Transport Phenomena In Hydrothermal Systems: Cooling Plutons

The Nature Of Heat And Mass Transport In Pluton Environments Has Been Described By Partial Differential Equations And Simulated By Numerical Approximations To These Equations. A Series Of Heuristic Models Computed On The Basis Of These Equations Describes The General Features Of Fluid Circulation In The Vicinity Of An Intrusive Igneous Body Within The Upper 10 Km Of The Earths Crust. Analysis Of These Models Indicates That Fluid Circulation Is An Inevitable Consequence Of The Emplacement Of Magmas In The Crust. The Magnitude Of This Fluid Circulation Generates Convective Heat Fluxes Which Predominate Over Conductive Heat Fluxes When Host Rock Permeabilities Exceed 10-14 Cm2. However, Cooling Rates For The Pluton Are Not Significantly Shortened Unless The Pluton Permeability Is Also > 10-14 Cm2. The Geometries Of Fluid Circulation And Isotherms Arc Directly Affected By Variations In Pluton Size, Width, Level Of Emplacement, And Permeability, As Well As The Distribution Of Permeable Zones In The Host Rocksmost Striking. However, Is The Effect Of The Fluid Properties On Heat And Mass Transport. The Overall Style Of Fluid Circulation Is Effectively Controlled By Coincident Maxima Of The Isobaric Thermal Coefficient Of Expansion And Heat Capacity With The Viscosity Minima In The Supercritical Region Of The H20-System.Waters In Natural Pluton Systems Are Predicted To Move From Their Points Of Origin To Positions Several Kilometers Away In A Few Hundred Thousand Years. This Redistribution Affects Magmatic Fluids And Fluids In Host Rocks Up To Several Kilometers Away From The Pluton. Typically, Temperature And Pressure Changes Along The Fluid Flow Paths Produce Dramatic Changes In Solvent Properties. Hence, The Fluid-Rock Interactions Along The Path Lines Should Generate Diagnostic Mineral Assemblages And Shifts In Isotopic Compositions. Average Fluid:Rock Mass Ratios Of 0.4 Are Realized Over The Entire Permeable Portions Of The Systems. This Analysis Reveals The Extent Of Fluid Circulation, And Magnitude Of Convective Heat Flux Over Broad Crustal Regions And Along Crustal Plate Boundaries Where Igneous Activity Is Voluminous May Be Much Greater Than Heretofore Realized. Egi Reference Number Gl03760

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Citation Date 1977-01-01T00:00:00

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Original ID 78C1778F21064975B3C9F5ACF1D07AB0
Index Date 2014-06-17T13:31:52
Original Format ISO-USGIN
Original Version 1.2


Organization D. Norton And J. Knight