Industrial minerals in the Pan Amazon

The mineral resources that characterize the High Andes of Peru are conspicuously absent north of the Huancabamba Gap, the altitudinal low point in the Andes linked to the deflection zone that created the Amazon Rift Valley. There is, however, an unusual mountain range located east of the Cordillera Oriental on the border between Peru and Ecuador. The Cordillera del Condor is a fold and thrust belt created in one of the earlier phases of the Andean orogeny when magmatic plutons were intruded into older sedimentary strata that created copper porphyries with significant mineral resources.

There are several mines under development, but the most advanced is the Mirador Project, which will exploit an estimated 3.1 million tonnes of copper, 3.2 million ounces of gold and 25 million ounces of silver. This is Ecuador’s first industrial-scale open-pit mine and will include a processing facility that will convert the ore into a concentrate. The mine, which has a projected lifespan of thirty years, is being developed with Chinese capital and will generate billions of dollars in royalty and tax revenues, while contributing to the balance of payments equation that motivates finance ministries. There are four other copper mines and two industrial-scale gold mines under development. On the Peruvian side of the border, wild-cat gold miners are active, but there are no economically significant reserves of copper or other base metals.

The copper porphyries in the Northern Andes

Ecuador and Southern Colombia are renowned for their volcanoes that are commonly associated with copper and gold porphyries. Recent exploration has revealed the existence of copper-rich formations near the border between Ecuador and Colombia. On the Ecuadorian side, the Empresa Nacional Minera del Ecuador (ENAMI EP) is in the early stages of developing La Bonita, a copper deposit first discovered in the 1990s where exploratory drilling extracted samples with copper concentrations between 0.35 per cent and 0.86 per cent, with similarly attractive potential for gold, molybdenum and lead. La Bonita encompasses three large concessions covering 13,500 hectares that border (and slightly overlap) lands claimed by the Cofan Indigenous people.

Approximately 300 kilometres to the north, a similar copper-gold porphyry, known as the Mocoa Copper-Molybdenum Project, is being developed by a Canadian junior mining company. The initial discovery was made in 1978 by the Colombian Geological Service (Ingeominas) but wasn’t seriously explored until 2004 when a Canadian junior acquired the concession, who eventually sold it to the current holder (Libero Copper Corporation). In a recent report for investors, the developer estimates the ore body has approximately 2.1 million tonnes of copper and 231,818 tonnes of molybdenum, which would be valued at approximately US $20 billion at current market valuations for copper. The mine, if it is developed, would be located only fifteen kilometres north of the city of Mocoa, the capital of Putumayo Department; the ore-body overlaps with the Reserva Forestal Alto Rio Mocoa and is adjacent to the Resguardo Indígena Yungillo.

Amazonian bauxite

Brazil produced more than 35 million tonnes of bauxite in 2020. This is about ten per cent of global demand and represents a level of production that could be maintained for ~100 years based on estimated reserves of 2,700 million tonnes. There are three operating bauxite mines located in three municipalities in the state of Pará, which generated approximately US$935 million in gross revenues in 2020.

The largest mine was opened in 1979 by the Mineração Rio Norte (MNR), a joint venture involving five multinational and Brazilian corporations. It is located on the north bank of the Amazon River in the municipality of Oriximiná. Just across the river on the south bank is a mine operated by Alcoa in the municipality of Juruti that initiated operations in 2010. Both mines are enclave mines surrounded by natural forest with dedicated industrial mills, a rail line and port facilities. The third mine was established in 2007 by Norsk Hydro in Eastern Pará (Paragominas) on a landscape that has been heavily impacted by deforestation. Two additional bauxite mines are under development by the Companhia Brasileira de Alumínio, both of which are located a few kilometres from the existing mine in Paragominas.

The bauxite deposits in Western Pará are located on old sedimentary plains (peneplains) that were created between fifty and sixty million years ago in what is essentially the former floodplain of the Proto-Amazon River when it flowed from the east to the west. The mines in Eastern Pará have a different geological history but were formed by similar weathering processes on what was once an expansive coastal plain situated east of the Amazon Craton.

Interest in future bauxite development is revealed by the number of concessions solicited by investors and mining companies (< 1000), which reflects the potential in the landscapes around existing mines but also in the municipalities of Nhamundá, Urucurá, Borba, Autazes and Careiro in Amazonas state.

