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Brazil
Riacho dos Machados (RDM) Mine

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 Location:
11 km SW from Riacho dos Machados, Brazil

  Address:
4° Andar Avenida do Contorno 5919 Savassi
Belo Horizonte
Brazil
30110-927
Phone  ...  Subscription required
WebsiteWeb
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • Filings & News

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Overview

StatusTemporary Suspension
Mine TypeOpen Pit
Commodities
  • Gold
Mining Method
  • Truck & Shovel / Loader
Processing
  • Carbon re-activation kiln
  • Hydrochloric acid (reagent)
  • Smelting
  • Agitated tank (VAT) leaching
  • Carbon in leach (CIL)
  • Carbon adsorption-desorption-recovery (ADR)
  • Elution
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)
Mine Life7 years (as of Jan 1, 2020)
May 16, 2022 - Equinox Gold Corp. (TSX: EQX) (NYSE American: EQX) ("Equinox Gold" or the "Company") announces that, as previously disclosed, permits for the scheduled tailings storage facility ("TSF") raise at the Company's RDM Mine in Brazil have been delayed. Equinox Gold has temporarily suspended RDM operations until this matter can be resolved.
Equinox Gold expects that full operations could restart as soon as two months from the receipt of regulatory approval, which is anticipated during Q2 2022.
Latest NewsEquinox Gold Temporarily Suspends Operations at RDM Mine     May 16, 2022


Owners

Source: p. 17
CompanyInterestOwnership
Mineração Riacho Dos Machados Ltda. (operator) 100 % Direct
Equinox Gold  Corp. 100 % Indirect
Equinox Gold acquired RDM on March 10, 2020 as part of the Leagold Merger.

Mineral tenure for the Mine is held under the name of Mineração Riacho dos Machados, a wholly-owned subsidiary of Leagold, incorporated under the laws of Brazil.

Deposit Type

  • Mesothermal
  • Orogenic
  • Vein / narrow vein


Summary:

The Riacho dos Machados gold deposit is considered to be a classic mesothermal orogenic gold deposit in a sheared and deformed Archean to Proterozoic age greenstone belt sequence. It is comprised of metamorphosed volcanic-sedimentary rock units intruded by slightly younger post-tectonic igneous bodies.

The principal host for the gold mineralization is the quartz-muscovite schist of the RMG. The mineralization occurs in a belt of hydrothermally altered rock developed along a district-scale shear zone that extends almost 30 km along a N20°E strike direction and dips 40° to 45° east. The mineralization has a typical amphibolite facies mineral association which is progressively altered to greenschist facies assemblage. The gold mineralization occurs as “stacked” tabular horizons that are mostly concordant with the principal rock foliation (shear zone). These tabular zones typically consist of a main zone which may be sided by a thinner footwall or hanging wall zones, separated by three meters to ten meters of unmineralized rock. Continuity along strike and at depth is good with gold mineralization occurring continuously over a 2,000 m strike length and up to 1,000 m down dip.

Gold grades in the mineralized zone are closely related to sulphide content, especially arsenopyrite. Gold occurs as microscopic native-gold grains typically finer than 400 mesh (37 µm). The gold grains occur interstitial to quartz grains, muscovite grains, and sulphide grains, and also as inclusions in arsenopyrite, and less commonly in pyrrhotite, quartz-veinlets, tourmaline, and pyrite.

The following minerals and features, listed from high to low importance, are noted as indicators of gold mineralization:

-Arsenopyrite (both anhedral and euhedral needles);
- Pyrrhotite;
- Abundant quartz veinlets (sheared into foliation plane);
- Pyrite;
- Crenulation folding;
- Tourmaline veins (fine-grained massive intergrown).

The arsenic content of the mineralization is relatively high, with an average of approximately 4,000 ppm for samples greater than 1.0 g/t Au. Silver content is very low, with the average Ag/Au ratio of 0.5:1.0 for samples with a gold concentration of greater than 1.0 g/t. Antimony, copper, lead, and zinc are not commonly anomalous.

The gold mineralization is closely related to the structural fabric. The mineralizing fluid was probably channelled upward in the thrust-related shear zones with minor or local lateral escape into intersecting shear zones. Brittle deformation at the RDM deposit is limited to poorly defined crossfaults that may have anomalous geochemistry but do not host gold mineralization.

