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Australia
Costerfield Operation

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 Location:
10 km NE from Heathcote, Victoria, Australia

  Address:
1023 Heathcote Nagambie Road Costerfield
Victoria, Australia
3523
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  • Filings & News

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Overview

StageProduction
Mine TypeUnderground
Commodities
  • Gold
  • Antimony
Mining Method
  • Longhole stoping
  • Longitudinal retreat
  • Longitudinal stoping
  • Cemented backfill
Processing
  • Gravity separation
  • Flotation
Mine Life2023
Costerfield Operation includes the Augusta, Cuffley, Brunswick and Youle deposits
Latest NewsMandalay Resources Corporation Announces Recent Drilling Results For Costerfield Youle Deposit, Highlighting High-Grade Gold Depth Extensions     October 21, 2020


Owners & OPERATOR

Source: p. 5
CompanyInterestOwnership
Mandalay Resources Corp. 100 % Indirect
Mandalay Resources Costerfield Operations Pty Ltd. (operator) 100 % Direct
Mandalay Resources Corporation through its subsidiary Mandalay Resources Australia Pty owns 100% Mandalay Resources Costerfield Operations Pty Ltd.

Deposit Type

  • Vein / narrow vein
  • Mesothermal


Summary:

The Costerfield field is part of a broad gold-antimony province mainly confined to the Siluro-Devonian Melbourne Zone. Although antimony often occurs in an epithermal setting (in association with silver, bismuth, tellurium, molybdenum and other minerals), the quartz-stibnite-gold narrow veins of the Melbourne Zone are mesothermal-orogenic and are part of a 380–370 Ma tectonic event. Gold in Central Victoria is believed to have been derived from the underlying Cambrian greenstones. The origin of the antimony is less certain.

The mineralisation occurs as narrow veins or lodes, typically 500 mm wide, hosted within low-grade (anchizone) mudstone and siltstone of the Lower Silurian Costerfield Formation. Gold mineralisation of >20 g/t with an average grade of ~9 g/t is typically hosted within and/ or alongside veined stibnite with ~4% antimony (Fromhold et al., 2016). Mineralised shoots in the Costerfield Property are structurally controlled by the intersection of the lodes with major cross-cutting, puggy, sheared fault structures.

The economic mineralisation in the property occurs at the southern end of a system of steeply-dipping quartz-stibnite lodes, with thicknesses ranging from millimetres to 1 m, and extending over a strike of at least 4 km. Individual lodes can persist for up to 800 m strike and 300 m down-dip. The lode system is centred in the core of the doubly-plunging Costerfield Anticline and is hosted by Costerfield Siltstones.

Vein fill mineralogical contents and proportions are found to differ from vein to vein throughout the Augusta, Cuffley and Brunswick lodes. However, the texture and chronological order of each vein mineral generation remains remarkably consistent across all lodes. The overall paragenetic sequence is ordered as follows: laminated quartz, fibrous carbonate (siderite and ankerite), crystalline quartz (rhombic quartz), stibnite, opaline quartz and milky quartz. Acicular stibnite and botryoidal calcite are not generally associated with the main quartzstibnite vein structures and are therefore regarded as a post-mineralisation mineralogical occurrence most likely associated with meteoric events.

The Costerfield lodes are typically anastomosing, en échelon style, narrow-vein systems, dipping from 25° to 70° west to steeply east (70° to 90°). Mineralised shoots are observed to plunge to the north (when structurally controlled) and south (when bedding controlled).

The mineralisation occurs as single lodes and vein stockworks associated with brittle fault zones. These bedding and cleavage parallel faults that influence the lode structures, range from sharp breaks of less than 1 mm to dilated shears up 3 m wide that locally contain fault gouge, quartz, carbonate, and stibnite. Cross faults, such as those seen offsetting other Costerfield lodes, have been identified in both open pit and underground workings.

Mineralised lodes vary from massive stibnite with microscopic gold to quartz-stibnite, with minor visible gold, pyrite and arsenopyrite. Stibnite is clearly seen to replace quartz. Gold can also be hosted by quartz.

