Structures Of Ophiolites And Dynamics Of Oceanic Lithosphere

The proceedings from the September 1998 conference in Marshall, California contain 39 papers on the following topics: ophiolites, ocean crust, and global tectonics; oceanic lower crust and upper mantle; structure and physical properties of upper oceanic crust; hydrothermal processes; Pacific Rim ophiolites; and, Ophiolites from Iapetus, Rheic-Pleionic, Neotethyan, and Indian Oceans. Contributors include scientists with backgrounds in structural geology, tectonics, geophysics, petrology, and geochemistry. Numerous black and white illustrations (and one in color) are included. Annotation copyrighted by Book News Inc., Portland, OR

The papers in this volume fall into two categories. In the first section the nature and formation of oceanic lithosphere is discussed from integrated and individual studies of the present ocean crust and ophiolite complexes. The papers are divided into 5 sub-groups on: magma chambers, their products & processes; fracture zones; mantle structures; lavas and sediments; isotope studies & metamorphism. The second section contains both review and original articles on the emplacement (obduction) of ophiolites and the use to which they can be put in understanding the processes of plate collision.

Proceedings of the Ophiolite Conference, held in Muscat, Oman, January 7-18, 1990

This volume follows a Specialized Symposium on "Mantle denudation in slow spreading ridges and in ophiolites", held at the XII EUG Meeting in Strasbourg, spring 1993. During the meeting it was felt that the contribu tions to the Symposium justified a volume presenting its main scientific achievements. The present title of the volume shows that the center of inter est has slightly shifted with respect to the initial objective: in order to under stand the processes involved in accretion taking place at oceanic ridges, it is crucial to study the interaction between uppermost mantle and lower crust. The approach favored here is that of petrological and structural analysis of oceanic rocks in present-day oceanic ridges combined with similar studies in ophiolites. Rock specimen collected by submersibles or dredge hauls in oceanic ridge environments provide a "ground truth". However, except for areas such as the MARK (Mid-Atlantic Ridge ne ar Kane fracture zone) where, thanks to multiple submersible dives, the local geology is known with aprecision even better than in many onshore ophiolites, mutual rela tionships between uppermost mantle and lower crust are poorly known. In contrast, onshore ophiolites provide a necessary large-scale picture built up over many years of structural and petrological mapping.

I was invited to write this book as part of the Minerals, Rocks and Organic Materials Series of Springer-Verlag by Professor Peter J. Wyllie in 1974. Ophiolites have preoccupied me ever since 1948 as a graduate student and up to the present time as part of my research with the U.S. Geological Survey. During this period ophiolite, an obscure European geological term, has attained an ever-increasing importance, is now used to include all fragments of ancient oceanic lithosphere incorporated into the orogenic zones of modern and ancient continental margins, and is a standard part of the plate tectonic paradigm. The purpose of this book is to provide a starting point for anyone interested in the background and state of knowledge concerning ophiolites (ancient oceanic lithosphere). Because ophiolites represent fragments of old oceanic crust their tectonic setting and age are extremely important in the reconstruction of ancient plate boundaries. Present day plate tectonic theories involve the generation and disposal of oceanic lithosphere, so that these ancient fragments of oceanic lithosphere can be used directly to reconstruct conditions within the ancient oceans. Since 1970, numerous meetings and conferences directly related to ophiolites have stimulated worldwide interest in the subject. As part of the International Correlation Program, the project "Ophiolites of Continents and Comparable Oceanic Rocks," was initiated by Dr. N. Bogdanov, Geological Institute, Moscow. This project has brought together an international group that has focused on the outstanding problems and is now producing a world map of ophiolite distribution.