Resource Assessment of Polymetallic Nodules Using Acoustic Backscatter Intensity Data from the Korean Exploration Area, Northeastern Equatorial Pacific
Tóm tắt
A high level of confidence in resource data is a key prerequisite for conducting a reliable economic feasibility study in deep water seafloor mining. However, the acquisition of accurate resource data is difficult when employing traditional point-sampling methods to assess the resource potential of polymetallic nodules, given the vast size of the survey area and high spatial variability in nodule distribution. In this study, we analyzed high-resolution acoustic backscatter intensity images to estimate nodule abundance and increase confidence levels in nodule abundance data. We operated a 120 kHz deep-towed sidescan sonar (DSL-120) system (1×1 m resolution) across a 75 km2 representative area in the Korean Exploration Area for polymetallic nodules in the Northeastern Equatorial Pacific. A deep-towed camera system was also run along two tracks in the same area to estimate the abundance of polymetallic nodules on the seafloor. Backscatter data were classified into four facies based on intensity. The facies with the weakest and strongest backscatter intensities occurred in areas of high slope gradient and basement outcrops, respectively. The backscatter intensities of the two other facies correlated well with the nodule abundances estimated from still-camera images. A linear fit between backscatter intensity and mean nodule abundance for 10 zones in the study area yielded an excellent correlation (r2 = 0.97). This allowed us to compile a map of polymetallic nodule abundance that shows greater resolution than a map derived from the extrapolation of point-sampling data. Our preliminary analyses indicate that it is possible to greatly increase the confidence level of nodule resource data if the relationship between backscatter intensity and nodule abundance is reliably established. This approach has another key advantage over point sampling and image analyses in that detailed maps of mining obstacles along the seafloor are produced when acquiring data on the abundance of polymetallic nodules. The key limitation of this work is a poor correlation between nodule coverage, as observed from photographs, and nodule abundance. Significant additional ground truth sampling using well located box cores should be completed to determine whether or not there is a real correlation between the backscatter and abundance.
Tài liệu tham khảo
citation_title=Handbook of sidescan sonar; citation_publication_date=2009; citation_id=CR1; citation_author=P Blondel; citation_publisher=Springer-Praxis
citation_journal_title=Geosci J; citation_title=Chirp (2-7 kHz) echo characters in the Ulleung Basin; citation_author=SK Chough, SH Lee, JW Kim, SC Park, DG Yoo, HS Han, SH Yoon, SB Oh, YB Kim, GG Back; citation_volume=1; citation_publication_date=1997; citation_pages=143-153; citation_doi=10.1007/BF02910206; citation_id=CR2
CRIRSCO (2014) International reporting template. Committee for Mineral Reserves International Reporting Standards, 41 p
citation_journal_title=Mar Geol; citation_title=Echo character of the western equatorial Atlantic floor and its relationship to the dispersal and distribution of terrigenous sediments; citation_author=JE Damuth; citation_volume=18; citation_publication_date=1975; citation_pages=17-45; citation_doi=10.1016/0025-3227(75)90047-X; citation_id=CR4
citation_journal_title=Mar Geol; citation_title=Use of high-frequency (3.5–12 kHz) echograms in the study of near-bottom sedimentation processes in the deep-sea: a review; citation_author=JE Damuth; citation_volume=38; citation_publication_date=1980; citation_pages=51-75; citation_doi=10.1016/0025-3227(80)90051-1; citation_id=CR5
citation_journal_title=Oceanography; citation_title=Seamount mineral deposits: a source of rare metals for high-technology industries; citation_author=JR Hein, TA Conrad, H Staudigel; citation_volume=23; citation_publication_date=2010; citation_pages=184-189; citation_doi=10.5670/oceanog.2010.70; citation_id=CR6
citation_journal_title=Ore Geol Rev; citation_title=Deep-ocean mineral deposits as a source of critical metals for high- and green-technology applications: comparison with land-based resources; citation_author=JR Hein, K Mizell, A Kochinsky, TA Conrad; citation_volume=51; citation_publication_date=2013; citation_pages=1-14; citation_doi=10.1016/j.oregeorev.2012.12.001; citation_id=CR7
ISA (2014) Workshop on polymetallic nodules resource classification. International Seabed Authority.