The area presents the occurrence of graphite, which influences the metallurgical behaviour of the ore. Graphite occurs in shear zones filling intrafolial planes, ranging from 2 to 20 cm thick, and in the form of boulders, with lenticular geometry or symmetrical boudins associated with quartz veins, with thicknesses of up to 1.5 m. They have dark grey and black coloration and low hardness, and due to graphite's lubricating characteristics, act as zones of geomechanical weakness. Graphite is in nonmineralized areas, associated with domains of marginal or waste contents, or in mineralized areas with the presence of high sulphidation.


Mining Methods

  • Truck & Shovel / Loader


Summary:

Conventional open pit mining methods are employed at the Mine, including drilling, blasting, loading, and hauling. Waste mining is performed by a contractor, while ore mining is conducted using an owner’s fleet.

The operation’s strip ratio is relatively high, at approximately 6.9:1 (waste:ore). The mining rate will be relatively constant throughout the life-of-mine (LOM); total daily waste material movement is estimated at 70,000 t/d and ore mining at 7,890 t/d (2.88 Mt/a).

Current pit bottom elevations of the north and south ends of the open pit are approximately 717 and 705 masl, respectively, and the crusher elevation is 865 masl. Surface rights cover a sufficient area to locate all the mining infrastructure required for the LOM, including waste management facilities (WMF), TSF, WSF, and processing plant.

Pit dewatering is carried out using in-pit sumps and perimeters wells.

The mine design bench height is 12 m; however, mining occurs on 4 m lifts in waste and 3 m lifts in ore.

The final pit design is approximately 1,750 m long and 750 m wide, with elevations that range from 600 to 900 masl. Final pit exits for the south and north ramps are at approximately 860 masl. The crusher dump pocket is less than 500 m horizontal distance from the pit exit. Adequate buffers exist around the open pit for possible future expansion, for example if the gold price increases. Some condemnation holes have been drilled in the infrastructure and waste dump areas to ensure economical mineralization is not sterilized.

The pit slopes used in the mine design for material on the west side (footwall) of the pit are up to 60°, and hanging wall bench face angles are up to 85°. Operating practices can have an impact on pit slopes, and careful blasting practices will be required near the final pit slopes. Final pit slopes have begun to be established on the west side (footwall) of the pit. There is not much potential for increasing the ultimate pit slopes, based on field investigation and operational challenges.

Bench-by-bench, monthly production schedules have been developed to identify ore types, waste removal, and stripping requirements. A lower stripping ratio will be realized in the later years. The granularity of the mine planning process is appropriate for this stage of production. The primary reason for this level of detail of the mine scheduling is the need to have accurate information for production and budgeting.


Crushing and Grinding
Flow Sheet: Source
Crusher / Mill TypeModelSizePowerQuantity
Jaw crusher ....................... Subscription required 185 kW 1
Cone crusher ....................... Subscription required 370 kW 2
Ball mill 6.7m x 11.1m 4500 kW 1

Summary:

Crushing
Briefly, the process entails dumping ore into a feed hopper from which a variable-speed apron feeder reclaims the ore onto a vibrating grizzly with openings set at 152 mm. The oversize from the grizzly feeds a Metso C140 primary jaw crusher with a closed side setting of 130 mm. The undersize from the grizzly is combined with the crushed product from the jaw crusher and fed onto a conveyor belt. The belt feeds the primary double-deck vibrating screen. The first deck opening is set at 56 mm; the second is set to 19 mm. The undersize (<19 mm) is conveyed to a fine-ore bin via conveyor belt; the oversize feeds a secondary Metso HP500 cone crusher with a closed side setting of 24 mm. The product from the secondary cone crusher is transferred to a secondary double-deck vibrating screen with openings set at 34 and 19 mm. The undersize from the secondary screen is conveyed to the same fine-ore bin. The oversize feeds a tertiary Metso HP500 cone crusher with a closed side setting of 13 mm.

The product from the tertiary crusher returns to the feed of the secondary screen, thus operating the tertiary crusher in a closed circuit.

The nominal rate of the crushing circuit is designed to be 408 t/h. The plant can potentially be expanded to 475 t/h with the addition of another tertiary crusher and another tertiary screen.

The ore is reclaimed from the fine-ore bin by four feeders with a nominal rate capacity of 342 t/h.

The ore from the fines bin can be fed to an emergency stockpile with a capacity of 10 kt. The emergency stockpile provides feed to the ball mill during crushing circuit shutdowns.

Grinding
The crushed ore is transferred from the ore storage bin to the ball mill feed conveyor. The water mixes with the ore in the ball mill feed chute and the hydrocyclone underflow feeds the ball mill through the feed chute, closing the circuit.

