United States

Hermosa (Taylor) Project

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Overview

Mine TypeUnderground
StageConstruction
Commodities
  • Zinc
  • Lead
  • Silver
Mining Method
  • Longhole open stoping
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SnapshotThe Hermosa project comprises the zinc-lead-silver sulphide Taylor deposit, the zinc-manganese-silver oxide Clark deposit and the potential for further polymetallic and copper mineralisation. In addition to the Taylor and Clark deposits, Hermosa has a highly prospective broader land package, which includes the copper-lead-zinc-silver Peake exploration target, as well as the Flux prospect.

South32 have completed study work that confirmed that the Taylor Deposit and the Clark Deposit can be developed independently.

During September 2023, South32 progressed construction of key infrastructure at Hermosa project and commenced federal permitting process under FAST-41.

Owners

SourceSource
CompanyInterestOwnershipInvestor's Info
South32 Limited 100 % Indirect
Hermosa is 100% owned by South32. Title to the mineral rights is vested in South32’s wholly owned subsidiary Arizona Minerals Inc.

Contractors

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Deposit type

  • Carbonate replacement
  • Manto
  • Skarn

Summary:

The Taylor Deposit is a carbonate replacement style zinc-lead-silver massive sulphide deposit. It is hosted in Permian carbonates of the Pennsylvanian Naco Group of south-eastern Arizona. The Taylor Deposit comprises the upper Taylor sulphide (Taylor Mains) and lower Taylor deeps (Taylor Deeps) domains that have a general northerly dip of 30° and are separated by a low angle thrust fault.

The Taylor Deposit has an approximate strike length of 2,500m and a width of 1,900m. The stacked profile of the thrusted host stratigraphy extends 1,200m from near-surface and is open at depth and laterally.

Cretaceous-age intermediate and felsic volcanic and intrusive rocks cover much of the Hermosa project area and host low-grade disseminated silver mineralisation, epithermal veins and silicified breccia zones that have been the source of historic silver and lead production.

Mineralisation styles in the immediate vicinity of the Hermosa project include the carbonate replacement deposit (CRD) style zinc-lead-silver base metal sulphides of the Taylor Deposit and deeper skarn-style copper-zinc-lead-silver base metal sulphides of the Peake prospect and an overlying manganese-silver oxide manto deposit of the Clark Deposit.

The Taylor Deposit comprises the overlying Taylor Sulphide, and Taylor Deeps domains that are separated by a thrust fault. Approximately 600–750m lateral and south to the Taylor Deeps domain, the Peake copper-skarn sulphide mineralisation is identified in older lithological stratigraphic units along the interpreted continuation of the thrust fault.

The Taylor Sulphide Deposit extends to a depth of around 1,000m and is hosted within approximately a 450m thickness of Palaeozoic carbonates that dip 30°NW, identified as the Concha, Scherrer and Epitaph Formations.

Taylor Sulphide mineralisation is dominantly constrained within a tilted and thrusted carbonate stratigraphy and to a lesser degree the overlying volcanic stratigraphy. The mineralising system is yet to be fully drill tested in multiple directions. At Taylor, the sulphide mineralisation is constrained up-dip where it merges into the overlying oxide manto mineralisation of the Clark Deposit, representing a single contiguous mineralising system.

The north-bounding edge of the thrusted carbonate rock is marked by a thrust fault where it ramps up over the Jurassic/Triassic ‘Older Volcanics’ and ‘Hardshell Volcanics’. This interpreted pre-mineralising structure that created the sequence of carbonates also appears to be a key mineralising conduit. The thrust creates a repetition of the carbonate formations below the Taylor Sulphide domain, which host the Taylor Deeps mineralisation.

The Taylor Deeps mineralisation dips 10°N to 30°N, is approximately 100m thick, and primarily localised near the upper contact of the Concha Formation and the unconformably overlying ‘Older Volcanics’. Some of the higher-grade mineralisation is also accumulated along a westerly plunging lineation intersection where the Concha Formation contacts the Lower Thrust. Mineralisation has not been closed off down-dip or along strike.

Lateral to the Taylor Deeps mineralisation, skarn sulphide mineralisation is identified in older lithological stratigraphic units along the interpreted continuation of the thrust fault. This creates an interpreted continuous structural and lithological controlled system from the deeper skarn Cu domain into Taylor Deeps, Taylor Sulphide, and associated volcanic hosted mineralisation and the Clark oxide Deposit.

The Peake prospect is comprised of a series of stacked horizons that have a general north-westerly dip of 300 hosting disseminated to semi-massive sulphide. The upper and lower extents of the horizons tend to have polymetallic mineralisation with the central component dominated by copper sulphides, predominantly chalcopyrite. Mineralisation within the stacked profile is approximately 130m thick, for an approximate 450m strike and 300m width.

Dimensions
The mineralising system is yet to be fully drill tested in multiple directions. The Taylor sulphide mineralisation is constrained up-dip where it transitions to oxide mineralisation, representing a single contiguous mineralised system. Taylor is open in multiple directions.

The north-bounding edge of the thrusted carbonate rock is marked by a thrust fault where it ramps up over the Jurassic/Triassic ‘Older Volcanics’ and ‘Hardshell Volcanics’. This interpreted pre-mineral structure that created the sequence of carbonates also appears to be a key conduit for mineralisation.

The Taylor deposit has an approximate strike length of 2,500m and width of 1,900m. The stacked profile of the thrusted host stratigraphy extends 1,200m from near-surface and is open in several directions.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

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Processing

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Production

CommodityUnitsAvg. AnnualLOM
Lead M lbs 3046,614
Silver M oz 7.3160
Zinc Equivalent M lbs 61713,669
All production numbers are expressed as payable metal.

Operational metrics

Metrics
Annual mining capacity  ....  Subscribe
Annual milling capacity  ....  Subscribe
* According to 2022 study.

Production Costs

CommodityUnitsAverage
Credits (by-product) Zinc Equivalent USD  ....  Subscribe
Total cash costs Zinc Equivalent USD  ....  Subscribe
Total cash costs Zinc Equivalent USD  ....  Subscribe
All-in sustaining costs (AISC) Zinc Equivalent USD  ....  Subscribe
Assumed price Lead USD  ....  Subscribe
Assumed price Zinc USD  ....  Subscribe
Assumed price Silver USD  ....  Subscribe
* According to 2022 study / presentation.
** Net of By-Product.

Operating Costs

Currency2022
UG mining costs ($/t milled) USD 35 *  
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G&A ($/t milled) USD  ....  Subscribe
Total operating costs ($/t milled) USD  ....  Subscribe
* According to 2022 study.

Project Costs

MetricsUnitsLOM Total
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Heavy Mobile Equipment

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Personnel

Mine Management

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