Using white mica 40Ar/ 39Ar data as a tracer for fluid flow and permeability under high-P conditions: Tauern Window, Eastern Alps

C. J. Warren, A. J. Smye, S. P. Kelley, S. C. Sherlock

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

New single-grain-fusion muscovite and paragonite 40Ar/ 39Ar data from eclogite and blueschist units exposed in the Tauern Window, Eastern Alps yield a range of apparent ages from 90 to 23Ma. These apparent ages are generally older than expected for 40Ar/ 39Ar cooling ages, given constraints from other geochronological systems such as Rb-Sr and U-Pb. Numerical Ar-in-muscovite diffusion models for Tauern Window nappe P-T paths in an open system suggest that 40Ar/ 39Ar ages should lie between 29 and 24Ma, and that they should constrain cooling and decompression following the post-high pressure Barrovian overprint. The measured ranges of apparent 40Ar/ 39Ar dates suggest that the assumption of open system behaviour is not valid for this region. The local and/or regional generation of fluid during exhumation promoted pervasive recrystallization of high pressure lithologies throughout the Tauern Window to greenschist and amphibolite facies assemblages. The old apparent 40Ar/ 39Ar white mica dates in all lithologies are therefore interpreted as being due to inefficient removal of grain boundary Ar by the grain boundary fluids during the Barrovian overprint, due to high Ar concentrations or limited connectivity or both. This caused spatially (mm-scale) and temporally variable fluxes of Ar out of, and probably into, white mica in both metasedimentary and metabasic lithologies.

Original languageEnglish (US)
Pages (from-to)63-80
Number of pages18
JournalJournal of Metamorphic Geology
Volume30
Issue number1
DOIs
StatePublished - Jan 1 2012

Fingerprint

Lithology
mica
fluid flow
Flow of fluids
tracer
Open systems
permeability
lithology
Grain boundaries
grain boundary
muscovite
Cooling
Fluids
cooling
paragonite
blueschist
fluid
Fusion reactions
greenschist facies
decompression

All Science Journal Classification (ASJC) codes

  • Geology
  • Geochemistry and Petrology

Cite this

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title = "Using white mica 40Ar/ 39Ar data as a tracer for fluid flow and permeability under high-P conditions: Tauern Window, Eastern Alps",
abstract = "New single-grain-fusion muscovite and paragonite 40Ar/ 39Ar data from eclogite and blueschist units exposed in the Tauern Window, Eastern Alps yield a range of apparent ages from 90 to 23Ma. These apparent ages are generally older than expected for 40Ar/ 39Ar cooling ages, given constraints from other geochronological systems such as Rb-Sr and U-Pb. Numerical Ar-in-muscovite diffusion models for Tauern Window nappe P-T paths in an open system suggest that 40Ar/ 39Ar ages should lie between 29 and 24Ma, and that they should constrain cooling and decompression following the post-high pressure Barrovian overprint. The measured ranges of apparent 40Ar/ 39Ar dates suggest that the assumption of open system behaviour is not valid for this region. The local and/or regional generation of fluid during exhumation promoted pervasive recrystallization of high pressure lithologies throughout the Tauern Window to greenschist and amphibolite facies assemblages. The old apparent 40Ar/ 39Ar white mica dates in all lithologies are therefore interpreted as being due to inefficient removal of grain boundary Ar by the grain boundary fluids during the Barrovian overprint, due to high Ar concentrations or limited connectivity or both. This caused spatially (mm-scale) and temporally variable fluxes of Ar out of, and probably into, white mica in both metasedimentary and metabasic lithologies.",
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Using white mica 40Ar/ 39Ar data as a tracer for fluid flow and permeability under high-P conditions : Tauern Window, Eastern Alps. / Warren, C. J.; Smye, A. J.; Kelley, S. P.; Sherlock, S. C.

In: Journal of Metamorphic Geology, Vol. 30, No. 1, 01.01.2012, p. 63-80.

Research output: Contribution to journalArticle

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