Mining Intelligence and News
Mongolia

ATO Phase 2 Expansion Project

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Summary

Mine TypeOpen Pit
Study CompletedFeasibility
Study in ProgressFeasibility Update
StageConstruction
Commodities
  • Gold
  • Silver
  • Lead
  • Zinc
Mining Method
  • Truck & Shovel / Loader
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SnapshotThe ATO Phase 2 Expansion will increase gold production and generate saleable concentrates of lead, zinc, and pyrite through the development of underlying fresh rock ores and the construction of a larger, conventional processing facility.

As of 2024, the Phase 2 Expansion is progressing according to the updated timelines and budgets. Increases in annual capacity and metallurgical improvements are being reviewed with the EPC and engineering partners. A revised feasibility study is being developed in 2025, which will reflect the impact of higher current gold prices.

Owners

SourceSource
CompanyInterestOwnership
Boroo Pte Ltd. 55.9 % Indirect
The Altan Tsagaan Ovoo (ATO) mine is owned and operated by Steppe Gold LLC, a subsidiary of Steppe Gold Ltd.

On April 11, 2024, Steppe Gold Ltd. entered into a share exchange agreement with Centerra and Boroo Pte Ltd. to acquire all shares of Boroo Gold in exchange for shares representing 55.9% of Steppe Gold Ltd’s fully diluted shares.

On August 1, 2024, the acquisition was completed.

Contractors

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Deposit type

  • Epithermal
  • Breccia pipe / Stockwork

Summary:

The geology of the property consists of metamorphosed Devonian sedimentary rock overlain by a volcanic and sedimentary sequence of Permian age and remnant scraps of probable Jurassic volcaniclastic units, intruded by Jurassic plutons ranging from diorite to granite in composition and including rhyolitic phases mainly as dikes. Petrographic study suggests simple, single-pulse injections of the intrusions, with late-stage generation/expulsion of felsic phases and contemporaneous concentration of metal-rich fluids.

Mineralization at ATO is probably related to the Jurassic intrusive magmatic rocks as sources of heat, metals, and fluids. The main ATO system is associated with a stratigraphic unit that appears to be localized in a graben or collapse feature that is possibly but not certainly Jurassic in age; any stratigraphy could potentially be prospective for this style of mineralisation. The ATO mineralisation appears to have occurred as a protracted single-stage process in separately upward-flaring pipe-shaped bodies, with temperatures ranging from ~300-350°C at depth to possibly ambient temperature in surficial sinter.

Metal zonation: In a broad sense, metal zoning shows a clear, classic pattern of intrusion-centred copper (plus or minus molybdenum, tungsten, gold, and other elements) outward to country-rock hosted lead, zinc, and silver (plus or minus gold, arsenic, antimony, mercury, and other elements). It is presumed that this lateral zonation also occurs vertically, as evidenced by increasing copper values at depth in ATO.

It is believed that the ATO deposit is an epithermal gold and polymetallic deposit of transitional sulphides in breccia pipes in a Mesozoic continental rift zone in eastern Mongolia. Formation of breccia pipe: Tectonic-magmatic activities began to take place in the area around ATO deposit in Early Jurassic when hydrothermal and metasomatic alterations and mineralisation were formed in relation to intrusions and dykes. Absolute age of an intrusive massive located outside and east of ATO prospect area was determined to 189 million years.

The pipes that have been identified in the deposit are aligned in a row in a structure with a trend from southeast to northwest and form mineralisation with differing horizontal geochemical zonation with certain metallic concentrations. Noel White (2001) devised a pattern of flow of fluids based on this geochemical zonation similarity with that found adjacent to porphyry copper intrusions. White’s model postulates that the horizontal mineral zonation between the ATO pipes could originate from a large intrusion (such as a porphyry copper) located tens of kilometres away from ATO deposit.

Reserves

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Mining Methods

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Required Heavy Mobile Equipment

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Comminution

Crushers and Mills

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Processing

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Commodity Production

CommodityProductUnitsAvg. AnnualLOM
Lead Concentrate kt 184
Zinc Concentrate kt 293
Pyrite Concentrate kt 612
Gold Equivalent Metal in concentrate koz 106

Operational metrics

Metrics
Annual ore mining rate  ....  Subscribe
Annual processing capacity  ....  Subscribe
Tonnes processed, LOM  ....  Subscribe
* According to 2021 study.

Production Costs

CommodityUnitsAverage
Assumed price Lead USD  ....  Subscribe
Assumed price Zinc USD  ....  Subscribe
Assumed price Silver USD  ....  Subscribe
Assumed price Gold USD  ....  Subscribe
* According to 2021 study / presentation.

Project Costs

MetricsUnitsLOM Total
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Sustaining CapEx $M USD  ......  Subscribe
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Gross revenue (LOM) $M USD  ......  Subscribe
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EBITDA (LOM) $M USD  ......  Subscribe
Pre-tax Cash Flow (LOM) $M USD  ......  Subscribe
After-tax Cash Flow (LOM) $M USD  ......  Subscribe
Pre-tax NPV @ 5% $M USD  ......  Subscribe
Pre-tax NPV @ 10% $M USD  ......  Subscribe
Pre-tax NPV @ 8% $M USD  ......  Subscribe
After-tax NPV @ 5% $M USD  ......  Subscribe
After-tax NPV @ 10% $M USD  ......  Subscribe
After-tax NPV @ 8% $M USD  ......  Subscribe
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Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Jul 29, 2025
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....................... Subscription required ....................... Subscription required Subscription required Oct 27, 2021
....................... Subscription required ....................... Subscription required Subscription required Oct 27, 2021

Workforce

EmployeesYear
...... Subscription required 2021

Aerial view:

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