GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 2015-2019  (217)
Document type
Keywords
Publisher
Language
Years
Year
  • 1
    Online Resource
    Online Resource
    SO 231 - PAGE FOUR - Leg 2 - Der passive und der gescherte Kontinentrand vor Mosambik: früher Zerfall Gondwanas und der rezente Einfluss des ostafrikanischen Riftsystems (Weitwinkelseismik - AWI) : Schlussbericht : Laufzeit des Vorhabens: 01.02.2014-30.03.2017, Berichtszeitraum: 01.02.2014-30.03.2017 (2017)
    Bremerhaven : Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung
    Details Availability
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (23 Seiten, 7,28 MB) , Illustrationen, Diagramme
    URL: https://doi.org/10.2314/GBV:1009834037
    DOI: 10.2314/GBV:1009834037
    Language: German
    Note: Förderkennzeichen BMBF 03G0231B , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GEOMAR CATALOGUE
    Link to Library Catalog
    get availability status
  • 2
    Online Resource
    Online Resource
    SO 230 - MOCOM: Asymmetrisches Aufbrechen von Gondwana im Mosambik Becken : Schlussbericht : Berichtszeitraum: 01.10.2013-30.11.2016 (2017)
    Bremerhaven : Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
    Details Availability
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (19 Seiten, 5,51 MB) , Diagramme
    URL: https://edocs.tib.eu/files/e01fb17/893658049.pdf
    URL: https://doi.org/10.2314/GBV:893658049
    DOI: 10.2314/GBV:893658049
    Language: German
    Note: Förderkennzeichen BMBF 03G0230A , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GEOMAR CATALOGUE
    Link to Library Catalog
    get availability status
  • 3
    facet.materialart.
    Unknown
    Seismicity in the vicinity of the Tristan da Cunha hotspot: Particular plate tectonics and mantle plume presence (2017)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Solid Earth, 122 (12). pp. 10427-10439.
    Details
    Publication Date: 2020-02-06
    Description: Earthquake locations along the southern Mid-Atlantic Ridge have large uncertainties due to the sparse distribution of permanent seismological stations in and around the South Atlantic Ocean. Most of the earthquakes are associated with plate tectonic processes related to the formation of new oceanic lithosphere, as they are located close to the ridge axis or in the immediate vicinity of transform faults. A local seismological network of ocean-bottom seismometers and land stations on and around the archipelago of Tristan da Cunha, allowed for the first time a local earthquake survey for one year. We relate intra-plate seismicity within the African oceanic plate segment north of the island partly to extensional stresses induced by a bordering large transform fault and to the existence of the Tristan mantle plume. The temporal propagation of earthquakes within the segment reflects the prevailing stress field. The strong extensional stresses in addition with the plume weaken the lithosphere and might hint at an incipient ridge jump. An apparently aseismic zone coincides with the proposed location of the Tristan conduit in the upper mantle southwest of the islands. The margins of this zone describe the transition between the ductile and the surrounding brittle regime. Moreover, we observe seismicity close to the islands of Tristan da Cunha and nearby seamounts, which we relate to ongoing tectono-magmatic activity.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1002/2017JB015017
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
    facet.materialart.
    Unknown
    Hotspot tracks in the South Atlantic located above bands of fast flowing asthenosphere driven by waning pulsations from the African LLSVP (2018)
    Elsevier
    In:  Gondwana Research, 53 . pp. 197-208.
