scholarly journals An Attempt to Study Natural H2 Resources across an Oceanic Ridge Penetrating a Continent: The Asal–Ghoubbet Rift (Republic of Djibouti)

Geosciences ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 16
Author(s):  
Gabriel Pasquet ◽  
Rokiya Houssein Hassan ◽  
Olivier Sissmann ◽  
Jacques Varet ◽  
Isabelle Moretti
Keyword(s):  
Rift Zone ◽  
Rift System ◽  
Surface Sampling ◽  
Simultaneous Reduction ◽  
H2 Generation ◽  
Ocean Ridges ◽  
Geological Features ◽  
Geothermal Drilling ◽  
Existing Data ◽  
Initial Exploration

Dihydrogen (H2) is generated by fluid–rock interactions along mid-ocean ridges (MORs) and was not, until recently, considered as a resource. However, in the context of worldwide efforts to decarbonize the energy mix, clean hydrogen is now highly sought after, and the production of natural H2 is considered to be a powerful alternative to electrolysis. The Afar Rift System has many geological features in common with MORs and offers potential in terms of natural H2 resources. Here, we present data acquired during initial exploration in this region. H2 contents in soil and within fumaroles were measured along a 200 km section across the Asal–Ghoubbet rift and the various intervening grabens, extending from Obock to Lake Abhe. These newly acquired data have been synthesized with existing data, including those from the geothermal prospect area of the Asal–Ghoubbet rift zone. Our results demonstrate that basalt alteration with oxidation of iron-rich facies and simultaneous reduction in water is the likely the source of the hydrogen, although H2S reduction cannot be ruled out. However, H2 volumes at the surface within fumaroles were found to be low, reaching only a few percent. These values are considerably lower than those found in MORs. This discrepancy may be attributed to bias introduced by surface sampling; for example, microorganisms may be preferentially consuming H2 near the surface in this environment. However, the low H2 generation rates found in the study area could also be due to a lack of reactants, such as fayalite (i.e., owing to the presence of low-olivine basalts with predominantly magnesian olivines), or to the limited volume and slow circulation of water. In future, access to additional subsurface data acquired through the ongoing geothermal drilling campaign will bring new insight to help answer these questions.

Radon and CO2 tracer for radioxenon subsurface sampling in the On Site Inspection

2020 ◽  
Author(s):  
Chiara Telloli ◽  
Barbara Ferrucci ◽  
Antonietta Rizzo ◽  
Stefano Salvi ◽  
Alberto Ubaldini ◽  
...  
Keyword(s):  
Radon Concentration ◽  
Underground Nuclear Explosion ◽  
Surface Sampling ◽  
Atmospheric Gases ◽  
Auxiliary Equipment ◽  
Geological Features ◽  
Strong Indicator ◽  
Gaseous Sample ◽  
On Site Inspection ◽  
Radon Detection

<p>The detection of anomalous concentration of Xenon radiosotopes in the subsurface gases during an On Site Inspection (OSI) is a strong indicator of a suspicious underground nuclear explosion. This implies that the sampling methodology ensure the collection of a reliable representative subsurface gaseous sample, avoiding the mixing with atmospheric gases. Radioxenon sampling in shallow layers can provide reliable results for desert areas, but different local geological features could result in more complex migration of subsurface gases to the very near superficial layers affecting the representativeness of the sample.</p><p>Radon is currently use as tracer to reveal the effective sampling of gases form the deep surface, so its measurement is coupled with the collection of radioxenon subsurface gases. The detection of radon anomalous concentration in subsurface gases could indicate different causes: high Radon content in subsurface indicate high radon concentration underground caused by the accumulation in an underground and confined cavity; on the other side, low radon detection in subsurface indicate low radon concentration underground that can be indicative of the absence of an underground cavity or the presence of rocks in the cavity absorbing radon. This lead to the consideration that radon is not a univocal tracer for Xe surface sampling in the OSI. A portable isotopic analyzer (that measures d13C and CO2) could be used to localize the faults and fracturing that could lead to a seeping of the subsurface gases. Therefore, this technique could be proposed as an auxiliary equipment for a preliminary activity during an OSI and a monitoring tool during subsurface gas sampling.</p>

Monitoring of diffuse CO2 degassing at NERZ, NWRZ and NSRZ volcanic systems of Tenerife, Canary Islands

2021 ◽  
Author(s):  
Fátima Rodríguez ◽  
Eleazar Padrón ◽  
Gladys Melián ◽  
María Asensio-Ramos ◽  
Mar Alonso ◽  
...  
Keyword(s):  
Rift Zone ◽  
Emission Rate ◽  
Interpolation Method ◽  
Sampling Site ◽  
Sequential Gaussian Simulation ◽  
Rift System ◽  
Volcanic Complex ◽  
North East ◽  
The North ◽  
Volcanic Seismicity

