Catastrophic slab loss in southwestern Pangea preserved in the mantle and igneous record

Abstract

The Choiyoi Magmatic Province represents a major episode of silicic magmatism in southwestern Pangea in the mid-Permian-Triassic, the origin of which remains intensely debated. Here, we integrate plate-kinematic reconstructions and the lower mantle slab record beneath southwestern Pangea that provide clues on late Paleozoic-Mesozoic subducting slab configurations. Also, we compile geochronological information and analyze geochemical data using tectono-magmatic discrimination diagrams. We demonstrate that this magmatic event resulted from a large-scale slab loss. This is supported by a paleogeographic coincidence between a reconstructed 2,800-3,000-km-wide slab gap and the Choiyoi Magmatic Province and geochemical data indicating a slab break-off fingerprint in the latter. The slab break-off event is compatible with Permian paleogeographic modifications in southwestern Pangea. These findings render the Choiyoi Magmatic Province the oldest example of a geophysically constrained slab loss event and open new avenues to assess the geodynamic setting of silicic large igneous provinces back to the late Paleozoic.

Palaeozoic – Early Mesozoic geological history of the Antarctic Peninsula and correlations with Patagonia: Kinematic reconstructions of the proto-Pacific margin of Gondwana

“…However, accurate correlations between Permian volcanic deposits, magmatic centres and emplacement mechanisms are lacking across large parts of the West Pangean/Gondwana proto-Pacific margin, particularly the Antarctic Peninsula. Castillo et al (2017) dated magmatism at ~255 Ma from Tierra del Fuego, which represents the southerly extent of Late Permian magmatism in South America (Gianni and Navarrete, 2022) and records a significant crustal component relative to magmatism further north. This episode of magmatism from Tierra del Fuego overlaps with the granitoid gneisses dated from eastern Graham Land and northwest Palmer Land (Millar et al, 2002;Riley et al, 2012;Castillo et al, 2020), andCastillo et al (2017) suggested a close link between southern Patagonia and the Antarctic Peninsula during the Late Permian (Fig.…”

“…Primary volcanic successions crop out in central Patagonia (e.g. Gianni and Navarrete, 2022;Falco et al, 2022) and subvolcanic equivalents are preserved across large parts of Patagonia, into Tierra del Fuego and sectors of the Antarctic Peninsula (eastern Graham Land and western Palmer Land; Fig. 11).…”

“…extension in La Golondrina basin, Patagonia; Giacosa et al, 2012). A comprehensive analysis of Permian Choiyoi magmatism (Gianni and Navarrete, 2022) integrated plate-kinematic reconstructions and the lower mantle slab record beneath southwestern Pangea to understand Late Palaeozoic -Mesozoic subducting slab dynamics. They demonstrated that the Choiyoi magmatic event was the result of large-scale slab loss, recoded by a 2800-3000 km slab gap.…”

“…Following collision and initial compressive deformation along the Gondwanide Fold Belt, Early Permian slab break off resulted in significant granitoid magmatism and post-tectonic ignimbrite complexes. An interrupted, slab loss model (Gianni and Navarrete, 2022) may have been triggered by continental terrane collisions during the assembly of Patagonia (e.g. Pankhurst et al, 2006) and the accretion of buoyant oceanic highs, which would have lead to the large-scale destruction of the subducting slabs.…”

“…However, prior to Gondwana breakup, the pre-Jurassic geological and tectonic evolution of this margin is poorly constrained as a consequence of restricted geochronology, sparse exposure of some units and difficulties in correlating widely dispersed successions across West Antarctica and Patagonia (Hervé et al, 2006a). Nelson and Cottle (2017) suggested that the paleo-Pacific margin of Gondwana was a relatively continuous active convergent margin from at least the Ediacaran through to the Cenozoic, whilst Gianni and Navarrete (2022) have demonstrated an interrupted subduction model through the Late Palaeozoic.…”