Geochemistry of a Triassic dyke swarm in the North Patagonian Massif, Argentina. Implications for a postorogenic event of the Permian gondwanide orogeny

GONZÁLEZ, P.D.; VARELA, R.; GONZÁLEZ, S.N.; SATO, A.M.; GRECO, G.A.; LLAMBÍAS, E.J.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 70 p. 69 - 82

0895-9811

Permo-Triassic magmatism is widespread in the eastern North Patagonian23 Massif and has been related to the Gondwanide orogeny. Although a magmatic24 arc setting is widely accepted for the Permian plutonic rocks, the origin and25 geotectonic setting for the Triassic plutonic and volcanic rocks are still unknown.26 A NW-SE Triassic dyke swarm composed of andesites and latites with minor27 rhyolites was previously described in the Sierra Grande ? Rincon de Paileman28 area. The dyke swarm was associated with extensional tectonics which was29 linked to a postorogenic process.30 In this paper we present new geochemical data of the rocks that form the31 swarm. Trachyandesites and rhyolites were separated based on their32 geochemical characteristics. Both groups may be considered originated from33 different sources. On the other hand, the content of incompatible elements34 (LILE and HFSE) indicates a strong relation between the swarm and an active35 continental margin. In tectonic discrimination diagrams the samples show a36 transitional signature between continental-arc and postcollisional or anorogenic37 settings.38 The new geochemical data on the dyke swarm support the idea of a39 magmatism that was linked to a postorogenic extensional tectonic regime40 related to a continental magmatic arc. Such an extension started in the41 Paleopacific margin of Pangea during the Anisian and might indicate the42 beginning of the Pangea break-up.