scholarly journals Motion in the north Iceland volcanic rift zone accommodated by bookshelf faulting

2013 ◽  
Vol 7 (1) ◽  
pp. 29-33 ◽  
Author(s):  
Robert G. Green ◽  
Robert S. White ◽  
Tim Greenfield
Keyword(s):  
Rift Zone ◽  
The North ◽  
Bookshelf Faulting

scholarly journals A broken plate beneath the North Baikal Rift Zone revealed by gravity modelling

1994 ◽  
Vol 21 (2) ◽  
pp. 129-132 ◽  
Author(s):  
E. B. Burov ◽  
F. Houdry ◽  
M. Diament ◽  
J. Déverchère
Keyword(s):  
Rift Zone ◽  
Baikal Rift Zone ◽  
Gravity Modelling ◽  
The North

scholarly journals Rift zone-parallel extension during segmented fault growth: application to the evolution of the NE Atlantic

2017 ◽  
Author(s):  
Alodie Bubeck ◽  
Richard J. Walker ◽  
Jonathan Imber ◽  
Robert E. Holdsworth ◽  
Christopher J. MacLeod ◽  
...  
Keyword(s):  
Rift Zone ◽  
Vertical Axis ◽  
Continental Rift ◽  
Normal Faults ◽  
Ne Atlantic ◽  
Rift Basins ◽  
Volume Increase ◽  
Bookshelf Faulting ◽  
Fault Growth ◽  
Parallel Extension

Abstract. The mechanical interaction of propagating normal faults is known to influence the linkage geometry of first-order faults, and the development of second-order faults and fractures, which transfer displacement within relay zones. Natural examples of growth faults from two active volcanic rift zones (Koa’e, Big Island, Hawaii and Krafla, northern Iceland) illustrate the importance of relay zone heave gradients and associated vertical axis rotations in evolving continental rift systems. Detailed field mapping of deformation within two relay zones, located at the tips of en echelon rift faults, reveals pronounced heave displacement deficits that are accommodated by: (1) extensional-shear faults that strike at a low angle ( 45°) and accommodate a significant component of rift zone-parallel extension. Such extension parallel to the rift axis may oppose any shear-induced shortening that is typically required for vertical axis rotations (e.g. bookshelf faulting models). At the surface, this volume increase is accommodated by open fractures, but may be accommodated in the subsurface by veins or dikes oriented oblique- and normal to the rift axis. This proposal is consistent with data from exhumed contemporaneous fault and dike systems seen on the Faroe Islands and in Kangerlussuaq (East Greenland). Based on the findings presented here we propose a new conceptual model for the evolution of segmented continental rift basins on the NE Atlantic margins.

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>

Diffuse H2 and He degassing survey to study of hidden potential geothermal systems in La Palma, Canary Islands

2020 ◽  
Author(s):  
Fátima Rodríguez ◽  
Antonio Polo Sánchez ◽  
Katherine Dale ◽  
Chloe Codner ◽  
Alba Martín ◽  
...  
Keyword(s):  
Rift Zone ◽  
Average Distance ◽  
Hydrothermal Systems ◽  
Soil Gas ◽  
Geothermal Systems ◽  
Soil Matrix ◽  
North West ◽  
The North ◽  
La Palma ◽  
Cumbre Vieja

