scholarly journals Insights from Fumarole Gas Geochemistry on the Recent Volcanic Unrest of Pico do Fogo, Cape Verde

2021 ◽  
Vol 9 ◽  
Author(s):  
Gladys V. Melián ◽  
Pedro A. Hernández ◽  
Nemesio M. Pérez ◽  
María Asensio-Ramos ◽  
Eleazar Padrón ◽  
...  
Keyword(s):  
Time Series ◽  
Isotopic Composition ◽  
Cape Verde ◽  
Time Lags ◽  
Volcanic System ◽  
Volcanic Unrest ◽  
Source Contributions ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Fogo Volcano

We report the results of the geochemical monitoring of the fumarolic discharges at the Pico do Fogo volcano in Cape Verde from 2007 to 2016. During this period Pico do Fogo experienced a volcanic eruption (November 23, 2014) that lasted 77 days, from a new vent ∼2.5 km from the fumaroles. Two fumaroles were sampled, a low (F1∼100°C) and a medium (F2∼300°C) temperature. The variations observed in the δ18O and δ2H in F1 and F2 suggest different fluid source contributions and/or fractionation processes. Although no significant changes were observed in the outlet fumarole temperatures, two clear increases were observed in the vapor fraction of fumarolic discharges during the periods November 2008–2010 and 2013–2014. Also, two sharp peaks were observed in CO2/CH4 ratios at both fumaroles, in November 2008 and November 2013. This confirms that gases with a strong magmatic component rose towards the surface within the Pico do Fogo system during 2008 and 2013. Further, F2 showed two CO2/Stotal peaks, the first in late 2010 and the second after eruption onset, suggesting the occurrence of magmatic pulses into the volcanic system. Time series of He/CO2, H2/CO2 and CO/CO2 ratios are low in 2008–2009, and high in 2013–2014 period, supporting the hypothesis of fluid input from a deeper magmatic source. Regarding to the isotopic composition, increases in air-corrected 3He/4He ratios are observed in both fumaroles; F1 showed a peak in 2010 from a minimum in 2009 during the first magmatic reactivation onset and another in late 2013, while F2 displayed a slower rise to its maximum in late 2013. The suite of geochemical species analyzed have considerably different reactivities, hence these integrated geochemical time-series can be used to detect the timing of magmatic arrivals to the base of the system, and importantly, indicate the typical time lags between gas release periods at depth and their arrival at the surface. The high 3He/4He ratios in both fumaroles in the range observed for mid-ocean ridge basalts, indicating that He is predominantly of upper mantle origin. This work supports that monitoring of the chemical and isotopic composition of the fumaroles of the Pico do Fogo volcano is a very important tool to understand the processes that take place in the magmatic-hydrothermal system and to be able to predict future episodes of volcanic unrest and to mitigate volcanic risk.

Insights from fumarole gas geochemistry on the recent volcanic unrest of Pico do Fogo, Cape Verde

2021 ◽  
Author(s):  
Gladys V. Melián ◽  
Pedro A. Hernández ◽  
María Asensio-Ramos ◽  
Nemesio M. Pérez ◽  
Eleazar Padrón ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Active Volcano ◽  
Cape Verde ◽  
Volcanic System ◽  
Volcanic Unrest ◽  
Source Contributions ◽  
Volcanic Chain ◽  
Work Supports ◽  
System Time ◽  
Fogo Volcano

