scholarly journals A subduction influence on ocean ridge basalts outside the Pacific subduction shield

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
A. Y. Yang ◽  
C. H. Langmuir ◽  
Y. Cai ◽  
P. Michael ◽  
S. L. Goldstein ◽  
...  
Keyword(s):  
Upper Mantle ◽  
The Arctic ◽  
Mantle Flow ◽  
Mantle Heterogeneity ◽  
Gakkel Ridge ◽  
The Pacific ◽  
Mid Ocean Ridge ◽  
The Pacific Ocean ◽  
Back Arc ◽  
Ocean Ridge

AbstractThe plate tectonic cycle produces chemically distinct mid-ocean ridge basalts and arc volcanics, with the latter enriched in elements such as Ba, Rb, Th, Sr and Pb and depleted in Nb owing to the water-rich flux from the subducted slab. Basalts from back-arc basins, with intermediate compositions, show that such a slab flux can be transported behind the volcanic front of the arc and incorporated into mantle flow. Hence it is puzzling why melts of subduction-modified mantle have rarely been recognized in mid-ocean ridge basalts. Here we report the first mid-ocean ridge basalt samples with distinct arc signatures, akin to back-arc basin basalts, from the Arctic Gakkel Ridge. A new high precision dataset for 576 Gakkel samples suggests a pervasive subduction influence in this region. This influence can also be identified in Atlantic and Indian mid-ocean ridge basalts but is nearly absent in Pacific mid-ocean ridge basalts. Such a hemispheric-scale upper mantle heterogeneity reflects subduction modification of the asthenospheric mantle which is incorporated into mantle flow, and whose geographical distribution is controlled dominantly by a “subduction shield” that has surrounded the Pacific Ocean for 180 Myr. Simple modeling suggests that a slab flux equivalent to ~13% of the output at arcs is incorporated into the convecting upper mantle.

The subduction influence on ocean ridge basalts and its significance

2021 ◽  
Author(s):  
Alexandra Yang Yang ◽  
Charles Langmuir ◽  
Yue Cai ◽  
Steven Goldstein ◽  
Peter Michael ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Upper Mantle ◽  
The Arctic ◽  
Plate Tectonic ◽  
Gakkel Ridge ◽  
The Pacific ◽  
Mid Ocean Ridge ◽  
The Pacific Ocean ◽  
Back Arc ◽  
Ocean Ridge

Abstract The plate tectonic cycle produces chemically distinct mid-ocean ridge basalts (MORB) and arc volcanics, with the latter enriched in fluid-mobile elements and depleted in Nb owing to fluxes from the subducted slab. Basalts from back-arc basins (BABB), with intermediate compositions, show that the subduction flux can escape the arc. Hence it is puzzling why arc signatures have rarely been recognized in MORB. Here we report the first MORB samples with distinct arc signatures, akin to BABB, from the Arctic Gakkel Ridge. A new high precision dataset for 576 Gakkel samples suggests a pervasive subduction influence. This influence can also be identified in Atlantic and Indian MORB with a “BABB filter”, but is nearly absent in Pacific MORB. This global distribution reflects the control of a “subduction shield” that has surrounded the Pacific Ocean for 180Myr. Statistics suggest that a flux equivalent to ~ 13% of output at arcs is incorporated into the convecting upper mantle.

scholarly journals Competing effects of spreading rate, crystal fractionation and source variability on Fe isotope systematics in mid-ocean ridge lavas

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marianne Richter ◽  
Oliver Nebel ◽  
Martin Schwindinger ◽  
Yona Nebel-Jacobsen ◽  
Henry J. B. Dick
Keyword(s):  
Partial Melting ◽  
Upper Mantle ◽  
Crystal Fractionation ◽  
The Arctic ◽  
Iron Isotope ◽  
Mid Ocean Ridge ◽  
Fast Spreading ◽  
Ocean Ridge ◽  
Isotope Systematics ◽  
Source Heterogeneity

AbstractTwo-thirds of the Earth is covered by mid-ocean ridge basalts, which form along a network of divergent plate margins. Basalts along these margins display a chemical diversity, which is consequent to a complex interplay of partial mantle melting in the upper mantle and magmatic differentiation processes in lower crustal levels. Igneous differentiation (crystal fractionation, partial melting) and source heterogeneity, in general, are key drivers creating variable chemistry in mid-ocean ridge basalts. This variability is reflected in iron isotope systematics (expressed as δ57Fe), showing a total range of 0.2 ‰ from δ57Fe =  + 0.05 to + 0.25 ‰. Respective contributions of source heterogeneity and magma differentiation leading to this diversity, however, remain elusive. This study investigates the iron isotope systematics in basalts from the ultraslow spreading Gakkel Ridge in the Arctic Ocean and compares them to existing data from the fast spreading East Pacific Rise ridge. Results indicate that Gakkel lavas are driven to heavier iron isotope compositions through partial melting processes, whereas effects of igneous differentiation are minor. This is in stark contrast to fast spreading ridges showing reversed effects of near negligible partial melting effects followed by large isotope fractionation along the liquid line of descent. Gakkel lavas further reveal mantle heterogeneity that is superimposed on the igneous differentiation effects, showing that upper mantle Fe isotope heterogeneity can be transmitted into erupting basalts in the absence of homogenisation processes in sub-oceanic magma chambers.

