scholarly journals The Mode of Trench-Parallel Subduction of the Middle Ocean Ridge

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaobing Shen ◽  
Wei Leng
Keyword(s):  
Evolutionary Process ◽  
Pacific Plate ◽  
North American Plate ◽  
Plate Motion ◽  
Western Boundary ◽  
Ridge Subduction ◽  
Ocean Ridges ◽  
The Pacific ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Trench-parallel subduction of mid-ocean ridges occurs frequently in plate motion history, such as along the western boundary of the Pacific plate in the early Cenozoic and along the eastern boundary of the Pacific plate at present. Such subduction may strongly alter the surface topography, volcanic activity and slab morphology in the mantle, whereas few studies have been conducted to investigate its evolutionary process. Here, we construct a 2-D viscoelastoplastic numerical model to study the modes and key parameters controlling trench-parallel subduction of mid-ocean ridges. Our model results show that the subduction modes of mid-ocean ridges can be primarily categorized into three types: the fast spreading mode, the slow spreading mode, and the extinction mode. The key factor controlling these subduction modes is the relative motion between the foregoing and the following oceanic plates, which are separated by the mid-ocean ridge. Different subduction modes exert different surface geological expressions, which may explain specific evolutionary processes related to mid-ocean ridge subduction, such as topographic deformation and the eruption gap of volcanic rocks in East Asia within 55–45 Ma and in the western North American plate during the late Cenozoic.

Evidence from ocean islands suggesting movement in the Earth

1965 ◽  
Vol 258 (1088) ◽  
pp. 145-167 ◽  
Keyword(s):  
Upper Jurassic ◽  
Oceanic Islands ◽  
Chemical Characteristics ◽  
Ocean Ridges ◽  
East Pacific ◽  
The Earth ◽  
The Pacific ◽  
Mid Ocean Ridge ◽  
Volcanic Islands ◽  
Ocean Ridge

Oceanic islands increase in age from the mid-ocean ridges towards continents and the andesite line reaching a maximum known age of Upper Jurassic. The Seychelles appear to be a continental fragment. Several pairs of lateral aseismic ridges extend from islands on the mid-ocean ridge to adjacent continents. Their continental junctions mark points on opposite coasts which would also fit if the continents were reassembled according to the criteria used by Wegener. As Holmes has shown each pair of ridges tends to have distinctive chemical characteristics. One possible explanation is that convection currents in the mantle rising along the mid-ocean ridges and sinking beneath trenches have carried the crust apart across the Atlantic, India and East Pacific Oceans. The lateral ridges may be approximately streamlines. Although Darwin showed that most volcanic islands sink, a few have been uplifted. Most of these lie a few hundred kilometres in front of deep trenches, suggesting that they may be on the crest of a standing wave in front of the trenches and that the crust is rigid. Of eleven straight chains of young islands in the Pacific ten get older away from the East Pacific Ridge. They could also be streamlines, fed by lava rising from deep within convection cells with stagnant cores. The regularity of ridges suggests non-turbulent flow.

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.

Convection tectonics: some possible effects upon the Earth's surface of flow from the deep mantle

1988 ◽  
Vol 25 (8) ◽  
pp. 1199-1208 ◽  
Author(s):  
J. Tuzo Wilson
Keyword(s):  
Land Surface ◽  
Angle Of Incidence ◽  
Gulf Of Aden ◽  
Upward Flow ◽  
New Techniques ◽  
Ocean Ridges ◽  
The Earth ◽  
Mid Ocean Ridge ◽  
The Subject ◽  
Ocean Ridge