<p>The Cape Verde islands are located about 800 km west of Senegal, at 14°-17° latitude and 21°-25° longitude. The archipelago consists of a volcanic chain of 10 major islands and eight minor islands The only currently active volcano in the Cape Verde archipelago is Pico do Fogo, which is located on the island of Fogo. Rising to 2829 m a.s.l., it is the most active volcano of the Cabo Verde Island. We report the results of the geochemical monitoring of the fumarolic discharges at the Pico do Fogo volcano in Cape Verde from 2007 to 2016. During this period Pico do Fogo experienced a volcanic eruption (November 23, 2014) that lasted 77 days. Two fumaroles were sampled, a low (F1~100ºC) and a medium (F2~300ºC) temperature. The variations observed in the δ<sup>18</sup>O and δ<sup>2</sup>H in F1 and F2 suggest different fluid source contributions and/or fractionation processes. Although no significant changes were observed in the outlet fumarole temperatures, two clear increases were observed in the vapor fraction of fumarolic discharges during the periods 2008-2009 and 2013-2014. Also, two sharp peaks were observed in CO<sub>2</sub>/CH<sub>4</sub> ratios at both fumaroles, in November 2008 and November 2013, coinciding with significant increases in the emission rate of diffuse CO<sub>2</sub> and He, and heat flow measured in the crater of Pico do Fogo volcano. This confirms that gases with a strong magmatic component rose towards the surface within the Pico do Fogo system during 2008 and 2013. Further, F2 showed two CO<sub>2</sub>/St peaks, the first in late 2010 and the second after eruption onset, suggesting the occurrence of magmatic pulses into the volcanic system. Time series of He/CO<sub>2</sub>, H<sub>2</sub>/CO<sub>2</sub> and CO/CO<sub>2</sub> ratios are low in 2008-2009, and high in 2013-2014 period, supporting the hypothesis of fluid input from a deeper magmatic source. Regarding to the isotopic composition, increases in <sup>3</sup>He/<sup>4</sup>He (R/R<sub>A</sub>)<sub>cor</sub> are observed in both fumaroles; F1 showed a peak in 2010 from a minima in 2009 during the first magmatic reactivation onset and another in late 2013, while F2 displayed a slower rise to its maximum in late 2013. The high <sup>3</sup>He/<sup>4</sup>He ratios in both fumaroles are close to the magmatic end-member, indicating that He is predominantly of upper mantle origin. This work supports that monitoring of the chemical and isotopic composition of the fumaroles of the Pico do Fogo volcano is a very important tool to understand the processes that take place in the magmatic-hydrothermal system and to be able to predict future episodes of volcanic unrest and to mitigate volcanic risk.</p>

Mineralogy of the mid-ocean-ridge basalt source from neodymium isotopic composition of abyssal peridotites

Nature ◽  
2002 ◽  
Vol 418 (6893) ◽  
pp. 68-72 ◽  
Author(s):  
Vincent J. M. Salters ◽  
Henry J. B. Dick
Keyword(s):  
Isotopic Composition ◽  
Ridge Basalt ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

scholarly journals The stable strontium isotopic composition of ocean island basalts, mid-ocean ridge basalts, and komatiites

2018 ◽  
Vol 483 ◽  
pp. 595-602 ◽  
Author(s):  
Elsa Amsellem ◽  
Frédéric Moynier ◽  
James M.D. Day ◽  
Manuel Moreira ◽  
Igor S. Puchtel ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Ocean Island ◽  
Ocean Island Basalts ◽  
Mid Ocean Ridge ◽  
Stable Strontium ◽  
Ocean Ridge

Oxygen isotope geochemistry of rocks from DSDP Leg37

1977 ◽  
Vol 14 (4) ◽  
pp. 771-776 ◽  
Author(s):  
K. Muehlenbachs
Keyword(s):  
Isotopic Composition ◽  
Oxygen Isotope ◽  
Oceanic Crust ◽  
Isotope Geochemistry ◽  
Altered Rock ◽  
Ocean Ridges ◽  
Dredged Materials ◽  
Mid Ocean Ridge ◽  
Intrusive Rocks ◽  
Ocean Ridge

The isotopic compositions of minerals separated from DSDP Leg 37 samples indicate that the primary, unaltered δ18O of both the intrusive and extrusive rocks are identical (~5.7 ‰, SMOW) to those of unaltered basalts dredged from mid-ocean ridges. All of the analyzed basalts (6 to 10 ‰) have been enriched in 18O due to weathering by cold seawater, whereas the intrusive rocks (2.4 and 5.0 ‰) are depleted of 18O probably as a result of exchange with hot seawater at the mid-ocean ridge. Both kinds of altered rock are also known from the study of dredged materials. 18O is preferentially removed from seawater by the first process, but is added to seawater by the second. Exchange of oxygen between oceanic crust and seawater must be considered in any discussion of the evolution of the isotopic composition of the oceans, because large volumes of rock are altered each year as the oceanic crust is formed.

