Journal ArticleDOI
Emplacement of mantle rocks in the seafloor at mid-ocean ridges
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In this article, the authors discuss the geological and geophysical data available on mid-ocean ridges with outcrops of serpentinized mantle peridotites, with the objective of better constraining the modes of emplacement of these rocks in the seafloor.Abstract:
This paper discusses the geological and geophysical data available on mid-ocean ridges with outcrops of serpentinized mantle peridotites, with the objective of better constraining the modes of emplacement of these rocks in the seafloor. Ridges with serpentinized peridotites outcrops are in most cases characterized by slow-spreading rates, and in every case by deep axial valleys. Such deep axial valleys are thought, based on geophysical constraints and on mechanical modelling results, to characterize ridges with a thick axial lithosphere. A predictable effect of a thick axial lithosphere is that it should prevent magmas from pooling at crustal depths in a long-lasting magma chamber: gabbroic magmas should instead form shortlived dike or sill-like intrusions. Samples from axial outcrops of serpentinized peridotites are often cut by dikelets of evolved gabbros which are interpreted as apophyses of such dike and sill-like intrusions. This observation leads to a discontinuous magmatic crust model, in which mantle-derived peridotites form screens for numerous gabbroic intrusions. This discontinuous magmatic crust is expected to form in magma-poor ridge regions, where there is not enough magma to produce a 4-to 7-km-thick magmatic crust, and where the uppermost kilometers of oceanic lithosphere therefore have to be at least partially made of tectonically uplifted mantle material. Because the dimensions of individual mantle-derived ultramafic screens may be smaller than seismic experiments detection limits, the discontinuous magmatic crust model discussed in this paper may produce a layer 3-type seismic signature, even without extensive serpentinization of its ultramafic component. It therefore provides an alternative to Hess's [1962] serpentinite layer 3 model, for the geological interpretation of seismic data from oceanic areas with frequent outcrops of deep crustal and mantle-derived rocks.read more
Citations
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Journal ArticleDOI
Bulk-rock Major and Trace Element Compositions of Abyssal Peridotites: Implications for Mantle Melting, Melt Extraction and Post-melting Processes Beneath Mid-Ocean Ridges
TL;DR: In this paper, the first comprehensive major and trace element data for 130 abyssal peridotite samples from the Pacific and Indian ocean ridge transform systems was presented, which revealed important features about the petrogenesis of these rocks, mantle melting and melt extraction processes beneath ocean ridges, and elemental behaviours.
Journal ArticleDOI
Petrology of subducted slabs
Stefano Poli,Max W. Schmidt +1 more
TL;DR: In this article, the subducted lithosphere is composed of a complex pattern of chemical systems that undergo continuous and discontinuous phase transformation, through pressure and temperature variations, through volatile recycling.
Journal ArticleDOI
Geochemistry of subduction zone serpentinites: A review
TL;DR: A review of the geochemistry of serpentinites, based on the compilation of ~900 geochemical data of abyssal, mantle wedge and exhumed serpentinite after subduction, is presented in this paper.
Journal ArticleDOI
Corrugated slip surfaces formed at ridge–transform intersections on the Mid-Atlantic Ridge
Johnson R. Cann,Donna K. Blackman,Deborah K. Smith,E. McAllister,B. Janssen,Sidney L. M. Mello,E. Avgerinos,A. R. Pascoe,Javier Escartín +8 more
TL;DR: In this article, the authors present sonar images of two ridge-transform intersections on the Mid-Atlantic Ridge (near 30° N), which show that both active and fossilized inside-corner highs are capped by planar, dipping surfaces marked by corrugations and striations oriented parallel to the plate spreading direction.
Book ChapterDOI
Orogenic, ophiolitic and abyssal peridotites
TL;DR: Orogenic, ophiolitic, and abyssal peridotites represent subcontinental, suboceanic, and subarc mantle rocks that were exhumed to the surface in various tectonic settings as mentioned in this paper.
References
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Journal ArticleDOI
Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness
TL;DR: In this paper, the global major element variations can be explained by ∼8-20% melting of the mantle at associated mean pressures of 5-16 kbar, and the lowest extents of melting occur at shallowest depths in the mantle and are associated with the deepest ocean ridges.
Journal ArticleDOI
Rheology of the lithosphere
TL;DR: In this paper, the authors present a review of the work on materials appropriate to the oceanic lithosphere with emphasis on contributions during the quadrennial period and the need for future work.
Journal ArticleDOI
Mid-ocean ridge magma chambers
John M. Sinton,Robert S. Detrick +1 more
TL;DR: In this paper, it was shown that the composition of the melt lens is mainly moderately fractionated ferrobasalt, which is consistent with a model that effectively separates the processes of magma mixing and fractionation into different parts of a composite magma chamber.
Journal ArticleDOI
Multi-channel seismic imaging of a crustal magma chamber along the East Pacific Rise
Robert S. Detrick,Peter Buhl,E. E. Vera,John C. Mutter,John A. Orcutt,J. Madsen,Thomas M. Brocher +6 more
TL;DR: A reflection observed on multi-channel seismic profiles along and across the East Pacific Rise between 8°50′ N and 13°30′ N is interpreted to arise from the top of a crustal magma chamber located 1.2-2.4 km below the sea floor as discussed by the authors.
Mid-ocean ridge magna chambers
J. M. Sinton,R. S. Detrick +1 more
TL;DR: In this article, the authors show that the composition of the melt lens is mainly moderately fractionated ferrobasalt with isolated pockets of magma in the transition zone of the East Pacific Rise (EPR).
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