• What are the driving mechanisms for seafloor spreading? How does crustal accretion vary 



with time? What are the local scales of accretion and tectonics in space and time? How are 

 volcanic processes coupled to hydrothermal circulation at midocean ridges? What are 

 the controlling factors on sulfide mineralization and the extent of deposits? What is the 

 variability and alteration of oceanic crust as it moves off-axis? 



• What are the chemical and thermal properites of hydrothermal fluids from vents and what 



is their role in the mineralization process? What is the contribution of vent fluxes to 

 chemical balance of the oceans? What chemical reactions occur? What is the relation 

 between fluids and biologic communities? 



Answering these questions requires modern detailed survey capabilities (e.g., Seabeam, 

 Seamarc, Alvin) for expanded field programs to determine the history and scale of crustal 

 accretion ($IM in FY 1989, $2M in FY 1990, increasing to $6 in FY 1992). Research 

 submersibles must be used to mount integrated geological, chemical, and biological studies to 

 examine a spectrum of representative sites including high and low temperature fluids, seamount 

 localities, and sedimented and unsedimented regions. In situ instrumentation for long-term 

 monitoring of hydrothermal vents and crustal accretion must be developed and deployed ($2M 

 per year beginning in FY 1989). 



These systems must include flow meters, chemical and thermal sensors, strain gauges, and ocean 

 floor seismometers. Improved techniques for multichannel seismics must be used in selected 

 areas to conduct experiments focused on determining thermo-mechanical properties of the 

 oceanic lithosphere under varying conditions of age, stress/strain, and thermal regimes ($IM in 

 FY 1 989 and $2M/year from FY 1 990 through FY 1 996). For complete integration of spatial, 

 temporal, and in situ processes, crustal drilling by ODP on bare rock hydrothermal sites is 

 required. An appropriate set of instrumented holes would form a long-term natural laboratory. 



The additional funding requested is essential if existing capabilities are to be upgraded. Use of 

 new multichannel seismic, side-scan sonar, Seabeam and submersible systems in integrated 

 studies of geochemical and mineralization processes requires new resources. Development and 

 implementation of in situ monitoring systems for geophysical, tectonic, chemical, volcanic, and 

 biological changes require support beyond that available within current support levels. 

 Application of these new suites of observational systems over the next ten years will lead to 

 greater understanding of these basic elements of the earth-ocean system. 



2. Related Programs 



Research being conducted under two other subinitiatives is important to the study of sediment 

 transport and fluxes, production and processes involved - the flux of organic materials to the 

 seafloor and the fate of biogenic materials. These programs are Open Ocean Fluxes and Coastal 

 Ocean Dynamics and Fluxes and funding requirements for these programs accompany their 

 program descriptions. 



IV. Funding Requirements 



Funding requirements for the marine geology and geophysics program, including the core 

 program, critical needs, and major new programs are presented in Table D in Section IV. 



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