Aripuana polymetallic project is a zinc-lead-silver-gold mine being developed in Serra do Expedito region of Brazil. Termed as one of the world’s biggest undeveloped zinc projects, the Aripuana underground project is being developed by Aripuana Mineração Dardanelos, a company formed by the subsidiaries of Nexa Resources and Karmin Exploration.

Preliminary environmental license for the zinc project was granted by the environmental authorities in April 2018. Feasibility study of the project was completed in October 2018, while the project is expected to commence production in 2021.

With an estimated capital expenditure of $392m, the greenfield project involves the extraction and beneficiation of zinc, copper, silver, gold, and lead ores. It is expected to create approximately 1,600 construction and 750 operational jobs.

The project is expected to produce an average of 120,000 tonnes per annum (tpa) of zinc-equivalent over its mine life of 13 years. The annual production is estimated to contain an average of 66,700t of zinc, 23,000t of lead, and 3,700t of copper, respectively. It is also expected to produce 1.87Moz of silver and 13,000oz of gold a year.

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Aripuana project ownership

Nexa Recursos Minerais, a subsidiary of Nexa Resources, holds 62.3% interest in the project and is also the operator of the project. Nexa Resources Perú, a subsidiary of Nexa Resources, holds 7.7% interest, while Mineração Rio Aripuana, a subsidiary of Karmin Exploration, holds 30% carried interest in the project.

Karmin is currently undertaking strategic alternatives review to evaluate the options to participate in the project and engaged CIBC World Markets as its exclusive financial advisor for the review.

Aripuana polymetallic project location, geology, and mineralization

Located in Serra do Expedito, approximately 25km from Aripuana, the project is located in the north-west of the state of Mato Grosso. The project hosts three mineralized zones namely Arex, Link, and Ambrex, along with additional mineralized bodies such as Massaranduba, Boroca, Mocoto, Arpa, and Babaçú.

The Aripuana polymetallic deposits host volcanogenic massive sulfide mineralization similar to the Noranda-type. The property is located beneath the Aripuana meta-volcano-sedimentary sequence, which is associated with a major intra-continental suture. The sequence is bounded by granites and gneisses of the Xingu Complex in the north.

Hosting poly-metallic deposits, the sequence comprises three major meta-volcano-sedimentary units. The upper sequence is made up of inter-layered meta-argillites, meta-tuffs, and meta-cherts.

Sulphide mineralization found at Arex and Ambrex deposits is categorized as massive and strata-bound.

Aripuana polymetallic project reserves

The ore reserves at Aripuana polymetallic project are estimated to be 26.2 million tonnes (Mt) grading 3.7% zinc, 1.4% lead, and 0.2% copper.

The mine is expected to contain 2.1 billion pounds of zinc, 784 million pounds (Mlbs) of lead, 143Mlbs of copper, 250,000oz of gold, and 28.8Moz of silver.

Mining at Aripuana project

A combination of longitudinal longhole retreat stoping (bench stoping) and vertical retreat mining (VRM) will be used at the underground Aripuana polymetallic project.

Longhole retreat stoping will be applied to extract ore from the narrow zones of the deposits, while vertical retreat mining will be employed at the thicker zones. Cemented paste fill and uncemented rock fill will be used to backfill the stopes.

The Arex, Link, and Ambrex underground mineral zones will be accessed through separate ramps to ensure operational flexibility.

Ore processing at Aripuana

The processing plant will have a throughput capacity of 2.268Mtpa of run-of-mine (ROM) ore from the three mineral zones. The ROM ore will be trucked from the underground mine and stockpiled before feeding the jaw crusher. It will undergo primary crushing and semi-autogenous grinding, followed by ball milling and pebble crushing.

The output from the pebble crusher will be conveyed to semi-autogenous grinding (SAG) mill through a conveyor belt. Undersize screen material from the SAG mill discharge will be transferred to a pump box and the slurry will feed a set of hydro-cyclones.

Hydro-cyclone underflow material will be returned to the ball mill, while overflow will be sent back to the flotation feed pump box for further grinding.

The ball mill discharge will be screened and the pulp will be combined with the screen undersize from the SAG mill discharge and recirculated as feed to the hydro-cyclones. It will undergo sequential flotation activity in four independent circuits followed by thickening and filtration to produce copper, zinc, and lead concentrates.

The three concentrates will be filtered and the resultant copper and zinc concentrates will be reclaimed by wheel loader and transported by truck. The filtered lead concentrates will be bagged in one metric tonne bags and delivered to a storage unit.

Infrastructure facilities at Aripuana polymetallic project

Access to the Aripuana project is through 935km of paved roads and land from the town of Cuiaba in Mato Grosso.

Power supply required by the project will be sourced from the Dardenelos hydroelectric plant located near the project. A 69kV transmission line and associated infrastructure will be developed to connect the project with the Dardenelos transmission system.

A water dam will be constructed along with a fresh water lake in the valley adjacent to the project site. 

Contractors involved

Nexa has engaged Roscoe Postle Associates (RPA) to prepare an independent Technical Report on the Aripuana project, while SNC Lavalin was contracted to develop the feasibility study.

Worley Parsons conducted additional engineering works of the project with regard to capital costs and mine plan.