Nicolas Structures of Ophiolites and Dynamics of Oceanic Lithosphere

1989
ISBN: 978-94-009-2374-4
Verlag: Springer Netherland
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, Band 4, 370 Seiten, eBook

Reihe: Petrology and Structural Geology

Zielgruppe

Research

Autoren/Hrsg.

Nicolas, A.

Inhaltsverzeichnis

I - Introduction and Analytical Methods.- 1. Introduction.- 1.1. Historical development of the ophiolite concept.- 1.2. Interest of ophiolite studies.- 1.2.1. Ophiolites as key for the study of oceanic lithosphere and asthenosphere.- 1.2.2. Ophiolites as markers of past plate tectonics.- 1.3. Scope and structure of the book.- 2. Analytical methods in ophiolites.- 2.1. Introduction.- 2.2. The oceanic reference frame.- 2.2.1. The ridge referential.- 2.2.2. Ridge side of origin of a given ophiolite.- 2.3. Structural studies in the hypovolcanic and volcanic sequences.- 2.4. Structural studies in the plutonic sequence.- 2.4.1. Principal structures.- 2.4.2. Viscous/plastic deformation.- 2.4.3. Importance of viscous flow.- 2.5. Structural studies in the ultramafic section.- 2.5.1. Homogeneity of mantle structures.- 2.5.2. Principal structures.- 2.5.3. Melt products: evidence for segregation/impregnation.- 2.5.4. Microstructures in peridotites and kinematic analysis.- 2.5.5. Microstructural imprint of asthenospheric and lithospheric flow.- 2.5.6. Serpentinization and low temperature deformations.- 2.6. Expected asthenospheric flow patterns.- II - Typical Ophiolite Complexes.- 3. Oman ophiolite: the harzburgite ophiolite type.- 3.1. Introduction.- 3.2. Geological setting.- 3.2.1. Geodynamic setting.- 3.2.2. History of the Hawasina basin.- 3.3. General description of the ophiolite.- 3.3.1. Introduction.- 3.3.2. Mafic section.- 3.3.3. Ultramafic section.- 3.3.4. Metamorphic aureoles.- 3.3.5. High pressure metamorphism.- 3.4. Structure of the Oman ophiolite.- 3.4.1. Introduction-main structural events.- 3.4.2. Structures related to accretion at the spreading center.- 3.4.3. Structures related to oceanic thrusting and obduction.- 3.5. General interpretation of the Oman ophiolite.- 3.5.1. Introduction.- 3.5.2. Spreading rate estimation.- 3.5.3. Paleo-environment of origin and obduction history.- 4. Xigaze and Trinity ophiolites-Plagioclase lherzolite massifs: the lherzolite ophiolite type.- 4.1. Introduction.- 4.2. Xigaze ophiolite.- 4.2.1. Introduction.- 4.2.2. Geological setting.- 4.2.3. Description.- 4.2.4. Structural analysis.- 4.2.5. Geochemistry.- 4.2.6. Discussion.- 4.3. Trinity ophiolite.- 4.3.1. Introduction.- 4.3.2. Geological setting.- 4.3.3. Description.- 4.3.4. Structural analysis.- 4.3.5. Melt extraction and melt reaction.- 4.3.6. Petrology and geochemistry.- 4.3.7. Discussion.- 4.4. The western Alps ophiolites.- 4.5. The spinel-plagioclase lherzolite massifs.- 4.5.1. Penological zonation.- 4.5.2. Structural zonation.- 4.5.3. Structure and geodynamic environment.- 4.5.4. Contact metamorphism and nature of metamorphosed formations.- 5. Bogota Peninsula and N.E. districts of New Caledonia — Wadi Tayin in Oman — Coastal Complex of Newfoundland: possible origin in transform faults.- 5.1. Introduction.- 5.2. Bogota Peninsula and N.E. ophiolitic districts of New-Caledonia.- 5.2.1. Introduction.- 5.2.2. Geological setting.- 5.2.3. Description of the Bogota Peninsula shear zone.- 5.2.4. Description of the Tiebaghi-Poum-Belep shear zone.- 5.2.5. Discussion.- 5.3. Coastal Complex of Newfoundland.- 5.3.1. Introduction.- 5.3.2. Geological setting.- 5.3.3. Description.- 5.3.4. Petrology and geochemistry.- 5.3.5. Interpretation.- 5.4. Wadi Tayin massif in Oman.- 5.4.1. Introduction.- 5.4.2. Structural description.- 5.4.3. Discussion.- 5.5. Conclusion.- 5.5.1. The diversity of ophiolitic transforms.- 5.5.2. Dike orientation in transform zones.- 6. Canyon Mountain ophiolite: possible origin in an island arc.- 6.1. Introduction.- 6.2. Geological setting.- 6.3. Description.- 6.4. Structural analysis.- 6.5. Petrology and geochemistry.- 6.6. Discussion.- 6.6.1. Specific characteristics of the Canyon Mountain ophiolite.- 6.6.2. Structural models.- 6.6.3. Geodynamic environment of origin.- III - Activity of Oceanic Spreading Centers and the Origin of Ophiolites.- 7. Melt generation and extraction in mantle diapers.- 7.1. Introduction.- 7.2. Melt extraction from the asthenosphere.- 7.2.1. Conditions of adiabatic melting.- 7.2.2. Asthenospheric path and the meeting with lithospheric conditions.- 7.2.3. Depth of first melting.- 7.2.4. Maximum depth of melt extraction.