Mineral-laden water emerging from a hydrothermal vent
Hydrothermal vent chimney from the southwest Pacific Ocean
Ferromanganese crust from the south Pacific Ocean
Ferromanganese nodule being sampled from the North Atlantic seafloor
The Global Marine Mineral Resources project studies deep ocean minerals that occur within the U.S. Exclusive Economic Zone and areas beyond national jurisdictions. Our research concerns the setting, genesis, and metal enrichment processes of mineral occurrences, the relationship between marine minerals related and deep-sea biota, and the potential geochemical footprint of any seafloor mining. We aim to provide stakeholders with the best available science regarding potential resources and environmental impacts associated with accessing those resources.
Research Overview
The Global Marine Mineral Resources project objectives include:
-
Geochemical characterization of mineral samples, including mineralogy and metal concentrations, and their variability regionally and globally
-
Correlation of oceanographic and geographic parameters with mineralogy and metal content to elucidate the controls on mineral formation and element enrichment, and to map prospective mineral regions within the global ocean
-
Investigation of mineral stability and metal mobility with exposure to seawater over time through experimental geochemistry to constrain geochemical effects of mineral disturbance
-
Collaboration with biologists to determine associations between minerals and the biological communities which inhabit and surround them
Our findings inform stakeholders, including the public, government, industry, academics and NGOs, about mineral wealth and its environmental setting within the vast offshore territory of the U.S. and helps them determine which regions and deposits may warrant further research.
Ferromanganese Crusts
Seafloor pavements and encrusted rocks are known as ferromanganese crusts (also called cobalt-rich crusts). These crusts grow very slowly, at several millimeters per million years, and precipitate onto exposed rock surfaces throughout the global ocean—they do not form where sediment blankets the seafloor. In the oldest parts of the seafloor in the northwest Pacific Ocean, some crusts have been forming for over 70 million years and can be over 20 centimeters thick. Crusts act as a sponge of sorts, adsorbing metals and other elements from seawater over these long periods of time, and are especially enriched in cobalt, manganese, rare metals such as tellurium, precious metals such as platinum, and rare earth elements.
Manganese Nodules
Over millions of years, spheroidal rocks called manganese nodules (or polymetallic nodules) form atop sediment covering the abyssal plains of the global ocean. These nodules form by the accretion of iron and manganese oxides around a tiny nucleus, such as a large grain of sand, a shark tooth, or older nodule fragment. Manganese nodules are usually golf-ball to baseball size and grow very slowly like ferromanganese crusts if they acquire all their metals directly from seawater, or they grow faster if they also acquire their metals from the pore-waters of the sediment on which they sit. Nodules are currently of great interest for mining due to high concentrations of manganese, nickel, copper, and sometimes lithium, as well as the straightforward nature of quantifying their distribution and density.
Seafloor Massive Sulfides
Also known as polymetallic sulfides, seafloor massive sulfides form at hydrothermal vents when seawater penetrates the ocean’s crust and becomes heated and chemically modified through interaction with crustal rocks and, sometimes, by input of magmatic fluids. The hot hydrothermal fluids then rise back toward the seafloor and precipitate minerals as they cool along flow paths and upon mixing with seawater.
A wide variety of minerals form through hydrothermal activity, but seafloor massive sulfides are formed from reduced sulfur and may be enriched in copper, zinc, iron, gold, and silver. Hydrothermal vents exist along mid-ocean ridge spreading centers, extensional systems associated with subduction zones, volcanoes, and intraplate hotspots. Yet, seafloor massive sulfides likely extend beyond these active hydrothermal zones. We know the minerals persist after removal from the heat source because of the presence of volcanogenic massive sulfide deposits on land.
Marine Phosphorites
Marine phosphorites primarily occur along continental margins where upwelling of cold, nutrient-rich, deep water is strong. These areas include the Peru-Chile margin, on plateaus such as Chatham Rise offshore New Zealand, and the Blake-Bahamas Plateau off the southeast United States; but they can also form on seamounts where ferromanganese crusts grow. Phosphorites form when abundant phosphate in seawater replaces carbonate in calcareous sediments or precipitates in situ as apatite to form hardgrounds, phosphatic nodules, or cements in breccias of multiple rock types. Marine phosphorites are sources of phosphate used as fertilizer for agriculture and phosphoric acid in the food industry. Phosphorites can also contain high concentrations of valuable, heavy, rare-earth elements that may be economically recoverable and can contain up to 4% fluorine.
Marine Mining Context
The oceans cover nearly three quarters of the surface of the earth, and in the U.S., the area of seafloor comprising the Exclusive Economic Zone is greater than the land area on shore. This enormous ocean realm hosts many types of minerals that differ from those occurring terrestrially. Ferromanganese crusts, manganese nodules, phosphorites, and hydrothermal vent deposits, which occur from the Arctic to the Antarctic, are enriched in many metals including those currently deemed societally critical. It is therefore important to understand these minerals and the role they may play as future mineral resources.
People around the world demand metals and mineral resources for many uses, including technology, electronics, and green energy infrastructure such as wind turbines and electric cars. Critical minerals are defined as those that are essential to the economic and national security of a nation but that have a supply-chain vulnerable to disruption. In 2022, the Department of the Interior released a list of 50 critical minerals, with the list to be reconsidered biannually. Across the USGS, research is underway to define and prioritize focus areas throughout the United States with resource potential for these 35 critical minerals. The Global Marine Mineral Resources project specifically informs the marine component.
To date, there is no mining of deep-sea minerals. In Areas Beyond National Jurisdiction, any marine mining is governed by the International Seabed Authority, which is currently drafting exploitation regulations. The Global Marine Mineral Resources project has provided scientific advice to the U.S. State Department and has served as a member of the U.S. delegation to the International Seabed Authority as an Observer Nation since 2007.
