RT Journal Article
T1 A conceptual model for the evolution of a magmatic system based on U-Pb zircon studies on the Devonian granites of Sierra de San Luis, Argentina
A1 Dahlquist, Juan A.
A1 Morales Cámera, Matías M.
A1 Moreno Moreno, Juan Antonio
A1 Basei, Miguel A.S.
A1 Santos da Cruz, Gilmara
A1 Oliveira, Elson P.
AB It is widely acknowledged that thermal models clearly demonstrate that crustal magma bodies should solidify rapidly upon emplacement. Small plutons can cool below the solidus in thousands of years, while even large plutons require hundreds of thousands of years, but not more than a million years. However, recent U-Pb zircon geochronological data contradict these results, strongly suggesting that magmatic systems are often characterized by protracted events. Therefore, a conceptual framework that reconciles thermal models and the geochronology data is necessary. The Devonian foreland magmatism of the Sierra de San Luis is made up of two distinctive suites, the Monzonite suite (<65 wt.% SiO2) and the Granite suite (>65 wt.% SiO2), both emplaced at ca. 3.7 kbar. Classification of the studied Devonian granitoids is debatable because they have a hybrid I- to A-type granite signature. Based on a robust geochronological U-Pb zircon dataset we corroborate the development of a protracted magmatic activity with three major crystallization events for this Devonian magmatism: 391 ± 1, 384 ± 1, and 379 ± 2 Ma. Considering these geochronological data, we postulate the presence of a deep mush reservoir, where a prolonged magmatic activity, permitted the prolonged crystallization of antecrysts (ca. 395–384 Ma). Migration of the parental magma from the mush reservoir zone occurred near the time of emplacement and culminated in the formation of an ephemeral magma chamber located at shallow levels, where zircon autocrysts crystallized (ca. 379 Ma). Age spectra reported within individual samples support the idea of a massive migration of magma when conditions were favourable (e.g. thermally matured crust). Individual crystallization ages recorded by monazites hosted in two-mica granites are comparable to those obtained from zircons, supporting the presence of a long-lasting hot source. Additional geochronological data indicate that a later thermal event (ca. 353 Ma) could have partially affected some areas of the Devonian magmatic zircons promoting Pb loss, with subsequent partial resetting of the isotopic clock.
PB Taylor and Francis
SN 0020-6814
YR 2024
FD 2024-03-30
LK https://hdl.handle.net/20.500.14352/104390
UL https://hdl.handle.net/20.500.14352/104390
LA eng
NO Dahlquist, Juan A., et al. «A Conceptual Model for the Evolution of a Magmatic System Based on U-Pb Zircon Studies on the Devonian Granites of Sierra de San Luis, Argentina». International Geology Review, vol. 66, n.o 9, mayo de 2024, pp. 1794-814
NO Consejo Nacional de Investigaciones Científicas y Técnicas
NO Fondo para la Investigación Científica y Tecnológica
NO Fundação de Amparo à Pesquisa do Estado de São Paulo
NO Secretaria de Ciencia y Tecnología - Universidad Nacional de Córdoba
DS Docta Complutense
RD 10 abr 2025