Rapid dewatering of the crust deduced from ages of mesothermal gold deposits

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The large-scale migration of fluids through the continental crust has been well documented, but there is no consensus regarding the timing of fluid migration relative to erogenic episodes, or rates of crustal dewatering1. Here we present 40Ar/39Ar dates for muscovites from quartz veins along a major shear zone in southeast Alaska, which show that the veins were emplaced in the early Eocene, during the late stages of orogenic deformation. Hydrothermal activity took place for only about 1 Myr and along a distance of at least 200 km. The fluids were generated by metamorphic reactions in subducted crust along the North American plate margin, and were apparently trapped in the crust by the low permeabilities accompanying a convergent tectonic regime until 56 Myr ago. The rapid dewatering event coincided with a change in plate motion at 56-55 Myr, which caused a shift from convergent to partly transcurrent tectonics. We suggest that this change in tectonic regime led to increased crustal permeabilities and hence the possibility of large-scale fluid migration.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Rapid dewatering of the crust deduced from ages of mesothermal gold deposits
Series title Nature
Volume 354
Issue 6351
Year Published 1991
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Nature
First page 296
Last page 298
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