Two-component mantle melting-mixing model for the generation of mid-ocean ridge basalts: Implications for the volatile content of the Pacific upper mantle

2016 ◽  
Vol 176 ◽  
pp. 44-80 ◽  
Author(s):  
Kei Shimizu ◽  
Alberto E. Saal ◽  
Corinne E. Myers ◽  
Ashley N. Nagle ◽  
Erik H. Hauri ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Mixing Model ◽  
Mantle Melting ◽  
Volatile Content ◽  
The Pacific ◽  
Mid Ocean Ridge ◽  
Two Component ◽  
Ocean Ridge

Spatiotemporal Relationship between Arctic Mid-Ocean Ridge System and Intraplate Seismicity of the European Arctic

2021 ◽  
Author(s):  
Galina N. Antonovskaya ◽  
Irina M. Basakina ◽  
Natalya V. Vaganova ◽  
Natalia K. Kapustian ◽  
Yana V. Konechnaya ◽  
...  
Keyword(s):  
Correlation Coefficients ◽  
Seismic Energy ◽  
The Arctic ◽  
Time Lags ◽  
Novaya Zemlya Archipelago ◽  
Gakkel Ridge ◽  
Novaya Zemlya ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Ridge System

Abstract In this article, we investigate the influence of the Arctic mid-ocean ridge system (AMORS), including the Gakkel and Mohns ridges, and the Knipovich ridge–Lena trough (KL) segment, on seismicity of the Novaya Zemlya archipelago area (NZ) and the northernmost margin of the East-European Platform (EEP) for 1980–2019. For each individual area, the annual seismic energy was obtained by adding the energies of all earthquakes. To do this, we have converted various types of magnitude by different seismic networks into moment magnitude Mw. We compiled the updated catalog for the NZ, the northern EEP, and the northern part of the Ural fold belt (UFB). As a result, we constructed time distributions of annual seismic energy releases for each composing ridges of AMORS, NZ, and EEP combined with UFB. A model based on the Elsasser’s one describing the transfer of lithospheric stress disturbances in the horizontal direction was built, and quantitative calculations of the disturbance propagations from AMORS were performed. Results are in good agreement with the annual seismic energy time lags between rifts and NZ and EEP together with the UFB. We calculated correlation coefficients between the seismic energy releases over the time for the structures, enabling identification of the characteristic excitation cycles and estimation of the interval of disturbance transfer from AMORS. As a result, disturbances from the Gakkel ridge appear 3 yr later in NZ, from the KL segment in 4 yr, and from the Mona ridge in 8 yr. For the EEP + UBF combined area, we found the following disturbances spreading lags as 7 yr for the Mona ridge, 4 yr for the KL segment, and 5 yr for the Gakkel ridge. The obtained damping amplitudes of the disturbance spreading from the arctic ridges are sufficient to affect the intraplate seismic activity.

Tholeiitic volcanic rocks of the late Archean Blake River Group, southern Abitibi greenstone belt: origin and geodynamic implications

1992 ◽  
Vol 29 (7) ◽  
pp. 1448-1458 ◽  
Author(s):  
M. R. Laflèche ◽  
C. Dupuy ◽  
J. Dostal
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Incompatible Trace Element ◽  
Progressive Change ◽  
Abitibi Greenstone Belt ◽  
Mid Ocean Ridge ◽  
Compositional Variations ◽  
Arc Setting ◽  
Back Arc ◽  
Ocean Ridge

The late Archean Blake River Group volcanic sequence forms the uppermost part of the southern Abitibi greenstone belt in Quebec. The group is mainly composed of mid-ocean-ridge basalt (MORB)-like tholeiites that show a progressive change of several incompatible trace element ratios (e.g., Nb/Th, Nb/Ta, La/Yb, and Zr/Y) during differentiation. The compositional variations are inferred to be the result of fractional crystallization coupled with mixing–contamination of tholeiites by calc-alkaline magma which produced the mafic–intermediate lavas intercalated with the tholeiites in the uppermost part of the sequence. The MORB-like tholeiites were probably emplaced in a back-arc setting.

