Magmatism and tectonics in continental Chiloé, Chile (42°-42°30′S)

R. J. Pankhurst, F. Hervé, L. Rojas, J. Cembrano

Resultado de la investigación: Article

66 Citas (Scopus)

Resumen

The Chiloé-Chonos region seems to preserve the oldest depositional events in the fore-arc accretionary complex of the Southeast Pacific margin. There are isolated occurrences of low-grade metamorphic rocks, including slates with a Devonian trilobite fauna and schists that give Rb-Sr evidence of a ca. 290 Ma metamorphism. Pillow basalts and ultramafic rocks may represent parts of the Pan-Thalassic ocean floor on which the Palaeozoic sediments were laid down. Emergence of a magmatic arc is indicated by Jurassic to Early Cretaceous volcanogenic and marine deposits. During the mid-Cretaceous climax of plutonic activity, these were intruded by monzogranites, which here constitute the eastern portion of the North Patagonian batholith. They give Rb-Sr isochron ages of 120-100 Ma (Barremian-Albian). Initial 87Sr/86Sr ratios of 0.7040-0.7045, and ε{lunate}Ndt values of +0.5 to +1.5, indicate a simple petrogenesis with a mantle source. The western part of the batholith is petrologically more primitive, being composed predominantly of tonalite, diorite and gabbro, and initial 87Sr/86Sr ratios are more variable. Late Cenozoic movement of the Liquiñe-Ofqui fault zone (LOFZ) generated deep pull-apart basins to the west of the uplifted batholith/basement complex. These were filled by thick marine sequences of volcanogenic debris, indicating the wide extent of a mainly rhyolitic volcanic field during Miocene times. Pliocene tonalite and granodiorite plutons (dated by a Rb-Sr whole-rock isochron at 4.7 ± 0.5 Ma) and Holocene andesite-basalt stratovolcanoes are located along the LOFZ. The latter feature has thus been a major influence on the tectonic evolution of the area. There is no evidence for major post-Palaeozoic compression or crustal shortening.

Idioma originalEnglish
Páginas (desde-hasta)283-294
Número de páginas12
PublicaciónTectonophysics
Volumen205
N.º1-3
DOI
EstadoPublished - 30 abr 1992

Huella dactilar

Chile
batholith
basalt
magmatism
tectonics
arcs
tonalite
rocks
diorite
petrogenesis
gabbro
schist
metamorphic rocks
andesite
fault zone
Paleozoic
basements
debris
Cretaceous
animals

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes

Citar esto

Pankhurst, R. J. ; Hervé, F. ; Rojas, L. ; Cembrano, J. / Magmatism and tectonics in continental Chiloé, Chile (42°-42°30′S). En: Tectonophysics. 1992 ; Vol. 205, N.º 1-3. pp. 283-294.
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title = "Magmatism and tectonics in continental Chilo{\'e}, Chile (42°-42°30′S)",
abstract = "The Chilo{\'e}-Chonos region seems to preserve the oldest depositional events in the fore-arc accretionary complex of the Southeast Pacific margin. There are isolated occurrences of low-grade metamorphic rocks, including slates with a Devonian trilobite fauna and schists that give Rb-Sr evidence of a ca. 290 Ma metamorphism. Pillow basalts and ultramafic rocks may represent parts of the Pan-Thalassic ocean floor on which the Palaeozoic sediments were laid down. Emergence of a magmatic arc is indicated by Jurassic to Early Cretaceous volcanogenic and marine deposits. During the mid-Cretaceous climax of plutonic activity, these were intruded by monzogranites, which here constitute the eastern portion of the North Patagonian batholith. They give Rb-Sr isochron ages of 120-100 Ma (Barremian-Albian). Initial 87Sr/86Sr ratios of 0.7040-0.7045, and ε{lunate}Ndt values of +0.5 to +1.5, indicate a simple petrogenesis with a mantle source. The western part of the batholith is petrologically more primitive, being composed predominantly of tonalite, diorite and gabbro, and initial 87Sr/86Sr ratios are more variable. Late Cenozoic movement of the Liqui{\~n}e-Ofqui fault zone (LOFZ) generated deep pull-apart basins to the west of the uplifted batholith/basement complex. These were filled by thick marine sequences of volcanogenic debris, indicating the wide extent of a mainly rhyolitic volcanic field during Miocene times. Pliocene tonalite and granodiorite plutons (dated by a Rb-Sr whole-rock isochron at 4.7 ± 0.5 Ma) and Holocene andesite-basalt stratovolcanoes are located along the LOFZ. The latter feature has thus been a major influence on the tectonic evolution of the area. There is no evidence for major post-Palaeozoic compression or crustal shortening.",
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Magmatism and tectonics in continental Chiloé, Chile (42°-42°30′S). / Pankhurst, R. J.; Hervé, F.; Rojas, L.; Cembrano, J.