The Augusta Lodes occur within NNW-trending shear zones, which dip steeply to the west. They include E and W-Lodes, previously mined; N-Lode, currently being mined; and the smaller C-Lode. The E-Lode vein is approximately 0.4 m thick with a strike length of about 500 m. W-Lode averages approximately 0.4 m thick and has a strike length of approximately 230 m. [2019 AIF, p. 49]

The Cuffley Lode lies approximately 200 m to the west of E-Lode. The lode dips at about 85° to the east and occurs over a strike length of approximately 750 m, with a down-dip extent of approximately 250 m. It has an average true thickness of approximately 0.53 m. At present, the Cuffley Lode is open at depth. [2019 AIF, p. 49]

The Brunswick Lode lies approximately 600 m northwest of the northernmost point of the Cuffley Lode. The lode is sub-vertical and occurs over a strike length of approximately 450 m, with a down-dip extent of approximately 200 m and an average true thickness of approximately 1.28 m. Recent exploration drilling has identified mineralization to the south and at depth below the known Brunswick Lode. Mineralization is broken into two zones of mineralization below the Brunswick Lode, called the P-K domain and Brunswick Deeps. The P-K domain is capped by the shallow west-dipping Penguin Fault,and extends to the Kiwi Fault. The Brunswick Deeps zone is defined by the west-dipping Kiwi Fault and Adder Fault. Similar in nature to Cuffley and N-Lodes, the mineralization in the two domains is generally confined to sub-vertical quartz– stibnite veins. [2019 AIF, p. 49]

The Youle deposit extends below the historical Costerfield, Minerva and Bombay group of mines located approximately 1.2 km northeast of Brunswick. Mineralization was identified in 2011 in drill hole MB012, which struck the down-dip continuation of the vertical Kendall Lode, offset westward over the west-dipping No. 3 thrust fault. In 2016, drill hole BC006W1 revealed the existence of a high-grade north–northwest striking, west-dipping lode structure, Youle. The Youle Lode dips at a shallower angle to the mineralized lodes in Augusta and Cuffley and has been identified as the down-dip continuation of the vertical Kendall Lode offset westward over the west-dipping No.5 thrust fault. [2019 AIF, p. 50]

Youle has thus far demonstrated consistent structural and grade continuity over much of its extent. The Youle Lode has a strike length of 600 m (width of 150 m) and ranges in true thickness between 0.16 m and 1.37 m. Similar to the Augusta and Brunswick Lodes, mineralization is confined to quartz-stibnite veins. [2019 AIF, p. 50]


Mining Methods

  • Longhole stoping
  • Longitudinal retreat
  • Longitudinal stoping
  • Cemented backfill


Summary:

The Augusta Mine is serviced by a decline haulage system developed from a portal within a box-cut with the majority dimensions of 4.8 m high by 4.5 m wide at a gradient of 1:7 down. Most of the decline development was completed with a twin boom jumbo; however, development of the decline from the portal to 2 Level was completed with a road-header and this section of decline has dimensions of 4.0 m high by 4.0 m wide. The decline provides primary access for personnel, equipment and materials to the underground workings.

Mill feed is produced by three different mining methods: full face development, long-hole CRF stoping and half upper stoping. All mined material is transported to the Augusta box-cut before being hauled to either the Brunswick RoM pad or Augusta waste rock storage facility.

The Cuffley Decline currently extends down to approximately 895 mRL. At 935 mRL, the Cuffley Incline extends off the Cuffley Decline and accesses mineral resources from 945 mRL to 1050 mRL. This incline is used to extract N and NV lodes. Mining of Cuffley Lode on the Incline is complete. A second decline within Cuffley, known as the 4800 Decline, accesses the southern part of the Cuffley Lode, which is positioned south of the East Fault. This decline commences at 960 mRL and extends to 814 mRL.

