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

Abstract

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.

Predictive Models for Detrital Titanite Provenance With Application to the Nanga Parbat—Haramosh Syntaxial Massif, Western Himalaya

“…Although titanite displays a slight preference for the MREE under equilibrium crystallization conditions (Prowatke & Klemme, 2005; Tiepolo et al., 2002), the REE signature of natural titanite is strongly dependent on element availability during crystallization. Specifically, the concentration of the LREEs in titanite correlates with the presence of minerals containing LREEs as formula or trace elements (Farias et al., 2023; Walters et al., 2022). The concentrations of HREEs in titanite may vary according to the presence and abundance of garnet in the source rock during (re)crystallization (Cioffi et al., 2019; Scibiorski et al., 2019).…”