En: Tectonophysics, Vol. 205, N.º 1-3, 30.04.1992, p. 283-294.

Resultado de la investigación: Article

TY - JOUR

T1 - Magmatism and tectonics in continental Chiloé, Chile (42°-42°30′S)

AU - Pankhurst, R. J.

AU - Hervé, F.

AU - Rojas, L.

AU - Cembrano, J.

PY - 1992/4/30

Y1 - 1992/4/30

N2 - The Chiloé-Chonos region seems to preserve the oldest depositional events in the fore-arc accretionary complex of the Southeast Pacific margin. There are isolated occurrences of low-grade metamorphic rocks, including slates with a Devonian trilobite fauna and schists that give Rb-Sr evidence of a ca. 290 Ma metamorphism. Pillow basalts and ultramafic rocks may represent parts of the Pan-Thalassic ocean floor on which the Palaeozoic sediments were laid down. Emergence of a magmatic arc is indicated by Jurassic to Early Cretaceous volcanogenic and marine deposits. During the mid-Cretaceous climax of plutonic activity, these were intruded by monzogranites, which here constitute the eastern portion of the North Patagonian batholith. They give Rb-Sr isochron ages of 120-100 Ma (Barremian-Albian). Initial 87Sr/86Sr ratios of 0.7040-0.7045, and ε{lunate}Ndt values of +0.5 to +1.5, indicate a simple petrogenesis with a mantle source. The western part of the batholith is petrologically more primitive, being composed predominantly of tonalite, diorite and gabbro, and initial 87Sr/86Sr ratios are more variable. Late Cenozoic movement of the Liquiñe-Ofqui fault zone (LOFZ) generated deep pull-apart basins to the west of the uplifted batholith/basement complex. These were filled by thick marine sequences of volcanogenic debris, indicating the wide extent of a mainly rhyolitic volcanic field during Miocene times. Pliocene tonalite and granodiorite plutons (dated by a Rb-Sr whole-rock isochron at 4.7 ± 0.5 Ma) and Holocene andesite-basalt stratovolcanoes are located along the LOFZ. The latter feature has thus been a major influence on the tectonic evolution of the area. There is no evidence for major post-Palaeozoic compression or crustal shortening.

AB - The Chiloé-Chonos region seems to preserve the oldest depositional events in the fore-arc accretionary complex of the Southeast Pacific margin. There are isolated occurrences of low-grade metamorphic rocks, including slates with a Devonian trilobite fauna and schists that give Rb-Sr evidence of a ca. 290 Ma metamorphism. Pillow basalts and ultramafic rocks may represent parts of the Pan-Thalassic ocean floor on which the Palaeozoic sediments were laid down. Emergence of a magmatic arc is indicated by Jurassic to Early Cretaceous volcanogenic and marine deposits. During the mid-Cretaceous climax of plutonic activity, these were intruded by monzogranites, which here constitute the eastern portion of the North Patagonian batholith. They give Rb-Sr isochron ages of 120-100 Ma (Barremian-Albian). Initial 87Sr/86Sr ratios of 0.7040-0.7045, and ε{lunate}Ndt values of +0.5 to +1.5, indicate a simple petrogenesis with a mantle source. The western part of the batholith is petrologically more primitive, being composed predominantly of tonalite, diorite and gabbro, and initial 87Sr/86Sr ratios are more variable. Late Cenozoic movement of the Liquiñe-Ofqui fault zone (LOFZ) generated deep pull-apart basins to the west of the uplifted batholith/basement complex. These were filled by thick marine sequences of volcanogenic debris, indicating the wide extent of a mainly rhyolitic volcanic field during Miocene times. Pliocene tonalite and granodiorite plutons (dated by a Rb-Sr whole-rock isochron at 4.7 ± 0.5 Ma) and Holocene andesite-basalt stratovolcanoes are located along the LOFZ. The latter feature has thus been a major influence on the tectonic evolution of the area. There is no evidence for major post-Palaeozoic compression or crustal shortening.

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