## A model for coupled fluid-flow and mixed-volatile mineral reactions with applications to regional metamorphism

### Détails

ID Serval

serval:BIB_728186A03A47

Type

**Article**: article d'un périodique ou d'un magazine.

Collection

Publications

Fonds

Titre

A model for coupled fluid-flow and mixed-volatile mineral reactions with applications to regional metamorphism

Périodique

Contributions to Mineralogy and Petrology

ISSN-L

0010-7999

Statut éditorial

Publié

Date de publication

1991

Peer-reviewed

Oui

Volume

106

Pages

273-285

Langue

anglais

Résumé

The effect of fluid flow on mixed-volatile reactions in metamorphic

rocks is described by an expression derived from the standard equation

for coupled chemical-reaction and fluid-flow in porous media. If local

mineral-fluid equilibrium is assumed, the expression quantitatively

relates the time-integrated flux at any point in a flow-system to the

progress of devolatilization reactions and the temperature- and

pressure-gradients along the direction of flow. Model calculations

indicate that rocks are generally devolatilized by fluids flowing

up-temperature and/or down-pressure. Flow down-temperature typically

results in hydration and carbonation of rocks. Time-integrated fluid

fluxes implied by visible amounts of mineral products of

devolatilization reactions are on the order of 5.10(2)-5.10(4) mol/cm2.

The model was applied to regionally metamorphosed impure carbonate rocks

from south-central Maine, USA, to obtain estimates of fluid flux,

flow-direction, and in-situ metamorphic-rock permeability from

petrologic data. Calculated time-integrated fluxes are 10(4)-10(6)

cm3/cm2 at 400-degrees-450-degrees-C, 3,500 bars. Fluid flowed from

regions of low temperature to regions of high temperature at the peak of

the metamorphic event. Using Darcy's Law and estimates for the duration

of metamorphism and hydrologic head, calculated fluxes are 0.1-20.10(-4)

m/year and minimum permeabilities are 10(-10)-10(-6) Darcy. The range

of inferred permeability is in good agreement with published laboratory

measurements of the permeability of metamorphic rocks.

rocks is described by an expression derived from the standard equation

for coupled chemical-reaction and fluid-flow in porous media. If local

mineral-fluid equilibrium is assumed, the expression quantitatively

relates the time-integrated flux at any point in a flow-system to the

progress of devolatilization reactions and the temperature- and

pressure-gradients along the direction of flow. Model calculations

indicate that rocks are generally devolatilized by fluids flowing

up-temperature and/or down-pressure. Flow down-temperature typically

results in hydration and carbonation of rocks. Time-integrated fluid

fluxes implied by visible amounts of mineral products of

devolatilization reactions are on the order of 5.10(2)-5.10(4) mol/cm2.

The model was applied to regionally metamorphosed impure carbonate rocks

from south-central Maine, USA, to obtain estimates of fluid flux,

flow-direction, and in-situ metamorphic-rock permeability from

petrologic data. Calculated time-integrated fluxes are 10(4)-10(6)

cm3/cm2 at 400-degrees-450-degrees-C, 3,500 bars. Fluid flowed from

regions of low temperature to regions of high temperature at the peak of

the metamorphic event. Using Darcy's Law and estimates for the duration

of metamorphism and hydrologic head, calculated fluxes are 0.1-20.10(-4)

m/year and minimum permeabilities are 10(-10)-10(-6) Darcy. The range

of inferred permeability is in good agreement with published laboratory

measurements of the permeability of metamorphic rocks.

Création de la notice

02/10/2012 20:34

Dernière modification de la notice

18/11/2016 15:02