The Global Marine Mineral Resources project studies deep ocean minerals that occur within the U.S. Exclusive Economic Zone and areas beyond national jurisdictions. Our research concerns the setting, genesis, and metal enrichment processes of mineral occurrences, the relationship between marine minerals related and deep-sea biota, and the potential geochemical footprint of any seafloor mining. We aim to provide stakeholders with the best available science regarding potential resources and environmental impacts associated with accessing those resources.
Research Overview
The Global Marine Mineral Resources project objectives include:
-
Geochemical characterization of mineral samples, including mineralogy and metal concentrations, and their variability regionally and globally
-
Correlation of oceanographic and geographic parameters with mineralogy and metal content to elucidate the controls on mineral formation and element enrichment, and to map prospective mineral regions within the global ocean
-
Investigation of mineral stability and metal mobility with exposure to seawater over time through experimental geochemistry to constrain geochemical effects of mineral disturbance
-
Collaboration with biologists to determine associations between minerals and the biological communities which inhabit and surround them
Our findings inform stakeholders, including the public, government, industry, academics and NGOs, about mineral wealth and its environmental setting within the vast offshore territory of the U.S. and helps them determine which regions and deposits may warrant further research.
Ferromanganese Crusts
Seafloor pavements and encrusted rocks are known as ferromanganese crusts (also called cobalt-rich crusts). These crusts grow very slowly, at several millimeters per million years, and precipitate onto exposed rock surfaces throughout the global ocean—they do not form where sediment blankets the seafloor. In the oldest parts of the seafloor in the northwest Pacific Ocean, some crusts have been forming for over 70 million years and can be over 20 centimeters thick. Crusts act as a sponge of sorts, adsorbing metals and other elements from seawater over these long periods of time, and are especially enriched in cobalt, manganese, rare metals such as tellurium, precious metals such as platinum, and rare earth elements.
Manganese Nodules
Over millions of years, spheroidal rocks called manganese nodules (or polymetallic nodules) form atop sediment covering the abyssal plains of the global ocean. These nodules form by the accretion of iron and manganese oxides around a tiny nucleus, such as a large grain of sand, a shark tooth, or older nodule fragment. Manganese nodules are usually golf-ball to baseball size and grow very slowly like ferromanganese crusts if they acquire all their metals directly from seawater, or they grow faster if they also acquire their metals from the pore-waters of the sediment on which they sit. Nodules are currently of great interest for mining due to high concentrations of manganese, nickel, copper, and sometimes lithium, as well as the straightforward nature of quantifying their distribution and density.
Seafloor Massive Sulfides
Also known as polymetallic sulfides, seafloor massive sulfides form at hydrothermal vents when seawater penetrates the ocean’s crust and becomes heated and chemically modified through interaction with crustal rocks and, sometimes, by input of magmatic fluids. The hot hydrothermal fluids then rise back toward the seafloor and precipitate minerals as they cool along flow paths and upon mixing with seawater.
A wide variety of minerals form through hydrothermal activity, but seafloor massive sulfides are formed from reduced sulfur and may be enriched in copper, zinc, iron, gold, and silver. Hydrothermal vents exist along mid-ocean ridge spreading centers, extensional systems associated with subduction zones, volcanoes, and intraplate hotspots. Yet, seafloor massive sulfides likely extend beyond these active hydrothermal zones. We know the minerals persist after removal from the heat source because of the presence of volcanogenic massive sulfide deposits on land.
Marine Phosphorites
Marine phosphorites primarily occur along continental margins where upwelling of cold, nutrient-rich, deep water is strong. These areas include the Peru-Chile margin, on plateaus such as Chatham Rise offshore New Zealand, and the Blake-Bahamas Plateau off the southeast United States; but they can also form on seamounts where ferromanganese crusts grow. Phosphorites form when abundant phosphate in seawater replaces carbonate in calcareous sediments or precipitates in situ as apatite to form hardgrounds, phosphatic nodules, or cements in breccias of multiple rock types. Marine phosphorites are sources of phosphate used as fertilizer for agriculture and phosphoric acid in the food industry. Phosphorites can also contain high concentrations of valuable, heavy, rare-earth elements that may be economically recoverable and can contain up to 4% fluorine.
Marine Mining Context
The oceans cover nearly three quarters of the surface of the earth, and in the U.S., the area of seafloor comprising the Exclusive Economic Zone is greater than the land area on shore. This enormous ocean realm hosts many types of minerals that differ from those occurring terrestrially. Ferromanganese crusts, manganese nodules, phosphorites, and hydrothermal vent deposits, which occur from the Arctic to the Antarctic, are enriched in many metals including those currently deemed societally critical. It is therefore important to understand these minerals and the role they may play as future mineral resources.
People around the world demand metals and mineral resources for many uses, including technology, electronics, and green energy infrastructure such as wind turbines and electric cars. Critical minerals are defined as those that are essential to the economic and national security of a nation but that have a supply-chain vulnerable to disruption. In 2022, the Department of the Interior released a list of 50 critical minerals, with the list to be reconsidered biannually. Across the USGS, research is underway to define and prioritize focus areas throughout the United States with resource potential for these 35 critical minerals. The Global Marine Mineral Resources project specifically informs the marine component.
To date, there is no mining of deep-sea minerals. In Areas Beyond National Jurisdiction, any marine mining is governed by the International Seabed Authority, which is currently drafting exploitation regulations. The Global Marine Mineral Resources project has provided scientific advice to the U.S. State Department and has served as a member of the U.S. delegation to the International Seabed Authority as an Observer Nation since 2007.