Relationship between geoacoustic properties and chemical content of submarine polymetallic crusts from offshore Brazil

Abstract

Marine mining is the ocean’s new exploration frontier, and polymetallic crusts (PMCs) and ferromanganese nodules are considered a strategic resource for the future. Acoustic geophysical methods are a valuable tool for oceanic research and have been employed for several decades in the exploration of marine resources and environmental evaluations. The main objective of this work was to investigate the correlation between the chemical composition of PMCs from three different areas along the Brazilian continental margin and their physico-acoustic attributes (P-wave velocity, density and acoustic impedance). The results show that the geoacoustic properties of PMCs are correlated to their chemical composition. Measurements showed positive and negative trends between acoustic impedance and studied elements (Fe, Mn, Co, Cu, Zn, W and Ni) according to the direction of measurement, indicting high anisotropy levels. Our study sheds initial light on the correlation between acoustic properties and metal content of PMCs. The study facilitates assessments of the acoustic responses of PMCs allowing more efficient prospection and exploitation compared to ship-board geophysical techniques that are too qualitative to identify PMCs. The results can contribute to determining the best procedures and techniques for more efficient future exploration of this resource.

Keywords:

• Brazilian continental margin
• geoacoustics
• polymetallic crusts
• underwater mining

Acknowledgment

The authors want to thank the Brazilian Geological Survey (CPRM) and LEPLAC Project (Brazilian Navy) for the assignment of the samples used in the study

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by grant # E-26/111.340/2013 from FAPERJ – Science Foundation of the State of Rio de Janeiro, Brazil.