Structures of Ophiolites and Dynamics of Oceanic Lithosphere

ISBN-13: 9780792302551 / Angielski / Twarda / 1989 / 370 str.

Adolphe Nicolas; A. Nicolas

Opis

Ophiolites are distinctive assemblages of malic to ultramalic rocks representing fragments of the oceanic lithosphere. Nicolas (tectonophysics, U. of Montpelier) establishes a global comparison between ophiolites and their various oceanic environments, to aid in understanding the physical processes

Recenzje

`This is a very valuable book for both oceanographers and geologists interested in the formation of oceanic crust and its accretion into continents. The author has carefully gone through much of the literature on this subject, so the bibliography is extremely valuable for those trying to catch up or those just starting research in the field.'
Episodes, 13:1, 1990

Spis treści

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.