Thermal maturation of a complete magmatic plumbing system at the Sierra de Velasco, Northwestern Argentina

Abstract

The formation of magmatic plumbing systems in the crust involves mass and heat transfer from deep to shallow levels. This process modifies the local geotherm and increases the thermal maturation of the crust, affecting the rheological state of the host rock and the composition of magma. Here, we report a petrological, geochemical, isotopic and geochronological integrated study of the Huaco (~354 Ma) and Sanagasta (~353 Ma, from a new U–Pb zircon age) units from the Carboniferous (Lower Mississippian) Huaco Intrusive Complex, NW Argentina. Similar values of ϵNd t and δ18O, of −3.2 ± 0.7 and +11.2‰ ± 0.3‰ (V-SMOW), respectively, for both units indicate that they shared the same source, as a result of mixing and later homogenization of a crustal component at the Late Devonian (~378 to 366 Ma), with metasomatized mantle-derived melts. Slightly higher contents of TiO2, FeO, MgO, CaO and rare earth elements for the Sanagasta unit in comparison with the Huaco unit suggest an increase in the degree of partial melting, which may have been caused by a higher temperature at the lower crust. In addition, the previous structural model of the Huaco Intrusive Complex points to an increase in thermal maturation in the upper crust, which drives a change in the emplacement style from tabular subhorizontal (Huaco) to vertically elongated (Sanagasta) bodies. Therefore, the evolution of the intrusive complex may reflect a generalized thermal maturation of the complete magmatic column, at both upper and lower crustal levels.

Integrated U-Pb and Hf zircon and whole-rock Nd isotopes studies of Devonian granitic rocks from Sierra de San Luis (Sierras Pampeanas, Argentina): Petrogenetic implications

“…based on geochronological data, suggest a protracted magmatic activity during the building of the Las Chacras-Potrerillos batholith, and ongoing studies are focused on determining if this process is applicable to the Devonian magmatism of the Sierra de San Luis. This interpretation assumes a prolonged time in a deep hot zone maturation with a subsequent migration and emplacement of the granitic magma in shallow levels, as postulated by different authors (e.g., Kemp et al, 2007;Alasino et al, 2017;Macchioli Grande et al, 2020). This conceptual model is consistent with the studies of Dahlquist et al (2018b) on the Veladero granitic stock in Western Sierras Pampeanas of Argentina (Fig.…”

Age and petrogenesis of the beryl-bearing granitic magmatism of the Velasco Pegmatite District, Pampeana Province, NW Argentina

“…Based on these 87 Sr/ 86 Sr initial values as well as other observations such as field and petrographic and other analytical results, especially isotopic (εNd between -2.1 and -4.3), Grosse et al (2009) suggest that the Huaco granite (coupled with the adjacent Sanagasta granite) would have a mainly crustal source with some participation of a more primitive, possibly mantle-derived source, which is also similar to the conclusions of Dahlquist et al (2010) and Macchioli Grande et al (2020) for these granites.…”

“…McBride et al (1976) recorded absolute ages in several granitoids of the Velasco mountain range that would belong to the Achalian event using K-Ar methodology in minerals as well as in whole rock. More recently, the absolute ages using U/ Pb methodology (conventional, SHRIMP, and LA-ICP-Ms) in zircons and/or monazite of the Huaco and Sanagasta granites are in the 378-334 Ma range (Báez et al 2004, Dahlquist et al 2006, Grosse et al 2009, Dahlquist et al 2013, Dahlquist et al 2018, Söllner et al 2007, Macchioli Grande et al 2020.…”

Life and reproduction of titanosaurians: Isotopic hallmark of mid-palaeolatitude eggshells and its significance for body temperature, diet, and nesting

“…5). In contrast, the δ 18 O values of the silicate clasts eroded from the surrounding Carboniferous Sanagasta granite average 11.9‰, which clearly points to a magmatic origin (plutonic rocks usually have δ 18 O values between 5 and 15‰; Sheppard, 1986;Hoefs, 2009), possibly with some degree of crustal contamination (Macchioli Grande et al, 2020). The average Δ 47 -derived temperature for hydrothermal calcite precipitation is 37 • C (33 to 39 • C) and the average δ 18 O H2O value for the water is − 1.7‰ (− 3.0 to − 0.7‰) using the equation of Kim and O'Neil (1997).…”