<p>One of the main volcano-structural and geomorphological feature in Tenerife (2,034 km<sup>2</sup>) is the triple rift system, formed by aligned of hundreds of monogenetic eruptive products of shield basaltic volcanism. At the intersection of this triple rift system rises the Teide-Pico Viejo volcanic complex. These volcanic rifts are considered as active volcanic edifices. The North East volcanic Rift Zone (NERZ, 210 km<sup>2</sup>) form a main NE-SW structure. The North West volcanic Rift Zone (NWRZ, 72 km<sup>2</sup>) is oriented in NW-SE direction and the North South volcanic Rift Zone (NSRZ, 325 km<sup>2</sup>) comprises a more scattered area on the south of these monogenetic cones. The most recent eruptive activity of Tenerife has taken place in these rift systems. NERZ host the fissural eruption of Arafo-Fasnia-Siete Fuentes (1704-1705). NWRZ host two historical eruptions: Arenas Negras in 1706 and Chinyero in 1909. Recently the eruption of Boca Cangrejo (1492) has been added to the historical register through <sup>14</sup>C dating. NSRZ does not host historical volcanism, although it is recent, up to 10,000 years old.</p><p>In order to provide a multidisciplinary approach to monitor potential volcanic activity changes at the NERZ, NWRZ and NSRZ, diffuse CO<sub>2</sub> emission surveys have been undertaken since 2000, in general in a yearly basis, but with a higher frequency when seismic swarms have occurred in and around NWRZ volcano. Each study area for NERZ, NWRZ and NSRZ comprises hundreds of sampling sites homogenously distributed. Soil CO<sub>2</sub> efflux measurements at each sampling site were conducted at the surface environment by means of a portable non-dispersive infrared spectrophotometer (NDIR) LICOR Li820 following the accumulation chamber method. To quantify the CO<sub>2</sub> emission rate from the NERZ, NWRZ and NSRZ a sequential Gaussian simulation (sGs) was used as interpolation method.</p><p>The diffuse CO<sub>2</sub> emission rate for the NERZ ranged from 532 up to 2823 t d<sup>-1 </sup>between 2001 and 2020, with the highest value measured in 2020. In the case of NWRZ, the diffuse CO<sub>2</sub> emission rate ranged from 52 up to 867 t d<sup>-1 </sup>between 2000 and 2020, with the highest value measured in one of the surveys of 2005. Finally, and for NSRZ, the diffuse CO<sub>2</sub> emission rate ranged from 78 up to 819 t d<sup>-1 </sup>between 2002 and 2020, with the highest value measured in 2019. The temporal evolution of diffuse CO<sub>2</sub> emission at the NERZ, NWRZ and NSRZ shows a nice and clear relationship with the volcanic seismicity in and around Tenerife Island, which started to take place from the end of 2016. The good temporal correlation between the volcanic seismicity and the increase trend observed in the time series of diffuse CO<sub>2</sub> emission rates at NERZ, NWRZ and NSRZ is also coincident with the observed increase of diffuse CO<sub>2</sub> emission rate at the summit crater of Teide. This work demonstrates the importance of performing soil CO<sub>2</sub> efflux surveys at active rift systems in volcanic oceanic islands as an effective geochemical monitoring tool.</p>

The structure of the mid-oceanic rift zone of the Indian ocean and its place in the world rift system

1969 ◽  
Vol 8 (4-6) ◽  
pp. 377-401 ◽  
Author(s):  
A.P. Vinogradov ◽  
G.B. Udintsev ◽  
L.V. Dmitriev ◽  
V.F. Kanaev ◽  
Y.P. Neprochnov ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Rift Zone ◽  
Rift System ◽  
The World ◽  
The Indian Ocean

A Discussion on volcanism and the structure of the Earth - Volcanism of the Kenya rift valley

1972 ◽  
Vol 271 (1213) ◽  
pp. 185-208 ◽  
Keyword(s):  
Rift Valley ◽  
Rift Zone ◽  
Volcanic Rocks ◽  
Structural Evolution ◽  
Eastern Africa ◽  
Rift System ◽  
Kenya Rift ◽  
Northern Tanzania ◽  
Eastern Uganda ◽  
Kenya Rift Valley

