Deformation, annealing, reactive melt percolation, and seismic anisotropy in the lithospheric mantle beneath the southeastern Ethiopian rift: Constraints from mantle xenoliths from Mega

AbstractWe report on the petrology, microstructure, and seismic properties of 44 peridotite xenoliths extracted from the upper mantle beneath Marie Byrd Land (MBL), West Antarctica. The aim of this work is to understand how melt-rock reaction, refertilization, and deformation affected the seismic properties (velocities, anisotropy) of the West Antarctic upper mantle, in the context of MBL tectonic evolution and West Antarctic Rift System formation. Modal compositions, mineral major element compositions, microstructures, and crystallographic preferred orientations (CPOs) provide evidence for diachronous reactive melt percolation and refertilization. Olivine shows three main CPO patterns, the A-type, axial-[010], and axial-[100] texture types. Average seismic properties of the MBL mantle lithosphere are mainly controlled by the strength of olivine crystallographic texture. Reactive melt percolation and refertilization likely modified seismic velocities and anisotropy, as is suggested by a systematic decrease in maximum P-wave and S-wave anisotropies with increasing modal abundance of pyroxene. At larger spatial scales, the seismic properties of the MBL mantle xenoliths are dominated by the anisotropy resulting from the A-type olivine CPO. Variations between individual volcanic centers, however, attest to spatial variations in the mantle structure, potentially related to 3-D deformation and the prolonged tectonic history of MBL.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5315261

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Nature and evolution of lithospheric mantle beneath the southern Ethiopian rift zone: evidence from petrology and geochemistry of mantle xenoliths

International Journal of Earth Sciences ◽

10.1007/s00531-016-1342-z ◽

2016 ◽

Vol 106 (3) ◽

pp. 939-958 ◽

Cited By ~ 4

Author(s):

Melesse Alemayehu ◽

Hong-Fu Zhang ◽

Patrick Asamoah Sakyi

Keyword(s):

Lithospheric Mantle ◽

Rift Zone ◽

Mantle Xenoliths ◽

Ethiopian Rift ◽

Petrology And Geochemistry

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Deformation, Metasomatism and Seismic Anisotropy in the Lithospheric Mantle beneath Taiwan Straits, Southeast Asian Margin: Constraints from Mantle Xenoliths

10.46427/gold2020.1364 ◽

2020 ◽

Author(s):

Fatma Kourim ◽

Kuo-Lung Wang ◽

Katsuyoshi Michibayanchi ◽

Suzanne Yvette O'Reilly

Keyword(s):

Lithospheric Mantle ◽

Seismic Anisotropy ◽

Southeast Asian ◽

Mantle Xenoliths ◽

Taiwan Straits

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Mineral ages and zircon Hf isotopic composition of the Andong ultramafic complex: implications for the evolution of Mesozoic subduction system and subcontinental lithospheric mantle beneath SE Korea

Geological Magazine ◽

10.1017/s0016756813000757 ◽

2013 ◽

Vol 151 (5) ◽

pp. 765-776 ◽

Cited By ~ 5

Author(s):

GI YOUNG JEONG ◽

CHANG-SIK CHEONG ◽

KEEWOOK YI ◽

JEONGMIN KIM ◽

NAMHOON KIM ◽

...

Keyword(s):

Lithospheric Mantle ◽

Tectonic Setting ◽

Eastern China ◽

Mantle Xenoliths ◽

Late Triassic ◽

Magmatic Differentiation ◽

Suprasubduction Zone ◽

Ultramafic Complex ◽

Yeongnam Massif ◽

Subduction System

AbstractThe Phanerozoic subduction system of the Korean peninsula is considered to have been activated by at least Middle Permian time. The geochemically arc-like Andong ultramafic complex (AUC) occurring along the border between the Precambrian Yeongnam massif and the Cretaceous Gyeongsang back-arc basin provides a rare opportunity for direct study of the pre-Cretaceous mantle wedge lying above the subduction zone. The tightly constrained SHRIMP U–Pb age of zircons extracted from orthopyroxenite specimens (222.1±1.0 Ma) is indistinguishable from the Ar/Ar age of coexisting phlogopite (220±6 Ma). These ages represent the timing of suprasubduction zone magmatism likely in response to the sinking of cold and dense oceanic lithosphere and the resultant extensional strain regime in a nascent arc environment. The nearly coeval occurrence of a syenite-gabbro-monzonite suite in the SW Yeongnam massif also suggests an extensional tectonic setting along the continental margin side during Late Triassic time. The relatively enriched ɛHf range of dated zircons (+6.2 to −0.6 at 222 Ma) is in contrast to previously reported primitive Sr–Nd–Hf isotopic features of Cenozoic mantle xenoliths from Korea and eastern China. This enrichment is not ascribed to contamination by the hypothetical Palaeozoic crust beneath SE Korea, but is instead attributable to metasomatism of the lithospheric mantle during the earlier subduction of the palaeo-Pacific plate. Most AUC zircons show a restricted core-to-rim spread of ɛHf values, but some grains testify to the operation of open-system processes during magmatic differentiation.

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Lithospheric and sublithospheric deformation under the Borborema Province of northeastern Brazil from receiver function harmonic stripping

Solid Earth ◽

10.5194/se-10-893-2019 ◽

2019 ◽

Vol 10 (3) ◽

pp. 893-905 ◽

Cited By ~ 3

Author(s):

Gaelle Lamarque ◽

Jordi Julià

Keyword(s):

Lithospheric Mantle ◽

Seismic Anisotropy ◽

Receiver Function ◽

Seismic Station ◽

Atlantic Coast ◽

Shear Zones ◽

Receiver Functions ◽

Azimuthal Anisotropy ◽

Northeastern Brazil ◽

Borborema Province

Abstract. The depth-dependent anisotropic structure of the lithosphere under the Borborema Province in northeast Brazil has been investigated via harmonic stripping of receiver functions developed at 39 stations in the region. This method retrieves the first (k=1) and second (k=2) degree harmonics of a receiver function dataset, which characterize seismic anisotropy beneath a seismic station. Anisotropic fabrics are in turn directly related to the deformation of the lithosphere from past and current tectonic processes. Our results reveal the presence of anisotropy within the crust and the lithospheric mantle throughout the entire province. Most stations in the continental interior report consistent anisotropic orientations in the crust and lithospheric mantle, suggesting a dominant northeast–southwest pervasive deformation along lithospheric-scale shear zones developed during the Brasiliano–Pan-African orogeny. Several stations aligned along a northeast–southwest trend located above the (now aborted) Mesozoic Cariri–Potiguar rift display large uncertainties for the fast-axis direction. This non-azimuthal anisotropy may be related to a complex anisotropic fabric resulting from a combination of deformation along the ancient collision between Precambrian blocks, Mesozoic extension and thermomechanical erosion dragging by sublithospheric flow. Finally, several stations along the Atlantic coast reveal depth-dependent anisotropic orientations roughly (sub)perpendicular to the margin. These results suggest a more recent overprint, probably related to the presence of frozen anisotropy in the lithosphere due to stretching and rifting during the opening of the South Atlantic.

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