Gorda Ridge Gregory R. McMurray Editor Gorda Ridge A Seafloor Spreading Center in the United States' Exclusive Economic Zone Proceedings of the Gorda Ridge Symposium May 11-13,1987, Portland, Oregon Sponsored by The Gorda Ridge Technical Task Force With 122 Illustrations in 179 Parts Springer-Verlag New York Berlin Heidelberg London Paris Tokyo Hong Kong Dr. GREGORYR. McMuRRAY Oregon Department of Geology and Mineral Industries, 910 State Office Building, Portland, Oregon 97201; Dames & Moore, 1750 SW Harbor Way, Portland, OR 97201, USA On the front cover: Figure 5.7A . Schematic east-west section of SESCA area, p. 86. Library of Congress Cataloging-in-Publication Data Gorda Ridge Symposium (1987: Portland, Or.) Gorda Ridge: a seafloor spreading center in the United States' exclusive economic zone: proceedings of the Gorda Ridge Symposium, May 11-13, 1987, Portland, Oregon/ Gregory R. McMurry, editor; sponsored by the Gorda Ridge Technical Task Force. p. cm. ISBN-13: 978-1-4612-7937-2 e-ISBN-13: 978-1-4612-3258-2 001: 10.1007/978-1-4612-3258-2 1. Sulphides-Gorda Ridge-Congresses. 2. Hydrothermal vent ecology-Gorda Ridge-Congresses. 3. Sea-floor spreading-Gorda Ridge-Congresses. I. McMurray, Gregory R., 1925- . II. Gorda Ridge Technical Task Force. III. Title. ~495.S9G67 1987 553.6'68-dc20 89-21586 © 1990 Springer-Verlag New York Inc. Softcover reprint of the hardcover 1st edition 1990 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer-Verlag New York, Inc., 175 Fifth Avenue, New York, NY 10010, USA), except for brief excerpts in connection with reviews or scholarly analy sis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. Copyright is not claimed for works of employees of the US Federal Government performed as part of their official duties. The use of general descriptive names, trade names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as under stood by the Trade Marks and Merchandise Act, may accordingly be used freely by anyone. Typeset by Asco Trade Typesetting Ltd., Hong Kong. 987654321 Foreword This volume is the product of an innovative intergovernmental scientific investigation of Gorda Ridge, an ocean floor spreading center in the north eastern Pacific Ocean which is marked by dynamic geologic and biologic processes. The papers contained herein summarize the results of the investi gation as reported at a symposium held in Portland, Oregon, in May 1987. The sections in this volume contain papers that describe the mineral potential of the study area, the technology used in the search for ocean floor minerals, and the benthic ecology of Gorda Ridge and other spreading centers. The interdisciplinary nature of the studies makes this volume especially valuable and comprehensive as a case history of recent study of an active ocean spread ing center. The studies reported in this volume are an outgrowth of the creation by Presidential proclamation of the Exclusive Economic Zone (EEZ) of the United States in March 1983, followed by a proposal to consider leasing of minerals in a broad area encompassing Gorda Ridge offshore of the states of Oregon and California. Gorda Ridge is the only known spreading center wholly within the EEZ of the United States. Important previous scientific discoveries of geologic processes and mineral deposits at other spreading cen ters suggested that Gorda Ridge might be the locus of potentially important mineral resources. Public comments regarding the proposed lease sale led to the creation in 1984 of a technical task force appointed by federal and state government of ficials. The mission of the task force was to investigate the mineral and living resources along Gorda Ridge in order to ascertain the economic and environ mental impacts of mineral leasing and possible subsequent development. The task force undertook a series of investigations between 1984 and 1988 using a combination of surface and submersible platforms to locate and sample mas sive sulfide deposits and associated biologic communities at multiple locations along the 300-km length of the ridge. The research program was designed by the task force during public meetings and involved cooperation among federal agencies, state governments, several universities, and individuals from numerous scientific disciplines. Federal government agencies from the United States included the U.S. Geological Survey, Minerals Management Service, U.S. Bureau of Mines, National Marine Fisheries Service, National Oceanic and Atmospheric Admin- vi Foreword istration, Environmental Protection Agency, U.S. Fish and Wildlife Service, U.S. Coast Guard, U.S. Army Corps of Engineers, and U.S. Navy. Oregon members represented state government organizations including the Oregon Department of Geology and Mineral Industries, Oregon Department of Land Conservation and Development, and Oregon Coastal Zone Management Association. California state agencies were the Division of Mines and Geolo gy and the Office of the Secretary of Environmental Affairs. Academia was represented by scientists from