La Demajagua Gold/Silver Mine

SITE LOCATION AND INFRASTRUCTURE

  • The La Demajagua gold/silver deposit is located on the Isle of Youth, 100km from mainland Cuba.
  • The mine site is accessible from the port city of Nueva Gerona by 35km paved highway.
  • A dedicated port can be constructed for landing craft, 4km from mine.
  • Connected to water, electricity, and fibre optic.
  • 900ha mining concession at 20m above sea level.


Location La Demajagua Gold/Silver Project

LOWER
Tonnes 16,000,000
Grade (Au g/t) 2.3
oz Au 1,200,000
Grade (Ag g/t) 17
oz Ag 8,700,000
UPPER
Tonnes 20,000,000
Grade (Au g/t) 2.7
oz Au 1,700,000
Grade (Ag g/t) 25
oz Ag 14,800,000

Data from 50,000m of historic drilling by Canadian mining companies together with a 21,000m program completed to date by the joint venture has allowed the establishment of maiden JORC Resources.

Initial Indicated and Inferred JORC Resources for the proposed open pit mine were advised to ASX on 28 January 2022:

7.7Mt @ 2.9 g/t Au (720,000 oz Au) and 38.6 g/t Ag (9.57M oz Ag)

Based on these Resources and metallurgical test work, the open pit mine is planned to operate for six years at a mining rate of 950,000 tpa of ore with a stripping ratio of 8.5:1, and produce 70,000 tpa of concentrate containing approximately 100,000 oz Au equivalent.

Additional drilling will be required for the second stage underground operations which are expected to be at around 60% of the production rate for the open pit for a minimum of 10 years.

Drilling at La Demajagua

Drilling Highlights

HISTORY

The La Demajagua gold/silver deposit incorporates the Delita deposit which was discovered around 1900 but received only cursory attention until the 1920s when a North American company acquired the concession. Production was minimal until after World War ll.

In the period 1947 – 1950, approximately 60,000 t of ore were mined underground. As mining progressed in depth, the material changed from shallow, oxide-zone material, to sulphidic arsenic mineralization. Reports suggest that 60,000 t were mined at a recovered grade of 14 g/t gold. A 40 tpd beneficiation plant was constructed to drive off arsenic and sulphur, and concentrates were shipped offshore to a smelter for direct refining. The property was abandoned in 1958 when the concentrator ceased operating.

During the 1970s and 1980s, regional exploration, mapping and geophysical surveys were conducted, and between 1977 and 1980, trenching and drilling were conducted on the Delita property. This work expanded resources considerably.

Following a 1980 study, a new shaft was sunk and a flotation and gravity process plant constructed, with approximately 80,000 t of ore processed through the plant. High recoveries of gold and silver, reporting to flotation and gravity concentrates, were achieved in the plant, which had a nominal 60-80 tpd capacity. However, the inability to process the refractory concentrates prevented operations from being expanded to full scale production.

Concentrate product was reported as 30g/t to 60g/t Au, 15% to 20% As and 20% to 30% S.

 

Previous Preliminary Feasibility Studies

Boliden Contech, working under a technical assistance program for Cuba, prepared a Prefeasibility Study of the Delita deposit in June 1990. It was concluded that the project was not viable at gold prices prevailing at that time, primarily because the metallurgical treatment was likely to be expensive and a costly undercut-and-fill method was proposed for underground mining.

In May 1992, Minproc Engineers prepared a Prefeasibility Study of Delita for Matlock Mining NL of Australia. Minproc evaluated metallurgical test work and concluded that the project was economically viable.

Minera Mantua SA acquired its interest in the Delita project in 1993 and engaged Davy Engineering to conduct a Preliminary Feasibility Study for the project, which was completed in March 1995 and reported average head grades that reflect the anticipated grades assessed by the Company’s consultants after geological modelling of historic drill data.

In September 1994, after metallurgical test work on the Delita ore, Davy Engineering reported concentrate grades of 46.8g/t Au, 380g/t Ag, 18%As, and 16%S.

FINANCIAL

The current Financial Model for the open pit mine indicates a total capital cost of US$75 million including pre-development costs, financing and administration costs during construction.

Antilles Gold is contributing US$13.0 million of this amount between October 2020 and March 2023 for its 49% shareholding in joint venture.

Modelling is based on quotations for the mining fleet and turnkey offers for the design and construction of the crushing, milling, and flotation circuits, and an 8Mw power station.

