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Monograph available for loan

Mid-ocean ridges : hydrothermal interactions between the lithosphere and oceans (2004)

German, Christopher R. [Hrsg.] ; Lin, Jian [Hrsg.] ; Parson, Lindsay M. [Hrsg.]

Washington : American Geophysical Union

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Call number: 5/M 07.0216

In: Geophysical monograph

Description / Table of Contents: Processes of heat transfer from Earth's mantle, via mid-ocean ridges, to the oceans. - Global variations in hydrothermal vents and heat flux. - Morphology, rheology, internal structure, and geology of the oceanic lithosphere and their controls on hydrothermal circulation. - Physical and chemical reaction processes in hydrothermal circulation systems. -Direct observations and measurements of hydrothermal vents from submersibles.

Type of Medium: Monograph available for loan

Pages: VIII, 318 S. , Ill., graph. Darst., Kt.

ISBN: 0875904130

Series Statement: Geophysical monograph 148

Classification:

Lithosphere

Location: Reading room

Branch Library: GFZ Library

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Electronic Resource

Uneven depths in marine geology (1982)

Weaver, Philip ; Parson, Lindsay

[s.l.] : Nature Publishing Group

Nature 297 (1982), S. 521-521

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] SINCE the inception of the Deep Sea Drilling Project, which has played a major role in providing data from previously unsampled horizons in both sediments and the basaltic basement, marine geology has emerged from infancy and into an exciting period of discovery. More recent work using manned ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/297521a0

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Segmentation and Morphotectonic Variations Along a Super Slow-Spreading Center: The Southwest Indian Ridge (57° E-70° E) (1997)

Mendel, Véronique ; Sauter, Daniel ; Parson, Lindsay ; [et al.]

Springer

Marine geophysical researches 19 (1997), S. 505-533

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ISSN: 1573-0581

Keywords: Southwest Indian Ridge ; bathymetry ; segmentation

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract Bathymetric data along the Southwest Indian Ridge (SWIR) between 57°E and 70° E have been used to analyze the characteristics of thesegmentation and the morphotectonic variations along this ridge. Higheraxial volcanic ridges on the SWIR than on the central Mid-Atlantic Ridge(MAR) indicate that the lithosphere beneath the SWIR axis that supportsthese volcanic ridges, is thicker than the lithosphere beneath the MAR. Astronger/thicker lithosphere allows less along-axis melt flow andenhances the large crustal thickness variations due to 3D mantle upwellings.Magmatic processes beneath the SWIR are more focused, producing segmentsthat are shorter (30 km mean length) with higher along-axis relief (1200 mmean amplitude) than on the MAR. The dramatic variations in the length andamplitude of the swells (8–50 km and 500–2300 m respectively),the height of axial volcanic ridges (200–1400 m) and the number ofvolcanoes (5–58) between the different types of segments identifiedon the SWIR presumably reflect large differences in the volume, focusing andtemporal continuity of magmatic upwelling beneath the axis. To the east ofMelville fracture zone (60°42′ E), the spreading center isdeeper, the bathymetric undulation of the axial-valley floor is less regularand the number of volcanoes is much lower than to the west. The spreadingsegments are also shorter and have higher along-axis amplitudes than to thewest of Melville fracture zone where segments are morphologically similar tothose observed on the central MAR. The lower magmatic activity together withshorter and higher segments suggest colder mantle temperatures withgenerally reduced and more focused magma supply in the deepest part of thesurvey area between 60°42′ E and 70° E. The non-transformdiscontinuities show offsets as large as 70 km and orientations up toN36° E as compared to the N0° E spreading direction. We suggest thatin regions of low or sporadic melt generation, the lithosphere neardiscontinuities is laterally heterogeneous and mechanically unable tosustain focused strike-slip deformation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004232506333

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Evolution of the Axial Geometry of the Southwest Indian Ocean Ridge between the Melville Fracture Zone and the Indian Ocean Triple Junction – Implications for Segmentation on Very Slow-Spreading Ridges (1997)

Parson, Lindsay ; Sauter, Daniel ; Mendel, Véronique ; [et al.]

Springer

Marine geophysical researches 19 (1997), S. 535-552

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ISSN: 1573-0581

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract Geophysical data from 900 km of the Southwest Indian Ridge are used todescribe the pattern of evolution of the plate boundary between 61° Eand 70° E over the past 20 million years. The SWIR is anobliquely-opening, ultra slow-spreading axis, and east of61° E comprises a series of ridge sections, each about 100–120 kmin length. The orientation of these sections varies fromsub-orthogonal to oblique to the approximately N–S spreadingdirection. In general, the suborthogonal sections are shallower, commonlysubdivided into an array of discrete axial segments, and carry recognisablecentral magnetic anomalies. The majority of the oblique sections are single,continuous rifts without continuous axial magnetic signatures.Morphotectonics of the Southwest Indian Ridge crust have not previously beenwell constrained off-axis, and we here present sidescan sonar andswath bathymetric data up to 100 km from the ridge to demonstrate the complexities of its spatial and temporal evolution.A model is proposed that the segmentation style correlates with analong-axis variation between: (a) relatively thick crustal sections which overlie mantle sections with higher magmatic supply created in orthogonally-spreading segments and (b) those oblique sections associated with cooler, magmatically-starved mantle and thinner crust. These latter sections are formed at broad offset zones in theplate boundary, more precisely defined on faster-spreading ridges asnontransform discontinuities. The nonsystematic pattern of crustalconstruction, extensional basin formation and the absence of extension-parallel traces of discontinuities off-axis suggest that the oblique spreading sections are not fixed in space or time.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004335919592

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Accretionary processes in the axial valley of the Mid-Atlantic Ridge 27° N–30° N from TOBI side-scan sonar images (2000)

Briais, Anne ; Sloan, Heather ; Parson, Lindsay M. ; [et al.]