<p>La Palma is one of the eastern islands of the Canary Archipelago located off the West African continental margin. Volcanic activity in the last 123 ka has taken place exclusively at the southern part of the island, where Cumbre Vieja volcano has been formed. Cumbre Vieja, one of the most active basaltic volcano in the Canaries, host seven historical eruptions being Teneguía eruption (1971) the most recent one. Cumbre Vieja volcano, characterized by a main north–south rift zone 20 km long and covering an area of 220 km<sup>2</sup>, does not show any visible degassing that show the existence of active geothermal systems. For that reason, geochemical prospecting of soil gases and volatiles in the soil matrix itself of Cumbre Vieja can provide useful information to investigate the presence of permeable areas and potential upflow areas for the degassing of geothermal systems at depth.</p><p>We report herein the results of an intensive soil gas study, focused on non-reactive and/or highly mobile gases such as helium (He) and hydrogen (H<sub>2</sub>), in Cumbre Vieja, with geothermal exploration purposes. He has unique characteristics as a geochemical tracer: it is chemically inert and radioactively stable, non-biogenic, highly mobile and relatively insoluble in water. H<sub>2</sub> is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas.</p><p>Soil gas samples were collected at 1,201 sites selected from June 2019 to September 2019, with an average distance between sites of ≈ 250 m, at ≈ 40 cm depth using a metallic probe. He content was analyzed by means of a quadrupole mass spectrometer (QMS; Pfeiffer Omnistar 422) and hydrogen concentrations by a micro-gas chromatograph (microGC; VARIAN CP490). Soil He concentration showed values up to 23.9 ppm with an average of 5.73 ppm. Soil H<sub>2</sub> concentrations measured ranged from typical atmospheric values (≈ 0.5 ppm) up to 19.8 ppm. The mean value measured for H<sub>2</sub> was 0.78 ppm. Although He concentration values showed high spatial variability, the highest values can be observed in the north–south rift zone of Cumbre Vieja and around the surface contact with Cumbre Nueva ridge. Spatial distribution of H<sub>2</sub> concentration showed the highest values in the north-west area of Cumbre Vieja volcano. The results showed here are useful to identify the possible existence of permeable portions of deep-seated actively degassing geothermal reservoirs. However, a multidisciplinary approach is essential to obtain additional information about possible geothermal systems underlying at Palma island with the last goal of the selection of appropriate locations for future exploratory wells.</p>

scholarly journals From continental platform towards rifting of the Tisza Unit in the Late Triassic to Early Cretaceous

2013 ◽  
Vol 64 (4) ◽  
pp. 279-290 ◽  
Author(s):  
Géza Császár ◽  
Balázs Szinger ◽  
Olga Piros
Keyword(s):  
Middle Jurassic ◽  
Middle Triassic ◽  
Rift Zone ◽  
Patch Reef ◽  
Upper Jurassic ◽  
Late Triassic ◽  
The North ◽  
Marine Carbonates ◽  
Points Of View ◽  
Thinned Continental Crust

Abstract The Upper Triassic-Lower Cretaceous successions of the Transdanubian part of the Mecsek and Villány- Bihor Zones of the Tisza Unit have been studied from the lithological, lithostratigraphical, sedimentological, microfossil and microfacies points of view in order to correlate and interpret the significant differences between them and to draw a conclusion about their geological and paleogeographical history. After an overview of the paleogeographical reconstructions of the broader area, the succession of the Mecsek and Villány-Bihor Zones and the debated Máriakéménd-Bár Range are introduced. Until the end of the Middle Triassic the study area acted as an entity. The first fundamental difference between the two zones can be recognized in the Late Triassic when marine carbonates were replaced by thick fluvial siliciclastics in the Mecsek Zone, while it is represented only by small, local lenses with a few and thin dolostone intercalations in the Villány Zone. The Mecsek Zone is bordered southward by one of the large listric faults to the north of which very thick siliciclastics developed in the Early to Middle Jurassic, whereas it is highly lacunose in the larger western part of the Villány-Bihor Zone. The break at the base is subaerial, higher in the succession it is shallow submarine. The sediment is silty, occasionally sandy crinoidal limestone of late Early Jurassic or even Middle Jurassic in age. The Upper Jurassic in the Mecsek Zone is composed of deep-water cherty limestone while in the Villány Zone it became a thick, shallowing pelagic limestone with reworked patch reef fragments. It is clear evidence that the Mecsek Zone had a thinned continental crust thanks to the nearby rift zone while in the Villány Zone the crust remained thick. The actualized version of the Plašienka’s paleogeographical model (Plašienka 2000) is introduced

