Mapping seafloor massive sulfides with the Golden Eye frequency-domain EM profiler

Müller, Hendrik; Schwalenberg, Katrin; Reeck, Konstantin; Barckhausen, Udo; Schwarz-Schampera, Ulrich; Hilgenfeldt, Christian; Dobeneck, Tilo von

doi:10.3997/1365-2397.n0127

Cited by 15 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…By submerging the GOLDEN EYE in a seawater pool with various configurations, it was experimentally proven that the distortions were related to the pressure housings in close proximity of the TX and RX coils. Thus, substantial post-processing and calibration was required to successfully analyse and invert the data sets (Müller et al, 2018). Due to the nature of a compact multi-sensor platform, positioning of pressure housings out of the sensor's range is not possible.…”

Section: F R E Qu E N C Y -D O M a I N S Y S T E Mmentioning

confidence: 99%

“…GE-OMAR's MARTEMIS time-domain electromagnetic (TDEM) and the GOLDEN EYE frequency-domain electromagnetic (FDEM) loop system, operated by Germany's Federal Institute for Geosciences and Natural Resources (BGR), have been developed and deployed at various hydrothermal fields. Conductive structures at the TAG and Palinuro Seamount (Hölz et al, 2015) and in the German licence areas were successfully mapped for polymetallic sulphides at the Central Indian Ridge (Schwalenberg et al, 2016;Müller et al, 2018). Sensor operations in mid-ocean ridge settings, at seamounts of complex bathymetry, and under harsh weather conditions, require rigid and compact devices for safe on-board handling and deepwater surveying.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of metallic system components on marine electromagnetic loop data

Reeck

Müller

Hölz

et al. 2020

Geophysical Prospecting

Self Cite

View full text Add to dashboard Cite

Electromagnetic loop systems rely on the use of non‐conductive materials near the sensor to minimize bias effects superimposed on measured data. For marine sensors, rigidity, compactness and ease of platform handling are essential. Thus, commonly a compromise between rigid, cost‐effective and non‐conductive materials (e.g. stainless steel versus fibreglass composites) needs to be found. For systems dedicated to controlled‐source electromagnetic measurements, a spatial separation between critical system components and sensors may be feasible, whereas compact multi‐sensor platforms, remotely operated vehicles and autonomous unmanned vehicles require the use of electrically conductive components near the sensor. While data analysis and geological interpretations benefit vastly from each added instrument and multidisciplinary approaches, this introduces a systematic and platform‐immanent bias in the measured electromagnetic data. In this scope, we present two comparable case studies targeting loop‐source electromagnetic applications in both time and frequency domains: the time‐domain system trades the compact design for a clear separation of 15 m between an upper fibreglass frame, holding most critical titanium system components, and a lower frame with its coil and receivers. In case of the frequency‐domain profiler, the compact and rigid design is achieved by a circular fibreglass platform, carrying the transmitting and receiving coils, as well as several titanium housings and instruments. In this study, we analyse and quantify the quasi‐static influence of conductive objects on time‐ and frequency‐domain coil systems by applying an analytically and experimentally verified 3D finite element model. Moreover, we present calibration and optimization procedures to minimize bias inherent in the measured data. The numerical experiments do not only show the significance of the bias on the inversion results, but also the efficiency of a system calibration against the analytically calculated response of a known environment. The remaining bias after calibration is a time/frequency‐dependent function of seafloor conductivity, which doubles the commonly estimated noise floor from 1% to 2%, decreasing the sensitivity and resolution of the devices. By optimizing size and position of critical conductive system components (e.g. titanium housings) and/or modifying the transmitter/receiver geometry, we significantly reduce the effect of this residual bias on the inversion results as demonstrated by 3D modelling. These procedures motivate the opportunity to design dedicated, compact, low‐bias platforms and provide a solution for autonomous and remotely steered designs by minimizing their effect on the sensitivity of the controlled‐source electromagnetic sensor.

show abstract

Section: F R E Qu E N C Y -D O M a I N S Y S T E Mmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of metallic system components on marine electromagnetic loop data

Reeck

Müller

Hölz

et al. 2020

Geophysical Prospecting

Self Cite

View full text Add to dashboard Cite

show abstract

“…In the last decades, galvanometric and electromagnetic methods have been used for the exploration and assessment of SMS resources. These methods include the controlled source electromagnetic (CSEM) method, the direct current (DC) resistivity imaging method, the transient electromagnetic (TEM) method, and the passive self‐potential (SP) method (see case studies in Cairns et al., 1996; Constable et al., 2018; Galley et al., 2021; Gehrmann et al., 2019; Haroon et al., 2018; Ishizu et al., 2019; Kawada & Kasaya, 2018; Müller et al., 2018; Su, Tao, Shen et al., 2022; Szitkar et al., 2021; Zhu et al., 2020). However, ore bodies and metallic deposits are not always characterized by conductivity contrasts (Mao & Revil, 2016; Mao et al., 2016).…”

Section: Introductionmentioning

confidence: 99%

Joint Interpretation of Marine Self‐Potential and Transient Electromagnetic Survey for Seafloor Massive Sulfide (SMS) Deposits: Application at TAG Hydrothermal Mound, Mid‐Atlantic Ridge