Until a little more than a century ago the land surface not only was the only part of the Earth accessible to humans but also was the only part for which geophysical and geochemical methods could then provide any details. Since then scientists have developed ways to study the ocean floors and some details of the interior of the Earth to ever greater depths. These discoveries have followed one another more and more rapidly, and now results have been obtained from all depths of the Earth.New methods have not contradicted or greatly disturbed either old methods or old results. Hence, it has been easy to overlook the great importance of these recent findings.Within about the last 5 years the new techniques have mapped the pattern of convection currents in the mantle and shown that these rise from great depths to the surface. Even though the results are still incomplete and are the subject of debate, enough is known to show that the convection currents take two quite different modes. One of these breaks the strong lithosphere; the other moves surface fragments and plates about.It is pointed out that if expanding mid-ocean ridges move continents and plates, geometrical considerations demand that the expanding ridges must themselves migrate. Hence, collisions between ridges and plates are likely to have occurred often during geological time.Twenty years ago it was shown that the effect of a "mid-ocean ridge in the mouth of the Gulf of Aden" was to enter and rift the continent. This paper points out some of the conditions under which such collisions occur and in particular shows that the angle of incidence between a ridge and a coastline has important consequences upon the result. Several past and present cases are used to illustrate that collisions at right angles tend to produce rifting; collisions at oblique angles appear to terminate in the lithosphere in coastal shears, creating displaced terrane, but in the mantle the upward flow may continue to uplift the lithosphere far inland and produce important surface effects; collisions between coasts and mid-ocean ridges parallel to them produce hot uplifts moving inland. For a time these upwellings push thrusts and folds ahead of them, but they appear to die down before reaching cratons.

scholarly journals Ridge subduction sparked reorganization of the Pacific plate‐mantle system 60–50 million years ago

2015 ◽  
Vol 42 (6) ◽  
pp. 1732-1740 ◽  
Author(s):  
Maria Seton ◽  
Nicolas Flament ◽  
Joanne Whittaker ◽  
R. Dietmar Müller ◽  
Michael Gurnis ◽  
...  
Keyword(s):  
Pacific Plate ◽  
Ridge Subduction ◽  
The Pacific

Melvicalathis, a new brachiopod genus (Terebratulida: Chlidonophoridae) fromdeep sea volcanic substrates, and the biogeographic significance of the mid-oceanridge system

Zootaxa ◽  
2008 ◽  
Vol 1866 (1) ◽  
pp. 136 ◽  
Author(s):  
DAPHNE E. LEE ◽  
MURRAY R. GREGORY ◽  
CARSTEN LÜTER ◽  
OLGA N. ZEZINA ◽  
JEFFREY H. ROBINSON ◽  
...  
Keyword(s):  
Deep Sea ◽  
New Genus ◽  
Significant Component ◽  
Ocean Ridges ◽  
Southeast Indian Ridge ◽  
Mid Ocean Ridge ◽  
History Of ◽  
Cryptic Habitats ◽  
Ocean Ridge ◽  
Ridge System

Brachiopods form a small but significant component of the deep-sea benthos in all oceans. Almost half of the 40 brachiopod species so far described from depths greater than 2000 m are small, short-looped terebratulides assigned to two superfamilies, Terebratuloidea and Cancellothyridoidea. In this study we describe Melvicalathis, a new genus of cancellothyridoid brachiopod (Family Chlidonophoridae; Subfamily Eucalathinae) from ocean ridge localities in the south and southeast Pacific Ocean, and cryptic habitats within lava caves in glassy basalt dredged from the Southeast Indian Ridge, Indian Ocean. These small, punctate, strongly-ribbed, highly spiculate brachiopods occur at depths between 2009 m and 4900 m, and appear to be primary colonisers on the inhospitable volcanic rock substrate. The ecology and life-history of Melvicalathis and related deep-sea brachiopods are discussed. Brachiopods are rarely reported from the much-studied but localised hydrothermal vent faunas of the mid ocean ridge systems. They are, however, widespread members of a poorly known deep-sea benthos of attached, suspension-feeding epibionts that live along the rarely sampled basalt substrates associated with mid-ocean ridge systems. We suggest that these basalt rocks of the mid-ocean ridge system act as deep-sea “superhighways” for certain groups of deep-sea animals, including brachiopods, along which they may migrate and disperse. Although the mid-ocean ridges form the most extensive, continuous, essentially uniform habitat on Earth, their biogeographic significance may not have been fully appreciated.

