Fault controlled Carboniferous A-type magmatism in the proto-Andean foreland (Sierras Pampeanas, Argentina): Geochemical constraints and petrogenesis

Extensional Carboniferous magmatism at the western margin of Gondwana: Las Lozas valley, Catamarca, Argentina

“…(Pearce, 1983), of the studied volcanic rocks of Las Lozas section: A. samples <49,9% SiO 2 ; B. samples >69% SiO 2 ; C. samples 63,5%-65,5% SiO 2 . Gray shaded areas correspond to Ordovician volcanic rocks of Famatina reported by Cisterna et al (2010) and to Carboniferous E Sierras Pampeanas granites (Grosse et al, 2009;Dahlquist et al, 2010) . comparable to patterns shown by transitional MORB basalts and within-plate tholeiites from attenuated continental terranes (Pearce, 1996), including contribution of a mantle source affected by crustal contamination during the genesis of magmas. In the case of Ordovician basalts the Nb and Ta depletion relative to Th and Ce is marked giving indication of a subduction component (Fig.…”

“…These features are (Winchester and Floyd, 1977). The boundary between alkaline and subalkaline series (dashed line in a) is after Irvine and Baragar (1971 Cisterna et al (2010) and to Carboniferous E Sierras Pampeanas granites (Grosse et al, 2009;Dahlquist et al, 2010). (Pearce, 1983), of the studied volcanic rocks of Las Lozas section: A. samples <49,9% SiO 2 ; B. samples >69% SiO 2 ; C. samples 63,5%-65,5% SiO 2 .…”

“…The two rhyolite samples from Cazadero Grande presented by Martina et al (2011), as the Carboniferous Eastern Sierras Pampeanas granites show geochemical affinities with Las Lozas rhyolites in the Y versus Nb and Y+Nb versus Rb tectonic discrimination diagrams (Pearce et al, 1984) plotting in the within plate granites field (Fig. 9) Pankhurst et al (1998), Dahlquist and Galindo (2004), Dahlquist et al (2010), Martina et al (2011 (Dahlquist et al,2010). The last two magma types were probably extracted from a strongly enriched reservoir with negligible mantle contributions.…”

“…The Las Lozas rocks, previously mapped as Ordovician and considered to be part of the Famatinian magmatic system (Turner, 1967;Mpodozis et al, 1997;Rubiolo et al, 2001;Coira et al, 2005), were recently assigned by Cisterna et al (2013) and Zappettini et al (2015) to the Lower Pennsylvanian based on a zircon U-Pb SHRIMP age (320±2 Ma). Both, lower Pennsylvanian and Mississippian successions are new records of the Carboniferous magmatism in the region, locate west of the small and scattered A-type granites distributed along more than 1,000 km in the Sierras Pampeanas (Dahlquist et al, 2010). The geodynamic setting of the Carboniferous magmatism in the region remains controversial.…”

“…It has been considered product of crustal reheating during final phase of Famatinian orogeny (e.g., Grissom et al, 1998;Llambias et al, 1998;Höckenreiner et al, 2003;Grosse et al, 2009) or part of the Achalian orogen (e.g., Sims et al,1998;Siesgesmund et al, 2004;Dahlquist et al, 2006. Meanwhile Dahlquist et al, 2010 proposed that those Carboniferous granites represent a new tectonothermal event, considering their field and geochemical characteristics, indicative of an extensional within-plate setting and noncompressive tectonic regime and not syn-kinematic emplacement as has been invoked for Devonian granite of Sierras de Cordoba or San Luis (Sims et al,1998;Siesgesmund et al, 2004).…”