THE MENCUÉ GRANITE: PERMIAN EPISODIC ARC-RELATED MAGMATISM IN THE WESTERN NORTH PATAGONIAN MASSIF, ARGENTINA

GREGORI , DANIEL ALFREDO; STRAZZERE, LEONARDO; BARROS, MERCEDES; BENEDINI, LEONARDO; MARCOS, PAULO; KOSTADINOFF, J.

INTERNATIONAL GEOLOGY REVIEW

TAYLOR & FRANCIS INC

Lugar: Londres; Año: 2020 vol. xx p. 1 - 23

0020-6814

The Mencué Granite, in the western North Patagonian Massif, includes four lithofacies, I) migmatites, gray biotitic-hornblendiferous granodiorites, white to pink two-mica coarse-grained foliated granodiorites, II) coarse-grained porphyritic granites, III) syenogranites, and IV) alkaline granites and, finally, basic dikes.The Mencué Granite represents several episodes of magmatism, with ages varying between 294 and 250 Ma. The older granitic rocks are solid-state deformed and are S-type granites that can be classified as monzogranite, granite, granodiorite, and tonalite. They have high-K and normal calc-alkaline affinities. These rocks contain significant quantities of subduction-zone components that decrease towards younger lithofacies. The syenogranites and alkaline granites lack subduction zone components and represent A-type granite, typical of within-plate magmatism. The partial melting of metapelites with lower contents of graywackes could be the process of formation of these bodies. The older lithofacies of the Mencué Granite, found westernmost, display a stronger deformation, but there is a progressive eastward change to younger and mildly deformed bodies and even non-deformed bodies. The evolution of the Mencué Granite shows that during the Sakmarian-Roadian (Early Permian) period, a subduction zone was active to the west and its thermal influence affected sedimentary or metamorphic rocks producing S-type granites During the Wordian and Capitanian, (Middle Permian) periods, the Mencué Granite was mildly deformed, possibly in the process of the vanishing of the deformation and has a minor subduction signature.Between the Wuchiapingian and Olenekia periods, the alkaline facies of the Mencué Granite show an absence of deformation and the characteristics of within-plate magmatism.The Early Permian magmatic events in the western North Patagonian Massif are represented by the older lithofacies of the Mencué Granite and were produced by subduction in the western margin of the Gondwanan continent.The Late Permian-Early Triassic magmatic events show a noticeable decreasing influence of subduction and an increasing influence of within-plate components.