    Details
    Publication Date: 2018-12-17
    Description: Highlights • Hotspot tracks occur above fast flow anomalies in the asthenosphere. • Flow channels driven by broad plumes from the African LLSVP. • Zoned intraplate sub-tracks sample shallow convection from the top of LLSVP plumes. • Multiple pulsating African LLSVP plumes drive regional plate tectonics. Abstract The location and crustal structure of hotspot tracks in the South Atlantic reflect where melts related to sluggishly flowing plume material can reach the plate surface. This raises the paradox of how long-lived, age progressive hotspot tracks can arise in the absence of closely spaced, narrow mantle plumes. Here we show that young hotspot trails in the southern South Atlantic are located above bands of seismically slow material in the asthenosphere, which we interpret as channels of fast-flowing asthenosphere fed by a large scale plume upwelling from the African LLSVP. A broad region of seismically slow asthenosphere in the vicinity of Paraná continental flood basalts may be indicative of a long-lived, large scale plume under the South American plate. We propose that hotspot tracks developed above fast flow channels in the asthenosphere that evolved between these large-scale plumes as they migrated apart with the African and South American plates, respectively. A progression from continental flood basalts to broad aseismic ridges (e.g., Walvis Ridge-Rio Grande Rise), to low volume intraplate hotspot tracks (e.g., Tristan-Gough; Discovery; Shona and Bouvet) reflects the interplay between tectonic setting and asthenosphere flow channels driven by waning pulsations from these diverging LLSVP plumes. We link the splitting of the Walvis Ridge into isotopically distinct, age-progressive intraplate sub-tracks about 72 Ma to the first sampling of material rising from the African LLSVP plume, perhaps as weak shallow long-lived plumes. Faster flowing asthenosphere enables melts related to LLSVP plumes to reach the plate surface via spreading and tectonic boundaries, and as low-volume intraplate hotspot (sub)tracks. The concept that asthenosphere flow channels and hotspot tracks evolve together between pulsating deep-seated plumes under Africa and South America suggests that LLSVPs might be a significant force in driving continental rifting and (absolute) plate motion.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gr.2017.05.014
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
    facet.materialart.
    Unknown
    Crustal structure of northwest Namibia: Evidence for plume-rift-continent interaction (2015)
    GSA, Geological Society of America
    In:  Geology, 43 (8). pp. 739-742.
    Details
    Publication Date: 2017-05-17
    Description: The causes for the formation of large igneous provinces and hotspot trails are still a matter of considerable dispute. Seismic tomography and other studies suggest that hot mantle material rising from the core-mantle boundary (CMB) might play a significant role in the formation of such hotspot trails. An important area to verify this concept is the South Atlantic region, with hotspot trails that spatially coincide with one of the largest low-velocity regions at the CMB, the African large low shear-wave velocity province. The Walvis Ridge started to form during the separation of the South American and African continents at ca. 130 Ma as a consequence of Gondwana breakup. Here, we present the first deep-seismic sounding images of the crustal structure from the landfall area of the Walvis Ridge at the Namibian coast to constrain processes of plume-lithosphere interaction and the formation of continental flood basalts (Paraná and Etendeka continental flood basalts) and associated intrusive rocks. Our study identified a narrow region (〈100 km) of high-seismic-velocity anomalies in the middle and lower crust, which we interpret as a massive mafic intrusion into the northern Namibian continental crust. Seismic crustal reflection imaging shows a flat Moho as well as reflectors connecting the high-velocity body with shallow crustal structures that we speculate to mark potential feeder channels of the Etendeka continental flood basalt. We suggest that the observed massive but localized mafic intrusion into the lower crust results from similar-sized variations in the lithosphere (i.e., lithosphere thickness or preexisting structures)
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/G36768.1
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
    facet.materialart.
    Unknown
    Deformation-related volcanism in the Pacific Ocean linked to the Hawaiian–Emperor bend (2015)
    Nature Publishing Group
    In:  Nature Geoscience, 8 (5). pp. 393-397.
    Details
    Publication Date: 2019-09-23
    Description: Ocean islands, seamounts and volcanic ridges are thought to form above mantle plumes. Yet, this mechanism cannot explain many volcanic features on the Pacific Ocean floor and some might instead be caused by cracks in the oceanic crust linked to the reorganization of plate motions. A distinctive bend in the Hawaiian–Emperor volcanic chain has been linked to changes in the direction of motion of the Pacific Plate, movement of the Hawaiian plume, or a combination of both. However, these links are uncertain because there is no independent record that precisely dates tectonic events that affected the Pacific Plate. Here we analyse the geochemical characteristics of lava samples collected from the Musicians Ridges, lines of volcanic seamounts formed close to the Hawaiian–Emperor bend. We find that the geochemical signature of these lavas is unlike typical ocean island basalts and instead resembles mid-ocean ridge basalts. We infer that the seamounts are unrelated to mantle plume activity and instead formed in an extensional setting, due to deformation of the Pacific Plate. 40Ar/39Ar dating reveals that the Musicians Ridges formed during two time windows that bracket the time of formation of the Hawaiian–Emperor bend, 53–52 and 48–47 million years ago. We conclude that the Hawaiian–Emperor bend was formed by plate–mantle reorganization, potentially triggered by a series of subduction events at the Pacific Plate margins.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: archive
    DOI: 10.1038/ngeo2416
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
    facet.materialart.