Earthquakes off the north Pacific Coast of the United States*

1956 ◽  
Vol 46 (3) ◽  
pp. 165-173
Author(s):  
Don Tocher
Keyword(s):  
United States ◽  
North Pacific ◽  
Linear Extension ◽  
Pacific Coast ◽  
Rift Zone ◽  
The United States ◽  
The Other ◽  
The North ◽  
San Andreas ◽  
The North Pacific

Abstract Epicenters of most of the larger earthquakes occurring off the coast of northern California and Oregon lie in two zones. One zone includes the north-facing submarine Gorda Escarpment, which extends nearly due west from Punta Gorda, and the south-facing Mendocino Escarpment as far offshore as long. 127° W. The other zone extends northwestward from the region of Cape Mendocino, indicating a linear extension of the San Andreas Rift zone as far as lat. 44° or 45° N.

Subduction of a rifted passive continental margin: the Pohorje case of Eastern Alps - constraints from geochronology and geochemistry

2020 ◽  
Author(s):  
Ruihong Chang ◽  
Franz Neubauer ◽  
Johann Genser ◽  
Yongjiang Liu ◽  
Sihua Yuan
Keyword(s):  
Continental Crust ◽  
Rift Zone ◽  
Eastern Alps ◽  
Ultrahigh Pressure ◽  
Geochemical Data ◽  
Late Permian ◽  
The North ◽  
Hp Metamorphism ◽  
Zircon Crystallization ◽  
Alternative Scenarios

<p>A-type subduction is considered to occur at the final stage of continent-continent collision. In many cases, the UHP/HP metamorphic conditions are well known but data on the type of subducted continental crust is lacking. In terms of end members, the type of subducted crust is either (1) normal thick continental crust or (2) the crust from the center of a rift zone, which is influenced by strong extension, high-temperature metamorphism due to thinning of even the continental mantle lithosphere and strong magmatism. To resolve these alternative scenarios, we investigated the southernmost part of the Eclogite-Gneiss Unit (EGU) of Cretaceous metamorphic age exposed in the Pohorje Mountains in Eastern Alps. There, UHP eclogites and ultramafic mantle rocks are exposed in a matrix of paragneiss and hitherto undated granitic orthogneises (Kirst et al., 2010). This study presents, for the first time, geochronological and geochemical data from newly discovered Permian granitic orthogneisses in this area. LA-ICP-MS zircon U–Pb ages of the orthogneisses are 255±2.2 Ma and 260±0.81 Ma, which are interpreted as the age of zircon crystallization in a magma. In contrast, all rounded zircons from paragneissic rocks give Cretaceous ages (89.34±0.69 Ma and 90.8±1.2 Ma), considered as the age of UHP/HP metamorphism. These zircons overgrew older zircons of Permian and rare older ages tentatively indicating that the metasedimentary could be not older than latest Permian. Zircon εHf(t) values of the four ortho- and paragneisses with (<sup>176</sup>Hf/<sup>177</sup>Hf) initial from 0.282201 to 0.282562, T<sub>DM2</sub> are Proterozoic (1390~1970 Ma). The granitic orthogneisses show the geochemical features (high (La/Lu)<sub> N</sub> ratios (160.3–307.3), strong negative Eu anomalies) of an evolved granite molten from continental crust. This type of orthogneisses could be considered as the source magma of seemingly rootless Late Permian to Triassic pegmatites (Knoll et al., 2018) widespread within the EGU further to the north. The paragneisses are heterogeneously composed and are associated with eclogites and ultramafic cumulates of oceanic affinity (De Hoog et al., 2011). We argue that the Permian granitic orthogneisses might be derived from partial melting of lower crust in a rift zone. We consider, therefore, this segment of the EGU as part of the distal Late Permian rift zone, which finally led to the opening of the Meliata Ocean during Middle Triassic times. If true, the new data also imply that the stretched continental crust was potentially not much wider than ca. 100 km, was subducted and then rapidly exhumed during early Late Cretaceous times.</p><p> </p><p><strong>References</strong></p><p>De Hoog, J.C.M., Janák, M., Vrabec, M., Hatton, K.H., 2011. In: Dobrzhinetskaya, L., Faryad, S.W., Wallis, S., Cuthbert, S. (Eds.), Ultrahigh-pressure Metamorphism: 25 Years After the Discovery of Coesite and Diamond. Elsevier Insights, pp. 399–439.</p><p>Janák, M., Froitzheim, N., Yoshida, K., Sasinková, V., Nosko, M., Kobayashi, T., Hirajima, T., Vrabec, M., 2015. Journal of Metamorphic Geology 33, 495–512.</p><p>Kirst, F., Sandmann. S., Nagel. T., et al. 2010. Geologica Carpathica 61(6), 451-461.</p><p>Knoll, T., Schuster, R., Huet, B., Mali, H., Onuk, P., Horschinegg, M., Ertl, A., Giester, G., 2018. Canadian Mineralogist 56, 489-528.</p>

