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Margins A Research Initiative for Interdisciplinary Studies of the Processes Attending Lithospheric Extension and Convergence (1989) / Chapter Skim
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6 Passive Margins: Group 3
Pages 61-72

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From page 61...
... It is important scientifically, economically, and environmentally that we understand how these giant reactors operate. Because fluid flow is fundamentally involved in almost all the reactor processes and products, the single most important scientific objective is to understand the causes and interactions that control fluid flow in post-riftina divergent margins.
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From page 62...
... Case studies addressing, first, present fluid and chemical fluxes in basins, and then the integrated effects of such fluxes as they have operated over the history of basin development appear to be particularly pertinent. We believe that sedimentary basins on divergent continental margins are especially amenable to effective study at the present time because highly evolved and complimentary land- and sea-based technologies and observations can be merged today in these locations.
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From page 63...
... Fluids moving within divergent continental margins often precipitate minerals on preexisting sediment grains or dissolve these grains. This chemical alteration can completely plug or completely remove entire sedimentary units.
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From page 64...
... Cal KgedImentatio~ Folding Faulting, Fracturing, Jointing Salt Heat Flow Fluid Generation Rock Alteration metamorphism diagenesis Seal Formation gas hydra~ces C~3 Overpressure - Density Differences salinity therma1 Topographic FIGURE 1 Interrelated processes controlling fluid flow in divergent margin teas ins .
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From page 65...
... What is particu~arly-needed at this point is a quantitative understanding of the linkages between individual processes, and the formulation of an integrated model that can describe post-rift internal processes in divergent continental margins as a whole. NEEDED STUDIES The studies required to meet our principal scientif ic goal of understanding the interactions that control f luid f low and 65
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From page 66...
... Obtaining Snapshots of Fluid and Chemical Far uses in Divergent Margin Basins Understanding the present rates and directions of fat uicI flow In divergent margins is the most direct approach to determining overall flux rates and the evolution of fluid flow through time. We strongly endorse studies that measure or def ine the velocities of fluid flow across any surface within a given basin.
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From page 67...
... Determining the Cumulative Effects of Fluid and Chemical Fluxes in Divergent Margin Basins The previously suggested studies would provide a current snapshot of fluid movements and chemical fluxes. Studies of the cumulative products of diagenesis and fluid flow would potentially provide a record of all post-rifting alteration and fluid flow.
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From page 68...
... Fat ux Snapshots Ef fects of Cumulative Fluxes Interpolation and Process Models Downhole devices 1. In-situ pore water samplers.
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From page 69...
... Developing Integrated Models to Simulate Fluid-Chemical Processes in Divergent Margins Snapshot and integrated fluxes measured must be interpolated and simulated by process models. Local interpolation models are needed to convert borehole measurements, chemical logs, or seismic images to measures of alteration over relatively large 69
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From page 70...
... Integrated process moclels are needed to bring data from different basins to bear on common problems of understanding basin reactors. Local Models Sectimentol ogists are enjoying considerable success with ''dif fusion" models that simulate how highlands erode and depressions fit 1.
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From page 71...
... STRATEGY REQUIRED TO ACHIEVE GOALS The most appropriate strategy for achieving the scientific goal of understanding the interactions that control fluid flow and its chemical and tectonic consequences as a function of time is to fund a series of case studies that are loosely coordinated around the objective of developing an overall process model. Observational case studies will undoubtedly and very properly occur on a variety of divergent basins, as exposures, data availability, and investigator interest dictate.
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From page 72...
... Finally, fluid overpressures are thought to fundamentally control the shape and tectonics of accretionary prisms. Progress in detecting, modeling, and predicting overpressured fluid flow in divergent margins will contribute directly to similar research efforts in convergent continental margins where the processes involved are more complex.
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Key Terms

  • divergent margins
  • continental margins
  • divergent margin
  • process model
  • margin basins

  • heat flow
  • divergent continental
  • integrated process
  • chemical fluxes
  • sedimentary basins

  • pore fluids
  • fluid movement
  • fluid fluxes
  • tectonic consequences
  • process models

  • pore pressure
  • fluid overpressures
  • flow surveys
  • chemical alteration
  • control fluid

  • history investigations
  • cumulative products
  • teas ins
  • fit uid
  • upper sediment

  • sedimentary teas
  • basin pore
  • chemical processes
  • local models
  • internal processes


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