Protracted Thermal Evolution of a Migmatitic Terrane as Revealed by Multiple Geochronometers From the Retro-Arc of the Early Paleozoic Famatinian Orogen in NW Argentina

Farias, Pablo, Weinberg, Roberto F., Sola, Alfonso, and Finch, Melanie (2023) Protracted Thermal Evolution of a Migmatitic Terrane as Revealed by Multiple Geochronometers From the Retro-Arc of the Early Paleozoic Famatinian Orogen in NW Argentina. Tectonics, 42 (3). e2021TC007027.

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U-Pb dates of zircon, monazite, and titanite combined with trace element composition, allows characterization of the thermal evolution of the migmatitic Agua del Sapo complex. This complex comprises Al-rich and Ca-rich metasedimentary rocks with a detrital zircon maximum depositional age of 550 Ma. The rocks record two consecutive early Paleozoic orogenies. During subduction associated with the 550–510 Ma Pampean orogeny, the complex was in the fore-arc region and was intruded by 550–520 Ma granites indicative of anomalous heating possibly related to ridge subduction. During the subsequent 500–440 Ma Famatinian orogeny, the arc migrated trenchwards and the region became part of a retro-arc that underwent melting at upper-amphibolite facies. This event was recorded differently by each of the accessory phases. Detrital zircon cores were overgrown by rare Famatinian rims that range from 500 to 420 Ma, while monazite records only Famatinian dates with a growth peak at ∼457 Ma that extends to 410 Ma, possibly due to coupled dissolution-precipitation. Published titanite dates define a 120 Myr thermal history, starting at ∼500 Ma with temperatures of ∼750°C ± 25°C, ending at 380 Ma and ∼700°C ± 25°C. Cooling was accompanied by a decrease in titanite light rare earth element contents in response to increased abundance of allanite/epidote. Thus, the complementary time-compositional record of the accessory phases reveals continued high heat flow, associated with deformation, to 380 Ma. This prolonged event blurs the boundary between the Famatinian and the subsequent Achalian/Chanic orogenies and extends the Silurian Rinconada tectonic phase of the Famatinian orogeny to the east into the Eastern Sierras Pampeanas.

Item ID: 79202
Item Type: Article (Research - C1)
ISSN: 1944-9194
Keywords: geochronology, hot orogen, monazite, petrochronology, titanite, zircon
Copyright Information: © 2023. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Funders: Australian Research Council (ARC)
Projects and Grants: ARC DP110102543
Date Deposited: 16 Aug 2023 02:43
FoR Codes: 37 EARTH SCIENCES > 3705 Geology > 370502 Geochronology @ 70%
37 EARTH SCIENCES > 3705 Geology > 370503 Igneous and metamorphic petrology @ 30%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280107 Expanding knowledge in the earth sciences @ 100%
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