The Evolution of Central Volcanoes in Ultraslow Rift Systems: Constraints From D. João de Castro Seamount, Azores

Abstract

Volcanic activity along diverging plate boundaries in oceanic and continental settings commonly is the result of interacting magmatic and tectonic processes. Magmatism at oceanic and continental rift systems and mid-ocean ridges (MOR) plays a significant role in global plate tectonics, for example, leading to continental breakup and new oceanic crust formation (Heezen, 1960;Wilson, 1968). MORs as well as oceanic and continental rifts erupt a variety of chemically distinct lavas and have different morphological appearances depending among other processes on the extension rate. Fast-spreading MORs, for example, the East Pacific Rise (EPR), have continuous volcanically active segments and erupt large volumes of melt from the depleted

The submarine Azores Plateau: Evidence for a waning mantle plume?

“…1). Expedition M79/2 focussed on the region around São Miguel island, M113/1 performed multibeam mapping and seismic surveys along the Terceira Rift axis from the Hirondelle Basin to west of Graciosa with several seismic lines crossing Dom João de Castro Seamount (Romer et al, 2021), along the eastern and western (Beier et al, 2019;Romer et al, 2018) margins of Princesa Alice Bank, in the vicinity of the East Azores Fracture Zone and towards Santa Maria island (Hübscher et al, 2016). A bathymetric transect from SW of São Miguel towards the East Azores Fracture Zone allowed us to eliminate a strong bathymetric artefact in the ETOPO dataset starting in Ponta Delgada and heading southwest towards South America (Fig.…”

“…The data processing of the bathymetric and seismic data obtained during R/V Meteor cruises M79/2, M113/1 and M128 followed techniques previously described for subregions of the entire dataset (Beier et al, 2018a;Hübscher, 2012;Hübscher et al, 2016;Hübscher and Gohl, 2014;Romer et al, 2021;Romer et al, 2018;Romer et al, 2019;Weiß et al, 2015;Weiß et al, 2016). Onboard, the bathymetry data were gridded to 20 m resolution using MB-system software, the seismic data were processed using frequency filtering (15-350 Hz), gain and velocity analysis (every 50 CMPs), NMO-correction, coherency filtering, stacking, time-migration, bandpass filtering, white noise removal, dip filtering, and fx-deconvolution following methods described in detail in (Hübscher and Gohl, 2014).…”

“…Seven volcanic islands are situated east of the MAR, six of which show recent volcanic activity, whereas the easternmost island of Santa Maria and the submarine Formigas Bank were active between 5.5 and 1.0 Ma (Abdel Monem et al, 1975;Sibrant et al, 2016). Three islands (São Miguel, Terceira, Graciosa) and one seamount (Dom João de Castro) are situated along the slow-spreading Terceira Rift axis in the northern part of the Azores Plateau (Beier et al, 2008;Fernandes et al, 2018;Romer et al, 2021;Vogt and Jung, 2018;Vogt and Jung, 2004).…”

“…The geological and geodynamic evolution of the Azores has been subject of numerous geological, geochemical, and geophysical works (Abdel Monem et al, 1975;Beier et al, 2006;Beier et al, 2012;Beier et al, 2010;Bourdon et al, 2005;Cannat et al, 1999;Davies et al, 1989;Elliott et al, 2007;Féraud et al, 1980;França, 2006;França et al, 2006;Genske et al, 2013;Genske et al, 2012;Gente et al, 2003;Haase and Beier, 2003;Hildenbrand et al, 2008;Kueppers and Beier, 2018;Larrea et al, 2013;Larrea et al, 2014;Luis and Miranda, 2008;Luis et al, 1998;Luis et al, 1994;Madureira et al, 2011;Madureira et al, 2005;Marques et al, 2021;Marques et al, 2013;Metrich et al, 2014;Millet et al, 2009;Miranda et al, 1998;Prytulak et al, 2014;Romer et al, 2021;Schaefer et al, 2002;Sibrant et al, 2016;Soderman et al, 2021;Weiß et al, 2015;Weiß et al, 2016). None of the suggested models of plateau formation and evolution however fully addresses the conundrum that active, historic volcanism occurs both east and west of the MAR, and that the bathymetric anomaly appears to be asymmetric, covering a much larger area in the east than in the west (Fig.…”

“…1). Only few studies have addressed the temporal and spatial evolution of larger areas or the entire Azores Plateau including its submarine and subaerial edifices (Beier et al, 2015;Cannat et al, 1999;Gente et al, 2003;Marques et al, 2013;Romer et al, 2021;Romer et al, 2018;Romer et al, 2019;Storch et al, 2020).…”