Structure of the crust and upper mantle beneath the Bransfield Strait (Antarctica) using P receiver functions

• Published in: Tectonophysics Vol. 802; p. 228744
• Main Authors: Parera-Portell, Joan Antoni, Mancilla, Flor de Lis, Morales, José, Almendros, Javier, Jiménez-Morales, Vanessa
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 05-03-2021; Elsevier BV
• Subjects: Antarctic Peninsula; Archipelagoes; Bransfield Strait; Continental crust; Crustal and lithospheric structure; Crustal thickness; Lava; Moho; P waves; Receiver functions; Spatial variability; Spatial variations; Thickness; Transition zone; Upper mantle; Volcanic activity; Volcanism; Bransfield Strait; Receiver functions; Antarctic Peninsula; Bransfield Strait; Crustal and lithospheric structure
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2021.228744

The Bransfield Strait is a tectonically active back-arc rift basin located between the South Shetland archipelago (SSI) and the Antarctic Peninsula (AP). We use teleseismic P-wave receiver functions from twelve seismic stations in order to improve the current understanding of the crustal and upper mantle structure of the region. We calculate the thickness and average Vp/Vs ratio of the crust, the thickness of the Mantle Transition Zone (MTZ) and their spatial variability along the study area. Our analysis reveals a homogeneous crustal thickness in the AP, averaging 33.5 ± 1.2 km. The VP/VS ratio increases from east to west, with an average of 1.78 ± 0.04 typical of continental crust. In the SSI results are highly heterogeneous. The minimum crustal thickness is observed in Deception Island (~15 km), near the rift axis, while the crust thickens towards the edges of the basin to ~30 km. High crustal VP/VS ratios (>1.95) in the archipelago correlate with a shallow Moho and may be linked to the presence of melts in the crust, in accordance with the active volcanism in the region. We detected an underplating layer and the Moho of the Phoenix slab beneath the SSI. There is evidence of a low velocity zone (LVZ) in the mantle wedge under the SSI and also under the AP, suggesting there is widespread partial melting of the upper mantle. We infer that the Phoenix slab dips steeply, as we observe a thickened MTZ under the AP.
•The South Shetland Islands feature large heterogeneity regarding crustal thickness and Vp/Vs.•An underplating layer is found below the South Shetland Islands.•Low velocity bodies in the upper mantle may indicate widespread partial melting.•The Phoenix slab affects the Mantle Transition Zone below the Antarctic Peninsula.