Antilles Gold’s equity will meet the costs of the DFS and overheads to December 2022 (US$8.0 million), and mine infrastructure in 2023 (US$5.0 million).

Financing for US$62 million of development costs is anticipated to be provided by a combination of supplier credit and project loans.

Concentrate is expected to be sold to international trading companies or foreign smelters.

Results from the Scoping Study for the La Demajagua open pit mine were advised to ASX on 24 February 2022.

FINANCIAL RESULTS include;

Antilles Gold’s share of Surplus Cash from the Open Pit Mine (6 years) – A$221.0 million.

The results demonstrate excellent returns on Antilles Gold’s modest A$18.0 million equity for the 49% shareholding in the joint venture.

Antilles Gold’s share of NPV8 – A$148.0 million.

Returns should increase from the planned underground operations to follow open pit mining for 10 years.

La Demajagua Underground Mine

The drilling program necessary to establish JORC Resources for the underground operation planned to follow the open pit mining will be undertaken as soon as practicable after commissioning of the open pit mine, and be followed by a DFS.

Antilles Gold will re-invest US$6.0 million from open pit mine dividends to undertake the DFS including the drilling to establish JORC Resources and mine planning, and will later contribute an additional US$7.0 million for underground development.

Underground mining is planned to commence in 2030-2031.

Based on historic drilling data, the underground mining rate is expected to be around 600,000 tpa to produce concentrates containing approximately 60,000 oz Au equivalent annually for a period of 10 years.

The underground operation will benefit from the availability of the existing processing plant and infrastructure, and require relatively low additional capital costs for the mine development which should be able to be met from retained earnings of MLV.

Los Llanos Project

  • The Los Llanos Project will allow Antilles Gold to undertake preliminary exploration activities and studies of a number of previously explored gold and copper/gold deposits in Cuba to determine those with development potential.
  • Antilles Gold may explore and study deposits that are listed in a formal International Economic Assessment (“IEA”), which is effectively a ’global’ Exploration Agreement between subsidiaries of Antilles Gold and GeoMinera.
  • The Los Llanos Project will be an “incubator” for determining the development potential of properties offered to Antilles Gold by GeoMinera.
  • Properties can be added to the list of gold and copper/gold deposits, or deleted, from time to time on Antilles Gold’s recommendation.
  • A cluster of highly prospective porphyry copper-gold deposits near Ciego de Avila in central Cuba with potential for a major open pit operation have been included in the Los Llanos Project IEA after review by Antilles Gold.
  • Other listed properties include a large VSM deposit at Golden Hills, and the Florencia/Maclama sulphide gold deposits in south east Cuba.
  • Antilles Gold is currently reviewing an extensive VMS style polymetallic mineral belt with previous Cu, Zn, Au, and Ag production.
  • Subject to the results of early-stage exploration, Antilles Gold can request a property be transferred to the joint venture mining company, for further exploration and possible development.
  • Antilles Gold will be reimbursed for any expenditure on an IEA property if its ultimately developed.
  • The IEA expiry date is February 2027 but can be extended at the request of Antilles Gold.
  • A group of geologists and support staff based in Camaguey in southeast Cuba, and managed by Antilles Gold’s Australian Exploration Director, will undertake the Los Llanos activities.

Activities between mid 2022 and end 2023 will include:

  • re-interpretation of existing data, geological mapping, and geophysical surveys including ground magnetics and induced polarisation programs (IP), for the porphyry copper-gold deposits at Ciego de Avila, and the VMS deposit at Golden Hills.
  • drilling programs totalling 10,000m followed by Scoping Studies for the two projects.

The properties are expected to then be transferred to the joint venture mining company for additional exploration and possible development.

Ciego de Avila Porphyry Copper-Gold Project

Antilles Gold’s Exploration Director has reported the following with respect to the Ciego de Avila Project:

