ◽  
Vol 7 (7) ◽  
pp. n/a-n/a ◽  
Author(s):  
Timothy Watson ◽  
Andrew Nyblade ◽  
Douglas A. Wiens ◽  
Sridhar Anandakrishnan ◽  
Margaret Benoit ◽  
...  
Keyword(s):  
Travel Time ◽  
Upper Mantle ◽  
Velocity Structure ◽  
Ross Sea ◽  
Travel Time Tomography ◽  
Transantarctic Mountains

Structure and mobility of the crust and mantle in the vicinity of island arcs

1968 ◽  
Vol 5 (4) ◽  
pp. 985-991 ◽  
Author(s):  
Jack Oliver ◽  
Bryan Isacks
Keyword(s):  
Upper Mantle ◽  
Seismic Waves ◽  
Current Knowledge ◽  
Average Rate ◽  
Seismic Wave Propagation ◽  
Rift System ◽  
Island Arcs ◽  
Deep Earthquake ◽  
Anomalous Zone ◽  
The World

A detailed study of seismic wave propagation in the Fiji-Tonga region shows that there exists in the upper mantle an anomalous zone whose thickness is about 100 km and whose upper surface is approximately defined by the zone of seismic foci extending to depths of about 700 km. Attenuation of seismic waves within the zone is anomalously low and velocities are high. Other island arcs appear to be associated with similar zones.The anomalous zone in Tonga can be interpreted as the westernmost portion of a block of lithosphere that has been thrust, or dragged, or has settled beneath the island arc. Such mobility of the lithosphere suggests a key role in geotectonics for this layer of strength and raises a number of possible new solutions to long standing problems. For example, assuming that deep earthquake zones throughout the world are a measure of the amount of underthrusting during the last 107 years, an average rate of spreading over the entire worldwide rift system can be obtained as a check, but not a proof, of the hypothesis. The half-velocity obtained is 1.3 cm/year and is reasonable in light of current knowledge.

scholarly journals Regional seismic stratigraphic correlations of the Ross Sea: Implications for the tectonic history of the West Antarctic Rift System

2007 ◽  
Author(s):  
Robert C. Decesari ◽  
Christopher C. Sorlien ◽  
Bruce P. Luyendyk ◽  
Douglas S. Wilson ◽  
Louis Bartek ◽  
...  
Keyword(s):  
Ross Sea ◽  
Rift System ◽  
The West ◽  
West Antarctic ◽  
Tectonic History ◽  
History Of ◽  
West Antarctic Rift System ◽  
West Antarctic Rift

Upper-mantle metasomatism beneath a continental rift: clinopyroxenes in alkali mafic lavas and nodules from Sruth West Uganda

1981 ◽  
Vol 44 (335) ◽  
pp. 315-323 ◽  
Author(s):  
F. E. Lloyd
Keyword(s):  
Upper Mantle ◽  
Significant Proportion ◽  
Mantle Metasomatism ◽  
Continental Rift ◽  
Published Data ◽  
East African ◽  
South West ◽  
Mafic Lavas ◽  
Bulk Chemistry

AbstractClinopyroxenes are dominant in highly potassic, silica undersaturated mafic volcanics occurring on the western rim of the uplifted, rifted East African craton. A kimbcrlite style of eruption provides nodules of alkali clinopyroxenite (clinopyroxene + titaniferous phlogopite+titanomagnetite, apatite, sphene, and rare corroded olivine) which have similar bulk chemistry to the feldspathoid-bearing lavas. Many nodules display metasomatic textures supporting a formation from the alteration of pre-existing material; clinopyroxene growth is characterized by complex, non-oscillatory colour zoning. Comparison of natural clinopyroxene chemistry with published data for elinopyroxenes crystallized from synthetic potassium-rich mafic material, suggests that a significant proportion of the nodules crystallized at upper-mantle pressures. Neither garnet- nor orthopyroxene-bearing nodules have ever been recorded from south-west Uganda, suggesting that metasomatism of the local mantle has proceeded far enough to obliterate all recognizable remnants of four-phase lherzolite.

Sign in / Sign up

Export Citation Format

Share Document