Ophiolite Genesis and Evolution of the Oceanic Lithosphere: Proceedings of the Ophiolite Conference, held in Muscat, Oman, 7–18 January 1990(5 Petrology and Structural Geology)

Ophiolites are key sources of information regarding the genesis and evolution of oceanic lithosphere. Over the past decades, the geological ~tudy of ophio- lites has provided a wealth of insight into lithospheric processes and has proved to be an indispensible prerequisite to interpreting geophysical and other investigations of the crust underlying recent oceans. The Oman Ophiol- ite offers the most complete and structurally undisturbed sections of the oceanic crust in vast, clean exposures. It is, therefore, most fortunate for the scientific community that Mhd. Kassim, Director General of Minerals and Dr. Hilal Al Azri, Director of the Geological Survey, took upon themselves the task of organizing in Oman an international meeting on ophiolites. Having planned for an attendance of only 100 to 150 persons, the logistics of the organizing committee were put to a severe test by th~ 300 participants who eventually arrived from 27 countries. The 14 field trips, most of which were conducted twice, provided the participants with an excellent introduc- tion to the geology of Oman, the ophIolite sequence, and re~ated phenomena.

Table of Contents:
I: Processes at Spreading Centers.- A) Crust.- Ridge Crest Magma Chambers: A Review of Results from Marine Seismic Experiments at the East Pacific Rise.- Accommodation Zones and Transfer Faults: Integral Components of Mid-Atlantic Ridge Extensional Systems.- Rooting of the Sheeted Dike Complex in the Oman Ophiolite.- Diabase Dikes Emplacement in the Oman Ophiolite: A Magnetic Fabric Study with Reference to Geochemistry.- Geometry and Flow Pattern of the Plutonic Sequence of the Salahi Massif (Northern Oman Ophiolite) — A Key to Decipher Successive Magmatic Events.- B) Mantle.- The Upward Migration of Self-Convecting Magma Bodies.- Melt Migration and Depletion — Regeneration Processes in Upper Mantle of Continental and Ocean Rift Zones.- Evidences for a Paleo-Spreading Center in the Oman Ophiolite: Mantle Structures in the Maqsad Area.- Structural and Petrological Features of Peridotite Intrusions from the Troodos Ophiolite, Cyprus.- Evolutional History of the Uppermost Mantle of an Arc System: Petrology of the Horman Peridotite Massif, Japan.- II: Magmatic Ores.- Cu-Ni-PGE Magmatic Sulfide Ores and their Host Layered Gabbros in the Haymiliyah Fossil Magma Chamber (Haylayn Block, Semail Ophiolite Nappe, Oman).- Platinum-Group Elements and Gold in Ophiolitic Complexes: Distribution and Fractionation from Mantle to Oceanic Floor.- Chromite-Rich and Chromite-Poor Ophiolites: The Oman Case.- Diamonds: the Oceanic Lithosphere connection with Special Reference to Beni Bousera, North Morocco.- III: Hydrothermalism.- Lithospheric Stretching and Hydrothermal Processes in Oceanic Gabbros from Slow-Spreading Ridges.- Evidences for Polyphased Oceanic Alteration of the Extrusive Sequence of the Semail Ophiolite from the Salahi Block (Northern Oman).- A Geochemical Study of aFossil Oceanic Hydrothermal Discharge Zone in the Oman Ophiolite (Zuha Sulphide Prospect): Evidence for a Polyphased Hydrothermal History.- Lead Isotope Geochemistry of Various Sulphide Deposits from the Oman Mountains.- Hydrothermal Metamorphism in Oceanic Crust from the Coast Range Ophiolite of California: Fluid-Rock Interaction in a Rifted Island Arc.- A Sulfur Isotopic Profile Through the Troodos Ophiolite, Cyprus: Preliminary Results and Implications.- IV: Tectonics of Emplacement and Metamorphism.- Obduction Versus Subduction and Collision in the Oman Case and other Tethyan Settings.- The Obduction of the Northern Oman Ophiolite — Crustal Loading and Flexure.- Amagmatic Extension and Tectonic Denudation in the Kizildag Ophiolite, Southern Turkey: Implications for the Evolution of Neotethyan Oceanic Crust.- Process of Ophiolite Emplacement in Oman and Newfoundland.- Sr, Nd and Pb Isotopic Constraints in the Genesis of a Calc-Alkaline Plutonic Suite in Oman Ophiolite Related to the Obduction Process..- Mineral Equilibria in Metagabbros: Evidence for a Polymetamorphic Evolution of the Asimah Window, Northern Oman Mountains, United Arab Emirates.- V: Palaeogeographic Setting of the Oman Ophiolite.- Al Aridh Formation, Oman: Stratigraphy and Palaeogeographic Significance.- Igneous Rocks in the Hawasina Nappes and the Hajar Supergroup, Oman Mountains: Their Significance in the Birth and Evolution of the Composite Extensional Margin of Eastern Tethys.- The Uplift History of the Precambrian Crystalline Basement of the Jabal J’alan (Sur Area).- Meta-Carbonatites in the Metamorphic Series Below the Semail Ophiolite in the Dibba Zone, Northern Oman Mountains.- Chert-Hosted Manganese Deposits in the Wahrah Formation: A Depositional Model.- Tertiary Basaltic Intrusions inthe Central Oman Mountains.- VI: Palaeoenvironment of Other Ophiolites.- Geology, Geochemistry, and the Evolution of an Oceanic Crustal Rift at Sithonia, NE Greece.- Upper Triassic-Early Jurassic Sedimentary Breccias in the Ophiolitic Suite of the Lesser Caucasus.- Origin of Volcanics in the Tethyan Suture Zone of Pakistan.- Time-Space Distribution and Petrologic Diversity of Japanese Ophiolites.- Tectonostratigraphic Relationships and Obduction Histories of Scandinavian Ophiolite Terranes.- Genesis and Emplacement of the Supra-Subduction Zone Pindos Ophiolite, Northwestern Greece.- The Circum-Izu Massif Peridotite, Central Japan, as Back-Arc Mantle Fragments of the Izu-Bonin Arc System.- Geology and Chemistry of the Early Proterozoic Purtuniq Ophiolite, Cape Smith Belt, Northern Quebec, Canada.- VII: Mapping Ophiolites.- The Use of Digitally Processed Spot Data in the Geological Mapping of the Ophiolite of Northern Oman.- Comparison Between Mapping at 1:25000 Scale and Decorrelation Stretched Landsat Thematic Mapper Images in the Wuqbah Block (Oman Mountains).