Throughout most of the twentieth century, Guyana and Suriname were global leaders in production and export of bauxite; however, the easily exploitable mineral deposits in the two countries were exhausted in the first decade of the twenty-first century. Guyana exports only a small fraction of its former production, while Suriname closed its last mine and processing facility in 2016. Both countries still have considerable bauxite reserves, but their exploitation is not, apparently, cost-effective in today’s global mining industry. Venezuela has very large, high-quality reserves and the installed capacity to exploit them; however, its mineral sector has collapsed due to economic mismanagement and structural constraints linked to its socialist economic model.

The cassiterite mines of the Brazilian Amazon

Cassiterite is a conglomerate ore with high concentrations of tin-oxide [SnO2]; it exists both as a ‘primary’ deposit in hard rock formations associated with magmatic intrusions in metamorphic rocks and as ‘secondary’ deposits in depositional landscapes located adjacent to the primary ore body. Brazil has about fifteen per cent of the global reserves of cassiterite and has been a major producer of tin since the 1960s when it was part of an international tin cartel. High prices (~$35,000 per ton) fuelled a mining boom that targeted the alluvial deposits which were particularly abundant in northwest Rondônia (municipalities of Porto Velho and Ariquemes), as well as selected landscapes in Pará (São Félix de Xingu) and Amazonas (Presidente Figueroa).

Market dynamics eventually prevailed and a precipitous drop in the price ($5,000 per ton) led to the collapse of the cartel in l985 and, shortly thereafter, the end of the small-scale cassiterite mines in the Brazilian Amazon. The price of tin recovered in the commodity super cycle between 2007 and 2012 (US$15,000 and US$20,000), but its exploitation is now restricted to corporations with the capital resources needed to exploit hard rock deposits. In 2022, two Canadian companies signed a joint venture to exploit the tailing dumps and abandoned placer mines in Arequimes and surrounding municipalities.

The largest and longest operating corporate mine is located near the northern border of Amazonas state in the municipality of Presidente Figueroa. Known as the Pitinga mine, it is infamous for its history of environmental damage and social conflict. The mine was opened in 1982 when the military government was pursuing a ‘development at all costs’ strategy that discounted the impact of environmental degradation and ignored the rights of Indigenous people.

The mineral resource was located within the traditional lands of the Waimiri–Atroari, a tribe that had been brutally suppressed in the 1960s when they resisted the construction of the highway between Manaus and Boa Vista. Their reserve, which had been created in 1971 as a form of compensation for the brutality of the previous decade, was unilaterally reconfigured in 1981 to exclude the land for the proposed mine site.

That mine is now operated by Mineração Taborca, a subsidiary of a Peruvian mining company, MINSUR, that acquired the 130,000-hectare concession and associated processing facilities in 2008. Although the mine had already begun its transition into a modern open-pit operation, the new owner continued to use placer mining technology until 2012. Placer mining is particularly noxious because it selectively targets, and destroys, riparian habitats, and its use within the Pitinga concession has created a massive long-term environmental liability that threatens the health of the mine’s Indigenous neighbours.

The Pitinga open-pit mine continues to be highly profitable and the hard-rock ore body is considered to be the world’s largest tin reserve (500,000 tonnes of refined tin). In 2020, the mine produced about 7,400 tonnes of enriched cassiterite with estimated gross revenues of ~US$220 million. More importantly, the processing mill has started recovering both niobium and tantalum, strategic minerals with reserves estimated at 775,000 and 106,000 tonnes of refined mineral, respectively.

Niobium, tantalum and rare earth elements

Niobium (Nb) is used in the steel industry to manufacture specialized (stainless) steels that are used in the construction, shipbuilding, automotive and oil and gas industries. Tantalum (Ta) is similarly resistant to corrosion, but is used in the manufacture of miniaturised electronic devices, including cell phones, medical equipment and aerospace applications. Both elements tend to be found together in a mineral ore known as coltan, which is, apparently, present on landscapes long renowned for their cassiterite deposits.

Revenues from niobium and tantalum at the Pitinga tin mine now represent about fifty per cent of the gross mine revenues, contributing another US$200 million dollars to corporate revenues in 2020. The diversification of production and revenues may undergo yet another transition in the near future, because the mine would appear to be a globally important source of a strategically significant class of mineral known as rare earth elements (REE).