The mill has a diameter of 6.7 m and is 11.1 m long, with twin 4500 kW GE motors. After the power line was constructed, the steel load was increased from 19% to 27% (the current operational ball charge). The maximum steel ball charge is 33%.

The ground slurry passes through the trommel screens to remove ball chips. The ball mill BWi of open pit ores averages 17.4 kWh/t, and the ball consumption is in the range of 1,300 g/t. The ball mill operates at a slurry solids content of approximately 72%. The ground slurry is pumped to a battery of ten Weir Cavex 500 hydrocyclones. Nine hydrocyclones are operational, with one on standby, for spigot and vortex finder changes and to do maintenance. The hydrocyclones operate with an opening set at 90 mm diameter spigot and 140 mm diameter vortex finder. The hydrocyclone feed slurry density is controlled at approximately 40% solids, resulting in an overflow with 30% solids and a particle size distribution of P80 74 µm (the objective is to achieve P80 53 µm). The underflow solids content is approximately 75%.


Processing

  • Carbon re-activation kiln
  • Hydrochloric acid (reagent)
  • Smelting
  • Agitated tank (VAT) leaching
  • Carbon in leach (CIL)
  • Carbon adsorption-desorption-recovery (ADR)
  • Elution
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

The processing plant was designed to process 7,000 tpd (2.55 Mtpa). The plant can potentially be expanded to 9,000 tpd (3.28 Mtpa) with completion of the power line, addition of another tertiary crusher, installation of a larger mill discharge pump, and installation of larger conveyor belts.

The overall process flowsheet consists of:
• Three-stage crushing circuit;
• Ball mill grinding, in closed circuit with hydrocyclones;
• Thickening to produce a leach feed of up to 39% solids;
• CIL circuit;
• Cyanide detoxification;
• Zadra pressure stripping of the loaded carbon;
• Electrowinning of the carbon eluent;
• Casting of gold bars in an induction furnace.

Carbon in Leaching
The CIL tanks are fed with a volume of about 700 m3/h. The circuit consists of 10 tanks in total; each holds 1,924 m3 and is 13.5 m in diameter and 14.5 m high. The first tank is used as a pre-lime and pre-aeration tank.

A process improveme ........

Recoveries & Grades:

CommodityParameter20202019201820172016
Gold Recovery Rate, %  ......  Subscription required  ......  Subscription required828677.5
Gold Head Grade, g/t  ......  Subscription required  ......  Subscription required1.021.251.39

Production:

CommodityUnits202120202019201820172016
Gold koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required574348
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.
Subscription required - Subscription is required.

Operational Metrics:

Metrics20202019201820172016
Ore tonnes mined  ......  Subscription required2,458,895 t1,390 kt1,723,506 t1,054,574 t
Tonnes processed  ......  Subscription required2,548,393 t1,958 kt1,253,329 t850,029 t
Daily processing capacity  ......  Subscription required7,000 t7,000 t
Annual processing capacity  ......  Subscription required2.55 Mt2.55 Mt
Subscription required - Subscription is required.

Reserves at December 31, 2020:
Mineral Reserves are reported at a cut-off grade of 0.33 g/t gold.
Open pit Mineral Resources are reported at a cut-off grade of 0.30 g/t gold. Underground Mineral Resources are reported at a cut off grade of 1.36 g/t gold.

CategoryOreTypeTonnage CommodityGradeContained Metal
Proven Stockpiles 1,326 kt Gold 0.52 g/t 22 koz
Proven In-Situ (OP) 10,355 kt Gold 1.02 g/t 338 koz
Proven Total 11,681 kt Gold 0.96 g/t 360 koz
Probable In-Situ (OP) 5,872 kt Gold 1.04 g/t 196 koz
Proven & Probable Stockpiles 1,326 kt Gold 0.52 g/t 22 koz
Proven & Probable In-Situ (OP) 16,227 kt Gold 1.02 g/t 534 koz
Proven & Probable Total 17,553 kt Gold 0.99 g/t 556 koz
Measured In-Situ (OP) 264 kt Gold 1.19 g/t 10 koz
Indicated In-Situ (OP) 2,981 kt Gold 1.28 g/t 122 koz
Measured & Indicated In-Situ (OP) 3,245 kt Gold 1.27 g/t 132 koz
Inferred In-Situ (OP) 100 kt Gold 0.87 g/t 3 koz
Inferred In-Situ (UG) 3,514 kt Gold 1.98 g/t 223 koz
Inferred Total 3,614 kt Gold 1.95 g/t 226 koz

Commodity Production Costs:

CommodityUnits20212020201820172016
Cash costs (sold) Gold USD  ......  Subscription required ^  ......  Subscription required 946 / oz
Cash costs Gold USD 814 / oz 881 / oz
All-in sustaining costs (sold) Gold USD  ......  Subscription required ^  ......  Subscription required 1,009 / oz
All-in sustaining costs (AISC) Gold USD 989 / oz 1,001 / oz
^ Guidance / Forecast.
Subscription required - Subscription is required.