Oblique mid ocean ridge subduction modelling with the parallel fast multipole boundary element method

2012 ◽  
Vol 51 (4) ◽  
pp. 455-463 ◽  
Author(s):  
L. Quevedo ◽  
B. Hansra ◽  
G. Morra ◽  
N. Butterworth ◽  
R. D. Müller
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Fast Multipole ◽  
Ridge Subduction ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Element Method

scholarly journals Possibility of recovery of slip deficit rate between the North American plate and the Pacific plate off Sanriku, northeast Japan

2007 ◽  
Vol 34 (20) ◽  
Author(s):  
Shinzaburo Ozawa ◽  
Hisashi Suito ◽  
Takuya Nishimura ◽  
Mikio Tobita ◽  
Hiroshi Munekane
Keyword(s):  
North American ◽  
Pacific Plate ◽  
North American Plate ◽  
The North ◽  
Slip Deficit ◽  
The Pacific ◽  
Off Sanriku

Isotopic and trace element constraints on the genesis of a boninitic sequence in the Thetford Mines ophiolitic complex, Quebec, Canada

1997 ◽  
Vol 34 (9) ◽  
pp. 1258-1271 ◽  
Author(s):  
Valérie Olive ◽  
Réjean Hébert ◽  
Michel Loubet
Keyword(s):  
Trace Element ◽  
Trace Element Composition ◽  
Nd Isotope ◽  
Geodynamic Environment ◽  
The Pacific ◽  
Geochemical Study ◽  
Mid Ocean Ridge ◽  
Isochron Diagram ◽  
Component C ◽  
Ocean Ridge

The Mont Ham Massif (part of the Thetford Mines ophiolite, south Quebec) represents a magmatic sequence made up of tholeiitic and boninitic derived products. A geochemical study confirms the multicomponent mixing models that have been classically advanced for the source of boninites, with slab-derived components added to the main refractory harzburgitic peridotite. An isochron diagram of the boninitic rocks is interpreted as a mixing trend between two components: (i) a light rare earth element (LREE) enriched component (A), interpreted as slab-derived fluid–melts equilibrated with sedimentary materials (εNd = −3, 147Sm/144Nd = 0.140), and (ii) a LREE-depleted component (B) (0.21 < 147Sm/144Nd < 0.23), interpreted as slab-derived fluid–melt equilibrated with recycled Iapetus oceanic crust and equated to the Nd-isotope characteristics of the Iapetus mantle (εNd = 9). A multicomponent source is also necessary to explain the Nd-isotope and trace element composition of the tholeiites, which are explained by the melting of a more fertile, lherzolitic mantle and (or) mid-ocean ridge basalt source (component C), characterized by a large-ion lithophile element depleted pattern and an Iapetus mantle Nd isotopic composition (εNd = 9), mixed in adequate proportions with the two previously infered slab-derived components (A and B). The genesis of the boninites of Mont Ham is not significantly different from those of boninites located in the Pacific. An intraoceanic subduction zone appears to be an appropriate geodynamic environment for the Mont Ham ophiolitic sequence.

scholarly journals Distribution of Relative Plate Motion Along the Pacific-North American Plate Boundary Determined from Mobile VLBI Measurements

1988 ◽  
Vol 129 ◽  
pp. 365-366
Author(s):  
P. M. Kroger ◽  
G. A. Lyzenga ◽  
K. S. Wallace ◽  
J. M. Davidson
Keyword(s):  
North American ◽  
Plate Boundary ◽  
Temporal Distribution ◽  
North American Plate ◽  
Primary Sources ◽  
Plate Motion ◽  
Fault System ◽  
Pacific North American ◽  
The Pacific ◽  
San Andreas Fault System

The problem of understanding the deformation occurring along the Pacific-North American plate boundary in the western United States depends upon understanding the forces which drive the plates in this region. One of the primary sources of our knowledge concerning these forces lies in their manifestation as relative displacements which occur throughout the broad zone of deformation surrounding the San Andreas fault system. It is information concerning the spatial and temporal distribution of these motions which will be of greatest benefit in helping to determine which of several possible mechanisms is responsible for driving contemporary plate motions in this region.

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