https://www.isa.org.jm/workshop/workshop-polymetallic-nodule-resources-classification-october-2014
Accessed 11 Aug 2017
ISA (2015) Reporting standard of the International Seabed Authority for mineral exploration results assessment, mineral resources and mineral reserves. In: Recommendations for the guidance of contractors on the content, format and structure of annual reports, ISBA/21/LTC/15, Kingston, Jamaica, pp 22–43
citation_journal_title=Geo-Mar Lett; citation_title=Optimum sampling interval for evaluating ferromanganese nodule resources in the central Indian Ocean; citation_author=P Jauhari, VN Kodagali, SJ Sankar; citation_volume=21; citation_publication_date=2001; citation_pages=176-182; citation_doi=10.1007/s00367-001-0081-7; citation_id=CR10
citation_title=Report on visual data acquisition in the field and interpretation for SMnN; citation_publication_date=2017; citation_id=CR11; citation_author=T Kuhn; citation_author=M Rathke
citation_title=Classification of manganese nodule estimates: Can we reach the “measured resource” level; citation_inbook_title=45th Underwater Mining Conference (expanded abstract); citation_publication_date=2016; citation_pages=1-6; citation_id=CR12; citation_author=T Kuhn; citation_author=C Ruhlemann; citation_author=A Knobloch
citation_journal_title=Mar Geol; citation_title=Chirp (2–7 kHz) echo characters of the South Korea Plateau, East Sea: styles of mass movement and sediment gravity flow; citation_author=SH Lee, SK Chough, GG Back, YB Kim; citation_volume=184; citation_publication_date=2002; citation_pages=227-247; citation_doi=10.1016/S0025-3227(01)00283-3; citation_id=CR13
citation_journal_title=Mar Geol; citation_title=The relative importance of gravityinduced versus current-controlled sedimentation during the Quaternary along the mideast United-States outer continentalmargin revealed by 3.5 kHz echo character; citation_author=LF Pratson, EP Laine; citation_volume=89; citation_publication_date=1989; citation_pages=87-126; citation_doi=10.1016/0025-3227(89)90029-7; citation_id=CR14
citation_title=Improved signal processing and data acquisition electronics for the DSL-120; citation_inbook_title=IEEE Oceans 2002 Conference and Exhibition; citation_publication_date=2002; citation_pages=2264-2267; citation_id=CR15; citation_author=MR Rognstad; citation_author=M Naiman
citation_title=Current status of manganese nodule exploration in the German license area; citation_inbook_title=Proceedings of the ninth (2011) ISOPE ocean mining symposium; citation_publication_date=2011; citation_pages=168-173; citation_id=CR16; citation_author=C Ruhlemann; citation_author=T Kuhn; citation_author=M Wiedicke; citation_author=S Kasten; citation_author=K Mewes; citation_author=A Picard
citation_journal_title=Sci Rep; citation_title=Compact-morphology-based polymetallic nodule delineation; citation_author=T Schoening, DOB Jones, J Greinert; citation_volume=7; citation_publication_date=2017; citation_pages=13338; citation_doi=10.1038/s41598-017-13335-x; citation_id=CR17
citation_journal_title=Mar Geol; citation_title=Development of depositional systems in the southeastern Yellow Sea during the postglacial transgression; citation_author=YJ Shinn, SK Chough, JW Kim, JS Woo; citation_volume=239; citation_publication_date=2007; citation_pages=59-82; citation_doi=10.1016/j.margeo.2006.12.007; citation_id=CR18
citation_title=Seabed mineral deposits: a review of current mineral resources and future developments; citation_inbook_title=Deep Sea Mining Summit; citation_publication_date=2015; citation_pages=27; citation_id=CR19; citation_author=R Sterk; citation_author=JK Stein
TOML (2016}) TOML Clarion Clipperton Zone Project, Pacific Ocean. Tonga Offshore Mining Limited (TOML), NI 43-101 Technical Report, 254
citation_title=Image analyses for estimation of polymetallic nodule abundance in Korean Contract Area; citation_inbook_title=44th Underwater Mining Conference (expanded abstract); citation_publication_date=2015; citation_pages=1-2; citation_id=CR21; citation_author=CM Yoo; citation_author=K Hyeong; citation_author=HJ Kim; citation_author=S-B Chi; citation_author=J-K Kang