    Unknown
    Hunting for the Tristan Mantle Plume - An upper mantle tomography around the volcanic island of Tristan da Cunha (2017)
    Elsevier
    In:  Earth and Planetary Science Letters, 462 . pp. 122-131.
    Details
    Publication Date: 2020-02-06
    Description: The active volcanic island Tristan da Cunha, located at the southwestern and youngest end of the Walvis Ridge - Tristan/Gough hotspot track, is believed to be the surface expression of a huge thermal mantle anomaly. While several criteria for the diagnosis of a classical hotspot track are met, the Tristan region also shows some peculiarities. Consequently it is vigorously debated if the active volcanism in this region is the expression of a deep mantle plume, or if it is caused by shallow plate tectonics and the interaction with the nearby Mid-Atlantic Ridge. Because of a lack of geophysical data in the study area, no model or assumption has been completely confirmed. We present the first amphibian P-wave finite-frequency travel time tomography of the Tristan da Cunha region, based on cross-correlated travel time residuals of teleseismic earthquakes recorded by 24 ocean-bottom seismometers. The data can be used to image a low velocity structure southwest of the island. The feature is cylindrical with a radius of ~ 100 km down to a depth of 250 km. We relate this structure to the origin of Tristan da Cunha and name it the Tristan conduit. Below 250 km the low velocity structure ramifies into narrow veins, each with a radius of ~ 50 km. Furthermore, we imaged a linkage between young seamounts southeast of Tristan da Cunha and the Tristan conduit.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.epsl.2016.12.028
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
    facet.materialart.
    Unknown
    The wide-angle seismic image of a complex rifted margin, offshore North Namibia: Implications for the tectonics of continental breakup (2017)
    Elsevier
    In:  Tectonophysics, 716 . pp. 130-148.
    Details
    Publication Date: 2020-02-06
    Description: Highlights • Up to 33 km thick dominantly gabbroic crust beneath Walvis Ridge • Massive gabbro addition with subjacent cumulates to the COB south of Walvis Ridge. • Slow upper mantle at ~ 35 km depth beneath Etendeka Plateau • 4–6 km thick oceanic crust in the Angola Basin north of Florianopolis Transform • Velocity models suggest a dominant tectonic control on the location of magmatism. Abstract Voluminous magmatism during the South Atlantic opening has been considered as a classical example for plume related continental breakup. We present a study of the crustal structure around Walvis Ridge, near the intersection with the African margin. Two wide-angle seismic profiles were acquired. One is oriented NNW–SSE, following the continent–ocean transition and crossing Walvis Ridge. A second amphibious profile runs NW–SE from the Angola Basin into continental Namibia. At the continent–ocean boundary (COB) the mafic crust beneath Walvis Ridge is up to 33 km thick, with a pronounced high-velocity lower crustal body. Towards the south there is a smooth transition to 20–25 km thick crust underlying the COB in the Walvis Basin, with a similar velocity structure, indicating a gabbroic lower crust with associated cumulates at the base. The northern boundary of Walvis Ridge towards the Angola Basin shows a sudden change to oceanic crust only 4–6 km thick, coincident with the projection of the Florianopolis Fracture Zone, one of the most prominent tectonic features of the South Atlantic ocean basin. In the amphibious profile the COB is defined by a sharp transition from oceanic to rifted continental crust, with a magmatic overprint landward of the intersection of Walvis Ridge with the Namibian margin. The continental crust beneath the Congo Craton is 40 km thick, shoaling to 35 km further SE. The velocity models show that massive high-velocity gabbroic intrusives are restricted to a narrow zone directly underneath Walvis Ridge and the COB in the south. This distribution of rift-related magmatism is not easily reconciled with models of continental breakup following the establishment of a large, axially symmetric plume in the Earth's mantle. Rift-related lithospheric stretching and associated transform faulting play an overriding role in locating magmatism, dividing the margin in a magma-dominated southern and an essentially amagmatic northern segment.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.tecto.2016.06.024
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
    facet.materialart.
    Unknown
    Marine magnetotellurics imaged no distinct plume beneath the Tristan da Cunha hotspot in the southern Atlantic Ocean (2017)
    Elsevier
    In:  Tectonophysics, 716 . pp. 52-63.
