Peralkaline rocks in the Late Cretaceous Del Salto Pluton, Eastern Patagonian Andes, Aisén, Chile (47°35'S)

Early Cretaceous to Cenozoic Growth of the Patagonian Andes as Revealed by Low‐Temperature Thermochronology

“…Aliquot ROR5‐5 exhibited a distance >50% from the mean age and was discarded (Text S2 in Supporting Information S1). Slightly to the west, ROR1 to ROR4 yielded younger ages between 4.0 ± 0.3 Ma and 5.2 ± 1.6 Ma (Figures 2 and 3; Table 2) most of them postdating the San Lorenzo granite's crystallization age by 2 Myr (6.19 ± 0.12 Ma, 40 Ar/ 39 Ar in biotite, Welkner et al., 2002). Only aliquot ROR2‐4 was discarded from this set considering its difference from the mean age (Text S2 in Supporting Information S1).…”

“…The latter group of ages present similar ages and longitudes but highly dissimilar elevations: DES samples are between 147 and A sharp limit in cooling ages was recognized at 72.2°W, where samples LGC6 and ROR1 to ROR4 yielded ZHe ages <6 Ma (Figures 2 and 4). These samples were taken from two Miocene retroarc intrusives 60 Km apart from each other (Figure 2): LGC6 from Paso de las Llaves pluton (9 Ma, U-Pb on zircons; Sánchez, 2011), yielded a mean age of 4.6 ± 0.3 Ma, more than 5 Myr younger than its crystallization age (Figure 2; Table 2), whereas ROR1 to ROR4 were taken from the San Lorenzo granite (6.19 ± 0.12 Ma, 40 Ar/ 39 Ar in biotite, Welkner et al, 2002) and yielded mean ages between 4.0 ± 0.3 Ma and 5.2 ± 1.6 Ma (Figures 2 and 3; Table 2) most of them postdating the crystallization age by 2 Myr. The obtained ZHe ages are coherently younger than the reported crystallization ages of the sampled units.…”

High precision U/Pb zircon dating of the Chaltén Plutonic Complex (Cerro Fitz Roy, Patagonia) and its relationship to arc migration in the southernmost Andes

“…The San Lorenzo Pluton s.s. has been dated at 6.6 ± 0.5 Ma and 6.2 ± 0.1 Ma [ Welkner , 1999, Welkner et al , 2002] by K‐Ar and Ar‐Ar methods. A pluton exposed in Río de las Nieves yields a K‐Ar age of 3.2 ± 0.4 Ma [ Suárez et al , 2000].…”

“…Large scale map of Patagonia showing the location of Chaltén Plutonic Complex (CHPC) and other Miocene plutons [ Michael , 1983; Welkner , 1999; Welkner et al , 2002; Suárez et al , 2000; Suárez and De La Cruz , 2001; Michel et al , 2008; Leuthold et al , 2012], the lavas blocks from Cerro Zeballos [ Boutonnet et al , 2010], the Southern Patagonian Batholith [ Pankhurst et al , 1999, Hervé et al , 2007], the Patagonian plateau basalt [ Gorring et al , 1997], the Quaternary volcanoes [ Stern and Kilian , 1996], the front of deformation of the Patagonian Fold and Thrust Belt [ Ramos , 1989; Ramos and Kay , 1992], and the tectonic evolution of the plates [ Cande and Leslie , 1986; Breitsprecher and Thorkelson , 2009]. Ages: Paso de las Llaves at 10 Ma [ Suárez and De La Cruz , 2001] and 9.6 Ma [ Petford and Turner , 1996]; Río de las Nieves at 3.2 Ma [ Suárez et al , 2000]; San Lorenzo Pluton s.s. at 6.6 and 6.2 Ma [ Welkner , 1999; Welkner et al , 2002]; Fitz Roy at 18 Ma [ Nullo et al , 1978] and from 16.90 Ma to 16.39 Ma (this study); Torres del Paine Intrusive Complex from 12.59 Ma to 12.43 Ma [ Michel et al , 2008; Leuthold et al , 2012]; Cerro Donoso at 26 Ma [ Sánchez et al , 2008]; Balmaceda at 15.4 Ma [ Sánchez et al , 2008]. For more details on the ages see text.…”

“…However, the nature of these relatively small magmatic bodies is in general not well known. Only a few petrological, geochemical or chronological studies are available [ Michael , 1984, 1991; Vargas and Hervé , 1995; Petford and Turner , 1996; Welkner , 1999; Welkner et al , 2002; Kosmal and Spikermann , 2001, 2002; Suárez et al , 2000; Suárez and De La Cruz , 2001; Espinoza et al , 2008; Michel et al , 2008; Leuthold et al , 2012; Sánchez et al , 2009]. If the emplacement of the “Miocene back‐arc intrusion is related to the migration and subduction of the Chile ridge, magmatism should be time transgressive with successively younger intrusion ages from south to north.…”