Operating Costs:

Units202020192018
OP mining costs ($/t mined) USD 1.762.662.07
OP mining costs ($/t milled) USD  ......  Subscription required  ......  Subscription required  ......  Subscription required
Processing costs ($/t milled) USD  ......  Subscription required  ......  Subscription required  ......  Subscription required
G&A ($/t milled) USD  ......  Subscription required  ......  Subscription required  ......  Subscription required
Total operating costs ($/t milled) USD  ......  Subscription required  ......  Subscription required  ......  Subscription required
Subscription required - Subscription is required.

Financials:

Units202120202016
Capital expenditures (planned) M USD  ......  Subscription required
Sustaining costs M USD  ......  Subscription required
Capital expenditures M USD  ......  Subscription required 17.9  
Revenue M USD  ......  Subscription required 40.5  
Operating Income M USD 1.6  
Subscription required - Subscription is required


Heavy Mobile Equipment as of December 31, 2020:
HME TypeModelSizeQuantityLeased or
Contractor
Backhoe ....................... Subscription required ....................... Subscription required
Dozer ....................... Subscription required ....................... Subscription required Leased
Dozer (crawler) ....................... Subscription required ....................... Subscription required
Dozer (crawler) ....................... Subscription required ....................... Subscription required
Dozer (crawler) ....................... Subscription required ....................... Subscription required Leased
Drill (blasthole) ....................... Subscription required 5.5 inch ....................... Subscription required
Drill (blasthole) ....................... Subscription required ....................... Subscription required Leased
Drill (blasthole) ....................... Subscription required ....................... Subscription required Leased
Excavator ....................... Subscription required ....................... Subscription required Leased
Excavator ....................... Subscription required 6 cu. m ....................... Subscription required
Excavator ....................... Subscription required
Excavator ....................... Subscription required ....................... Subscription required Leased
Grader ....................... Subscription required ....................... Subscription required Leased
Grader ....................... Subscription required ....................... Subscription required
Grader ....................... Subscription required ....................... Subscription required Leased
Grader ....................... Subscription required ....................... Subscription required
Loader ....................... Subscription required ....................... Subscription required
Loader ....................... Subscription required ....................... Subscription required
Rockbreaker ....................... Subscription required
Truck (dump) ....................... Subscription required ....................... Subscription required
Truck (dump) ....................... Subscription required 65 t ....................... Subscription required
Truck (haul) ....................... Subscription required ....................... Subscription required Leased
Truck (haul) ....................... Subscription required ....................... Subscription required Leased
Truck (water) ....................... Subscription required ....................... Subscription required Leased
Truck (water) ....................... Subscription required ....................... Subscription required Leased
Truck (water) ....................... Subscription required ....................... Subscription required
Truck (water) ....................... Subscription required ....................... Subscription required
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Dec 30, 2021
....................... Subscription required ....................... Subscription required Subscription required Dec 30, 2021
....................... Subscription required ....................... Subscription required Subscription required Dec 30, 2021
....................... Subscription required ....................... Subscription required Subscription required Dec 30, 2021
Subscription required - Subscription is required.

Staff:

EmployeesContractorsTotal WorkforceYear
Subscription required Subscription required Subscription required 2020
Subscription required Subscription required Subscription required 2018

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2021
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
Corporate Presentation 2018
Corporate Presentation 2018
Management Discussion & Analysis 2018
Press Release 2018
Quarterly Report 2018
Technical Report 2018
Corporate Presentation 2017
Management Discussion & Analysis 2017
Financial Review 2016
Management Discussion & Analysis 2016
Year-end Mineral Reserves 2016
Technical Report 2015
Other 2013
Subscription required - Subscription is required.

News:

NewsDate
Equinox Gold Temporarily Suspends Operations at RDM Mine May 16, 2022
Leagold Mining Announces Restart of RDM Mine November 20, 2018
Leagold Mining Reports Sufficient Water to Support Restart of RDM Mine November 13, 2018
Leagold Mining reports temporary suspension of operations at RDM mine October 10, 2018

Aerial view:

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