MORGEN – The Mid Ocean Ridge GENerating algorithm

2021 ◽  
Author(s):  
Thomas van der Linden ◽  
Douwe van Hinsbergen
Keyword(s):  
Conceptual Knowledge ◽  
Smooth Curve ◽  
Weddell Sea ◽  
Plate Boundaries ◽  
Plate Tectonic ◽  
Transform Faults ◽  
Ocean Ridges ◽  
Euler Pole ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

<p>Paleo-digital elevation models (paleoDEM) based on plate tectonic and paleogeographic reconstructions use age grids of ocean floor to determine ocean bathymetry. In recent years, such age grids have also been developed for now-subducted oceans from the far geological past, as far back as the Neoproterozoic, using geology and paleomagnetism-based estimates of ocean opening. In such reconstructions, mid ocean ridges are drawn based on estimated Euler poles and rotations, and conceptual knowledge on the geometry consisting of spreading ridges and transform faults.</p><p>Current procedures to draw mid ocean ridges in plate tectonic reconstructions are laborious, as new ridges are drawn every time the Euler pole location changes. Fortunately this is also a task that can be automated. We have written an algorithm using pyGPlates that takes as input a smooth curve at the approximate position of the reconstructed mid ocean ridge at the moment of its formation, and then calculates spreading and transform segments according to their typical geometries in modern oceans, assuming symmetric spreading. The algorithm allows gradual readjustment of ridge orientations upon Euler pole changes comparable to documented cases in the modern oceans (e.g., in the Weddell Sea). The algorithm also contains modules that can convert the calculated mid ocean ridges with other plate boundaries to boundary topologies – which can be used as input for the recently published TracerTectonics algorithm, produce isochrons which can be converted to age grids, check for subduction of isochrons and subsequently create bathymetry grids. We illustrate the use of the MORGEN algorithm with recently published reconstructions of subducted, as well as future oceans.</p>

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.

Evolution of migrating transform faults in anisotropic oceanic crust: examples from Iceland

2019 ◽  
Vol 56 (12) ◽  
pp. 1297-1308 ◽  
Author(s):  
Jeffrey A. Karson ◽  
Bryndís Brandsdóttir ◽  
Páll Einarsson ◽  
Kristján Sæmundsson ◽  
James A. Farrell ◽  
...  
Keyword(s):  
Plate Boundary ◽  
Fault Zones ◽  
Plate Boundaries ◽  
Transform Fault ◽  
Eurasian Plate ◽  
Transform Faults ◽  
The North ◽  
Rift Propagation ◽  
Oriented Parallel ◽  
Ocean Ridge

Major transform fault zones link extensional segments of the North American – Eurasian plate boundary as it transects the Iceland Hotspot. Changes in plate boundary geometry, involving ridge jumps, rift propagation, and related transform fault zone migration, have occurred as the boundary has moved relative to the hotspot. Reconfiguration of transform fault zones occurred at about 6 Ma in northern Iceland and began about 3 Ma in southern Iceland. These systems show a range of different types of transform fault zones, ranging from diffuse, oblique rift zones to narrower, well-defined, transform faults oriented parallel to current plate motions. Crustal deformation structures correlate with the inferred duration and magnitude of strike-slip displacements. Collectively, the different expressions of transform zones may represent different stages of development in an evolutionary sequence that may be relevant for understanding the tectonic history of plate boundaries in Iceland as well as the structure of transform fault zones on more typical parts of the mid-ocean ridge system.

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.

Oxygen isotope geochemistry of rocks from DSDP Leg37

1977 ◽  
Vol 14 (4) ◽  
pp. 771-776 ◽  
Author(s):  
K. Muehlenbachs
Keyword(s):  
Isotopic Composition ◽  
Oxygen Isotope ◽  
Oceanic Crust ◽  
Isotope Geochemistry ◽  
Altered Rock ◽  
Ocean Ridges ◽  
Dredged Materials ◽  
Mid Ocean Ridge ◽  
Intrusive Rocks ◽  
Ocean Ridge

The isotopic compositions of minerals separated from DSDP Leg 37 samples indicate that the primary, unaltered δ18O of both the intrusive and extrusive rocks are identical (~5.7 ‰, SMOW) to those of unaltered basalts dredged from mid-ocean ridges. All of the analyzed basalts (6 to 10 ‰) have been enriched in 18O due to weathering by cold seawater, whereas the intrusive rocks (2.4 and 5.0 ‰) are depleted of 18O probably as a result of exchange with hot seawater at the mid-ocean ridge. Both kinds of altered rock are also known from the study of dredged materials. 18O is preferentially removed from seawater by the first process, but is added to seawater by the second. Exchange of oxygen between oceanic crust and seawater must be considered in any discussion of the evolution of the isotopic composition of the oceans, because large volumes of rock are altered each year as the oceanic crust is formed.

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.

