| Title | Quantifying water diffusivity and metamorphic reaction rates within mountain belts, and their implications for the rheology of cratons |
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| Author | Whyte, A J; Weller, O M; Copley, A C; St-Onge, M R |
| Source | Geochemistry, Geophysics, Geosystems (G3) vol. 22, issue 11, e2021GC009988, 2021 p. 1-24, https://doi.org/10.1029/2021GC009988  Open Access |
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| Year | 2021 |
| Alt Series | Natural Resources Canada, Contribution Series 20210334 |
| Publisher | American Geophysical Union |
| Publisher | (Wiley) |
| Document | serial |
| Lang. | English |
| Media | paper; digital; on-line |
| File format | pdf; html |
| Province | Quebec |
| NTS | 25E/05; 25E/12; 35G/08; 35G/09; 35G/16; 35H/05; 35H/06; 35H/07; 35H/08; 35H/09; 35H/10; 35H/11; 35H/12; 35H/13; 35H/14; 35H/15; 35H/16; 35I/01; 35I/02; 35I/03; 35I/04; 35I/05; 35I/06; 35J/01; 35J/02; 35J/03;
35J/04; 35J/05; 35J/06; 35J/08 |
| Area | Ungava Peninsula; Douglas Harbour |
| Lat/Long WENS | -75.7500 -71.0000 62.5000 61.4167 |
| Subjects | tectonics; igneous and metamorphic petrology; mineralogy; structural geology; Science and Technology; Nature and Environment; tectonic evolution; crustal evolution; continental crust; craton; orogenies;
metamorphism; decollement; rheology; bedrock geology; basement geology; phase equilibria; modelling; pressure-temperature conditions; structural controls; fluid flow; flow structures; strain; petrography; mineral zoning; Archean; Paleoproterozoic;
Trans-Hudson Orogen; Douglas Harbour Domain; Superior Craton; Cape Smith Belt; Precambrian; Proterozoic |
| Illustrations | location maps; geoscientific sketch maps; cross-sections; photomicrographs; phase diagrams; plots; profiles; schematic models |
| Program | Open Geoscience |
| Released | 2021 10 15 |
| Abstract | The distribution of rheologically strong cratons, and their weakening by metamorphic hydration reactions, is of fundamental importance for understanding first-order strength contrasts within the crust
and the resulting controls on the tectonic evolution of the continents. In this study, the Douglas Harbor structural window within the Paleoproterozoic Trans-Hudson orogen of Canada is used to study the hydration of the footwall Archean Superior
craton basement by water released from the overlying Paleoproterozoic Cape Smith thrust-fold belt. Phase equilibria modeling is applied to quantify the Archean and Paleoproterozoic metamorphic conditions, and to determine the effect of hydration on
basement mineralogy. The amount of structurally bound water within the basement is calculated and shown to decrease as a function of distance below the basal décollement of the thrust-fold belt. Applying a reactive fluid transport model to these
results, the rate coefficient for fluid-rock reaction is constrained to be 10¯19 mol¯1/m3/s, and the diffusivity of water through the grain boundary network to be 10¯9 m2/s at the ambient metamorphic conditions of 570°C and 7.5 kbar. This newly
documented rate of water diffusion is three orders of magnitude slower than thermal diffusion, implying that hydration by diffusion may be the rate-limiting factor in the weakening of cratons, and therefore plays an important role in their geological
persistence. This conclusion is consistent with field observations that Paleoproterozoic strain in the Douglas Harbor structural window is restricted to hydrated portions of the Archean Superior craton basement. |
| Summary | (Plain Language Summary, not published)
The distribution of strong cratons and their potential weakening by metamorphic hydration reactions is of fundamental importance for understanding the
tectonic evolution of continents. In this study we use an area of northern Quebec to study the hydration of cratonic basement by water released from the overlying Cape Smith thrust-fold belt. Using petrographic observations and petrological modelling
we calculate the amount of water within the basement and show that it decreases as a function of distance below the thrust-fold belt. Applying a reactive flow model to these results, we are able to demonstrate that water diffusion is three orders of
magnitude slower than thermal diffusion, implying that hydration by diffusion may be the rate-limiting factor in the weakening of cratons, thereby contributing to their geological longevity. |
| GEOSCAN ID | 328991 |
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