Reporting of Seafloor Mineral Resources
Interest in the exploration and mining of seafloor mineral deposits continues to grow, spurred on by a range of factors including decreasing deposit grades on land and the development of new subsea mining technology. Leading the race to seabed production is Nautilus Minerals, which announced in September 2015 the start of construction of the Production Support Vessel for its Solwara 1 copper-gold project in the Bismarck Sea. In early March of this year, the company’s three Seafloor Production Machines arrived safely at Port Duqm in Oman where they are scheduled to undergo extensive wet testing.
About a third of the world’s seafloor area is covered by Exclusive Economic Zones and other areas of continental shelf that fall under the jurisdiction of individual nations. In these areas, the reporting requirements for Mineral Resources and Mineral Reserves are set by the laws of the nations within which the exploration companies operate and/or the public exchanges on which the companies are listed.
Seabed drilling systems can be launched from a variety of vessels
The International Seabed Authority (ISA), which is responsible for the administration of seabed exploration and mining rights in international waters (known as the Area), recently issued a standard for the reporting and classification of Mineral Resources and Mineral Reserves in the Area (www.isa.org.jm/sites/default/files/files/documents/isba-21ltc-15_1.pdf). Pat Stephenson, Director and Principal Geologist at AMC Consultants and past co-Chairman of the Committee for Mineral Reserves International Reporting Standards (CRIRSCO), chaired the working group that identified the main items that would need to be addressed in an ISA reporting standard, and modified the CRIRSCO template to produce a draft standard for the ISA.
The standard applies to reporting of estimates that are not intended for public release or for the prime purpose of informing investors or potential investors and their advisors. Since the standard is based on the November 2013 edition of the international reporting template of CRIRSCO, it will ensure that private reports lodged with the ISA follow the same guiding principles and use the same definitions as public reports that comply with CRIRSCO-type reporting standards, such as JORC, NI 43-101, SAMREC etc.
The first seabed Mineral Resource reported under a public reporting standard was the NI 43-101 technical report on the Mineral Resource estimate for the Solwara 1 massive sulphide deposit in the Bismarck Sea, PNG, issued in 2008. The Qualified Person for this report, which was prepared for Nautilus Minerals Inc by Golder Associates Pty Ltd, was Ian Lipton, now Principal Consultant at AMC Consultants.
So, what is special about the estimation and reporting of seafloor Mineral Resources? The biggest challenge is obtaining sufficient representative samples at seafloor depths of 5,000 m or more.
Seafloor core drilling rig mounted on a remotely operated vehicle (ROV)
Sampling techniques vary according to deposit type. Loose mineral deposits on the seafloor can be sampled with grab-samplers with opposing jaws or box-corers which penetrate the upper part of the soft substrate under their own weight and have a mechanical plate that rotates and closes the base of the box. These tools are used to determine, for example, the abundance (kg/m2) of Ni-Co-Mn nodules or phosphate nodules on the seafloor.
For deposits with a significant depth extent beneath the seafloor, a variety of coring methods has been developed. Cylindrical gravity corers and piston corers, which penetrate substrate under their own weight, and vibrocorers may be used to sample soft sediments down to tens of metres and may achieve satisfactory recoveries in favourable circumstances.
For hard rock deposits, such as the volcanic-hosted massive sulphide deposit at Solwara 1, powered rotary drilling is required to cut through the rock. Vessel-mounted drilling systems, derived from oil and gas exploration methods, have been used but are hampered by the hundreds or thousands of metres of drill pipe in the water column and by the difficulty of controlling vessel heave.
Nautilus has pursued development of diamond core drills that sit on the seafloor and can be remotely positioned, monitored and operated from a ship via an umbilical cable. This type of rig was successfully used to define Indicated and Inferred Mineral Resources at Solwara 1 and Solwara 12.
Video cameras and side-scan sonar provide continuous records of seafloor operations
Sample recovery is the key issue. All the data required to support the assay data must be collected at the time of drilling. Because of the extremely high cost of seafloor drilling programmes, there are no economic options for going back and trying again if the first pass data collection is flawed or incomplete. Unlike terrestrial drilling, one can’t simply run out to resurvey the location of a box core sample or redrill a poorly-sampled drill hole. Thus, detailed planning of data acquisition programmes is absolutely critical. Clearly defined procedures, well-trained staff, rigorous QA/QC procedures, thorough record-keeping, and integrated independent audits help to provide maximum bang for buck and ensure that the best possible data is collected.
A conventional site visit to examine the geology is crushingly impossible, but this is not a serious impediment to Mineral Resource assessment since a well-designed programme will provide extensive sea floor video records, detailed bathymetric data and, probably, data from a range of geophysical sensing methods. Every last drop of information that can be used to support the Mineral Resource estimate needs to be extracted from these less conventional sources. For example, at Solwara 1, a deep water electromagnetic survey was used very successfully to map the lateral extents of the massive sulphide deposit; and the distribution of chimneys, mapped by high-resolution bathymetry, was used to identify the main pathways for the mineralizing fluids.
Massive sulphide core from Solwara 1
Survey control for the points of observation is also a challenge in the deep water environment, and accurately locating the position of a remote sensing device drifting at the end of several thousand metres of cable requires sophisticated equipment and experience.
The new ISA reporting standard provides extensive guidelines for the reporting of seafloor Mineral Resources. The over-riding principles of materiality and transparency, and the breadth of information required to be referenced by Enclosure 1 of the reporting standard, mean that investors reading reports prepared under the standard will be provided with a similar level of information to that provided for terrestrial deposits.
While there are significant challenges in discovering, defining and developing mineral deposits on the seafloor, the technology is advancing rapidly, driven by innovative mining and exploration companies with an eye on mineral deposits of exceptional grade and size. AMC Consultants is excited to provide project support at this new frontier.