- 7.3. Physical mechanisms of melt extraction.- 7.3.1. Fraction of stable melt in a peridotite.- 7.3.2. Melt extraction.- 7.4. A model of melt extraction by hydrofracturing.- 7.4.1. The model.- 7.4.2. Melt velocity within dikes, episodicity and duration of episodes of melt extraction.- 7.4.3. Geochemical implications.- 7.5. Melt extraction by solid compaction and melt percolation in transition zones of ophiolites.- 7.6. Focusing of melt extraction below oceanic ridges.- 8. The various ophiolites and their oceanic environments of origin.- 8.1. Introduction.- 8.2. Harzburgite and lherzolite types of ophiolites — Role of spreading rate.- 8.2.1. Distinctive characteristics.- 8.2.2. Harzburgite and lherzolite types of ophiolites and mantle partial melting.- 8.2.3. Harzburgite and lherzolite types of ophiolites and oceanic environments.- 8.3. Island-arc, back-arc or mid-ocean ophiolites.- 8.3.1. Geochemical characteristics.- 8.3.2. Other criteria.- 9. Mantle flow, tithospheric accretion and segmentation of oceanic ridges.- 9.1. Introduction.- 9.2. Mantle flow in the Oman ophiolite.- 9.2.1. Introduction.- 9.2.2. Homogeneous mantle flow away from the ridge-Relation with seismic anisotropy.- 9.2.3. Channeling of mantle flow along the ridge axis.- 9.2.4. Mantle flow in transform faults.- 9.2.5. Mantle flow in diapers.- 9.2.6. Mantle flow patterns beneath the Oman paleo-ridge.- 9.3. Mantle flow in the Trinity ophiolite and lherzolite massifs.- 9.4. Mantle diapirism and ridge segmentation.- 9.4.1. Introduction.- 9.4.2. Models of mantle diapers.- 9.4.3. Return flow and thickness of the buoyant layer.- 9.4.4. Spacing of mantle diapirs and ridge segmentation.- 9.4.5. Stability of mantle diapers.- 10. Magmatic processes in the uppermost mantle at oceanic spreading centers.- 10.1. Introduction.- 10.2. Principal characteristics of transition zones.- 10.3. Origin of the wehrlitic intrusions.- 10.4. Origin of dunites.- 10.4.1. Introduction.- 10.4.2. Field occurrences.- 10.4.3. Residual/magmatic origin.- 10.4.4. Mechanism of formation of residual dunites.- 10.4.5. Geochemical reequilibration.- 10.4.6. Conclusion as to the origin of dunites.- 10.5. Structure and origin of the chromite deposits.- 10.5.1. Introduction.- 10.5.2. Setting of chromite deposits.- 10.5.3. Structure of chromite deposits.- 10.5.4. Composition of chromite deposits.- 10.5.5. Origin of chromite deposits.- 11 - Generation of oceanic crust.- 11.1. Introduction.- 11.2. Lithology of ophiolites and seismic structure of the oceanic crust.- 11.3. Serpentinite sea-floor in slow spreading environments and LOT.- 11.3.1.Abyssal and ophiolitic peridotites.- 11.3.2. Serpentinized peridotites as sea-floor.- 11.3.3. Nature of the Moho.- 11.4. The plutonic section and the problem of magma chambers.- 11.4.1. Introduction.- 11.4.2. Origin of the layering in the plutonic gabbro sequence.- 11.4.3. Magma chamber models.- 11.4.4. Conclusions about magma chamber models.- 11.4.5. Plating of gabbros and diking at the roof of magma chambers.- 11.4.6. Initiation of a new magma chamber.- 11.5. Sheeted dikes and volcanic units.- 11.5.1. Introduction.- 11.5.2. Generation at rifts and ridges.- 11.5.3. Structural evolution of the volcanic-hypovolcanic units.- 11.6. Crustal discontinuities in lherzolite type of ophiolite and episodic oceanic spreading.- 11.6.1. Variable basalt delivery along ridge-strike.- 11.6.2. Episodic basalt delivery in time.- 11.7. Early metamorphism in ophiolites and hydrothermal activity at oceanic ridges.- 11.7.1. Introduction.- 11.7.2. Metamorphic-zonation in ophiolites.- 11.7.3. Relationship with the sequence of hydrothermal alteration in oceanic crust.- IV - Emplacement of Ophiolites Trough Space and Time.- 12 - Ophiolites emplacement.- 12.1. Introduction.- 12.2. Ophiolite belts.- 12.2.1. Passive margins of continents.- 12.2.2. Active margins of continents.- 12.2.3. Collision belts.- 12.3. Emplacement-related features in ophiolites.- 12.3.1. Introduction.- 12.3.2. Ophiolite nappes and high temperature aureoles.- 12.3.3. Ophiolitic mélanges and high pressure metamorphism.- 12.4. Mechanisms of ophiolite emplacement.- 12.4.1. Introduction.- 12.4.2. Thrusting on passive continental margins.- 12.4.3. Upheaval in the accretionary prism of active margins.- 12.5. Summary and concluding remarks.- 13 - Ophiolite belts through time.- 13.1. Introduction: a reappraisal of ophiolites and their oceanic environments.- 13.2. Ophiolites generation and emplacement through time.- 13.3. Ophiolites as witness of pangean cycles.