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The Pichidangui Formation; Some geochemical characteristics and tectonic implications of the Triassic marine volcanism in central Chile (31°55′ to 32°20′S)

By
Mario Vergara
Mario Vergara
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Leopoldo López-Escobar
Leopoldo López-Escobar
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Alejandro Cancino
Alejandro Cancino
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Beatriz Levi
Beatriz Levi
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Published:
January 01, 1991

The Triassic Pichidangui Formation in central Chile (31°55′ to 32°20′) is a bimodal volcanic sequence composed of rhyolites, ignimbrites, basalts and basaltic andesites, and turbiditic sedimentary rocks. The basic lavas are completely different from the Mesozoic calc-alkaline “Andean” Jurassic and Lower Cretaceous rocks. They show primitive chemical characteristics such as a convex-up rare-earth element pattern similar to the ocean-plate basalts from the Nazca Plate but their Sm/Lu ratios reflect a more advanced degree of differentiation, similar to the Southern Volcanic Zone of the Andes. The chemical signature of the Pichidangui volcanic rocks is consistent with volcanism in a volcanic arc floored by a quasi-oceanic crust, either formed at the rim of Gondwanaland before its dismembering, or belonging to an allochthonous terrane.

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Contents

GSA Special Papers

Andean Magmatism and Its Tectonic Setting

Russell S. Harmon
Russell S. Harmon
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Carlos W. Rapela
Carlos W. Rapela
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Geological Society of America
Volume
265
ISBN print:
9780813722658
Publication date:
January 01, 1991

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