Helium and lead isotope geochemistry of the Azores Archipelago

Moreira, Manuel; Doucelance, Régis; Kurz, Mark D.; Dupré, Bernard; Allègre, Claude J.

doi:10.1016/s0012-821x(99)00071-0

Cited by 128 publications

(84 citation statements)

References 66 publications

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“…3.15,3.16 and 3.17). Shallow magma degassing and radiogenic production cannot explain the observed compositions and the correlations seen with other isotopic systems, less sensitive to degassing and contamination (Hanyu and Kaneoka, 1997;Barfod et al, 1999;Moreira et al, 1999;Hilton et al, 2000a;Aka et al, 2004;Class et al, 2005;Gurenko et al, 2006;Day and Hilton, 2011;Hanyu et al, 2011;Moreira et al, 2012). The more-radiogenic-than MORB helium isotopic ratios observed on these OIB exhibit a mantle signature, which is clearly different to the "primitive" nature of most OIB.…”

Section: Figure 313mentioning

confidence: 95%

“…Moreover, these Reynolds-type glass machines cannot distinguish HD from 3 He, and although background of H 2 is low in these instruments, the HD peak is still too high to measure phenocrysts well compared to mass spectrometers made of stainless steel and with mass resolution higher than 600. Therefore, the helium systematics in OIB phenocrysts was performed by a few groups, and were only made in Paris after we modified the extraction and purification lines coupled to the ARESIBO mass spectrometers (Moreira et al, 1999;Madureira et al, 2005;Doucet et al, 2006;Mata et al, 2010;Mourão et al, 2012).…”

Section: Oceanic Island Basalts (Oib)mentioning

confidence: 99%

“…São Miguel (Azores archipelago), Canaries, Comoros, Gough, Tristan da Cuhna, Saint Helena, Cameroon line or Tubuai hotspots show more radiogenic helium than MORB (Kurz et al, 1982a;Kurz et al, 1990;Graham et al, 1993;Kurz, 1993;Barfod et al, 1999;Moreira et al, 1999;Class et al, 2005;Parai et al, 2009;Day and Hilton, 2011).…”

Section: Figure 310mentioning

confidence: 99%

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Noble gas constraints on the origin and evolution of Earth’s volatiles

Moreira¹

2013

GeochemPersp

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117

164

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Section: Figure 313mentioning

confidence: 95%

Section: Oceanic Island Basalts (Oib)mentioning

confidence: 99%

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Noble gas constraints on the origin and evolution of Earth’s volatiles

Moreira¹

2013

GeochemPersp

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117

164

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“…The cause for the volcanism in the islands is highly debated in the literature and most studies suggest the presence of a mantle plume (e.g., Schilling, 1975;Cannat et al, 1999;Moreira et al, 1999;Jean-Baptiste et al, 2009), even if some studies argue that the addition of H 2 O to the mantle together with a small temperature anomaly could be enough to induce melting (Bonatti, 1990;Asimow et al, 2004;Métrich et al, 2014).…”

Section: Geological Settingmentioning

confidence: 99%

“…Nowadays, the only visible secondary manifestations of volcanism in Faial correspond to residual steam emissions from the Capelinhos eruption (1957-58) (Ferreira, 1994;Gaspar and Ferreira, 1995 (Moreira et al, 1999).…”

Section: Volcanismmentioning

confidence: 99%

Soil CO2 Degassing Path along Volcano-Tectonic Structures in the Pico-Faial-São Jorge Islands (Azores Archipelago, Portugal)

Viveiros

Marcos²,

Faria

et al. 2017

Front. Earth Sci.

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The Azores archipelago is composed of nine volcanic islands located at the triple junction between the North American, Eurasian, and Nubian plates. Nowadays the volcanic activity in the archipelago is characterized by the presence of secondary manifestations of volcanism, such as hydrothermal fumaroles, thermal and cold CO 2 -rich springs as well as soil diffuse degassing areas, and low magnitude seismicity. Soil CO 2 degassing (concentration and flux) surveys have been performed at Pico, Faial, and São Jorge islands to identify possible diffuse degassing structures. Since the settlement of the Azores in the fifteenth Century these three islands were affected by seven onshore volcanic eruptions and at least six destructive earthquakes. These islands are crossed by numerous active tectonic structures with dominant WNW-ESE direction, and less abundant conjugate NNW-SSE trending faults. A total of 2,855 soil CO 2 concentration measurements have been carried out with values varying from 0 to 20.7 vol.%. Soil CO 2 flux measurements, using the accumulation chamber method, have also been performed at Pico and Faial islands in the summer of 2011 and values varied from absence of CO 2 to 339 g m −2 d −1 . The highest CO 2 emissions were recorded at Faial Island and were associated with the Pedro Miguel graben faults, which seem to control the CO 2 diffuse degassing and were interpreted as the pathways for the CO 2 ascending from deep reservoirs to the surface. At São Jorge Island, four main degassing zones have been identified at the intersection of faults or associated to WNW-ESE tectonic structures. Four diffuse degassing structures were identified at Pico Island essentially where different faults intersect. Pico geomorphology is dominated by a 2,351 m high central volcano that presents several steam emissions at its summit. These emissions are located along a NW-SE fault and the highest measured soil CO 2 concentration reached 7.6 vol.% with a maximum temperature of 77 • C. The diffuse degassing maps show that anomalous CO 2 degassing areas are controlled essentially by the tectonic structures and the lithology of the sites since the youngest volcanic systems are characterized by very low CO 2 emissions.

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The evolution of MORB and plume mantle volatile budgets: Constraints from fission Xe isotopes in Southwest Indian Ridge basalts

Parai

Mukhopadhyay

2015

Geochem. Geophys. Geosyst.

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We present high-precision measurements of the fission isotopes of xenon (Xe) Xe is recycled in origin), consistent with results from studies of plume-influenced basalts from Iceland and the Rochambeau Rift. While significant regassing of the mantle is evident, we also find differences in the extent of degassing of the MORB and plume sources. MORB sources are consistently characterized by a lower fraction of fission Xe derived from Pu-fission, indicating a greater extent of degassing relative to the plume source. The prevalence of recycled atmospheric Xe in mantle sources indicates incorporation of depleted recycled material even into mantle sources with primitive He and Ne isotopic compositions. Consequently, depleted lithophile isotopic compositions in mantle sources with primitive He and Ne cannot be interpreted as evidence for a nonchondritic bulk silicate Earth.

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Helium and lead isotope geochemistry of the Azores Archipelago

Cited by 128 publications

References 66 publications

Noble gas constraints on the origin and evolution of Earth’s volatiles

Noble gas constraints on the origin and evolution of Earth’s volatiles

Soil CO2 Degassing Path along Volcano-Tectonic Structures in the Pico-Faial-São Jorge Islands (Azores Archipelago, Portugal)

The evolution of MORB and plume mantle volatile budgets: Constraints from fission Xe isotopes in Southwest Indian Ridge basalts

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