Workshop Report - Ridge 2000 Program

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4 REPORTS OF THE WORKING GROUPS INTRODUCTION The following six reports, written during the workshop, present the deliberations of the working groups. Each working group focused on one of the six scientific themes of the mid-ocean ridge system. The working group members were asked to consider the following questions: 1. What is the single most important scientific objective within this theme? 2. What are the critical problems (primary and secondary) that must be solved in order to achieve this objective? 3. What are the specific physical processes that studied in order to understand the critical problems? be listed in priority order? need to be Can they 4. What data ought to be collected, and what is it realistic to expect in the future? 5. What laboratory, theoretical, and numerical developments are needed now and what capabilities should be developed? 6. What measurement capabilities are needed? capabilities exist, or can they be developed during decade? Do these the coming 7. What is the strategy for proceeding? What studies must be simultaneous? What needs to be done now for planning? 8. What cross-disciplinary coordination needs to be planned? 13
GROUP 1: MANTLE DYNAMICS: MAGMA GENERATION AND DELIVERY Members: Donald Forsyth. Co-Chairman John Whitehead. Co-Chairman Roger Buck. Charles Cox. Roger Denlinger. Henry Dick. Michael Gurnis. Adolphe Nicolas. John Orcutt. Jason Phipps Morgan. and Sean Solomon Scientific Rationale Pressure-release melting of upwelling mantle beneath a spreading center is the primary process by which magma is generated. The depth and degree of partial melting beneath the ridge is controlled by the rate of upwelling and the composition and temperature of the mantle. The spatial and temporal distribution of melting thus reflects the dynamics of mantle flow. Although some constraints on the pressure and temperature conditions of melt formation are provided by petrological studies. the physical processes which control magma generation and delivery. and their chemical consequences. are poorly understood. The primary scientific objective in the study of mantle dynamics at spreading centers is to understand the flow of the mantle. the generation of melt. and the transport of magmas beneath ridge systems. Separation of melt from residual mantle will control the redistribution and chemical stratification of mantle materials. the structure of young oceanic plates. the rate and geometry of melt delivery to the base of the crust. and the composition of parental melts emplaced in crustal magma bodies. Understanding these mechanisms is important for a broad range of topics. including the nature of mantle heterogeneity. the spatial and temporal variations in crustal morphology. structure. and composition. and segmentation of the ridge crest. Investigation of this problem can be separated into two questions: (1) what is the pattern of mantle flow and melt generation beneath a spreading center? and (2) how does melt segregate from the mantle and migrate to the base of the crust? The answers to these questions will require coordinated. interdisciplinary observational. laboratory. and theoretical efforts. In addition. understanding of the behavior of the upper mantle revealed by ophiolite studies is of great importance. 14
Page 2 and 3: The Mid-Oceanic Ridge A Dynamic G
Page 4 and 5: OCEAN STUDIES BOARD WALTER H. MUNK,
Page 6 and 7: PREFACE Recent discoveries of the w
Page 8 and 9: o Regional Scale: selected subsets
Page 10 and 11: 1 INTRODUCTION The global mid-ocean
Page 12 and 13: papers were compiled, printed, and
Page 14 and 15: 2 STATEMENT OF GOALS AND OBJECTIVES
Page 16 and 17: experience from land volcanic and m
Page 18 and 19: solid understanding of both the bio
Page 20 and 21: NEXT STEPS TOWARD A RIDGE INITIATIV
Page 24 and 25: Critical Investigations The specifi
Page 26 and 27: Seismic refraction methods provide
Page 28 and 29: New Instrument and Laboratory Capab
Page 30 and 31: GROUP 2: GEOMETRY AND DYNAMICS OF M
Page 32 and 33: FORMATION OF OCEAN CRUST AT SPREADI
Page 34 and 35: 3. Regional Surveys. The third comp
Page 36 and 37: provide efficient and economically
Page 38 and 39: 3. Adaptation of tomographic invers
Page 40 and 41: Consequently, the sin;J1e most impo
Page 42 and 43: Thermal stresses have been suggeste
Page 44 and 45: electromagnetic fields must be meas
Page 46 and 47: capability should include at least
Page 48 and 49: In order to understand subseafloor
Page 50 and 51: fossil hydrothermal systems in ophi
Page 52 and 53: instrumented to record the environm
Page 54 and 55: GROUP 5: BIOLOGY OF HYDROTHERMAL SY
Page 56 and 57: There are several key questions abo
Page 58 and 59: Dispersal of Organisms What are the
Page 60 and 61: Strategy Biological studies will em
Page 62 and 63: GROUP 6: WATER COLUMN DYNAMICS AND
Page 64 and 65: On the ridge segment scale, detaile
Page 66 and 67: standard transect sampling and Lagr
Page 68 and 69: APPENDIX I The Mid-Oceanic Ridge: A
Page 70 and 71: Forsyth, Donald Department of Geolo
Page 72 and 73:
Lonsdale. Peter Scripps Institution
Page 74 and 75:
Reeve, Michael National Science Fou
Page 76:
Tunnicliffe, Verena University of V
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Workshop Report - Ridge 2000 Program

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