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  • 1
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    Magnetic exploration of a low-temperature ultramafic-hosted hydrothermal site (Lost City, 30°N, MAR) (2017)
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 461 (2017): 40-45, doi:10.1016/j.epsl.2016.12.033.
    Description: A 2003 high-resolution magnetic survey conducted by the Autonomous Underwater Vehicle ABE over the low-temperature, ultramafic-hosted hydrothermal field Lost City reveals a weak positive magnetic anomaly. This observation is in direct contrast to recent observations of strong positive magnetic anomalies documented over the high-temperature ultramafic-hosted hydrothermal vents fields Rainbow and Ashadze, which indicates that temperature may control the production of magnetization at these sites. The Lost City survey provides a unique opportunity to study a field that is, to date, one of a kind, and is an end member of ultramafic-hosted hydrothermal systems. Our results highlight the key contribution of temperature on magnetite production resulting from serpentinization reactions. Whereas high temperature promotes significant production and partitioning of iron into magnetite, low temperature favors iron partitioning into various alteration phases, resulting in a magnetite-poor rock. Moreover, the distribution of magnetic anomalies confirms results of a previous geological survey indicating the progressive migration of hydrothermal activity upslope. These discoveries contribute to the results of 25 years of magnetic exploration of a wide range of hydrothermal sites, from low- to high-temperature and from basalt- to ultramafic-hosted, and thereby validate using high-resolution magnetics as a crucial parameter for locating and characterizing hydrothermal sites hosting unique chemosynthetic-based ecosystems and potentially mineral-rich deposits.
    Description: Geomar, Helmholtz Centre for Ocean Research (Kiel, Germany) supported this research.
    Keywords: Hydrothermal processes ; Magnetics ; Slow-spreading centers ; Oceanic core complex
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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    PAPER (OA)
  • 2
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    Magnetic and gravity surface geometry inverse modeling of the TAG active mound (2021)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 126(10),(2021): e2021JB022228, https://doi.org/10.1029/2021JB022228.
    Description: Seafloor massive sulfide deposits form in remote environments, and the assessment of deposit size and composition through drilling is technically challenging and expensive. To aid the evaluation of the resource potential of seafloor massive sulfide deposits, three-dimensional inverse modeling of geophysical potential field data (magnetic and gravity) collected near the seafloor can be carried out to further enhance geologic models interpolated from sparse drilling. Here, we present inverse modeling results of magnetic and gravity data collected from the active mound at the Trans-Atlantic Geotraverse hydrothermal vent field, located at 26°08′N on the Mid-Atlantic Ridge, using autonomous underwater vehicle and submersible surveying. Both minimum-structure and surface geometry inverse modeling methods were utilized. Through deposit-scale magnetic modeling, the outer extent of a chloritized alteration zone within the basalt host rock below the mound was resolved, providing an indication of the angle of the rising hydrothermal fluid and the depth and volume of seawater/hydrothermal mixing zone. The thickness of the massive sulfide mound was determined by modeling the gravity data, enabling the tonnage of the mound to be estimated at 2.17 ± 0.44 Mt through this geophysics-based, noninvasive approach.
    Description: The authors would like to thank the captain, crew, and scientific team from the 2016 R/V Meteor M127 and 1994 R/V Yokosuka MODE'94 cruises for all their work collecting the data modeled in this study. C. Galley is funded through an NSERC Discovery Grant and Memorial University's School of Graduate Studies Grant.
    Description: 2022-03-29
    Keywords: Seafloor massive sulfide deposit ; Potential field modeling ; Inverse modeling ; Gravity ; Magnetics
    Repository Name: Woods Hole Open Access Server
    Type: Article
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    PAPER (OA)
  • 3
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    Absolute magnetization of the seafloor at a basalt-hosted hydrothermal site: Insights from a deep-sea submersible survey (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 42 (4). pp. 1046-1052.
    Details
    Publication Date: 2017-11-22
    Description: The analysis of high-resolution vector magnetic data acquired by deep-sea submersibles (DSSs) requires the development of specific approaches adapted to their uneven tracks. We present a method that takes advantage of (1) the varying altitude of the DSS above the seafloor and (2) high-resolution multibeam bathymetric data acquired separately, at higher altitude, by an Autonomous Underwater Vehicle, to estimate the absolute magnetization intensity and the magnetic polarity of the shallow subseafloor along the DSS path. We apply this method to data collected by DSS Nautile on a small active basalt-hosted hydrothermal site. The site is associated with a lack of magnetization, in agreement with previous findings at the same kind of sites: the contrast between nonmagnetic sulfide deposits/stockwork zone and strongly magnetized basalt is sufficient to explain the magnetic signal observed at such a low altitude. Both normal and reversed polarities are observed in the lava flows surrounding the site, suggesting complex history of accumulating volcanic flows.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2014GL062791
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Near-seafloor magnetics reveal tectonic rotation and deep structure at the TAG (Trans-Atlantic Geotraverse) hydrothermal site (Mid-Atlantic Ridge, 26 N) (2015)
    GSA, Geological Society of America
    In:  Geology, 43 (1). pp. 87-90.
    Details
    Publication Date: 2015-01-20
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/G36086.1
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Dyking at EPR 16°N hypermagmatic ridge segment: Insights from near-seafloor magnetics (2016)
    Elsevier
    In:  Earth and Planetary Science Letters, 453 . pp. 288-297.