Little-known arctic species Montacuta spitzbergensis (Bivalvia: Montacutidae) from the north-western Pacific with notes on Montacuta substriata and Tellimya ferruginosa

2008 ◽  
Vol 88 (2) ◽  
pp. 347-356 ◽  
Author(s):  
Gennady M. Kamenev
Keyword(s):  
Sea Of Okhotsk ◽  
First Record ◽  
Western Pacific ◽  
The Arctic ◽  
Arctic Species ◽  
The North ◽  
The Pacific ◽  
The Pacific Ocean ◽  
North Western ◽  
North Western Pacific

An expanded description of a little-known arctic species Montacuta spitzbergensis from the Sea of Okhotsk with new data on its morphology, ecology and geographical distribution is given. This is the first record of M. spitzbergensis from the north-western Pacific. It differs from other species of Montacuta in its large (to 8.4 mm), elongate–ovate, thick shell with wide, slightly curved hinge plate, wide, short, and shallow resilifer, and weakly developed external ligament. This species occurs in the Arctic Ocean (Spitsbergen, Barents, Kara, Laptev and Chukchi Seas) and the Pacific Ocean (Sea of Okhotsk) at depths from 9 to 232 m at a bottom temperature from −1.62°C to +2.50°C. The hinge structure of the type species of the genera Montacuta and Tellimya is also discussed.

scholarly journals Supplemental Material: Seismic anisotropy in southern Costa Rica confirms upper mantle flow from the Pacific to the Caribbean

2020 ◽  
Author(s):  
Vadim Levin ◽  
et al.
Keyword(s):  
Data Analysis ◽  
Costa Rica ◽  
Upper Mantle ◽  
Seismic Anisotropy ◽  
Data Sources ◽  
Mantle Flow ◽  
Analysis Methodology ◽  
The Pacific ◽  
Wave Splitting ◽  
The Caribbean

Data sources, details of data analysis methodology, and additional diagrams and maps of shear wave splitting measurements.<br>

Rhabdothermus arcticus gen. nov., sp. nov., a member of the family Thermaceae isolated from a hydrothermal vent chimney in the Soria Moria vent field on the Arctic Mid-Ocean Ridge

2011 ◽  
Vol 61 (9) ◽  
pp. 2197-2204 ◽  
Author(s):  
Bjørn O. Steinsbu ◽  
Brian J. Tindall ◽  
Vigdis L. Torsvik ◽  
Ingunn H. Thorseth ◽  
Frida L. Daae ◽  
...  
Keyword(s):  
The Arctic ◽  
Rrna Gene ◽  
Organic Substrates ◽  
Mid Ocean Ridge ◽  
The Family ◽  
Optimum Ph ◽  
Casamino Acids ◽  
Ocean Ridge ◽  
Complex Organic ◽  
Acetate Butyrate

A novel thermophilic member of the family Thermaceae, designated strain 2M70-1T, was isolated from the wall of an active white smoker chimney collected in the Soria Moria vent field at 71 °N in the Norwegian–Greenland Sea. Cells of the strain were Gram-negative, non-motile rods. Growth was observed at 37–75 °C (optimum 65 °C), at pH 6–8 (optimum pH 7.3) and in 1–5 % (w/v) NaCl (optimum 2.5–3.5 %). The isolate was aerobic but could also grow anaerobically using nitrate or elemental sulfur as electron acceptors. The strain was obligately heterotrophic, growing on complex organic substrates like yeast extract, Casamino acids, tryptone and peptone. Pyruvate, acetate, butyrate, sucrose, rhamnose and maltodextrin were used as complementary substrates. The G+C content of the genomic DNA was 68 mol%. Cells possessed characteristic phospholipids and glycolipids. Major fatty acids constituted saturated and unsaturated iso-branched and saturated anteiso-branched forms. Menaquinone 8 was the sole respiratory lipoquinone. Phylogenetic analysis of 16S rRNA gene sequences placed the strain in the family Thermaceae in the phylum ‘Deinococcus–Thermus’, which is consistent with the chemotaxonomic data. On the basis of phenotypic and phylogenetic data, strain 2M70-1T ( = JCM 15963T  = DSM 22268T) represents the type strain of a novel species of a novel genus, for which the name Rhabdothermus arcticus gen. nov., sp. nov. is proposed.

Crustal structure of Pacific Ocean area from dispersion of Rayleigh waves

1963 ◽  
Vol 53 (1) ◽  
pp. 151-165
Author(s):  
Tetsuo A. Santô ◽  
Markus Båth
Keyword(s):  
Pacific Ocean ◽  
Upper Mantle ◽  
Rayleigh Waves ◽  
High Heat ◽  
The Pacific ◽  
New Type ◽  
The Pacific Ocean ◽  
Thin Crust ◽  
Oceanic Structure ◽  
Ridge System

Abstract The dispersion of Rayleigh waves along a great number of Pacific paths has been studied by means of records from Pasadena, California, U. S. A., and Huancayo, Peru. Combining these measurements with previous ones based on records at Tsukuba, Hongkong, Honolulu and Suva, it was found that the central part of the Pacific Ocean exhibits the most oceanic structure, with exception for the Hawaiian Islands. In the south-eastern Pacific Ocean an area could be delineated with a new type of dispersion characteristics, not found in any other part of the Pacific. This area agrees closely with the Easter Island Ridge system, and exhibits unusually thin crust and low upper-mantle velocities as well as exceptionally high heat flow.

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