First geochemical and geochronological characterization of Late Cretaceous mesosilicic magmatism in Gastre, Northern Patagonia, and its tectonic relation to other coeval volcanic rocks in the region

Abstract

This work characterizes Late Cretaceous calc-alkaline volcanic rocks in Gastre, Northern Patagonia, Argentina. These newly found porphyritic rocks bear an 40Ar–39Ar amphibole age of ~ 74–76 Ma, a subduction-type geochemical signature and a deep, garnet-bearing source. Extruded in a stage of low magmatic activity in the Northern Patagonian Andes (~ 41–44° S), they could represent an eastward migration of the Late Cretaceous magmatic arc that was associated with a regional compressive deformational stage in the South American margin.

Geochemical signature and reservoir conditions of Early Jurassic calc-alkaline volcanic rocks from Lonco Trapial Formation, Central Patagonia

“…11c-d). The greater depth found today would have been reached by thermal subsidence after the rifting period (by deposition of younger material in the Gastre basin, see for example Bilmes et al 2013) and during Mid-Cretaceous upper plate contraction (Zaffarana et al 2018;Echaurren et al, 2016;.…”

Paleomagnetic evidence of the brittle deformation of the Central Patagonian Batholith at Gastre area (Chubut Province, Argentina)

“…Nevertheless, this cannot be possible because it strongly contradicts the paleogeographic configuration of southwestern Gondwana during the Late Triassic (Hervé et al, 2008;Suárez et al, 2019;Vizán et al, 2017). Then, a tectonic event could have affected the batholith and produce the tilting of the block, during the Jurassic extensional period (Figari, 2005) and, or, during a compressional stage, during the Late Cretaceous or later, related to the Andean Orogeny (Bilmes et al, 2013(Bilmes et al, , 2014Savignano et al, 2016;Zaffarana et al, 2018b). The main fractures in the Gastre area show a NW-SE direction and could have been originated during the formation of the Cañadón Asfalto Basin (Figari, 2005), where they acted as normal faults (part of half grabens), probably developed aided by the previous Paleozoic structures (Renda et al, 2019).…”

The late Eocene–early Miocene El Maitén Belt evolution: Magmatic response to the changing subduction zone geodynamics

“…A change to compressional tectonics occurred during the mid-Cretaceous, promoting the initial development of the North Patagonian fold-thrust belt, at the same time as the eastward expansion of the North Patagonian Batholith and calc-alkaline arc-related correlative volcanic units (Echaurren et al, 2017;Zaffarana et al, 2019). The eastward migration of the magmatic locus, together with regional correlations of crustal deformation and basin inversion processes, has been interpreted as the development of a large (~1500 km along strike) flat-slab configuration (Gianni et al, 2018).…”

“…Contrastingly, a late Cretaceous transitional arc to intraplate magmatism crops out to the south (Tres Picos Prieto Formation and equivalents) (Fig. 1), whose distinct geochemical behavior was associated with the contribution of subslab asthenospheric magmas, controlled by a slab-tearing in response to a differential steepening of the slab (Zaffarana et al, 2019).…”