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The Capilla del Monte pluton, Sierras de Córdoba, Argentina: the easternmost Early Carboniferous magmatism in the pre-Andean SW Gondwana margin
Ist Teil von
International journal of earth sciences : Geologische Rundschau, 2016-07, Vol.105 (5), p.1287-1305
Ort / Verlag
Berlin/Heidelberg: Springer Berlin Heidelberg
Erscheinungsjahr
2016
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
New geochronological, geochemical, and isotopic data are reported for the Capilla del Monte two-mica granite pluton in the northeastern Sierras de Córdoba. An Early Carboniferous age is established by a U–Pb zircon concordia (336 ± 3 Ma) and a Rb–Sr whole-rock isochron (337 ± 2 Ma). Zircon saturation geothermometry indicates relatively high temperatures (735–800 °C). The granites have high average SiO
2
(74.2 %), Na
2
O + K
2
O (7.8 %), and high field-strength elements, high K
2
O/Na
2
O (1.7) and FeO/MgO ratios (5.1), with low CaO content (0.71 %). REE patterns with marked negative Eu anomalies (Eu/Eu* 0.14–0.56) indicate crystal fractionation, dominantly of plagioclase and K-feldspar, from a peraluminous magma enriched in F. Isotope data (
87
Sr/
86
Sr
initial
= 0.7086,
ε
Nd336
= −5.5 to −4.4 with
T
DM
= 1.5 Ga, zircon
ε
Hf336
+0.8 to −6.1; mean
T
DM
= 1.5 Ga) suggest a Mesoproterozoic continental source, albeit with some younger or more juvenile material indicated by the Hf data. The pluton is the easternmost member of a Carboniferous A-type magmatic suite which shows an increase in juvenile input toward the west in this part of the pre-Andean margin. The petrological and geochemical data strongly suggest a similar intraplate geodynamic setting to that of the nearby but much larger, Late Devonian, Achala batholith, although Hf isotope signatures of zircon suggest a more uniformly crustal origin for the latter. Further studies are required to understand whether these bodies represent two independent magmatic episodes or more continuous activity.