The Kenya rift valley is a sector of the rift system of eastern Africa which is marked by volcanic activity throughout its history from Miocene times to the present day. Activity is not confined to the rift zone but extends for distances of 200 km or more both to the west and east and is broadly centred on the Kenya ‘dome’, a topographic culmination in the course of the rift. The volcanic rocks show a considerable diversity of compositions ranging from basic to acid, but all are characteristically alkaline varying, however, from a mildly alkaline, alkali basalt-trachyte series, to strongly alkaline and undersaturated nephelinites and phonolites. The mode of extrusion and form of the volcanic accumulations are also very varied, evidently dependent in part on composition. There are thus the widespread ‘plateau’ phonolites of central and southern Kenya, possibly fissure eruptions; the large nephelinite central volcanoes of eastern Uganda, including Mt Elgon, and western Kenya; and the giant phonolite-trachyte or basalt-phonolite-trachyte volcanoes of Mts Kenya and Kilimanjaro. Extensive basalt fields were variously the products of fissure eruption, such as those of Samburu, or derived from numerous small centres as in the Nyambeni area or the Chyulu Hills. Large low-angle cones in the northern part of the rift are formed mostly of trachyte flows, whereas the axis of the rift is marked by a series of conspicuous trachyte-basalt volcanoes, often with spectacular calderas. The composition of the volcanic rocks shows variations with time, possibly indicating a dependence on the structural evolution of the rift, but sequences are not simple and cannot be easily defined. The nephelinite volcanoes of eastern Uganda are of Miocene age, but this composition also characterizes recent volcanoes of northern Tanzania. The basalt-basanite association dominates the earliest volcanic rocks of the rift zone itself, but has been repeatedly represented to the present. The flood phonolites were, however, largely confined to the upper Miocene; the Pliocene and earlier Pleistocene were marked by great eruptions of trachyte lavas and ignimbrite, whereas acid volcanic rocks, comendites and pantellarites, of Quaternary age are limited to a small area in the central part of the rift. The total volume of volcanic rocks cannot be estimated with any accuracy, but may be of the order of several 100 000 km 3 . The second part of this account presents in preliminary form the results of field mapping and chemical analytical programmes on the Cainozoic volcanics of the northern Kenya rift. It is shown that in this sector there is a distinct petrochemical evolution from the Miocene to the Pleistocene, the general trend being a decrease in silica undersaturation in both mafic and felsic rocks. The succession of lavas and sediments has a maximum thickness of 3 km and the main unconformities, indicating the major faulting episodes, coincide with the petrochemical changes.

scholarly journals Comparative analysis of Cenozoic volcanism in the East China block and Tunkinsky rift zone of the Baikal rift system

2020 ◽  
Vol 43 (1) ◽  
pp. 121-131
Author(s):  
Raisa Lobatskaya ◽  
◽  
Larisa Auzina ◽  
Yongzhan Zhang ◽  
Marina Vanteeva ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Rift Zone ◽  
East China ◽  
Rift System ◽  
Baikal Rift System ◽  
Cenozoic Volcanism

The tectonics of the Mid-Indian Ocean Ridge and the petrography of the solid rocks of its rift zones

1971 ◽  
Vol 268 (1192) ◽  
pp. 653-659 ◽  
Keyword(s):  
Indian Ocean ◽  
Rift Zone ◽  
Geological Features ◽  
International Indian Ocean Expedition ◽  
Rift Zones ◽  
Indian Ridge ◽  
Ocean Ridge

The structure of the Mid-Indian Ridge has been studied by many authors. Especially active investigations relate to the period of activity of the International Indian Ocean Expedition (1960 to 1965), and results of this work are well known from numerous papers cited in bibliographical list edited by Fox (1967), especially those by Matthews (1966), Vine (1966), Cann (1968), Cann & Vine (1966), Laughton (1966), Fisher (1965) and Engel & Fisher (1969). Russian expeditions in the area of the Mid-Indian Ridge (figure 1) paid particular attention to the correlation between different geophysical and geological features of the rift zone. These results are not so well known for language reasons and because there are few publications.

X V III. Discussion

1965 ◽  
Vol 258 (1088) ◽  
pp. 205-213 ◽  
Keyword(s):  
Red Sea ◽  
Continental Drift ◽  
Rift System ◽  
Gulf Of Aden ◽  
Vertical Movements ◽  
Red Sea Rift ◽  
Geological Features ◽  
Carlsberg Ridge ◽  
History Of ◽  
African Rift

We have heard many excellent arguments in favour of continental drift, based on the most recent results of studies of the ocean floors, the fit of the continents, the palaeomagnetic picture, and several instances of the relation between geological features and the supposed movement of the continents. It has struck me that these geological features are very restricted in number; they are either the oceanic rifts or wrench faults. Let us have a look first at the oceanic rifts. They are directly connected, through the Carlsberg Ridge and the Gulf of Aden with the Red Sea Rift and then through the Ethiopian faults with the famous African rifts. The history of the African rift system is relatively well known, and we know for certain that they represent principally vertical movements of the Earth’s crust, which have lasted at least from the Tertiary and probably since the Jurassic.

Structural Position of the Pleistocene Gesher Benot Ya'aqov Site in the Dead Sea Rift Zone

1989 ◽  
Vol 31 (3) ◽  
pp. 371-376 ◽  
Author(s):  
N. Goren-Inbar ◽  
S. Belitzky
Keyword(s):  
Rift Zone ◽  
Dead Sea ◽  
Tectonic Activity ◽  
Middle Pleistocene ◽  
Rift System ◽  
East African ◽  
Structural Position ◽  
Red Sea Rift ◽  
Geographical Position ◽  
The Dead

AbstractNewly discovered outcrops of the middle Pleistocene Benot Ya'aqov Formation are strongly disturbed due to recent tectonic activity along the Dead Sea Rift. The lacustrine-fluviatile sediments of this formation comprise the littoral facies of a paleo-lake that occupied the adjacent Hula Basin. Acheulian artifacts, found embedded in the formation, have typical African characteristics. The geographical position of the site (the northern extension of the East African Red Sea Rift System) is important for understanding hominid diffusion from Africa to Eurasia.

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