39Ar-40Ar geochronology of mono- and polymetamorphic basement rocks

Villa, Igor Maria (2015). 39Ar-40Ar geochronology of mono- and polymetamorphic basement rocks. Periodico di mineralogia, 84(3b), pp. 615-632. Bardi Editore 10.2451/2015PM0454

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The 39Ar-40Ar technique is often used to date the metamorphic evolution of basement rocks. The present review article examines systematic aspects of the K-Ar decay system in different mineral chronometers frequently found in mono- and polymetamorphic basements (amphibole, biotite, muscovite/phengite, K-feldspar). A key observation is that the measured dissolution rate of silicates in aqueous fluids is many orders of magnitude faster, and has a much lower activation energy, than the rate of Fickian diffusion of Ar. The effects of this inequality are patchy age zonations, very much like those observed in many U-Pb chronometers, unaccompanied by intra-crystalline bell¬shaped Ar loss profiles. Recognizing the importance of the respective rate constants in field situations leads to re-evaluating the ages and the interpretive paradigms in classic examples such as the Central Alpine "Lepontine" amphibolite event and the Western Alpine eclogitic event.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Villa, Igor Maria

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0369-8963

Publisher:

Bardi Editore

Language:

English

Submitter:

Igor Maria Villa-Toscani

Date Deposited:

08 Feb 2016 10:44

Last Modified:

17 Aug 2016 16:45

Publisher DOI:

10.2451/2015PM0454

Web of Science ID:

WOS:000367210100003

Uncontrolled Keywords:

39Ar-40Ar dating, diffusion, geochronology, eclogite dating, Lepontine event

BORIS DOI:

10.7892/boris.75173

URI:

https://boris.unibe.ch/id/eprint/75173

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