Springer

Marine geophysical researches 21 (2000), S. 87-119

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ISSN: 1573-0581

Keywords: tectonic faulting ; volcanic constructions ; oceanic crust ; side-scan sonar images

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract We analyse TOBI side-scan sonar images collected during Charles Darwin cruise CD76 in the axial valley of the Mid-Atlantic Ridge (MAR) between 27° N and 30° N (Atlantis Transform Fault). Mosaics of the two side-scan sonar swaths provide a continuous image of the axial valley and the inner valley walls along more than six second-order segments of the MAR. Tectonic and volcanic analyses reveal a high-degree intra-segment and inter-segment variability. We distinguish three types of volcanic morphologies: hummocky volcanoes or volcanic ridges, smooth, flat-topped volcanoes, and lava flows. We observe that the variations in the tectonics from one segment to another are associated with variations in the distribution of the volcanic morphologies. Some segments have more smooth volcanoes near their ends and in the discontinuities than near their mid-point, and large, hummocky axial volcanic ridges. Their tectonic deformation is usually limited to the edges of the axial valley near the inner valley walls. Other segments have smooth volcanoes distributed along their length, small axial volcanic ridges, and their axial valley floor is affected by numerous faults and fissures. We propose a model of volcano-tectonic cycles in which smooth volcanoes and lava flows are built during phases of high magmatic flux. Hummocky volcanic ridges are constructed more progressively, by extraction of magma from pockets located preferentially beneath the centre of the segments, during phases of low magma input. These cycles might result from pulses in melt migration from the mantle. Melt arrival would lead to the rapid emplacement of smooth-textured volcanic terrains, and would leave magma pockets, mostly beneath the centre of the segments where most melt is produced. During the end of the volcanic cycle magma would be extracted from these reservoirs through dikes with a low magma pressure, building hummocky volcanic ridges at low effusion rates. In extreme cases, this volcanic phase would be followed by amagmatic extension until a new magma pulse arrives from the mantle.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004722213652

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Segmentation of the Central Indian Ridge between 12°12′ S and the Indian Ocean Triple Junction (1993)

Parson, Lindsay M. ; Patriat, Philippe ; Searle, Roger C. ; [et al.]

Springer

Marine geophysical researches 15 (1993), S. 265-282

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ISSN: 1573-0581

Keywords: Mid-Ocean Ridge ; Central Indian Ridge ; GLORIA ; segmentation

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract The present morphology and tectonic evolution of more than 1500 kilometres of the Central Indian Ridge are described and discussed following the integration of GLORIA side-scan sonographs with conventional geophysical datasets. Segmentation of the ridge occurs by a series of ridge axis discontinuities ranging in periodicity along strike from 275 km to less than 30 km. These segment boundaries we have classified into two types: first order fracture zones of offsets greater than 50 km which bound five major (mega-) segments, and smaller scale structures of a variety of offset styles and amplitudes which cut four of these segments. We refer to these as ridge-axis discontinuities. The frequent opposite sense of offset identified between the first order structures and the subordinate discontinuities between these major structures is interpreted as resulting from the adjustment to new kinematic parameters after magnetic anomaly 20. As far as our data allows us to determine, the central major segment is not subdivided by minor ridge axis discontinuities, which we suggest is a result of its proximity to the Rodriguez hotspot.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01982385

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A Survey of the Southwest Indian Ridge Axis Between Atlantis II Fracture Zone and the Indian Ocean Triple Junction: Regional Setting and Large Scale Segmentation (1997)

Patriat, Philippe ; Sauter, Daniel ; Munschy, Marc ; [et al.]

Springer

Marine geophysical researches 19 (1997), S. 457-480

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ISSN: 1573-0581

Keywords: Slow-spreading mid-oceanic ridges ; geophysical survey ; Indian Ocean

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract The study of very low-spreading ridges has become essential to ourunderstanding of the mid-oceanic ridge processes. The Southwest Indian Ridge(SWIR) , a major plate boundary of the world oceans, separating Africa fromAntarctica for more than 100 Ma, has such an ultra slow-spreadingrate. Its other characteristic is the fast lengthening of its axis at bothBouvet and Rodrigues triple junctions. A survey was carried out in thespring of 1993 to complete a multibeam bathymetric coverage of the axisbetween Atlantis II Fracture Zone (57° E) and the Rodrigues triplejunction (70° E). After a review of what is known about the geometry,structure and evolution of the SWIR, we present an analysis of the newalong-axis bathymetric data together with previously acquiredacross-axis profiles. Only three transform faults, represented byAtlantis II FZ, Novara FZ, and Melville FZ, offset this more than 1000 kmlong section of the SWIR, showing that the offsets are more generallyaccommodated by ridge obliquity and non-transform discontinuities. From comparison of the axial geometry, bathymetry, mantle Bouguer anomaly and central magnetic anomaly, three large sections (east of Melville FZ, between Melville FZ and about 65°30′ E, and from there to the Rodrigues triple junction) can be distinguished. The central member, east of Melville FZ, does not resemble any other known mid-oceanic ridge section: the classical signs of the accretion (mantle Bouguer anomaly, central magnetic anomaly) are only observed over three very narrow and shallow axis sections. We also apply image processing techniques to the satellite gravity anomaly map of Smith and Sandwell (1995) to determine the off-axis characteristics of the Southwest Indian Ridge domain, more especially the location of the triple junction and discontinuities traces. We conclude that the large-scale segmentation of the axis has been inherited from the evolution of the Rodrigues triple junction.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004312623534

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