Obtaining Hyperspectral Signatures for Seafloor Massive Sulphide Exploration

Abstract

Seafloor massive sulphide (SMS) deposits are hosts to a wide range of economic minerals, and may become an important resource in the future. The exploitation of these resources is associated with considerable expenses, and a return on investment may depend on the availability of multiple deposits. Therefore, efficient exploration methodologies for base metal deposits are important for future deep sea mining endeavours. Underwater hyperspectral imaging (UHI) has been demonstrated to be able to differentiate between different types of materials on the seafloor. The identification of possible end-members from field data requires prior information in the form of representative signatures for distinct materials. This work presents hyperspectral imaging applied to a selection of materials from the Loki’s Castle active hydrothermal vent site in a laboratory setting. A methodology for compensating for systematic effects and producing the reflectance spectra is detailed, and applied to recover the spectral signatures from the samples. The materials investigated were found to be distinguishable using unsupervised dimensionality reduction methods, and may be used as a reference for future field application.

Underwater Hyperspectral Imaging (UHI): A Review of Systems and Applications for Proximal Seafloor Ecosystem Studies

“…Studies that used imaging spectroscopy without submerging the instrument but for similar research objectives were included for discussion purposes. We have excluded information and studies targeting underwater mineral spectral signatures [58,59], archeology [60], and aquaculture [61].…”

Underwater Optical Imaging: Key Technologies and Applications Review

“…In 2013, Johnsen et al [67] developed a push-broom underwater hyperspectral imagery (UHI) system based on grating diffraction. The detection band range, the number of bands, the spectral resolution, and the detection range of the UHI system are respectively 400-720 nm, 150-200, 2.2-5.5 nm, and 0.2-5 m. This system was the only one commercial underwater spectral imaging system, which was mainly used for benthic habitat mapping [68][69][70], marine mineral exploration [71][72][73] and underwater archaeology [23,74]. In 2018, Wu et al [75] developed a staring type underwater multispectral imaging (UMSI) system containing 31 narrowband color filters installed on double filter wheels.…”

Underwater Hyperspectral Imaging Technology and Its Applications for Detecting and Mapping the Seafloor: A Review

“…In previous studies on manganese nodules and hydrothermal materials, the hyperspectral data were nearly pseudo-reflectance spectra processed by the median-spectra approach, making it difficult to reflect the real components of minerals and perform subsequent quantitative analysis. Sture et al [ 74 ] proposed an underwater light propagation model to calculate the absolute reflectance spectra of the underwater objects. The model ignored the effects such as diffraction, wave interference and the secondary emission of photons from the target material and aimed to remove the interference irrelevant to the reflective properties of the target in a final step.…”