Lithospheric evolution of the Pre- and Early Andean convergent margin, Chile

Gondwanan Inheritance on the Building of the Western Central Andes (Domeyko Range, Chile): Structural and Thermochronological Approach (U‐Pb and40Ar/39Ar)

“…We propose that the NS‐striking orientation of master faults was controlled by parallel‐margin weaknesses associated with the slab‐pull force of a subducting slab (Figure 9a; Royden, 1993). Triassic subduction along southwestern Gondwana has been supported by recent large geochemical studies covering the Chilean‐Argentinean Andes between 19° and 40° latitude S (Coloma et al., 2017; del Rey et al., 2016; J. González et al., 2017; Oliveros et al., 2018, 2020), showing the presence of hydrated minerals, a high large‐ion lithophile elements/high‐field‐strength elements ratio, and a negative Nb‐Ta anomaly in Triassic magmas. This hypothesis is also supported by the detrital zircon fingerprint of Triassic units of the Domeyko Basin, which depicts a very proximal provenance with a significant contribution of syndepositional volcanism, plotting in the subduction field of the tectonic discrimination diagram proposed by P. A. Cawood et al.…”

“…The mixed affinity of the Cuyo basin volcanism has been explained as crustal assimilation during an intraplate rifting unrelated to subduction (Orellano et al., 2019). Close to the trench, basaltic to silicic volcanic products from the Domeyko and La Ternera basins have clear calc‐alkaline affinities with trace element compositions typical of volcanic arcs (Oliveros et al., 2020). Thus, the geochemical signature of volcanism in these rift basins can be explained in terms of their proximity to the Triassic paleotrench, with the increasing influence of the slab fluids in the magma genesis towards the continental margin.…”

“…Farther north, alkaline to sub‐alkaline basalts and andesites from the Triassic Mitu rift in Perú has been contrastingly interpreted as (1) developed on a continental rift unrelated to subduction (Noble et al., 1978; Spikings et al., 2016), or (2) developed in a back‐arc with a hypothesized arc obliterated by Cenozoic tectonic erosion (Reitsma, 2012). A significant tectonic segmentation has been proposed to explain active subduction conditions in northern Chile and intraplate rifting in Perú during the Triassic (Oliveros et al., 2020). Nonetheless, considering the >300–500 km distance between the arc hypothesized by Reitsma (2012) and the Mitu rift basin and the mixed mantle and volcanic arc affinities observed in the Mitu rift volcanism (Orellano et al., 2019) subtle influence of slab‐derived fluids in the genesis of Mitu magmas cannot be discarded.…”

“…In the latter case, however, some key aspects of the Triassic rifting process, such as the basin architecture and kinematics, have remained poorly constrained (M. Espinoza et al., 2019). Furthermore, the overall geotectonic setting during the Triassic along Southwestern Gondwana is highly debated (e.g., Oliveros et al., 2020), directly impacting the hypothesis about the driving mechanism of the Domeyko Basin synrift phase: (1) gravitational collapse of the former Permian orogen (Franzese & Spalletti, 2001; Llambías & Sato, 1995), (2) slab collapse and delamination (Mpodozis & Kay, 1992), or (3) slab‐rollback subduction (M. Espinoza et al., 2019) have been proposed for its origin. Assessing the influence of the basin architecture on the structural style of the Domeyko Range would shed light on the origin of this range.…”

Igneous Rock Associations 25. Pre-Pliocene Andean Magmatism in Chile

“…This particular tectonic scenario is known as the 'Pre-Andean' cycle and has been traditionally interpreted as a period of arrested subduction and extensive crustal reworking and anatexis, due to basalt underplating at the base of the thinned lithosphere (Mpodozis and Kay 1992;Llambías and Sato 1995). More recently though, several authors have questioned this model in light of new geochemical, petrological, geochronological and geological data, arguing that subduction may have persisted throughout the Late Paleozoic and the Mesozoic, making southwestern Gondwana a long-lived convergent margin (del Rey et al 2016;Coloma et al 2017;González et al 2018;Oliveros et al 2020). Recent global reconstructions also support the idea of an active subduction zone for western Pangea and Gondwana since the Carboniferous (Matthews et al 2016;Riel et al 2018).…”