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| Madeira hotspot | |
|---|---|
| Name | Madeira hotspot |
| Location | North Atlantic Ocean, near Madeira |
| Coordinates | 32°N 17°W (approx.) |
| Type | Mantle plume / hotspot |
| Range | Atlantic Ocean islands and seamounts |
| Last eruption | Holocene to Pleistocene (varies by edifice) |
| Age | Neogene to Quaternary |
Madeira hotspot is a proposed mantle plume responsible for Cenozoic volcanism in the northeastern Atlantic Ocean near the archipelago of Madeira Islands and associated seamounts. The feature is invoked to explain the posterior distribution of Madeira–Canaries-age volcanism, anomalous geochemical signatures, and a linear array of submarine edifices. Debate continues over plume versus plate-related origins, involving researchers from institutions such as the University of Lisbon, Geological Survey of Spain, and Woods Hole Oceanographic Institution.
The regional geology involves the interaction of the proposed hotspot with the northeastern Atlantic Ocean lithosphere, Iberia margin structures, and nearby oceanic plateaus such as the Azores Plateau. Studies reference mantle reservoir domains like DMM, EMI, and HIMU to interpret isotopic data, and invoke mechanisms including plume thermal anomalies, small-scale convection, and lithospheric drip. Seismic tomography from agencies including the Institut de Physique du Globe de Paris and ETH Zurich has imaged upper-mantle heterogeneities beneath the Madeira–Porto Santo region. Mantle source models consider contributions from recycled oceanic crust similar to signatures seen beneath Iceland, Canary Islands, and Cape Verde.
Surface volcanism produced stratovolcanoes, shield volcanoes, tuff cones, and littoral pyroclastic deposits on islands such as Madeira, Porto Santo, and submarine seamounts like the Dom João de Castro Bank analogues. Morphologies include subaerial lava fields, palagonitized hyaloclastites, and submerged guyots comparable to Seychelles plateau features. Eruptive styles range from effusive basaltic lava flows to explosive phonolitic and trachytic eruptions analogous to events documented at Gran Canaria and Teide on Tenerife. Long-lived volcanic centers produced lava tube systems and lava deltas comparable to those on Hawaii and Réunion.
The volcanic record spans Neogene to Quaternary, with oldest plateau volcanism correlated to Miocene activity and younger edifices dated to the Pleistocene–Holocene on islands like Madeira. Radiometric ages (K–Ar, Ar–Ar) from laboratories at Cambridge University, GFZ Potsdam, and USGS outline an age progression along a roughly NNE–SSW trend, though not a simple linear track like Hawaiian chains. Interpretations propose a primary pulse in the Miocene with later reactivation episodes synchronous with regional tectonic events such as the Messinian Salinity Crisis and changes in spreading at the Mid-Atlantic Ridge.
Lavas show a spectrum from tholeiitic basalts to alkaline basalts, phonolites, and trachytes. Major-element trends indicate fractional crystallization and crustal assimilation processes similar to magmas studied at Mount Etna, Mount Vesuvius, and Fogo. Isotopic ratios (Sr–Nd–Pb–Hf) have been reported by teams from University of Barcelona, Scripps Institution of Oceanography, and ETH Zurich, showing enrichment components resembling EMI and HIMU signatures found beneath Cape Verde and Canary Islands. Trace-element patterns display high incompatible-element enrichment and variable Nb–Ta–Ti anomalies, informing melting models and garnet-bearing source contributions analogous to studies of Kerguelen and Reunion.
The hotspot interacts with the passive margin of Iberia and the nearby transform and fracture zones including the Gloria Fault and the Tore-Madeira Fracture Zone. Lithospheric thickness variations across the Portuguese continental margin influence melt generation and eruption loci, with structural control by fracture zones comparable to emplacement patterns seen along the Azores Triple Junction and the Charlie-Gibbs Fracture Zone. Some tectonists argue for plume–lithosphere coupling, while others emphasize decompression melting related to small-scale mantle convection and lithospheric extension documented by the European Geosciences Union community.
Volcanism influenced regional paleogeography by building islands, altering sediment routing to basins such as the Gulf of Cádiz, and contributing volcaniclastics to stratigraphic successions examined by researchers at University of Salamanca and University of Évora. Large submarine landslides on volcanic flanks may have generated paleo-tsunamis affecting coasts documented in Mediterranean and Atlantic margin records, with possible correlations to abrupt events considered by paleoclimatologists at ETH Zurich and University of Oxford. Volcanic CO2 and SO2 emissions from eruptions could have had local to regional climate effects similar in mechanism to eruptions studied in the context of Mount Pinatubo and Laki.
Investigation history spans oceanographic cruises by vessels like RV Meteor and RRS Discovery, seismic reflection and refraction surveys by IFREMER, deep-sea drilling by ODP and IODP, and mapping with multibeam bathymetry from institutions including NOAA and CSIC. Methods include radiometric dating (K–Ar, Ar–Ar), geochemical analyses at facilities such as Lamont–Doherty Earth Observatory and Stanford University, seismic tomography, gravity and magnetic anomaly interpretation, and petrological experiments in high-pressure laboratories at Birkbeck, University of London and Universität Göttingen. Ongoing debates are informed by interdisciplinary work involving geophysicists, geochemists, and marine geologists from University of Lisbon, University of Azores, and international consortia.
Category:Geology of the Atlantic Ocean Category:Volcanism of Portugal