scholarly journals Unravelling the Crustal Architecture of Cape Verde from the Seamount Xenolith Record

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 90
Author(s):  
Abigail Barker ◽  
Thor Hansteen ◽  
David Nilsson
Keyword(s):  
Oceanic Crust ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Cape Verde ◽  
Mantle Xenoliths ◽  
Light Rare Earth ◽  
Oceanic Plateau ◽  
Mid Ocean Ridge ◽  
Crustal Xenoliths ◽  
Ocean Ridge

The Cape Verde oceanic plateau hosts 10 islands and 11 seamounts and provides an extensive suite of alkaline lavas and pyroclastic rocks. The volcanic rocks host a range of crustal and mantle xenoliths. These xenoliths provide a spectrum of lithologies available to interact with magma during transport through the lithospheric mantle and crust. We explore the origin and depth of formation of crustal xenoliths to develop a framework of magma-crust interaction and a model for the crustal architecture beneath the Cape Verde oceanic plateau. The host lavas are phononephelinites to phonolites and the crustal xenoliths are mostly mafic plutonic assemblages with one sedimentary xenolith. REE profiles of clinopyroxene in the host lavas are light rare-earth element (LREE) enriched whereas clinopyoxene from the plutonic xenoliths are LREE depleted. Modelling of REE melt compositions indicates the plutonic xenoliths are derived from mid-ocean ridge basalt (MORB)-type ocean crust. Thermobarometry indicates that clinopyroxene in the host lavas formed at depths of 17 to 46 km, whereas those in the xenoliths formed at 5 to 20 km. This places the depth of origin of the plutonic xenoliths in the oceanic crust. Therefore, the xenoliths trace magma-crust interaction to the MORB oceanic crust and overlying sediments located beneath the Cape Verde oceanic plateau.

Oxygen-isotopic composition of basalts from young spreading axes in the eastern Pacific

1987 ◽  
Vol 24 (11) ◽  
pp. 2105-2117 ◽  
Author(s):  
T. J. Barrett ◽  
H. Friedrichsen
Keyword(s):  
Low Temperature ◽  
Isotopic Composition ◽  
Gulf Of California ◽  
Oxygen Isotopic Composition ◽  
Eastern Pacific ◽  
Oxygen Isotope Exchange ◽  
Mid Ocean Ridge ◽  
Oxygen Isotopic ◽  
Local Water ◽  
Ocean Ridge

Oxygen-isotopic composition data are reported for young oceanic basalts from two different tectonic settings in the eastern Pacific: (1) the uppermost basement on the Galapagos Rift (< 1 Ma old), and (2) subbasement depths up to ≈150 m in the Gulf of California (≤ 3.5 Ma old). In the Galapagos area, whole-rock δ18O values exhibit a narrow range of 5.7–6.6‰, consistent with minimal to slight low-temperature alteration. Limited alteration probably reflects a combination of young basement age, low temperatures for solutions in the uppermost basement, and confinement of solutions mainly to discrete fractures. In the Gulf of California, by contrast, high whole-rock values are found at site 474A, near the Baja margin, where the greatest range in δ18O also occurs, from 2.5 to 12.5‰. This indicates considerable variation in both the temperature and degree of alteration at this site, probably a consequence of the heterogeneous basement sequence (intercalated pillow lavas, sills, and wet sediments). Differences in δ18O of up to 6‰ can exist over several metres, implying sharp changes in temperature or local water/rock ratio. The development of low-temperature alteration is more pronounced at site 474A (≈3.5 Ma) than at the several other (younger) crustal locations drilled in the Gulf of California, presumably because of longer exposure to seawater during recession of site 474A from the spreading axis.Analysis of primary magmatic phases at all sites yield 18O fractionations between plagioclase, clinopyroxene, and magnetite consistent with crystallization in a closed system and without high-temperature subsolidus reaction with seawater oxygen (even where sediments are intercalated within the basement). At site 485 in the Gulf of California, a thick basaltic sill yielded the lowest calculated crystallization temperatures (920 ± 50 °C) on the basis of plagioclase–magnetite fractionations; this agrees reasonably with groundmass quartz estimated to have formed at 860 ± 40 °C. Two vein carbonates from the uppermost part of the igneous sequence at this site were formed at temperatures of less than a few tens of degrees.We also report high-precision strontium- and oxygen-isotopic data on mineral separates from four basalts recovered at site 504B (6 Ma old). The most striking feature of these data is very substantial contamination of most mineral phases by seawater Sr, even though the same splits have typical primary magmatic oxygen-isotopic values. Relative to an unaltered mid-ocean ridge basalt 87Sr/86Sr value of 0.70265 ± 0.0001, 87Sr/86Sr ratios of plagioclase range from 0.70270 to 0.70359 (for apparently primary δ18O values of 5.35–5.75‰); for clinopyroxene, 87Sr/86Sr ratios range from 0.70309 to a very enriched value of 0.70695 (δ18O values of 4.97–5.30‰, with one value of 6.05‰). These results indicate that young basalts may have experienced significant interaction with seawater, which is not recorded in terms of oxygen-isotope exchange.

