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

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

INTERNATIONAL JOURNAL OF EARTH SCIENCES

SPRINGER

Lugar: Berlin; Año: 2016 vol. 105 p. 1287 - 1305

1437-3254

Newgeochronological, geochemical, and isotopicdata arereported for the Capilla del Monte two-micagranitepluton in the northeastern Sierras de C¨®rdoba. AnEarlyCarboniferous age is established by a U¨CPb zirconconcordia(336 ¡À 3 Ma) and a Rb¨CSr whole-rock isochron(337 ¡À 2Ma). Zircon saturation geothermometry indicatesrelativelyhigh temperatures (735¨C800 ¡ãC). The graniteshave highaverage SiO2 (74.2 %), Na2O + K2O (7.8 %),and highfield-strength elements, high K2O/Na2O (1.7) andFeO/MgOratios (5.1), with low CaO content (0.71 %). REEpatternswith marked negative Eu anomalies (Eu/Eu* 0.14¨C0.56)indicate crystal fractionation, dominantly of plagioclaseandK-feldspar, from a peraluminous magma enrichedin F.Isotope data (87Sr/86Srinitial = 0.7086, ¦ÅNd336 = −5.5 to−4.4 with TDM= 1.5 Ga, zircon ¦ÅHf336 +0.8to −6.1; meanTDM = 1.5 Ga) suggest a Mesoproterozoiccontinentalsource,albeit with some younger or more juvenile materialindicatedby the Hf data. The pluton is the easternmostmember ofa Carboniferous A-type magmatic suite whichshows anincrease in juvenile input toward the west in thispart ofthe pre-Andean margin. The petrological and geochemicaldatastrongly suggest a similar intraplate geodynamicsetting tothat of the nearby but much larger, LateDevonian,Achala batholith, although Hf isotope signaturesof zirconsuggest a more uniformly crustal origin for thelatter.Further studies are required to understand whetherthesebodies represent two independent magmatic episodesor more continuousactivity.