Stages of Late Palaeozoic deformation and intrusive activity in the western part of the North Patagonian Massif (southern Argentina) and their geotectonic implications

Abstract

Analyses of structures in the western part of the North Patagonian Massif (southern Argentina) suggest a polyphase evolution, accompanied by continuous intrusive activity. The first two deformations (D 1 , D 2 ) and metamorphism affected the upper Palaeozoic, partly possibly older Cushamen Formation clastic succession and different intrusive rocks. A second group of intrusions, emplaced after the second deformational episode (D 2 ), in many places contain angular xenoliths of the foliated country rocks, indicating high intrusive levels with brittle fracturing of the crust. Deformation of these magmatic rocks presumably began during (the final stage of) cooling and continued under solidstate conditions. It probably coincided with the third deformational event (D 3 ) in the country rocks. Based on published U-Pb zircon ages of deformed granitoids, the D 2 -deformation and younger event along with the regional metamorphism are likely to be Permian in age. An onset of the deformational and magmatic history during Carboniferous times, however, cannot be excluded. The estimated ∼ W-E to NE-SW compression during the D 2 -deformation, also affecting the first group of intrusive rocks, can be related to subduction beneath the western Patagonia margin or an advanced stage of collisional tectonics within extra-Andean Patagonia. The younger ∼ N-S to NE-SW compression might have been an effect of oblique subduction in the west and/or continuing collision-related deformation. As a cause for its deviating orientation, younger block rotations during strike-slip faulting cannot be excluded. The previous D 2 -event presumably also had an effect on compression at the northern Patagonia margin that was interpreted as result of Patagonia's late Palaeozoic collision with the southwestern Gondwana margin. With the recently proposed Carboniferous subduction and collision south of the North Patagonian Massif, the entire scenario might suggest that Patagonia consists of two different pieces that were amalgamated with southwestern Gondwana during Late Palaeozoic times.

The Late Paleozoic Tectonometamorphic Evolution of Patagonia Revisited: Insights From the Pressure‐Temperature‐Deformation‐Time (P‐T‐D‐t) Path of the Gondwanide Basement of the North Patagonian Cordillera (Argentina)

“…On the other hand, EPMA Th‐U‐Pb monazite ages of circa 300 Ma (section ) constrain the timing of deformation and metamorphism linked to the development of ubiquitous NNW‐SSE to WNW‐ESE striking S 2 and associated L 2 and F 2 fabrics (section ). Comparable NW‐SE to NNW‐SSE striking fabrics were also reported for medium‐grade basement rocks of the western North Patagonian Massif, where foliated late Carboniferous intrusions occur as well (Cerredo & López de Luchi, ; García‐Sansegundo et al, ; Giacosa et al, ; Pankhurst et al, ; Renda et al, ; von Gosen, ). Furthermore, metasedimentary rocks recording Upper Devonian‐Carboniferous low‐grade metamorphism of the Northern and Southern Neuquén Precordillera (Figure ) also exhibit NW‐SE to NNW‐SSE striking foliations (Franzese, , ; Zappettini et al, ).…”

“…Deformation and metamorphism of basement rocks of the North Patagonian Cordillera and the western North Patagonian Massif have been interpreted as the result of Late Paleozoic compression/transpression during the Gondwanide orogeny (García‐Sansegundo et al, ; Giacosa et al, ; von Gosen, ). Within this framework, rocks of the study area were assigned to a hinterland position (García‐Sansegundo et al, ).…”

“…In the particular case of northwestern Patagonia (Argentina), most contributions focused on the Late Paleozoic magmatism (Castillo et al, ; Cerredo & López de Luchi, ; Pankhurst et al, ; Urraza et al, ; Varela et al, , ), whereas constraints on the timing and characteristics of contemporaneous deformation and metamorphism are scarce (Figure ; Giacosa et al, ; von Gosen & Loske, ; García‐Sansegundo et al, ; von Gosen, ; Martínez et al, ; Urraza et al, ). In addition, no clear correlations have been so far established between the igneous‐metamorphic basement of the North Patagonian Cordillera/massif and accretionary complexes exposed further west in Chile in terms of their structural and metamorphic evolution, though the latter record coeval Late Paleozoic sedimentation and subsequent deformation and metamorphism (Hervé et al, ; Kato et al, ; Martin et al, ; Willner et al, ).…”

The Grenville-age basement of the Andes

“…This terrane detached during the Rodinia break-up, was later on accreted to the Gondwana margin during Neoproterozoic times. Patagonia underwent early Paleozoic rifting and was finally re-accreted to Gondwana during Permian times (see Ramos, 2008b;von Gosen, 2009, for details).…”

Isotopic studies on detrital zircons of Silurian–Devonian siliciclastic sequences from Argentinean North Patagonia and Sierra de la Ventana regions: comparative provenance

“…However, authors such as Rossello et al (1997) and more recently von Gosen (2002Gosen ( , 2003Gosen ( , 2009) and Gregori et al (2008) developed integrated tectonostratigraphic evolution.…”