The Capilla del Monte pluton, Sierras de Córdoba, Argentina: the easternmost Early Carboniferous magmatism in the pre‑Andean SW Gondwana margin

DAHLQUIST J.A.; PANKHURST, R.J; RAPELA, C.W.; BASEI, M; ALASINO, P.H.; SAAVEDRA, J.; BALDO, E.G.; MURRA, J.; COSTA CAMPO NETO, M.

INTERNATIONAL JOURNAL OF EARTH SCIENCES

SPRINGER

Lugar: Berlin; Año: 2016

1437-3254

New geochronological, geochemical, and isotopicdata are reported for the Capilla del Monte two-micagranite pluton in the northeastern Sierras de Córdoba. AnEarly Carboniferous age is established by a U?Pb zirconconcordia (336 ± 3 Ma) and a Rb?Sr whole-rock isochron(337 ± 2 Ma). Zircon saturation geothermometry indicatesrelatively high temperatures (735?800 °C). The graniteshave high average SiO2 (74.2 %), Na2O + K2O (7.8 %),and high field-strength elements, high K2O/Na2O (1.7) andFeO/MgO ratios (5.1), with low CaO content (0.71 %). REEpatterns with marked negative Eu anomalies (Eu/Eu* 0.14?0.56) indicate crystal fractionation, dominantly of plagioclaseand K-feldspar, from a peraluminous magma enrichedin F. Isotope data (87Sr/86Srinitial = 0.7086, εNd336 = −5.5 to−4.4 with TDM = 1.5 Ga, zircon εHf336 +0.8 to −6.1; meanTDM = 1.5 Ga) suggest a Mesoproterozoic continental source, albeit with some younger or more juvenile materialindicated by the Hf data. The pluton is the easternmostmember of a Carboniferous A-type magmatic suite whichshows an increase in juvenile input toward the west in thispart of the pre-Andean margin. The petrological and geochemicaldata strongly suggest a similar intraplate geodynamicsetting to that of the nearby but much larger, LateDevonian, Achala batholith, although Hf isotope signaturesof zircon suggest a more uniformly crustal origin for thelatter. Further studies are required to understand whetherthese bodies represent two independent magmatic episodesor more continuous activity