The Brunswick access is 5.5 m high by 4.5 m wide, starts from 925 mRL on the Cuffley Decline and accesses the Brunswick deposit at 955 mRL. The Youle access is 5.5 m high by 5.5 m wide and extends from the Brunswick Incline at 961 mRL and accesses the Youle deposit at 957 mRL. From this level, the Youle decline, 4.8 m high and 4.5 m wide, is planned to extend down to 700 mRL to access the Youle ore body.

Mining methods
The dominant mining method is longitudinal long-hole stoping with cemented rock fill (CRF), panels generally consisting of three to four operating levels mined bottom-up over CRF with longitudinal retreat to a quasi-central access.

Method description
Mining within the Augusta Mine targets several individual lodes (including the W, NM, E, K and Cuffley Lodes), which vary in width from 0.1 m to 1.5 m and dip between 45° and 85°. This lode geometry is favourable for long-hole cemented rock fill (CRF) stoping using mechanized mining techniques.

Throughout Cuffley, the sub-level spacing of 10 m floor to floor (7 m backs to floor) has predominantly been established to ensure stable spans, acceptable drilling accuracies and blasthole lengths. A sublevel spacing of 15 m has been developed for two select areas. This involved drilling up from the lower level to 8 m and drilling and firing the remainder from the upper level using downholes.

The Brunswick orebody has applied a sub-level spacing of 12 m floor to floor (9 m backs to floor). This has been established due to better drill accuracy and the wider orebody (average diluted stope width of 2.0 m vs 1.5 m in Cuffley and Augusta).

Stoping within the Youle orebody has been designed with a sub-level spacing of 9 m floor to floor (6 m backs to floor vertically, 6–13 m backs to floor along the dip of the orebody). This reduced sub-level spacing has been designed to minimize dilution and improve recovery in the flatter dipping Youle stopes. The orebody dip varies greatly in Youle between 40° and 85°, which is dependent on the influence of the No. 4, No. 3 and Orb Weaver Faults. To optimize the extraction of ore where the dip is shallower than 45°, ore development and stope geometry will be adjusted to steepen the footwall of the stopes.


Crushing and Grinding


Processing

  • Gravity separation
  • Flotation

Flow Sheet: Subscription required

Summary:

Brunswick Processing Plant
The Brunswick Processing Plant processes a sulphide gold–antimony ore through a conventional comminution and flotation-style concentrator. Since 2009, several processing plant upgrades have seen production increase to the current average of approximately 12,000 t/month over the 2015–2019 calendar years. The concentrator operates 24 hours per day, 7 days per week. Crushing operates under noise restriction guidelines during extended dayshift hours.

The surface crushing and screening system processes underground feed down to a particle size range suitable for milling through a two-stage, closed-circuit ball milling circuit. Centrifugal-style gravity concentrators are used on the combined primary milling product and secondary mill discharge to recover a gold-rich gravity concentrate. This is tabled and sold as a separate gold concentrate product that is sent to local refineries. Secondary milled products are classified based on size and processe ........

Recoveries & Grades:

CommodityParameter20192018201720162015
Gold Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Gold Head Grade, g/t 5.15.648.179.6310.7
Gold Concentrate Grade, g/t  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Antimony Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Antimony Head Grade, % 2.52.333.283.413.96
Antimony Concentrate Grade, %  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Subscription required - Subscription is required.

Production:

CommodityProductUnits202020192018201720162015
Gold Payable metal koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required324142
Antimony Payable metal t  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Gold Equivalent Payable metal oz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Gold Concentrate dmt  ......  Subscription required  ......  Subscription required9,05210,18810,731
^ Guidance / Forecast.
Subscription required - Subscription is required.

Operational Metrics:

Metrics20192018201720162015
Ore tonnes mined  ......  Subscription required  ......  Subscription required  ......  Subscription required158,351 t153,649 t
Tonnes processed  ......  Subscription required  ......  Subscription required  ......  Subscription required154,409 t153,869 t
Annual processing capacity  ......  Subscription required  ......  Subscription required  ......  Subscription required
Daily processing rate  ......  Subscription required  ......  Subscription required  ......  Subscription required420 t
Subscription required - Subscription is required.

