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

Abstract

Central Patagonia is traversed by a belt of Early to Middle Jurassic calc-alkaline intermediate volcanic rocks interspersed with more felsic volcanic rocks which are associated with the widespread magmatism that took place during Gondwana break-up times. This work uses K-Ar and Ar-Ar dating and whole-rock and phenocryst (plagioclase, amphibole, clinopyroxene and titanomagnetite) compositional data to refine the age, geochemical signature and reservoir conditions of these volcanic rocks, which are known as Lonco Trapial Formation. The andesites, dacites and trachydacites which were the object of this study have either amphibole or clinopyroxene as the main

Sedimentological and petrographic evolution of a fluvio‐lacustrine environment during the onset of volcanism: Volcanically‐induced forcing of sedimentation and environmental responses

“…The Lonco Trapial Formation is part of a north–south belt in Central Patagonia formed by calc‐alkaline intermediate volcanic rocks interspersed with more felsic volcanics. The Lonco Trapial lavas were considered the more mafic counterparts of the predominantly rhyolitic Chon Aike Volcanic Province (Gust et al ., ; Zaffarana et al ., , and references therein). This volcanism was in a back‐arc position with respect to the activity of a western Early Jurassic magmatic arc known as the Subcordilleran Plutonic Belt (Page & Page, ; Rapela et al ., ; Zaffarana et al ., , and references therein).…”

“…() have bracketed the Lonco Trapial Formation between 188·95 Ma and 178·77 Ma in the Valle Medio of the Chubut river, entirely within the Early Jurassic (Pliensbachian ± Toarcian) in agreement with the 185 Ma age obtained by Zaffarana & Somoza (). These ages are typical of the V1 volcanic event that took place between 188 to 178 Ma (Féraud et al ., ; Pankhurst et al ., ; Zaffarana et al ., ), in the large, siliceous, igneous province known as the Chon Aike Volcanic Province, one of the largest rhyolitic provinces in the world, which also extends to the Antarctic Peninsula (Pankhurst et al ., , ; Riley et al ., ). The V1 volcanic event is broadly contemporaneous to the peak of Early Jurassic voluminous basaltic magmatism of the Karoo‐Ferrar province in South Africa and Antarctica (Pankhurst et al ., ).…”

“…The Early Jurassic volcanic rocks of the Lonco Trapial Formation erupted coevally with widespread extension during the early stages of Gondwana break‐up. An extensional affinity is determined for this palaeo‐volcanic belt, formed above a Moho depth ≥35 km (Zaffarana et al ., ). Traditionally assigned to the Middle Jurassic sensu lato (e.g.…”

“…The Lonco Trapial lavas were considered the more mafic counterparts of the predominantly rhyolitic Chon Aike Volcanic Province (Gust et al ., ; Zaffarana et al ., , and references therein). This volcanism was in a back‐arc position with respect to the activity of a western Early Jurassic magmatic arc known as the Subcordilleran Plutonic Belt (Page & Page, ; Rapela et al ., ; Zaffarana et al ., , and references therein). The Early Jurassic volcanic rocks of the Lonco Trapial Formation erupted coevally with widespread extension during the early stages of Gondwana break‐up.…”

Sandstone petrography and provenance of the Chubut Group (Cretaceous) in the Cañadón Matasiete (Golfo San Jorge Basin, central Patagonia): Implications for basin evolution and alluvial organization

“…Several volcanic-volcaniclastic units included within the Lonco Trapial Formation (Lesta and Ferello, 1972) and, to a lesser extent, the Las Leoneras Formation (Nakayama, 1973;Figari, 2005) constitute the volcanic basement of the Cañadón Asfalto basin. Basic and intermediate rocks of the Lonco Trapial Formation are the substrate of Cretaceous successions northward of the study area (Anselmi et al, 2004a,b;Silva Nieto et al, 2002;Silva Nieto, 2005), and are the most probable source of the basic-intermediate components in the detrital fraction of the study succession (Zaffarana et al, 2018). The sedimentary components, although very subordinate, can be derived from the Middle-Upper Jurassic Cañadón Asfalto and Cañadón Calcáreo formations (Stipanicic et al, 1968;Proserpio, 1987;Cúneo et al, 2013;Figari et al, 2015).…”