On magma supply and spreading modes at slow and ultraslow mid-ocean ridges

2021 ◽  
Author(s):  
Mathilde Cannat
Keyword(s):  
Heat Carrier ◽  
Strain Localization ◽  
Normal Faults ◽  
Axial Region ◽  
Ocean Ridges ◽  
Magma Supply ◽  
Composition And Structure ◽  
Mid Ocean Ridge ◽  
Plate Separation ◽  
Ocean Ridge

<p>The availability of magma is a key to understand mid-ocean ridge tectonics, and specifically the distribution of the two contrasted spreading modes displayed at slow and ultraslow ridges (volcanically-dominated, and detachment fault-dominated). The part of the plate divergence that is not accommodated by magma emplaced as gabbros or basaltic dikes is taken up by normal faults that exhume upper mantle rocks, in many instances all the way to the seafloor. </p><p>Magma is, however, more than just a material that is, or is not, available to fill the gap between two diverging plates. It is the principal carrier of heat into the axial region and as such it may contribute to thin the axial lithosphere, hence diminishing the volume of new plate material formed at each increment of plate separation. Magma as a heat carrier may also, however, if emplaced in the more permeable upper lithosphere, attract and fuel vigorous hydrothermal circulation and contribute instead to overcooling the newly formed upper plate (Cochran and Buck, JGR 2001). </p><p>Magma is also a powerful agent for strain localization in the axial region: magma and melt-crystal mushes are weak; gabbros that crystallize from these melts are weaker than peridotites because they contain abundant plagioclase; and hydrothermally-altered gabbros, and gabbro-peridotite mixtures, are weaker than serpentinites because of minerals such as chlorite and talc. As a result, detachment-dominated ridge regions that receive very little magma probably have a stronger axial lithosphere than detachment-dominated ridge regions that receive a little more magma. </p><p>Because magma has this triple role (building material, heat carrier, and strain localization agent), and because it is highly mobile (through porosity, along permeability barriers, in fractures and dikes), it is likely that variations in magma supply to the ridge, in time and space, and variations in where this magma gets emplaced in the axial plate, cause a greater diversity of spreading modes, and of the resulting slow and ultraslow lithosphere composition and structure, than suggested by the first order dichotomy between volcanically-dominated and detachment-dominated spreading. </p><p>In this talk I illustrate these points using results of recent studies at the Mid-Atlantic and Southwest Indian ridges.</p>

Investigation into the influence of the Réunion plume on the Central Indian Ridge

2020 ◽  
Author(s):  
Clément Vincent ◽  
Jung-Woo Park ◽  
Sang-Mook Lee ◽  
Jonguk Kim ◽  
Sang-Joon Pak
Keyword(s):  
High Resolution ◽  
Leading Edge ◽  
Middle Part ◽  
Geochemical Data ◽  
Long Distance ◽  
Transform Faults ◽  
Central Indian Ridge ◽  
Mid Ocean Ridge ◽  
Indian Ridge ◽  
Ocean Ridge

<p>Plume-ridge interaction is an important thermal and geological process, which results in various physical and chemical anomalies along a significant length of the global mid-ocean ridge system. Despite numerous studies, some remaining questions to be solved are the origin and mechanisms of geochemical variations and their possible correlation with the morphology of mid-ocean ridges.</p><p>The Central Indian Ridge, with a slow to intermediate spreading rate, provides an ideal opportunity to explore the long-distance plume-ridge interactions. Presently, the ridge is moving away from the Réunion hotspot which is located 1000 km away from the Central Indian Ridge at Réunion Island. Paleogeographic reconstruction suggests that the hotspot crossed the middle part of the Central Indian Ridge (MCIR) between 8°S and 17°S at ~34 Ma. Previous studies argue that the plume material currently flows into the Central Indian Ridge at around 19°S, south of Marie Celeste Fracture Zone (MCFZ) and geochemical enrichments of the mid-ocean ridge basalts (MORB) from the MCIR 14°S and 19°S segments can be attributed to a fossil Réunion plume component. However, a recent geophysical study has suggested that the geochemical anomalies along the Rodrigues segment (18-21°S) can be ascribed to the asthenospheric flow from the Réunion plume, reopening the debate about the origin of the enriched anomalies along the MCIR (14-19°S).</p><p>In this study, we revisited the MCIR from 14°S to 17°S with new geochemical data obtained based on high-resolution sampling and ship-board high-resolution bathymetry data to constrain the influence of the Réunion plume on geochemistry and bathymetry of the MCIR. The results show that trace element ratios and isotopic compositions of on-axis MORB vary in association with ridge discontinuities such as transform faults and non-transform fault discontinuities. The MORB from the northern parts of segments display substantially enriched geochemical features and the enrichments correspond to a shallower axial bathymetry. We attribute the chemical and morphological anomalies along the ridge to the influence of a Réunion plume component focussed by a hotspot leading edge effect. The hotspot leading segments are offset in the direction of the plume and are more efficiently affected by the enriched plume materials. These findings suggest that lithospheric discontinuities such as transform faults and fracture zones may control the flow of mantle plume material into the ridge and the geometry of the ridge coupled to its hotspot proximity may play an important role, particularly in the long-distance plume-ridge interaction.</p>

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.

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