Petrology of the Azores Islands

Larrea, Patricia; França, Zilda; Widom, Elisabeth; Lago, M.

doi:10.1007/978-3-642-32226-6_10

Cited by 15 publications

(23 citation statements)

References 116 publications

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“…These observations are consistent with distinct mantle source compositions for each island/seamount with limited evidence of mixing between the magmatically active segments. On most islands in the Eastern Azores the occurrence of central volcanoes/volcanic centers is characterized by a progressive age propagation from east to west (Calvert et al, ; Feraud et al, ; Hildenbrand et al, ; Hildenbrand et al, ; Hildenbrand et al, ; Johnson et al, ; Larrea et al, ; Quartau et al, ) indicating that the deep magmatic systems and melting regions beneath the islands are not fixed within a segment and relative to a central volcano. Within the past 400 ka four central volcanoes have formed on Terceira displaying a gradual shift of the central volcanoes toward west (Calvert et al, ; Hildenbrand et al, ).…”

Section: Discussionmentioning

confidence: 99%

Progressive Changes in Magma Transport at the Active Serreta Ridge, Azores

Romer

Beier

Haase

et al. 2019

Geochem Geophys Geosyst

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Volcanism in the Eastern Azores Plateau occurs at large central volcanoes and along subaerial and submarine fissure zones, resulting from a mantle melting anomaly combined with transtensional stresses. Volcanic structures are aligned WNW‐ESE and NW‐SE, reflecting two tectonic stress fields that control the direction of lateral melt transport. Terceira Island is influenced by both stress fields, dividing the island into an eastern and western part. Several submarine volcanic ridges with variable orientations are located west of Santa Bárbara, the youngest central volcano on Terceira. Major, trace element and Sr‐Nd‐Pb‐Hf isotope compositions from submarine lavas and glasses, in part associated with the 1998–2001 Serreta Ridge eruption, vary between different lava suites, suggesting a formation from different mantle sources. Submarine lavas are more primitive than those from Santa Bárbara volcano, indicating that they are not laterally connected with the shallow magma reservoir located in 2‐ to 5‐km depth beneath the central volcano. Mineral thermobarometric data suggest that the older Serreta magmas were laterally transported at depths >5 km from Santa Bárbara predominantly in WNW direction. We propose that lithospheric extension controls magma transport from the central volcano to Serreta Ridge. The youngest Serreta lavas differ from Santa Bárbara and other submarine ridges in having less radiogenic Pb and higher Hf isotope ratios representing a new magma pulse ascending from the mantle. We conclude that lateral magma transport and the morphology of volcanic ridges are controlled by tectonic stresses in the lithosphere, whereas vertical melt transport is initiated by processes in the mantle.

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Section: Discussionmentioning

confidence: 99%

Progressive Changes in Magma Transport at the Active Serreta Ridge, Azores

Romer

Beier

Haase

et al. 2019

Geochem Geophys Geosyst

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“…Intermediate terms (mugearites, benmoreites) are volumetrically insignificant, probably because of a rapid and effective process of mafic phases removal occurring in small reservoirs below central volcanoes. The geochemical evolution path of the magmas erupted is similar for all the islands, and fractional crystallization and/or crystal accumulation are the main processes that explain the Azores volcanic evolution starting from small pockets of magma (Zanon 2015;Larrea et al 2018).…”

Section: Pico Rock Geochemistry In the Azores Frameworkmentioning

confidence: 98%

“…Mafic lavas (basalts, alkali basalts, hawaiites) and associated pyroclastic rocks forming cinder cones are by far more abundant than silicic rocks (trachytes, comendites, pantellerites). Mafic rocks are typical of the fissure zones present on each island and at the early stages of magmatism of central volcanoes, such as Pico Volcano; felsic rocks are erupted during plinian or sub-plinian eruptions, from vents located inside the summit calderas of the various stratovolcanoes or in forms of domes and coulees (Zanon 2015;Larrea et al 2018). Intermediate terms (mugearites, benmoreites) are volumetrically insignificant, probably because of a rapid and effective process of mafic phases removal occurring in small reservoirs below central volcanoes.…”

Section: Pico Rock Geochemistry In the Azores Frameworkmentioning

confidence: 99%

Magma water content of Pico Volcano (Azores Islands, Portugal): a clinopyroxene perspective

Nazzareni

Barbarossa

Skogby

et al. 2020

Contrib Mineral Petrol

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Clinopyroxenes from the Pico Volcano (Pico Island, Azores Archipelago) have been used as a proxy to define the water content of primitive magmas and the volcanological history of the erupted rocks. This very young volcano (53 ± 5 ka) is at a primordial stage of its evolution in comparison with the other volcanoes of the Azores. Clinopyroxenes from Pico Volcano underwent important dehydration processes and after annealing experiments under H2 gas flux, a pre-eruptive H2O content between 93 and 182 ppm was recovered. A moderately high cooling rate for the cpx-host lavas expressed by the clinopyroxene closure temperature (Tc = 755–928 °C ± 20 °C) correlates with the dehydration, suggesting that this process may have occurred during magma ponding at the Moho Transition Zone (17.3–17.7 km) and/or after the eruption. By applying an IVAl-dependent partition coefficient to the measured H amount in clinopyroxene, the pre-eruptive water content of the parental magma was calculated to vary between 0.71 and 1.20 (average of 1.0) wt%. Clinopyroxene geobarometry performed by combining X-ray diffraction with mineral chemistry points to a general crystallisation from the mantle lithosphere (~ 8–9 kbar) to the oceanic mantle/crust boundary (~ 4–5 kbar). The similar major and trace chemistry, water content and Fe3+/Fetot ratio of clinopyroxene, suggest similar conditions of oxygen fugacity, water content and fractional crystallisation of the magma from which clinopyroxene cores crystallised during the Pico Volcano central eruptions from 40 ka to historical times.

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“…Many of the intermediate lavas from the Caldeira Volcano have SiO 2 contents ranging from 53 to 57 wt. %, contrasting observations from other large volcanoes in the Azores, e.g., Santa Barbara Volcano on Terceira (Daly et al, 2012) and the central volcano on Graciosa (Larrea et al, 2018). A larger volume of highly evolved (trachytic) pyroclastic rocks (up to ∼64 wt.…”

Section: Geochemistry and Isotopesmentioning

confidence: 93%