Basement-involved deformation overprinting thin-skinned deformation in the Pampean flat-slab segment of the southern Central Andes, Argentina

Abstract

-In the southern Central Andes, the Andean foreland was deformed due to Neogene shallowing of the Nazca slab beneath the South America plate. In this 27-33º S Pampean flat-slab segment, the N-trending Argentine Precordillera transpressional fold-and-thrust belt and the Sierras Pampeanas broken foreland developed as a consequence of inward migration of the orogenic front. At 28º S, a NNE-trending westward-dipping, thick Neogene synorogenic sequence is exposed in the Sierra de los Colorados, which shares deformation features of the Precordillera and the Sierras Pampeanas. Integration of new structural and kinematic data and available structural, kinematic, geophysical and palaeomagnetic information allows consideration of the Sierra de los Colorados area as part of the northern sector of the Precordillera during the middle Neogene. At c. 9 Ma, basement block exhumation started with the uplift of the Sierra de Umango-Espinal that was triggered by deformation along the NE-trending Tucumán oblique belt. This stage marked the beginning of compartmentalization of the incipiently deformed Vinchina foreland. Since c. 6.8-6.1 Ma, basement block uplift linked to the Miranda-Chepes and Valle Fértil NNW-trending sinistral transpressional belts, as well as kinking of the Neogene sequence by localized WNW-striking cross-strike structures, resulted in multiple segmentation that produced a complex mosaic of basement-block pieces. The overprint of these regional, basement-involved, oblique, brittle-ductile transpressional and cross-strike megazones could be related to high interplate coupling. Localized mechanical and rheological changes introduced by magmatism favoured this thick-skinned deformation overprint.

Cenozoic Shift From Compression to Strike‐Slip Stress Regime in the High Andes at 30°S, During the Shallowing of the Slab: Implications for the El Indio/Tambo Mineral District

“…Tectonics 10.1002/2017TC004608 Fosdick et al, 2015;Japas et al, 2016;Levina et al, 2014;Mardonez et al, 2015;Suriano et al, 2017), and few studies describe structures other than those accommodating Miocene-Holocene contraction along the arc and backarc regions. In yet another interpretation, Charchaflié et al (2007) describe normal faults in the northern sector of the belt, in the Veladero area (29.3°S), generated during the 15 to 10 Ma period, apparently controlling the emplacement of ore deposits.…”

“…On the other hand, Bissig et al () argue that gold deposition occurred several million years after this shortening phase. Indeed, by the time of ore deposition in the metallogenic belt, crustal shortening was focused eastward, in the Argentine Precordillera fold‐and‐thrust belt (Allmendinger & Judge, ; Fosdick et al, ; Japas et al, ; Levina et al, ; Mardonez et al, ; Suriano et al, ), and few studies describe structures other than those accommodating Miocene‐Holocene contraction along the arc and backarc regions. In yet another interpretation, Charchaflié et al () describe normal faults in the northern sector of the belt, in the Veladero area (29.3°S), generated during the 15 to 10 Ma period, apparently controlling the emplacement of ore deposits.…”

Late Quaternary Intraplate Deformation Defined by the Las Chacras Fault Zone, West‐Central Argentina

“…The fault-bounded mountain range is composed of a Proterozoic igneous and metamorphic basement complex overlain by Triassic sedimentary rocks (Figures 3 and 6). The seismically active Valle Fértil Fault has accommodated backarc contractional deformation since the Miocene (Brooks et al, 2003;Fosdick et al, 2015;Ortiz et al, 2015;Japas et al, 2016). This structure also delimits the Famatinian suture (Ramos et al, 1996), which exhibits ductile deformation and accommodation of extensional deformation during Triassic and Cretaceous times (Jordan & Allmendinger, 1986;Ramos, 1994;Rossello & Mozetic, 1999;Uliana et al, 1989).…”

Alluvial to lacustrine sedimentation in an endorheic basin during the Mio-Pliocene: The Toro Negro Formation, Central Andes of Argentina

“…1). This segment is characterized by low-angle subduction of the Nazca Plate (Ramos et al, 2002) that converges at an oblique angle with respect to the South American Plate, producing a complex deformation pattern including some degree of strike-slip movement (Rossello et al, 1996;Introcaso and Ruiz, 2001;Japas et al, 2016). In this area several foreland basins were formed during the Cenozoic including the Vinchina Basin (28° and 29° S).…”