Aspects of Estimation and Reporting of Mineral Resources of Seabed Polymetallic Nodules: A Contemporaneous Case Study

Abstract

Exploration of seabed polymetallic nodules identifies the Clarion Clipperton Zone and the Indian Ocean Nodule Field to be of economic interest. Mineral resource estimation is important to the owner of the resource (all of mankind; and managed by the International Seabed Authority; ISA) and to developers (commercial and government groups holding contracts with the ISA). The Committee for Mineral Reserves International Reporting Standards was developed for the land-based minerals industry and adapted in 2015 for ISA-managed nodules. Nodules can be sampled in a meaningful manner using mechanical devices, albeit with minor issues of bias. Grade and moisture content are measured using the established methodology for land-based minerals. Tonnage of resource is determined via the abundance of nodules in kilograms per square metre of seabed. This can be estimated from physical samples and, in some cases, from photographs. Contemporary resource reporting for nodules classify the level of confidence in the estimate, by considering deposit geology, sample geostatistics, etc. The reporting of estimates also addresses reasonable prospects for eventual economic extraction, including factors such as mining technology, the marine environment, metallurgical processing, and metals markets. Other requirements are qualified persons responsible for estimation and reporting, site inspection, and sample chain of custody.

Application of General Linear Models (GLM) to Assess Nodule Abundance Based on a Photographic Survey (Case Study from IOM Area, Pacific Ocean)

“…This issue was widely discussed in many publications, e.g., [1,2,[4][5][6][7][8][9][10][11][12][13][14]. The exploitation of these deposits, apart from their proper recognition and estimation of their resource [15], requires solving a number of problems related to the technique of mineral extraction and ore processing [7,[16][17][18]. The development of an appropriate scenario and schedule for the future short and medium-term exploitation of nodules, after meeting the environmental protection requirements and solving technical problems of mining, depends on a detailed recognition of the distribution of nodule abundance and resources and an analysis of the ocean floor topography based on reliable contour maps.…”

“…They result mainly from the large distances between sampling stations (which vary depending on the stage of recognition of the nodule-bearing areas), high variability of nodule abundance, and to a lesser extent, from the inevitable errors during the sampling process [20]. Therefore, the attempts to combine the estimation of nodule abundance based on the classical direct sampling (e.g., using box corers) [15,21] with indirect methods, such as photographic surveys [22][23][24][25] or widely understood hydro-acoustic methods [26,27], seem natural and rational.…”

Empirical Application of Generalized Rayleigh Distribution for Mineral Resource Estimation of Seabed Polymetallic Nodules

“…The use of nodule long (or major) axis in predicting individual nodule weights has been long understood [12][13][14][15], even if application via seabed photographs is restricted to areas where the nodules are largely exposed in the host clay-ooze [4,16]. Ultimately, box-core samples are seen to be the most reliable source of abundance data [4], but their relatively high cost makes the use of seabed photographs appealing to workers trying to improve the confidence in abundance estimation [17]. Efforts to use percentage coverage to predict nodule abundance have so far not been effective [18,19].…”

Exploration of Polymetallic Nodules

“…The paper by Parianos et al [1] focuses on the estimation and reporting of nodule resources, which are mainly dependent on the determination of the abundance of nodules. The issues related to determining the abundance of nodules are also addressed by these authors from lessons learned in the TOML (Tonga Offshore Mining Limited) exploration area in the Clarion-Clipperton Zone (CCZ).…”