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

Katja Deckart, Elisa Ramírez-Sánchez, Francisco Hervé

Resultado de la investigación: Article

3 Citas (Scopus)

Resumen

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.

Idioma originalEnglish
Páginas (desde-hasta)389-396
Número de páginas8
PublicaciónGeological Magazine
Volumen145
N.º3
DOI
EstadoPublished - may 2008

Huella dactilar

encapsulation
metapelite
Paleozoic
batholith
gas
contact metamorphism
overprinting
muscovite
illite
emplacement
Cretaceous

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Geology

Citar esto

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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 K{\"u}bler 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.",
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Significance of 40Ar-39Ar encapsulation ages of metapelites from late Palaeozoic metamorphic complexes of Aysén, Chile. / Deckart, Katja; Ramírez-Sánchez, Elisa; Hervé, Francisco.

En: Geological Magazine, Vol. 145, N.º 3, 05.2008, p. 389-396.

Resultado de la investigación: Article

TY - JOUR

T1 - Significance of 40Ar-39Ar encapsulation ages of metapelites from late Palaeozoic metamorphic complexes of Aysén, Chile

AU - Deckart, Katja

AU - Ramírez-Sánchez, Elisa

AU - Hervé, Francisco

PY - 2008/5

Y1 - 2008/5

N2 - 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.

AB - 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.

KW - Ar-Ar encapsulation

KW - Chile

KW - Metamorphic complexes of Aysén

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