Tao

Zhu

et al. 2022

JGR Solid Earth

View full text Add to dashboard Cite

The self-potential (SP) method is expected to play an important role in the exploration of seafloor massive sulfide (SMS) resources. Since the redox potential changes with depth below the seafloor, SMS deposits are the source of an electrical (source) current density, generating in turn a recordable electrical field. This electrical field can be remotely measured at and above the seafloor. By integrating this electrical field, we obtained a so-called SP profile or map. The electrical conductivity distribution of SMS deposits is an important ingredient in the inversion of these SP data in order to distinguish between causative primary sources (i.e., associated with the SMS deposits themselves) and secondary current sources associated with conductivity contrasts below the seafloor. Such ingredient is therefore necessary to properly localize SMS deposits and eliminating ghosts associated with high conductivity contrasts. The conductivity structure of the seafloor is however unknown in most SP surveys. This study presents the first joint interpretation of transient electromagnetic and SP surveys. The field data were acquired at the Trans-Atlantic Geotraverse (TAG) hydrothermal mound. The conductivity structure of TAG mound was obtained by inverting transient electromagnetic data. This electrical conductivity distribution is then used to invert the SP data. The obtained (primary) source current distribution delineates the geometry of the SMS deposits. The deposits are located in the center of the mound as well as at its edges, in a way that is consistent with water column data. Combining the two geophysical methods improves our ability to better decipher the fine geometry of SMS deposits below the seafloor.Plain Language Summary Seafloor massive sulfide (SMS) deposits contain abundant amounts of Cu, Zn, Au, and Ag, which are of growing economic interest for our civilization. In recent years, the exploration of SMS deposits has entered into a new era with the goal of better assess and characterize these resources. In this perspective, geophysical methods are in high demand to localize SMS deposits and obtain their three-dimensional geometry. The self-potential (SP) method provides an efficient non-intrusive and cost-effective approach to image SMS deposits. Previous surveys have documented the existence of recordable negative SP anomalies above the seafloor in association with SMS deposits. SP tomography can be used to assess the 3D geometry of SMS deposits. That said, the conductivity pattern below the seafloor is unknown in previous SP surveys while it is an important ingredient in the inversion of the SP data. Active source measurements like the transient electromagnetic (TEM) method can be used to obtain the electrical conductivity distribution below the seafloor. So, we propose to combine SP and TEM data to improve our ability to image SMS deposits. We apply the new methodology to a famous submarine hydrothermal field located in the Atlantic mid-oceanic ridge Trans-Atlantic Geotraverse and investigated in the past...

show abstract

“…For instance, galvanometric and induction‐based electromagnetic methods are broadly used in seafloor massive sulfide explorations (e.g., Ishizu et al, 2019; Müller et al, 2018, and references therein). Active source methods include induced polarization (IP), electrical conductivity tomography, the time domain electromagnetic method (TEM), and controlled source frequency domain electromagnetic method (CSEM) (Gehrmann et al, 2019; Haroon et al, 2018; Ishizu et al, 2019; Müller et al, 2018; Schwalenberg et al, 2016). Among these methods, TEM and CSEM have been quite popular since continuous measurements can be performed while the sensors are towed by a vessel.…”

Section: Introductionmentioning

confidence: 99%

Self‐Potential Tomography of a Deep‐Sea Polymetallic Sulfide Deposit on Southwest Indian Ridge

et al. 2020

View full text Add to dashboard Cite

Deep-sea polymetallic sulfides associated with hydrothermal systems are considered a potential viable resource for base and precious metals. The Southwest Indian Ridge (SWIR, Indian Ocean) hosts active and inactive hydrothermal systems. Inactive hydrothermal fields are more abundant than active fields but are difficult to remotely characterize. We report a deep-sea self-potential investigation to locate inactive ore deposits at the Yuhuang hydrothermal field on the ultraslow-spreading SWIR. A horizontal array of six nonpolarizing AgCl electrodes are attached to a deep-towed transient electromagnetic system to record the electrical field at a height of 40 m above the seafloor. The observed electrical field strength near a previously recognized sulfide deposits (verified by drilling) reaches an amplitude of 0.5 mV/m. Negative self-potential anomalies (~−27 mV) were observed by integrating the measured electrical field. The high electrical conductivities (up to 12 S/m) of sulfide samples measured in the laboratory and the oxidized sulfides recovered from the surface of the deposit suggest that the self-potential anomalies are due to sulfide mineralization and corrosion of the polymetallic sulfides. Inversion of the self-potential data reveals a localized body with a thickness of~65 m, which is interpreted as the Yuhuang ore deposit. Our field data demonstrate that the self-potential method is a useful exploration method to identify and image seafloor massive sulfide deposits hosted in inactive hydrothermal fields at mid-ocean ridges.

show abstract

Mapping seafloor massive sulfides with the Golden Eye frequency-domain EM profiler

Cited by 15 publications

References 0 publications

Effects of metallic system components on marine electromagnetic loop data

Effects of metallic system components on marine electromagnetic loop data

Joint Interpretation of Marine Self‐Potential and Transient Electromagnetic Survey for Seafloor Massive Sulfide (SMS) Deposits: Application at TAG Hydrothermal Mound, Mid‐Atlantic Ridge

Self‐Potential Tomography of a Deep‐Sea Polymetallic Sulfide Deposit on Southwest Indian Ridge

Contact Info

Product

Resources

About