scholarly journals Alkaline magmatism in the Selwyn Basin, Yukon: relationship to SEDEX mineralization

2021 ◽  
Author(s):  
E J Scanlan ◽  
M Leybourne ◽  
D Layton-Matthews ◽  
A Voinot ◽  
N van Wagoner
Keyword(s):  
Volcanic Rocks ◽  
Alkaline Magmatism ◽  
Ongoing Research ◽  
Volcanic System ◽  
Temporal Relationships ◽  
Mid Ocean Ridge ◽  
Ideal Study ◽  
Ocean Ridge ◽  
Cathodoluminescence Imaging ◽  
The Relationship

Several sedimentary exhalative (SEDEX) deposits have alkaline magmatism that is temporally and spatially associated to mineralization. This report outlines interim data from a study of potential linkages between magmatism and SEDEX mineralization in the Selwyn Basin, Yukon. This region is an ideal study site due to the close spatial and temporal relationships between SEDEX deposits and magmatism, particularly in the MacMillan Pass, where volcanic rocks have been drilled with mineralization at the Boundary deposit. Alkaline volcanic samples were analysed from the Anvil District, MacMillan Pass, Keno-Mayo and the Misty Creek Embayment in the Selwyn Basin to characterise volcanism and examine the relationship to mineralization. Textural and field relationships indicate a volatile-rich explosive eruptive volcanic system in the MacMillan Pass region in comparison to the Anvil District, which is typically effusive in nature. High proportions of calcite and ankerite in comparison to other minerals are present in the MacMillan system. Cathodoluminescence imaging reveals zoning and carbonate that displays different luminescent colours within the same sample, likely indicating multiple generations of carbonate precipitation. Barium contents are enriched in volcanic rocks throughout the Selwyn Basin, which is predominately hosted by hyalophane with rare barite and barytocalcite. Thallium is positively correlated with Ba, Rb, Cs, Mo, As, Sb and the calcite-chlorite-pyrite index and is negatively correlated with Cu. Anvil District samples display a trend towards depleted mid-ocean ridge mantle on a plot of Ce/Tl versus Th/Rb. Hydrothermal alteration has likely led to the removal of Tl from volcanic rocks in the region. Ongoing research involves: i) the analysis of Sr, Nd, Pb and Tl isotopes of volcanic samples; ii) differentiating magmatic from hydrothermal carbonate using O, C and Sr isotopes; iii) examining sources of Ba in the Selwyn Basin; iv) and constraining age relationships through U-Th-Pb geochronology.

Spatiotemporal Relationship between Arctic Mid-Ocean Ridge System and Intraplate Seismicity of the European Arctic

2021 ◽  
Author(s):  
Galina N. Antonovskaya ◽  
Irina M. Basakina ◽  
Natalya V. Vaganova ◽  
Natalia K. Kapustian ◽  
Yana V. Konechnaya ◽  
...  
Keyword(s):  
Correlation Coefficients ◽  
Seismic Energy ◽  
The Arctic ◽  
Time Lags ◽  
Novaya Zemlya Archipelago ◽  
Gakkel Ridge ◽  
Novaya Zemlya ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Ridge System

