Upper mantle heterogeneity below the Mid-Atlantic Ridge, 0°–15°N

1992 ◽  
Vol 97 (B4) ◽  
pp. 4461 ◽  
Author(s):  
E. Bonatti ◽  
A. Peyve ◽  
P. Kepezhinskas ◽  
N. Kurentsova ◽  
M. Seyler ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Mantle Heterogeneity ◽  
Mid Atlantic Ridge

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.

scholarly journals Isotopic evidence for chaotic imprint in upper mantle heterogeneity

2010 ◽  
Vol 11 (5) ◽  
pp. n/a-n/a ◽  
Author(s):  
Pietro Armienti ◽  
Daniela Gasperini
Keyword(s):  
Upper Mantle ◽  
Mantle Heterogeneity ◽  
Isotopic Evidence

The age and distribution of mantle heterogeneity along the Mid-Atlantic Ridge (31–41°N)

1999 ◽  
Vol 170 (3) ◽  
pp. 269-286 ◽  
Author(s):  
Laure Dosso ◽  
Henri Bougault ◽  
Charles Langmuir ◽  
Claire Bollinger ◽  
Olga Bonnier ◽  
...  
Keyword(s):  
Mantle Heterogeneity ◽  
Mid Atlantic Ridge

Serpentinization at the Rainbow and Saldanha sites, Mid-Atlantic Ridge: Mineralogical, geochemical, and isotopic features

2019 ◽  
Vol 57 (5) ◽  
pp. 677-706
Author(s):  
Isabel Ribeiro da Costa ◽  
Frederick Joseph Wicks ◽  
Fernando J.A.S. Barriga
Keyword(s):  
Upper Mantle ◽  
Hydrothermal Activity ◽  
Isotopic Data ◽  
Geochemical Characterization ◽  
Textural Evolution ◽  
Mantle Peridotites ◽  
Carbonate Deposition ◽  
Mid Atlantic Ridge ◽  
Ree Patterns

Abstract The Rainbow hydrothermal field (36°14′N) and the Saldanha seamount (36°34′N), in the Mid-Atlantic Ridge (MAR), are tectonic exposures of serpentinized upper mantle peridotites, both associated with significant hydrothermal activity. On the basis of detailed mineralogical and geochemical characterization of serpentinites from both sites, several serpentinization-related issues are discussed in the present work. As expected in oceanic environments, most of the sampled rocks are lizardite-chrysotile serpentinites exhibiting a variety of pseudomorphic through non-pseudomorphic textures, such textural evolution probably being related to changing water/rock ratios during this retrograde process. Oxygen isotope temperatures indicate that the serpentinization took place at 300–200 °C; on the other hand, isotopic data suggest that replacement of early pseudomorphic lizardite by lizardite ± chrysotile non-pseudomorphic textures requires that temperatures and/or water/rock ratios are high enough to promote the necessary dissolution–recrystallization processes. Mass-balance calculations for olivine-serpentine and orthopyroxene-serpentine pairs provided a basis for establishing serpentinization reactions likely to have produced the present rocks. Moreover, these calculations also showed that, notwithstanding some noticeable loss of MgO from olivine and of SiO2 from orthopyroxene, serpentinization of both minerals implies volume increases on the order of 26–27%, therefore potentially promoting the overall expansion of the rock. The geochemical and isotopic features of the studied rocks indicate that unmodified seawater was responsible for the serpentinization of the MAR peridotites. However, the mineralogy and REE patterns of some of these serpentinites indicate occasional subsequent interaction of the serpentinized rocks with seawater at much lower temperatures (seafloor alteration, characterized by carbonate deposition and negative Ce anomalies), or with high-temperature ore-forming hydrothermal fluids (ore-forming alteration, characterized by sulfide precipitation and steep positive Eu anomalies).

scholarly journals An assessment of upper mantle heterogeneity based on abyssal peridotite isotopic compositions

2009 ◽  
Vol 114 (B12) ◽  
Author(s):  
J. M. Warren ◽  
N. Shimizu ◽  
C. Sakaguchi ◽  
H. J. B. Dick ◽  
E. Nakamura
Keyword(s):  
Upper Mantle ◽  
Mantle Heterogeneity ◽  
Abyssal Peridotite ◽  
Isotopic Compositions

scholarly journals Noble gas systematics in new popping rocks from the Mid-Atlantic Ridge (14°N): Evidence for small-scale upper mantle heterogeneities

2019 ◽  
Vol 519 ◽  
pp. 70-82 ◽  
Author(s):  
Sandrine Péron ◽  
Manuel A. Moreira ◽  
Mark D. Kurz ◽  
Joshua Curtice ◽  
Jerzy S. Blusztajn ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Noble Gas ◽  
Small Scale ◽  
Mantle Heterogeneities ◽  
Mid Atlantic Ridge
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