Significance of (40)Ar-(39)Ar encapsulation ages of metapelites from late Palaeozoic metamorphic complexes of Aysen, Chile

Ramirez-Sanchez, E; Deckart, K; Hervé F

Abstract

The ages obtained by the 40Ar-39Ar encapsulation technique (retention and total gas ages) on <2 μm fractions of five metapelites from the Eastern Andean Metamorphic Complex and two from the Chonos Metamorphic Complex allow discussion of the latest recorded metamorphic event in each zone. The Kübler Index (KI) of illite/muscovite (principal component of the metapelites) varies between 0.15° and 0.45° δ°2θ, indicating regional variation from diagenetic to epizonal metamorphic grade. The 40Ar-39Ar encapsulation analyses reveal 39Ar loss varying between 21 and 25%, which shows a limited positive correlation with KI values. The obtained retention and total gas metapelite ages reflect distinct metamorphic conditions. Retention ages most probably indicate burial or regional metamorphic events without plutonic influence in the southern Eastern Andean Metamorphic Complex. Total gas ages reflect contact ages for metapelites close to intrusions in the northern and southern Eastern Andean Metamorphic Complex and in the Chonos Metamorphic Complex. The thermal overprinting of metapelites occurred in Early Cretaceous times at 130 Ma and 145 Ma and is related to the contact metamorphism of an emplacement pulse of the North Patagonian Batholith. Total gas metapelite ages obtained from the western belt of the Chonos Metamorphic Complex suggest a thermal event related to a distinct pulse of the North Patagonian Batholith. © 2007 Cambridge University Press.

Más información

Título según WOS: Significance of (40)Ar-(39)Ar encapsulation ages of metapelites from late Palaeozoic metamorphic complexes of Aysen, Chile
Título según SCOPUS: Significance of 40Ar-39Ar encapsulation ages of metapelites from late Palaeozoic metamorphic complexes of Aysén, Chile
Título de la Revista: GEOLOGICAL MAGAZINE
Volumen: 145
Número: 3
Editorial: CAMBRIDGE UNIV PRESS
Fecha de publicación: 2008
Página de inicio: 389
Página final: 396
Idioma: English
URL: http://www.journals.cambridge.org/abstract_S0016756807004220
DOI:

10.1017/S0016756807004220

Notas: ISI, SCOPUS