Rare earth elements are the elements in the lanthanide series of the periodic table; with atomic numbers that range from 57 (lanthanum) through 71 (lutetium), they are grouped together because they all have a valency of +3 and share certain chemical properties that influence their distribution in nature. In spite of their name, they are not particularly rare, although the mining and commercialisation of REE has been dominated by China for about two decades. Geopolitics and high-stakes competition spawned by the energy transition has motivated investors in Western economies to prioritise the development of alternative sources of these strategic minerals. After China, Brazil has the second largest known reserve of REE, estimated at approximately 22 million tonnes. Most of the known reserves are located at a single mine in Goiás: Catalão. There are three areas in the Amazon that have potentially significant reserves of niobium, tantalum and REE.

Mineração Taborca has yet to start separating and processing the potential REE minerals within the Pitinga concession; apparently, they are present not only in the primary ore body but also in the more than 6,000 hectares of tailings ponds that contain more than 100 million tonnes of waste rock. The ongoing discoveries at the Pitinga mine, particularly the association of REE with cassiterite, niobium and tantalum, have stimulated renewed interest in the abandoned mining landscapes in Rondônia and elsewhere.

In January 2022, Auxico Resources Canada Inc, which was established specifically to discover and develop REE deposits, signed an agreement with the Cooperativa Estanífera de Mineradores da Amazônia Legal Ltda (CEMAL) for the exploitation and commercialisation of REE from the legacy tailings in the municipalities of Ariquemes and Monte Negro in Rondônia. The holdings are estimated to contain thirty million tonnes of tailings from previous alluvial and colluvial mining operations. Samples provided by CEMAL were analysed by a Canadian research institution and revealed total REE oxides content in excess of 63 per cent; these were particularly rich in cerium (35.9%), lanthanum (15.2%) and yttrium (1.14%). As at the Pitinga mine, the potential to exploit the unremediated mine tailings would be a unique (and unexpected) opportunity that could provide the resources needed to resolve a long-standing environmental hazard.

Morro dos Seis Lagos and adjacent regions in Colombia and Venezuela

The Moro de Seis Lagos is a remote mountain in Northern Amazonas state with geological features similar to the Catalão mine in Goiás. Long before it was recognised as a potential source of rare earth elements, it had been flagged as a world class deposit of niobium (236 Mt @ 2.81% Nb2O5) with economically significant reserves of titanium and manganese. The still poorly mapped ore body is known to contain monazite, florencite, rhabdophane and pyrochlore, minerals that are known sources of rare earth oxides. Preliminary surveys suggest there are ~43 Mt of ore with concentrations of rare earth oxides that average about 1.5 per cent. This would make the Morro dos Seis Lagos one of the main REE deposits of Brazil.

In spite of its mineral potential, there are numerous obstacles to its development, most importantly, its location within the boundaries of Parque Nacional Pico da Neblina, a high profile protected area created in 1979. Moreover, the surrounding landscapes are within the traditional foraging grounds of several Indigenous groups, including the Yanomami, who inhabit the forest landscapes to the northeast, and the Baniwa, Baré, Desana, Makú, Tariana and Tukan peoples, who reside along the Rio Negro to the south. The area has been further protected by the creation of a biological reserve within the national park that circumscribes the mountain itself.

Over the border in Colombia, there might be about 1,000 million tonnes of REE-bearing mineral ores in the departments of Guainía, Vichada and Vaupes. The national database of mining concessions shows numerous requests for exploration licences, many of which are deep within established Indigenous reserves. The government has been clear it will not grant any of these requests; nonetheless, a clandestine trade in coltan has existed for more than a decade. The only legal activity is a proposed mine near the village of Puerto Carenõ (Vichada) by the Canadian company, Auxicos Resources, which has also expressed interest in a geological formation that extends into the Amazon’s State of Venezuela near the existing Pijiguaos bauxite mine.

Banner image: The Alunorte refinery, Albras aluminium smelter and port facilities in Barcarena. Credit: Programa de Aceleração do Crescimento (PAC). Flickr.com

“A Perfect Storm in the Amazon” is a book by Timothy Killeen and contains the author’s viewpoints and analysis. The second edition was published by The White Horse in 2021, under the terms of a Creative Commons license (CC BY 4.0 license).

To read earlier chapters of the book, find Chapter One here, Chapter Two here, Chapter Three here and Chapter Four here.