Oregon State University, Scripps Institution of Oceanography, the University of California at Davis, Woods Hole Oceano graphic Institution, the University of Washington, and the University of Hawaii. The task force is especially grateful to the U.S. Navy, which provided both surface vessels and the deep submersible vehicle Sea Cliff. Surface-based oceanographic research was conducted from the S.P. Lee, which was made available by the U.S. Geological Survey; the NOAA ships Surveyor and Dis coverer; and the Wecoma, which was provided by Oregon State University. The task force's mission could not have been successful without the logistical support of these organizations. DONALD A. HULL, Cochair Gorda Ridge Technical Task Force Preface The Gorda Ridge Symposium was conceived by the cochairs of the joint federal/state Gorda Ridge Technical Task Force during September 1986. The task force membership voiced support for the symposium idea at a December 1986 meeting in San Francisco, the general concept being that of an exposi tion of recent Gorda Ridge research results supported by synoptic reviews with which to develop a context for the Gorda papers. Telephone confer ences among the task force cochairs, members, and myself resulted in this formal statement of the purpose of the Symposium: The purpose of the Gorda Ridge Symposium is to present the results of marine polymetallic sulfide mineral resource investigations and biological studies conducted over the past three years. The objectives ofthe Symposium are to: (1) provide a forum for presentation and discussion of scientific results of recent studies and discoveries; (2) provide for public awareness, information and involvement; (3) provide industry with an awareness of the nature of the mineral discoveries so that they can appraise the leasing potential of the Gorda Ridge and advise the Task Force accordingly; (4) pro vide for an awareness in the scientific community of the significance of the discoveries and opportunities for future research; and (5) provide a set of recommendations to the Secretary of the Interior and to the Governors of California and Oregon regarding the leasing potential of mineral resources on the Gorda Ridge and the respective roles industry, government and the scientific community can play in further evaluating these resources. The Symposium is intended as a series of progressive sessions. The first day, May 11, is designed to report the germane research results and set them into the appropri ate context. The second day, May 12, is designed to examine the practical aspects of this new information and to review existing and future technology for conducting mineral exploration programs on the Gorda Ridge. The third day, May 13, is designed to elicit responses from the public on the leasing potential of the mineral resources, economic and environmental impacts of leasing, and the respective roles government, industry and the scientific community should play in conducting future programs on the Gorda Ridge. The Gorda Ridge Technical Task Force will convene on Thursday, May 14, in order to discuss the results of the Symposium and to draft a set of recom mendations for the Secretary of the Interior and the Governors of the States. This volume follows the general format of the symposium. The Introduc tion section is a review paper on the geology and geophysics of Gorda Ridge. The Gorda Ridge Mineral Potential section reports the major results of the task force exploration program. It includes two papers on northern Gorda viii Preface Ridge, one on Blanco Fracture Zone, and two on Escanaba Trough. To put the Gorda deposits into some perspective, this section also contains a paper comparing the Gorda Ridge and other known seafloor deposits with the Bes shi deposits of Japan, one describing the Atlantis II Deep deposits in the Red Sea and one giving an economic perspective on the Gorda deposits. The Technology section covers developing technologies for undersea mineral ex ploration and also contains a forward-looking paper on possible mining tech nologies. The exploration tools include hydrography and geochemistry, pas sive and active geophysics, and deep-sea drilling. The papers in the Benthic Ecology section address both the preliminary results of work on Gorda Ridge and adjacent nonvent fauna, and summarize vent faunal investigations at other vent and seep areas. An update paper has been added that gives pre liminary biological results of 1988 dives which discovered active hydrothermal vents in Escanaba Trough. Lastly, a paper summarizing the symposium re sults and reporting the recommendations and findings of the five symposium workshops comprises the Conclusions section. Acknowledgement is due many persons who helped to scope and plan the Gorda Ridge Symposium and consequently this volume. I thank John B. Smith, James F. Davis, and Donald A. Hull, the task force cochairs, for their insightful guidance, patience, and support during the entire project; William R. Normark, Jack Dymond, and James