Abstract In this article, we investigate the influence of the Arctic mid-ocean ridge system (AMORS), including the Gakkel and Mohns ridges, and the Knipovich ridge–Lena trough (KL) segment, on seismicity of the Novaya Zemlya archipelago area (NZ) and the northernmost margin of the East-European Platform (EEP) for 1980–2019. For each individual area, the annual seismic energy was obtained by adding the energies of all earthquakes. To do this, we have converted various types of magnitude by different seismic networks into moment magnitude Mw. We compiled the updated catalog for the NZ, the northern EEP, and the northern part of the Ural fold belt (UFB). As a result, we constructed time distributions of annual seismic energy releases for each composing ridges of AMORS, NZ, and EEP combined with UFB. A model based on the Elsasser’s one describing the transfer of lithospheric stress disturbances in the horizontal direction was built, and quantitative calculations of the disturbance propagations from AMORS were performed. Results are in good agreement with the annual seismic energy time lags between rifts and NZ and EEP together with the UFB. We calculated correlation coefficients between the seismic energy releases over the time for the structures, enabling identification of the characteristic excitation cycles and estimation of the interval of disturbance transfer from AMORS. As a result, disturbances from the Gakkel ridge appear 3 yr later in NZ, from the KL segment in 4 yr, and from the Mona ridge in 8 yr. For the EEP + UBF combined area, we found the following disturbances spreading lags as 7 yr for the Mona ridge, 4 yr for the KL segment, and 5 yr for the Gakkel ridge. The obtained damping amplitudes of the disturbance spreading from the arctic ridges are sufficient to affect the intraplate seismic activity.

Changes in the thermal energy and the diffuse 3He and 4He degassing prior to the 2014-2015 eruption of Pico do Fogo volcano, Cape Verde

2021 ◽  
Author(s):  
Mar Alonso ◽  
Nemesio M. Pérez ◽  
Eleazar Padrón ◽  
Pedro A. Hernández ◽  
Gladys V. Melián ◽  
...  
Keyword(s):  
Thermal Energy ◽  
Isotopic Ratio ◽  
Cape Verde ◽  
Geophysical Research ◽  
Volcanic System ◽  
Thermal Output ◽  
Eruptive Cycle ◽  
Volcanic Islands ◽  
Emission Studies ◽  
Fogo Volcano

&lt;p&gt;Cape Verde archipelago is a cluster of several volcanic islands arranged in a westward opening horseshoe shape located in the Atlantic Ocean, between 550 and 800 km-west of the coast of Senegal (Africa). Fogo Island is located in the southwest of the archipelago, and as main feature is a 9-km-north to south wide collapse caldera opened toward the east, within Pico do Fogo volcano rises 2,829 m.a.s.l. Pico do Fogo crater has an area of 0.142 km&lt;sup&gt;2&lt;/sup&gt; and its characterized by a fumarolic field composed by low and moderate temperature fumaroles, with temperatures around 95&amp;#186;C and reaching 400&amp;#186;C respectively. The last eruption of Fogo volcanic system took place between November 2014 and February 2015, when four new eruptive vents were formed, and destroyed partially the villages of Portela and Bangaeira (Silva et. al., 2015) forcing the evacuation of 1,300 inhabitants. In this work we present the temporal evolution of &lt;sup&gt;3&lt;/sup&gt;He/&lt;sup&gt;4&lt;/sup&gt;He isotopic ratio, &lt;sup&gt;3&lt;/sup&gt;He and &lt;sup&gt;4&lt;/sup&gt;He emission and thermal energy released data measured from March 2007 to November 2018 in the crater of Pico do Fogo. In all the studied temporal evolutions, we can observe two main increases in the above parameters, the first in early 2010, suggesting a magmatic intrusion, and the second several months before the eruption onset. We have also observed that changes in the &lt;sup&gt;3&lt;/sup&gt;He emission might be accompanied by a significant increase in thermal output if the system is in an eruptive cycle. Our results confirm &lt;sup&gt;3&lt;/sup&gt;He emission studies are highly reliable indicator of imminent volcanic eruption and constitute a powerful tool to monitor the activity of volcanic areas around the world.&lt;/p&gt;&lt;p&gt;Silva et al., (2015), Geophysical Research Abstracts Vol. 17, EGU2015-13378, EGU General Assembly.&lt;/p&gt;

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