Article : [ART320]

Info : REPONSE 19, le 27/11/2002.

Titre : Late Paleozoic K/Ar ages of blueschists from Pichilemu, Central Chile, 1974.

Cité dans : [DIV376]  Recherche sur l'auteur Emmanuel GODOY, septembre 2004.

Source : Earth and Planetary Science Letters (Sept. 1974) vol.23, no.2, p.261-4. 14 refs.
CODEN : EPSLA2
ISSN : 0012-821X
Document_Type : Journal
Treatment_Code : Experimental
Info : Country of Publication : Netherlands
Language : English
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Abstract :
Two crossite concentrates and one blueschist whole rock were analyzed
by the K/Ar method. These samples belong to the high/intermediate pressure
Western Series of the Chilean metamorphic basement and, in this area, are
intruded by a small monzonite body. Ages obtained were 211 m.y. and 329
m.y. for the mineral concentrates and 211 m.y. for the whole rock.
Discussion based on crystal size as a factor for retention of 40Ar during
localized re-heating of the metamorphic rocks due to the monzonitic
intrusion leads to the acceptance of 329 m.y. as the minimum age of
crossite crystallization. This age agrees with the whole rock Rb/Sr
limiting reference isochrons (273-342 m.y.) previously obtained for the
metamorphic basement of Central Chile which did not include samples of the
present area. This age provides the first evidence of a Paleozoic
blueschist assemblage in the eastern Pacific border and would suggest the
existence of a Late Paleozoic subduction zone along the western margin of
South America.

Accession_Number : 1974:697287 INSPEC

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