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In this Special Issue, we present 11 of the 15 geoparks that show key aspects of the past and current volcanic development of Europe. The sites include currently active locations along the mid-Atlantic ridge, from the Canary Islands and the Azores in the south to Iceland in the north. Other sites in continental Europe, from Portugal and Spain in the west to Hungary, Slovakia, and the Czech Republic in the east, document the volcanic history of the continent over the past 500 million years. The Special Issue aims to show how geological and geoconservation research have contributed to a better understanding of the respective geoparks and broadened their significance for education and geotourism. [ABSTRACT FROM AUTHOR]

Chromite oxidation during serpentinization of host peridotites is a well-documented process. Detailed compositional characterization of chromites and Cr-rich spinels from three geotectonic settings provided the basis for this study, focused on the comparison of their oxidation patterns as a means to evaluate the relative mobility of spinel components during serpentinization-related oxidation in those different contexts, namely: (i) tectonic exposures of serpentinized oceanic upper-mantle in the Azores sector of the Mid-Atlantic Ridge (MAR); (ii) serpentinized peridotites from Cabeço de Vide (CV, Alter do Chão Massif, Portugal); and (iii) serpentinized subcontinental mantle peridotites from the Ronda Massif (Spain). Electron microprobe data show that: (i) irrespective of geotectonic setting and original composition, Cr-spinels follow similar oxidation trends; (ii) early Cr-spinel oxidation, involving significant Mg- and Al-depletion leading to the formation of ferritchromit rims, has been more intense in the CV serpentinites than in the more recent MAR and Ronda serpentinites; (iii) with the possible exception of Zn, trace components (Mn, Ti, V, Ni and Co) seem to be relatively immobile during spinel oxidation, thus becoming slightly enriched in ferritchromit rims; (iv) extreme Cr-spinel oxidation is responsible for incomplete outer rims of magnetite on several grains. Time, fluid pH, and fluid/rock ratios seem to be the main factors controlling the intensity and extension of chromite oxidation. [ABSTRACT FROM AUTHOR]

Graciosa is the westernmost island of the Terceira Rift, located to the east of the Mid-Atlantic Ridge, in the Azores archipelago. The three volcanic complexes recognized in the island have been characterized, including the study of lava flows, gabbroic xenoliths (alkaline and subalkaline), syenites and dunites. A detailed study of mineral compositions and whole-rock major and trace element concentrations has allowed the characterization of volcanic units and the investigation of the magmatic and temporal evolution of the island. Lava flows from the three volcanic complexes, alkaline gabbros (cumulate origin) and syenites (bulk trachyte liquid origin) can be related by polybaric fractional crystallization starting at ∼15 km depth; to explain the alternation of mafic and evolved products with time, magma chamber replenishment by primitive melts is needed. In contrast, the origin of the subalkaline gabbros, found for the first time in the Azores, appears to be related to fractionation of highly refractory melts at shallower levels (∼3 km). The lack of significant crustal assimilation in most Graciosa samples suggests that the range in Sr–Nd–Pb isotope compositions probably reflects those of a predominantly FOZO-like mantle source. Enriched (EMI- and EMII-type) mantle source components, similar to those of São Miguel and Faial, have also been recognized for the first time in Graciosa. [ABSTRACT FROM AUTHOR]

Corvo island is one of two Azorean islands located to the west of the Mid-Atlantic Ridge. Its small size and the existence of a single main eruptive center make it an ideal island for an in-depth study of the magmatic processes controlling its evolution. This study presents detailed petrographic and geochemical data for representative samples of the complete volcanostratigraphic sequence (Pre-, Syn- and Post-caldera stages), including lava flows, dikes and cumulate gabbroic xenoliths hosted in a Pre-caldera lava flow. Some lava flows and dikes contain large crystals that are not in equilibrium with the host magma. These crystals are antecrysts crystallized from progenitor magmas that have been reincorporated into the host lava before eruption. We note for the first time that the accumulation of antecrysts in Azorean magmas strongly affects the bulk composition of the rocks. Antecryst contents as high as 50–60% can result in whole-rocks with MgO contents of 15 wt %. This accumulation process obscures the magmatic processes responsible for the differentiation of the volcanic products. Accordingly, only antecryst-free samples are considered to identify the magmatic processes involved in the generation of the island. The least evolved antecryst-free rock was used as the closest composition to the primary magma for modeling of major element (MELTS) and trace element variations; our results establish a petrogenetic relationship between Corvo antecryst-free lava flows, dikes and cumulate xenoliths, all of which are products of polybaric fractional crystallization. Pre- and Post-caldera products are related to an ∼15 km deep magma chamber, whereas the Syn-caldera evolved products are related to a shallower magma chamber. These results suggest that Corvo island developed from a complex magmatic plumbing system in which magmas and their crystal cargo, derived from variable depths, have interacted and been tapped throughout the evolution of the island. [ABSTRACT FROM PUBLISHER]