Reserves at December 31, 2019:

CategoryTonnage CommodityGradeContained Metal
Proven 114 kt Gold 9.5 g/t 35 koz
Proven 114 kt Antimony 4.8 % 5.4 kt
Probable 360 kt Gold 14.6 g/t 169 koz
Probable 360 kt Antimony 3.4 % 12.4 kt
Proven & Probable 474 kt Gold 13.4 g/t 204 koz
Proven & Probable 474 kt Antimony 3.8 % 17.8 kt
Measured 283 kt Gold 9.6 g/t 87 koz
Measured 283 kt Antimony 4.5 % 12.7 kt
Indicated 830 kt Gold 9.6 g/t 256 koz
Indicated 830 kt Antimony 2.9 % 24 kt
Measured & Indicated 1,113 kt Gold 9.6 g/t 344 koz
Measured & Indicated 1,113 kt Antimony 3.3 % 36.7 kt
Inferred 533 kt Gold 6.8 g/t 117 koz
Inferred 533 kt Antimony 1.7 % 9 kt

Commodity Production Costs:

CommodityUnits202020192018201720162015
Cash costs Gold Equivalent USD  ......  Subscription required ^  ......  Subscription required  ......  Subscription required 701 / oz 640 / oz 559 / oz
All-in costs Gold Equivalent USD  ......  Subscription required ^  ......  Subscription required  ......  Subscription required 991 / oz 890 / oz 773 / oz
^ Guidance / Forecast.
Subscription required - Subscription is required.

Operating Costs:

Units20192018201720162015
UG mining costs ($/t milled) USD 148145169152148
Processing costs ($/t milled) USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Total operating costs ($/t milled) USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Subscription required - Subscription is required.

Financials:

Units202020192018201720162015
Capital expenditures (planned) M USD  ......  Subscription required
Capital expenditures M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 16.2  
Revenue M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 71.5  
Pre-tax Income M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 21.8  
After-tax Income M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 15.1  
EBIT M USD  ......  Subscription required  ......  Subscription required
EBITDA M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 37.9  
Subscription required - Subscription is required


Heavy Mobile Equipment as of December 31, 2019:
HME TypeModelQuantity
Drill (long hole) 2
Drill jumbo (single boom) 3
Load-Haul-Dump (LHD) ....................... Subscription required 2
Load-Haul-Dump (LHD) ....................... Subscription required 5
Truck (haul) 2
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Jun 27, 2020
....................... Subscription required ....................... Subscription required Subscription required Jun 27, 2020
....................... Subscription required ....................... Subscription required Subscription required Jun 27, 2020
Subscription required - Subscription is required.

Staff:

EmployeesContractorsTotal WorkforceYear
Subscription required Subscription required Subscription required 2019
Subscription required Subscription required Subscription required 2018
Subscription required Subscription required Subscription required 2016

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2018
................................... Subscription required 2018
................................... Subscription required 2018
................................... Subscription required 2018
Management Discussion & Analysis 2017
Technical Report 2017
Annual Information Form 2016
Management Discussion & Analysis 2016
Press Release 2016
Subscription required - Subscription is required.

News:

NewsDate
Mandalay Resources Corporation Announces Recent Drilling Results For Costerfield Youle Deposit, Highlighting High-Grade Gold Depth Extensions October 21, 2020
Mandalay Resources Corporation Provides Exploration Update And Announces Early Success of the Brown’s Prospect... June 22, 2020
Mandalay Resources Corporation Announces Approximately C$60 Million Financing Transaction and Provides Corporate Update February 11, 2019
Mandalay Resources Corporation Announces Filing of Updated NI 43-101 Technical Report for its Costerfield Mine February 6, 2019
Mandalay Resources Corporation Restates 2018 Mineral Reserves Update for Its Costerfield Operation, Including Restatement of Maiden Reserves Estimate for the Youle Lode; Announces Further Increases to Mineral Reserves January 22, 2019
Mandalay Resources Corporation Announces 2018 Mineral Resources and Reserves Update for Its Costerfield Operation, Including Maiden Resources and Reserves Estimate for the Youle Lode January 8, 2019

Aerial view:

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