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  • Safipour, Roxana  (3)
  • 2015-2019  (3)
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  • 2015-2019  (3)
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  • 1
    Online-Ressource
    Online-Ressource
    Society of Exploration Geophysicists ; 2017
    In:  GEOPHYSICS Vol. 82, No. 6 ( 2017-11-01), p. E297-E313
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 82, No. 6 ( 2017-11-01), p. E297-E313
    Kurzfassung: The transient electromagnetic (TEM) method has recently been proposed as a tool for mineral exploration on the seafloor. Similar to airborne TEM surveys conducted on land, marine TEM systems can use a concentric or coincident wire-loop transmitter and receiver towed behind a ship. Such towed-loop TEM surveys can be further augmented by placing additional stationary receivers on the seafloor throughout the survey area. We examine the electric fields measured by remote receivers from an inductive source transmitter within a 1D layered earth model. At sea, it is conceivable to deploy either a horizontal transmitter (such as the analogous standard airborne configuration) or a more exotic vertical transmitter. Therefore, we study and compare the sensitivity of the vertical and horizontal towed-loop systems with a variety of seafloor conductivity structures. Our results indicate that the horizontal loop system is more sensitive to the thickness of a buried conductive layer and would be advantageous over the vertical loop system in characterizing the size of a shallowly buried mineralized zone. The vertical loop system is more sensitive to a resistive layer than the horizontal loop system. The vertical electric field produced by the vertical loop transmitter is sensitive to greater depths than the horizontal fields, and measuring the vertical field at the receivers would therefore be advantageous. We also conducted a novel test of a towed horizontal loop system with remote dipole receivers in a marine setting. The system was tested at the Palinuro volcanic complex in the Tyrrhenian Sea, a site of known massive sulfide mineralization. Preliminary results are consistent with shallowly buried material in the seafloor of conductivities [Formula: see text].
    Materialart: Online-Ressource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Sprache: Englisch
    Verlag: Society of Exploration Geophysicists
    Publikationsdatum: 2017
    ZDB Id: 2033021-2
    ZDB Id: 2184-2
    SSG: 16,13
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    In: Geophysical Prospecting, Wiley, Vol. 66, No. 7 ( 2018-09), p. 1415-1432
    Kurzfassung: We study a new marine electromagnetic configuration that consists of a ship‐towed inductive source transmitter and a series of remote electric dipole receivers placed on the seafloor. The approach was tested at the Palinuro Seamount in the southern Tyrrhenian Sea, at a site where massive sulphide mineralization has been previously identified by shallow drilling. A 3D model of the Palinuro study area was created using bathymetry data, and forward modelling of the electric field diffusion was carried out using a finite volume method. These numerical results suggest that the remote receivers can theoretically detect a block of shallowly buried conductive material at up to ∼100 m away when the transmitter is located directly above the target. We also compared the sensitivity of the method using either a horizontal loop transmitter or a vertical loop transmitter and found that when either transmitter is located directly above the mineralized zone, the vertical loop transmitter has sensitivity to the target at a farther distance than the horizontal loop transmitter in the broadside direction by a few tens of metres. Furthermore, the vertical loop transmitter is more effective at distinguishing the seafloor conductivity structure when the vertical separation between transmitter and receiver is large due to the bathymetry. As a horizontal transmitter is logistically easier to deploy, we conducted a first test of the method with a horizontal transmitter. Apparent conductivities are calculated from the electric field transients recorded at the remote receivers. The analysis indicates higher apparent seafloor conductivities when the transmitter is located near the mineralized zone. Forward modelling suggests that the best match to the apparent conductivity data is obtained when the mineralized zone is extended southward by 40 m beyond the zone of previous drilling. Our results demonstrate that the method adds value to the exploration and characterization of seafloor massive sulphide deposits.
    Materialart: Online-Ressource
    ISSN: 0016-8025 , 1365-2478
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2018
    ZDB Id: 2020311-1
    ZDB Id: 799178-2
    SSG: 16,13
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Online-Ressource
    Online-Ressource
    Society of Exploration Geophysicists ; 2017
    In:  GEOPHYSICS Vol. 82, No. 6 ( 2017-11-01), p. A51-A56
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 82, No. 6 ( 2017-11-01), p. A51-A56
    Kurzfassung: The self-potential (SP) method detects naturally occurring electric fields, which may be produced by electrically conductive mineral deposits, such as massive sulfides. Recently, there has been increasing interest in applying this method in a marine environment to explore for seafloor massive sulfide (SMS) deposits, which may contain economic resources of base and precious metals. Although SMS sites that are associated with active venting and are not buried under sediment cover are known to produce an SP signal, the effectiveness of the method at detecting inactive and sediment-covered deposits remained an outstanding question. We built an instrument capable of recording SP data in a marine setting. We carried out a test of the instrument at the Palinuro Seamount in the Tyrrhenian Sea. Palinuro is one of only a few known sites containing an SMS occurrence that is buried under sediment and not associated with active hydrothermal venting, although diffuse seepage of hydrothermal fluids is known to occur at the site. Elevated electric field strengths recorded in and near the site of previously drilled massive sulfide samples are on the order of [Formula: see text]. A second zone of high field strengths was detected to the north of the drilling area where gravity coring later confirmed the existence of massive sulfides. Our observations indicate that an SP signal can be observed at the site of SMS mineralization even when the mineralized zone is shallowly buried and active hydrothermal venting is not present. These observations could aid in the planning of future marine research expeditions that use the SP method in the exploration of seafloor massive sulfides.
    Materialart: Online-Ressource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Sprache: Englisch
    Verlag: Society of Exploration Geophysicists
    Publikationsdatum: 2017
    ZDB Id: 2033021-2
    ZDB Id: 2184-2
    SSG: 16,13
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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