Ghost-arc geochemical anomaly at a spreading ridge caused by supersized flat subduction

• Published in: Nature Communications
• Main Authors: Gianni, Guido M., Likerman, Jeremías, Navarrete Granzotto, César Rodrigo, Gianni, Conrado R., Zlotnik, Sergio
• Other Authors: Universitat Politècnica de Catalunya. Departament d'Enginyeria Civil i Ambiental, Universitat Politècnica de Catalunya. LACÀN - Mètodes Numèrics en Ciències Aplicades i Enginyeria
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Àrees temàtiques de la UPC::Matemàtiques i estadística::Anàlisi numèrica; Àrees temàtiques de la UPC::Matemàtiques i estadística::Matemàtica aplicada a les ciències; Numerical analysis > Simulation methods; Strength of materials; Geophysics; Anàlisi numèrica; Resistència de materials; Geofísica; Classificació AMS::65 Numerical analysis::65C Probabilistic methods; simulation and stochastic differential equations; Classificació AMS::74 Mechanics of deformable solids::74S Numerical methods; Classificació AMS::86 Geophysics; Antarc*; Antarctic; Antarctic Peninsula
• Online Access: http://hdl.handle.net/2117/387320; https://doi.org/10.1038/s41467-023-37799-w

The Southern Atlantic-Southwest Indian ridges (SASWIR) host mid-ocean ridge basalts with a residual subduction-related geochemical fingerprint (i.e., a ghost-arc signature) of unclear origin. Here, we show through an analysis of plate kinematic reconstructions and seismic tomography models that the SASWIR subduction-modified mantle source formed in the Jurassic close to the Georgia Islands slab (GI) and remained near-stationary in the mantle reference frame. In this analysis, the GI lies far inboard the Jurassic Patagonian-Antarctic Peninsula active margin. This was formerly attributed to a large-scale flat subduction event in the Late Triassic-Early Jurassic. We propose that during this flat slab stage, the subduction-modified mantle areas beneath the Mesozoic active margin and surrounding sutures zones may have been bulldozed inland by >2280 km. After the demise of the flat slab, this mantle anomaly remained near-stationary and was sampled by the Karoo mantle plume 183 Million years (Myr) ago and again since 55 Myr ago by the SASWIR. We refer to this process as asthenospheric anomaly telescoping. This study provides a hitherto unrecognized geodynamic effect of flat subduction, the viability of which we support through numerical modeling. G. M. G. and C. R. N. recognize the support given by CONICET and the funding given by the Universidad Nacional de la Patagonia San Juan Bosco (Grant number: CIUNPAT no. 1399). S. Z. and J. L. acknowledge the funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 777778. S.Z. acknowledges the funding of Project PID2020-113463RB-C32 funded by MCIN/AEI /10.13039/501100011033 and the funding of Generalitat de Catalunya via the 2021 SGR 01049. Peer Reviewed Postprint (published version)