    Details
    Publication Date: 2019-02-01
    Description: Highlights • New inversion method resolves high-resolution magnetic anomaly along uneven routes. • Linear magnetic lows depict multiple shallow dyke swarms. • These dyke swarms confirm the hypermagmatic activity of the segment. Abstract High-resolution, near-seafloor magnetic data have been acquired over the 16°N hypermagmatic segment of the East-Pacific Rise using an Autonomous Underwater Vehicle. This survey proves to be ideal to test the relative efficiency of various inversion methods applied to data acquired at a more or less constant altitude above the seafloor. Unlike other methods, a recently published Bayesian inversion preserves the short wavelengths and allows for the resolution of a high-resolution reduced-to-the-pole magnetic anomaly. This anomaly unveils the presence of several laterally adjacent dykes associated with individually separated Axial Summit Troughs. The observation of such anomalies, and therefore of shallow dykes, confirms the hypermagmatic character of the segment in a location where complex magma chambers have been imaged in seismic reflection studies. Variable intensity of the magnetic anomalies reflects the depth of the dyke swarms and, ultimately, the timing and style of eruptive events, helping to constrain the spreading axis evolution.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    DOI: 10.1016/j.epsl.2016.08.020
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Magnetic exploration of a low-temperature ultramafic-hosted hydrothermal site (Lost City, 30°N, MAR) (2017)
    Elsevier
    In:  Earth and Planetary Science Letters, 461 . pp. 40-45.
    Details
    Publication Date: 2020-02-06
    Description: Highlights • First magnetic exploration of a low-temperature ultramafic-hosted hydrothermal site. • New inversion method resolves high-resolution magnetic anomaly in a steep environment. • Lost City bears a positive magnetization resulting from specific chemical processes. A 2003 high-resolution magnetic survey conducted by the Autonomous Underwater Vehicle ABEover the low-temperature, ultramafic-hosted hydrothermal field Lost City reveals a weak positive magnetic anomaly. This observation is in direct contrast to recent observations of strong positive magnetic anomalies documented over the high-temperature ultramafic-hosted hydrothermal vents fields Rainbow and Ashadze, which indicates that temperature may control the production of magnetization at these sites. The Lost City survey provides a unique opportunity to study a field that is, to date, one of a kind, and is an end member of ultramafic-hosted hydrothermal systems. Our results highlight the key contribution of temperature on magnetite production resulting from serpentinization reactions. Whereas high temperature promotes significant production and partitioning of iron into magnetite, low temperature favors iron partitioning into various alteration phases, resulting in a magnetite-poor rock. Moreover, the distribution of magnetic anomalies confirms results of a previous geological survey indicating the progressive migration of hydrothermal activity upslope. These discoveries contribute to the results of 25yrs of magnetic exploration of a wide range of hydrothermal sites, from low-to high-temperature and from basalt-to ultramafic-hosted, and thereby validate using high-resolution magnetics as a crucial parameter for locating and characterizing hydrothermal sites hosting unique chemosynthetic-based ecosystems and potentially mineral-rich deposits.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.epsl.2016.12.033
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Revisiting Near-Seafloor Magnetics on the TAG Hydrothermal Site (26°N, MAR): Tectonic and Hydrothermal Implications (2014)
    In:  [Talk] In: AGU Fall Meeting 2014, 15.-19.12.2014, San Francisco, USA .
    Details
    Publication Date: 2016-12-02
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Talk
  • 8
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    High-resolution magnetic signature of active hydrothermal systems in the back-arc spreading region of the southern Mariana Trough (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Solid Earth, 120 (5). pp. 2821-2837.
    Details
    Publication Date: 2017-05-02
    Description: High-resolution vector magnetic measurements were performed on five hydrothermal vent fields of the back-arc spreading region of the southern Mariana Trough using Shinkai 6500, a deep-sea manned submersible. A new 3-D forward scheme was applied that exploits the surrounding bathymetry and varying altitudes of the submersible to estimate absolute crustal magnetization. The results revealed that magnetic-anomaly-derived absolute magnetizations show a reasonable correlation with natural remanent magnetizations of rock samples collected from the seafloor of the same region. The distribution of magnetic-anomaly-derived absolute magnetization suggests that all five andesite-hosted hydrothermal fields are associated with a lack of magnetization, as is generally observed at basalt-hosted hydrothermal sites. Furthermore, both the Pika and Urashima sites were found to have their own distinct low-magnetization zones, which could not be distinguished in magnetic anomaly data collected at higher altitudes by autonomous underwater vehicle due to their limited extension. The spatial extent of the resulting low magnetization is approximately 10 times wider at off-axis sites than at on-axis sites, possibly reflecting larger accumulations of nonmagnetic sulfides, stockwork zones, and/or alteration zones at the off-axis sites.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2014JB011714
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    High-resolution magnetics reveal the deep structure of a volcanic-arc related basalt-hosted hydrothermal site (Palinuro, Tyrrhenian Sea) (2015)
    In:  [Poster] In: GeoBerlin 2015, 04.-07.10.2015, Berlin, Germany .
    Details
    Publication Date: 2016-12-02
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Poster
  • 10
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    Metal resource potential and fluxes at a slow-spreading mid-ocean ridge segment: M127 – Blue Mining @ Sea, seismic and magnetic investigations (2020)
    Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
    In:  In: DFG Status Conference Research Vessels 2020. Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Jülich, pp. 101-103. ISBN 978-3-95806-479-9
    Details
    Publication Date: 2020-07-08
    Type: Book chapter , NonPeerReviewed
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    OceanRep: Book chapter
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