Alboran volcanic province

Alboran volcanic province
Name	Alboran volcanic province
Location	Alboran Sea, western Mediterranean
Coordinates	36°N 3°W
Type	Submarine volcanic province
Last eruption	Holocene? (disputed)
Age	Neogene–Quaternary
Magma type	Alkaline to calc-alkaline mafic to intermediate

Alboran volcanic province is a submarine and insular cluster of volcanic centers located in the Alboran Sea between the Iberian Peninsula and the Rif Mountains of Morocco. The province sits within a complex plate boundary zone influenced by the interaction of the Eurasian Plate, the African Plate, and microplates such as the Alboran Block, and contains seamounts, volcanic islands, lava flows, and intrusive complexes whose petrology ranges from basalts to andesites. Regional significance derives from links to Mediterranean Neogene tectonics, the Western Mediterranean basin evolution, and contemporary seismicity.

Geography and setting

The province occupies the westernmost part of the Mediterranean Sea and lies south of Spain (including the autonomous communities of Andalusia and the province of Málaga) and north of Morocco (including the Rif region and provinces such as Al Hoceima Province), with proximity to the Strait of Gibraltar and islands including Alborán Island and Islas Alhucemas. Bathymetric surveys reveal submarine plateaus, ridges, and seamounts such as the Emile Baudot Seamount and the Gulf of Vélez knolls; these features are mapped in relation to coastal cities like Almería and Melilla and maritime corridors used by shipping between the Atlantic Ocean and the Mediterranean Sea via the Strait of Gibraltar. The province is bounded by structural domains including the Betic Cordillera, the Rifian Cordillera, and the Alboran Basin.

Geological background and tectonics

The province developed during the late Neogene to Quaternary as part of the complex convergence between the Eurasian Plate and the African Plate, with involvement of the Alboran microplate and slab dynamics tied to the closure of the Tethys Ocean and the opening of the Alpine orogeny system. Subduction rollback, lithospheric delamination, and mantle upwelling processes have been invoked in studies comparing the region to analogues like the Tyrrhenian Sea and the Aegean Sea. Regional structures include thrusts and nappes correlated to the Betic-Rif arc and strike-slip systems such as the Azores–Gibraltar Fault Zone, while GPS geodesy and seismic tomography link neotectonic deformation to mantle anomalies beneath the western Mediterranean.

Volcanic features and petrology

The province hosts both submarine cones and emergent centers including Alborán Island, where lavas exhibit a range from alkaline basalts to calc-alkaline andesites and basaltic andesites, with mineral assemblages of olivine, clinopyroxene, amphibole, and plagioclase. Petrological studies compare magmas to those in the Iberian Peninsula volcanic provinces and to back-arc settings such as the Tyrrhenian Sea; geochemical signatures show enrichment in incompatible elements and variable isotopic ratios (Sr–Nd–Pb) consistent with partial melting of an asthenospheric source modified by lithospheric components and recycled crustal material from the Tethyan realm. Intrusive bodies include gabbros and tonalites exposed on islands and in dredged cores, and polymagmatic volcanism is comparable to occurrences in the Canary Islands and the Vulcano area.

Eruption history and chronology

Radiometric dating (K–Ar, Ar–Ar, and U–Th methods) places most volcanism in the late Miocene to Pleistocene, with some evidence for Holocene activity debated in relation to tephra layers and submarine hydrothermal deposits. Stratigraphic correlations use regional marine terraces and sedimentary sequences from cores taken during expeditions by research vessels such as RRS Charles Darwin and RV Pourquoi Pas?; tephrochronology has tied eruptive pulses to Mediterranean events including sapropel formation and Pleistocene sea-level fluctuations. Historical records from ports like Almería and Málaga contain references that some researchers have tentatively linked to local volcanic unrest, but definitive historical eruptions remain unconfirmed.

Geophysical and geochemical studies

Multibeam bathymetry, side-scan sonar, and seismic reflection profiles from programs run by institutions including the Instituto Español de Oceanografía, the CNRS, and the National Oceanography Centre (UK) have imaged volcanic edifices, flow morphologies, and intrusive bodies. Seismic tomography studies by groups at ETH Zurich and University of Barcelona reveal low-velocity anomalies in the upper mantle beneath the Alboran region; gravity and magnetic surveys outline crustal heterogeneities and magmatic intrusions. Geochemical campaigns involving isotope systems (Sr–Nd–Pb–Hf) and volatile analyses (H2O–CO2–S) link magmatism to slab-derived fluids and mantle metasomatism, while hydrothermal studies detect metal-rich deposits analogous to those observed at volcanic arcs such as the Izu–Bonin arc.

Environmental impacts and hazards

Volcanism in the province poses submarine hazards including seafloor instability, submarine landslides, and localized gas release that can affect fishing grounds off Almería and Málaga coasts; tsunamigenic potential has been modeled in scenarios involving flank collapse similar to documented events near Capo Vaticano and Montserrat. Hydrothermal venting influences marine ecosystems and carbonate precipitation, with biological communities comparable to vents investigated near the Mid-Atlantic Ridge and the Mediterranean Ridge. Coastal communities and ports such as Motril, Algeciras, and Melilla consider monitoring of seismicity and submarine volcanic hazards within regional civil protection frameworks.

Research history and exploration

Early geological interest by explorers and geologists from institutions including the Comisión Oceanográfica Española and expeditions aboard ships like the HMS Challenger precursor surveys led to systematic studies in the 20th century, while late-20th and 21st-century work has involved multidisciplinary teams from CSIC, University of Granada, Universitat de Barcelona, and international collaborations with the European Union research programs. Key milestones include bathymetric mapping campaigns, dredging and drilling during programs by the IODP and related marine geology projects, and the integration of geochronology and geophysics by research groups at GEOMAR and the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER). Contemporary priorities focus on high-resolution imaging, mantle tomography, and monitoring of potential unrest using seafloor observatories and autonomous vehicles operated by centers such as MBARI and the Ifremer fleet.

Category:Volcanic provinces Category:Geology of the Mediterranean Sea