Detrital zircon records of late Paleoproterozoic to early Neoproterozoic northern North China Craton drainage reorganization: Implications for supercontinent cycles

2020 ◽  
Vol 132 (9-10) ◽  
pp. 2135-2153 ◽  
Author(s):  
Chaohui Liu ◽  
Guochun Zhao ◽  
Fulai Liu ◽  
Jianrong Shi ◽  
Lei Ji
Keyword(s):  
Detrital Zircon ◽  
North China Craton ◽  
North China ◽  
Rift Zone ◽  
Fennoscandian Shield ◽  
Detrital Zircons ◽  
Sediment Provenance ◽  
The North ◽  
Khondalite Belt ◽  
Early Neoproterozoic

Abstract Statherian through Tonian strata of the Langshan–Zha’ertai–Bayan Obo–Huade rift zone (LZBH) at the northern margin of the North China Craton provide an excellent record of changes in sediment provenance related to the supercontinent dispersal and amalgamation. During the late Paleoproterozoic to early Neoproterozoic, the LZBH developed over the Yinshan Block and was flanked by the Khondalite Belt to the south, the Trans–North China Orogen and Yanliao rift zone to the east, ultimately preserving a >7000-m-sequence of fluvial, marginal marine, and offshore marine sediments. In order to decipher the influence of these tectonic features on sediment delivery to the area, we evaluated 4955 U-Pb and 1616 Lu-Hf analyses from 66 samples across the entire LZBH, of which 1002 U-Pb and 271 Lu-Hf analyses from 12 samples are newly reported herein. The detrital zircon results indicate three stratigraphic intervals with internally consistent age peaks: (1) Changcheng to lower Jixian system (Statherian–lower Calymmian), (2) upper Jixian system (upper Calymmian), and (3) Qingbaikou system (Tonian). Statistical analysis of the detrital zircon results reveals two distinct changes in sediment provenance. The first transition, between the lower and upper Calymmian, reflects a provenance change from the basement of the Yinshan Block and the Khondalite Belt to a mixed signature, indicating derivation from both basement and Statherian rift-related magmatic products. Such a transition implies establishment of east–west drainage systems traversing the Paleoproterozoic Trans–North China Orogen caused by continued rifting since Statherian and pre-magmatic uplift during breakup of the North China Craton from the Columbia supercontinent. The second transition is indicated by the presence of Mesoproterozoic detrital zircons with juvenile Hf isotopic features since Tonian time and the up-section and northward increase of Mesoproterozoic detrital zircons. Their provenance is interpreted to be the Fennoscandian shield by a pancontinental drainage system related to aggregation of the Rodinia supercontinent. Thus, the detrital zircon spectra in the LZBH document the transition from initial unroofing of local uplifted basement of the Yinshan Block and Khondalite Belt to the distant Yanliao rift zone, then to the more distant Fennoscandian shield.

Sign in / Sign up

Export Citation Format

Share Document