While the Mid-Atlantic Region is a frequented migration route for multiple cetacean species, to date no whale falls have been encountered or studied in the area. In 2015, a juvenile sperm whale was sunk south of Faial (Azores, Portugal), implanted at 760m depth and its decomposition was monitored for one year with seven submersible dives. Based on imagery, two different successional stages were observed: the mobile/scavenging stage characterised by sharks and 3 different species of decapods and the enrichment/opportunistic stage, dominated by polychaetes. While all scavengers were known background fauna for the region, whale fall specialist fauna was observed during the enrichment-opportunistic stage, including bone-eating worms (Osedax spp.). After one year at the bottom, a vertebra and a rib were sampled to assess the species composition. While all Polychaeta, Arthropoda and Mollusca families were known from whale falls, few could be identified to species level, indicating species new to science. Based on the presence of sulphide tolerant organisms (Mytilidae aff. Bathymodiolinae and Polycladida, Platyhelminthes) in the samples, a transition to the chemosynthetic-based stage appeared to have been initiated. Taxon overlap at genus and possible species level of some Polychaeta was observed with the cow fall off the coast of Portugal (Ophryotrocha cf. lusa and O. cf. sadina) and with the whale fall off the coast of Brazil (Pleijelius , Sirsoe syn. Vrijenhoekia), thus connecting both sides of the Atlantic Ocean. • First whale fall on the Mid-Atlantic Ridge. • Two successional stages were visually observed over the course of 1 year. • Transition to the third sulphophilic stage was initiated. • Whale fall specialist fauna connects with other organic falls across the Atlantic. [ABSTRACT FROM AUTHOR]

Aliphatic hydrocarbons and PAHs in the whole soft tissues of Bathymodiolus azoricus from three Mid-Atlantic Ridge hydrothermal vents (Menez-Gwen, Lucky Strike and Rainbow), and Mytilus galloprovincialis from three contaminated coastal sites in South Portugal were analysed, and its effects on the digestive gland microsomes mixed-function oxygenase system (MFO) were assessed. Aliphatic hydrocarbons levels were present in the same magnitude in both coastal and hydrothermal environments, while the UCM (unresolved complex mixture) for coastal mussels were higher than in vent mussels. In general, significantly higher PAHs concentrations were found in coastal mussels, compared to B. azoricus where low molecular weight PAHs (2–3 rings) represented the majority of PAHs contrarily to what was observed in M. galloprovincialis. The MFO components were present in both mussel species, and were detected in vent mussels for the first time. However this system seems to have different roles in species from these contrasting environments. In coastal mussels MFO responded to hydrocarbon contamination while response in hydrothermal organisms appeared to be related mainly to endogenous factors. [Copyright &y& Elsevier]

This paper provides a summary description of the origin, activities and future of the East Atlantic Network of Biospheres (REDBIOS), demonstrating that despite the network's dynamism, there have been and continue to be many obstacles that, a priori, make its viability difficult. Four languages are spoken within the network (French, Spanish, Portuguese and Arabic), two religions are practiced and its participants (currently Azores, Portugal, Cabo Verde; the Canary Islands Spain, Madeira, Portugal, Morocco, Mauritania and Senegal) are located in three different geopolitical areas: Europe, Africa and countries. The direct or indirect benefit of the network has been: (1) the creation of the El Hierro Biosphere Reserve, (2) the creation of the Gran Canaria Biosphere Reserve, (3) the enlargement of the La Palma Biosphere Reserve to include the whole island, (4) the profound transformation experienced by the Arganeraie Biosphere Reserve and (5) the creation of the Senegal River Transboundary Biosphere Reserve between Mauritania and Senegal. In conclusion, the Network's future does not appear to be compromised and it is currently development a common group project called 'Local Agenda 21 of Macarnoesia'. [ABSTRACT FROM AUTHOR]