    Details
    Publication Date: 2020-02-06
    Description: Highlights • The electrical structure beneath the Tristan da Cunha (TDC) hotspot was investigated. • Plume-like structure was not imaged beneath TDC by 3-D inversion analysis. • The plume may be small and/or weak or take place elsewhere outside of the study area. • Conductivity and bathymetry anomalies show a contrast across the TDC fracture zone. • Mantle temperature and melting process at ridge may cause the conductivity anomaly. Abstract The Tristan da Cunha (TDC) is a volcanic island located above a prominent hotspot in the Atlantic Ocean. Many geological and geochemical evidences support a deep origin of the mantle material feeding the hotspot. However, the existence of a plume has not been confirmed as an anomalous structure in the mantle resolved by geophysical data because of lack of the observations in the area. Marine magnetotelluric and seismological observations were conducted in 2012–2013 to examine the upper mantle structure adjacent to TDC. The electrical conductivity structure of the upper mantle beneath the area was investigated in this study. Three-dimensional inversion analysis depicted a high conductive layer at ~ 120 km depth but no distinct plume-like vertical structure. The conductive layer is mostly flat independently on seafloor age and bulges upward beneath the lithospheric segment where the TDC islands are located compared to younger segment south of the TDC Fracture Zone, while the bathymetry is rather deeper than prediction for the northern segment. The apparent inconsistency between the absence of vertical structure in this study and geochemical evidences on deep origin materials suggests that either the upwelling is too small and/or weak to be resolved by the current data set or that the upwelling takes place elsewhere outside of the study area. Other observations suggest that 1) the conductivity of the upper mantle can be explained by the fact that the mantle above the high conductivity layer is depleted in volatiles as the result of partial melting beneath the spreading ridge, 2) the potential temperature of the segments north of the TDC Fracture Zone is lower than that of the southern segment at least during the past ~ 30 Myr.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.tecto.2016.09.033
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
    facet.materialart.
    Unknown
    Thickness of the oceanic crust, the lithosphere, and the mantle transition zone in the vicinity of the Tristan da Cunha hot spot estimated from ocean-bottom and ocean-island seismometer receiver functions (2017)
    Elsevier
    In:  Tectonophysics, 716 . pp. 33-51.
    Details
    Publication Date: 2020-02-06
    Description: Highlights • Receiver functions from ocean-bottom seismometer stations reveal no significant crustal thickening in the surrounding of the Tristan da Cunha hot spot. • The mantle transition zone to the NW of Tristan da Cunha is thickened and cool. • The mantle transition zone is potentially thinned to the south/southwest of Tristan da Cunha. • A thickness of 60 to 75 km beneath Tristan da Cunha argues for a compositional control on the seismological lithosphere in the South Atlantic. Abstract The most prominent hotspot in the South Atlantic is Tristan da Cunha, which is widely considered to be underlain by a mantle plume. But the existence, location and size of this mantle plume have not been established due to the lack of regional geophysical observations. A passive seismic experiment using ocean bottom seismometers aims to investigate the lithosphere and upper mantle structure beneath the hotspot. Using the Ps receiver function method we calculate a thickness of 5 to 8 km for the oceanic crust at 17 ocean-bottom stations deployed around the islands. Within the errors of the method the thickness of the oceanic crust is very close to the global mean. The Tristan hotspot seems to have contributed little additional magmatic material or heat to the melting zone at the mid-oceanic ridge, which could be detected as thickened oceanic crust. Magmatic activity on the archipelago and surrounding seamounts seems to have only effected the crustal thickness locally. Furthermore, we imaged the mantle transition zone discontinuities by analysing receiver functions at the permanent seismological station TRIS and surrounding OBS stations. Our observations provide evidence for a thickened (cold) mantle transition zone west and northwest of the islands, which excludes the presence of a deep-reaching mantle plume. We have some indications of a thinned, hot mantle transition zone south of Tristan da Cunha inferred from sparse and noisy observations, which might indicate the location of a Tristan mantle plume at mid-mantle depths. Sp receiver functions image the base of lithosphere at about 60 to 75 km beneath the islands, which argues for a compositionally controlled seismological lithosphere-asthenosphere boundary beneath the study area.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.tecto.2016.12.013
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...