M. Franklin for their assistance in scoping the geology sessions; Fred N. Spiess for helping to plan the technol ogy session; and William G. Pearcy for assistance with the biology sessions. I am grateful to the session chairs for their guidance and editing efforts: TS Ary, Andrew G. Carey, Michael J. Cruickshank, Robert F. Dill, Sylvia A. Earle, James M. Franklin, J. Fred Grassle, John A. Hildebrand, Mark L. Holmes, Ray G. Hunter, Randolph A. Koski, Janet L. Morton, William G. Pearcy, Joseph L. Ritchey, Peter A. Rona, Craig R. Smith, and Gary L. Taghon. The manuscript benefited greatly from review comments supplied by Jo Alexander, Sandra Ridlington, and Joseph S. Cone. I especially thank Karf B. LaPorta for her administrative assistance and support during this project. I thank the National Coastal Resources Institute for administrative support during the final phases of publication. Finally, I acknowledge the support and advice of the editorial and production staff of Springer-Verlag New York, Inc. Funding for the Gorda Ridge Symposium was provided by the Department of the Interior, Minerals Management Service, Office of Strategic and Inter national Minerals, through Cooperative Agreement No. 14-12-0001-30168 with the State of Oregon, Department of Geology and Mineral Industries. GREGORY R. McMURRAY Contents Foreword. DONALD A. HULL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Contributors ........................................................ xiii Part I. Introduction 1. Geology and Geophysics of Gorda Ridge MARTIN R. FISK and KATHERINE J . HOWARD . . . . . . . . . . . . . . . . . . . . . . 3 Part II. Gorda Ridge Mineral Potential 2. Hydrography and Geochemistry of Northern Gorda Ridge ROBERT W. COLLIER and EDWARD T. BAKER ..................... 21 3. Geology of the GR14 Site on Northern Gorda Ridge DAVID A. CLAGUE and PETER A. RONA .......................... 31 4. Multistage Hydrothermal Systems in the Blanco Fracture Zone ROGER HART, JOCHEN HOEFS, and DOUGLAS PYLE ................ 51 5. Distribution and Composition of Massive Sulfide Deposits at Escanaba Trough, Southern Gorda Ridge JANET L. MORTON, RANDOLPH A. KOSKI, WILLIAM R. NORMARK, and STEPHANIE L. Ross ......................................... 77 6. Submersible Observations in Escanaba Trough, Southern Gorda Ridge MARK L. HOLMES and ROBERT A. ZIERENBERG ................... 93 7. A Comparison of Sulfide Deposits from Modern Sediment Covered Spreading Axes with Besshi-Type Deposits of Japan RANDOLPH A. KOSKI.. .. ... ... .. . .. . .. .. . .. . .. . .. . .. . ... ... ... .. 117 x Contents 8. Deposition of Metalliferous Sediment Beneath a Brine Pool in the Atlantis II Deep, Red Sea ROBERT A. ZIERENBERG ......................................... 131 9. Economic Perspective on Development of Potential Gorda Ridge Sulfide Deposits JOSEPH L. RITCHEY, NICHOLAS WETZEL, SCOTT A. STEBBINS, and BENJAMIN W. HAYNES .......................................... 143 Part Ill. Technology 10. Hydrothermal Plume Prospecting: Hydrographic and Geochemical Techniques EDWARD T. BAKER ............................................. 155 11. Acoustic Techniques for Imaging Seafloor CHRISTOPHER G. Fox ........................................... 169 12. Technologies for Geophysical Exploration on the Ocean Bottom JOHN A. HILDEBRAND........................................... 179 13. Seafloor Electromagnetic Exploration Methods ALAN D. CHAVE ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 14. An Electric Drill for Deep-Sea Coring PATRICK J.e. RYALL ............................................ 201 15. Mining Technology for Gorda Ridge Sulfides MICHAEL J. CRUICKSHANK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Part W. Benthic Ecology 16. Distributional Ecology of Benthic Megaepifauna and Fishes in Gorda Ridge Axial Valley ANDREW G. CAREY JR., GARY L. TAGHON, DAVID L. STEIN, and PETER A.RONA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 17. Distributional Ecology of Selected Megaepifauna on Abyssal Plains Adjacent to Gorda Ridge, Northeast Pacific Ocean ANDREW G. CAREY JR. .......................................... 241 18. Spatial Variation in Faunal Composition of Hydrothermal Vent Communities on the East Pacific Rise and Galapagos Spreading Center CINDY LEE VAN DOVER and ROBERT R. HESSLER ................. 253 Contents xi 19. Regional-Scale Features of Northeast Pacific, East Pacific Rise, and Gulf of Aden Vent Communities S. KIM JUNIPER, VERENA TUNNICLIFFE, and DANIEL DESBRUYERES 265 20. Notes on Fauna from Several Deep-Sea Hydrothermal Vent and Cold Seep Soft-Sediment Communities ROSEMARIE F. PETRECCA and J. FREDERICK GRASSLE .............. 279 21. Hydrothermal Vent Fauna of Escanaba Trough (Gorda Ridge) CINDY LEE VAN DOVER, J. FREDERICK GRASSLE, and MICHEL BOUDRIAS .............................................. 285 Part V. Conclusions 22. Results of the Gorda Ridge Symposium GREGORY R. McMURRAY ........................................ 291 Index............................................................... 299