  • The group of three copper-gold porphyry deposits (El Pilar, San Nicholas, and Gaspar) were originally discovered in the 1990’s by MacDonald Mines from Canada.
  • Mapping, soil sampling, ground magnetics, and shallow drilling was carried out but failed to identify the exposures as being a large leached porphyry system.
  • Copper grades are widespread with the gold mineralization, and generally are located at the saprolite/saprock contact as the copper is leached downwards in the weathering profile above fresh rock.
  • The surface exposures at both El Pilar and San Nicholas are leached phyllic caps to a cluster of copper-gold porphyry cores.
  • Given the size of the phyllic alteration zones at surface at both El Pilar and San Nicholas, the size potential of the mineralized copper-gold porphyry orebodies could easily surpass 500Mt, indicating it as a large porphyry open pit target, and an excellent exploration opportunity.
  • All porphyry systems in tropical environments are leached at surface due to the large amount of pyrite that oxidizes and leaches metals downwards in the oxidized saprolite, to the fresh rock.
  • The interpreted porphyry systems are fertile as both copper and gold are abundant in the saprolite at both the El Pilar and San Nicholas prospects and are outcropping in an area of excellent access and infrastructure.
  • The level of erosion of the porphyry systems is low, indicating that the porphyry system(s) should extend vertically over 1,000m.
  • The Ciego de Avila Project is located adjacent to major highway and HT power in cleared farmland.
  • The Project is highly recommended as an advanced exploration prospect that has multiple copper-gold porphyry targets and the potential for a major open pit mining operation.
  • Minimal exploration is required to advance the targets to a drill-ready stage.

Geology and Mineralisation

  • The El Pilar and San Nicholas prospects are located 4 km apart in volcaniclastic rocks that are intruded by two individual porphyry clusters.
  • El Pilar and San Nicholas are individual porphyry centres and indicate the potential for multiple porphyry copper-gold discoveries.
  • El Pilar and San Nicholas have undergone shallow drilling confirming the existence of copper-gold mineralization in weathered saprolite near surface.
  • The surficial hydrothermal alteration noted at both prospects represent a classic porphyry phyllic cap and the dimensions of the phyllic alteration (upper parts of in-situ porphyry systems) are >1km indicating the porphyry intrusions are of large dimensions.
  • The in-situ copper-gold sulphide mineralization of the target potassic porphyry core is interpreted to be immediately below the surficial phyllic caps and remains untested with deeper drilling.

Aeromagnetic Survey

Drilling at El Pilar Indicating the Previously Overlooked Porphyry Copper-Gold Potential

  • Shallow drilling at El Pilar has shown oxide mineralization of both gold and copper
  • The copper mineralization has been leached and is located below the gold zone and represents a classic leached oxide cap to a porphyry copper-gold system that has not been tested at depth
  • A program of ground magnetics and I.P. geophysics will map the intrusive porphyry phases, locate the potassic sulphide core and guide drilling to locate the in-situ sulphide (chalcopyrite-bornite- magnetite) target zone

3D view of the previous drilling at El Pilar with the modelling of the Au and Cu ore bodies. The field of view of the image is about 500 m.

Surface Mineralisation of the El Pilar Deposit

Strong phyllic alteration and porphyry D-veins overprinting a copper-gold porphyry system at surface

Golden Hills Project

The Golden Hills sulphide deposit was explored by MacDonald Mines between 1994 and 1998 when they conducted ground and airborne geophysical surveys, mapping, geochemical surveys, trenching, and 199 cored drill holes to an average depth of 80m (50 m into the shallow sulphide mineralization). The database generated by this work was well archived and available for Antilles Gold.

A cluster of three oxide deposits at Golden Hills that have already been mined are underlaid by a large interconnected volcanogenic massive sulphide (“VMS”) deposit which is located near Guaimaro, 100km south east of the Provincial capital of Camaguey.

The mineralisation discovered to date lies in a 1.5km long by 1.0km wide west-northwest oriented zone, and within a lens shaped body 7.0km long and 2.0km in true thickness that has been interpreted to be a section through a volcanic edifice.

The extensive geological data for the property provided by GeoMinera will assist in preparing an efficient and cost-effective program to complete the initial exploration and a Prefeasibility Study for the project in 2022-24.

Antilles Gold is attracted to the Golden Hills deposit as it could be a viable producer of large volumes of copper/gold concentrate.

Consulting Geologist’s Report

Geology

“The Golden Hills Au-Cu deposits are hosted in Cretaceous volcaniclastic rocks, that dip moderately west-northwest. These rocks outline a lens shaped body 7.0km long and about 2.0km in true thickness that is interpreted to be a section through a volcanic edifice.

The mineralization is spatially and probably genetically related to a 2.0km² intrusive body that is centered 1.5km south of Big Golden Hill. The mineralization lies within a 1.0km wide by 1.5 km long west-northwest oriented zone on the northwest side of the intrusive.

The Golden Hills Au-Cu deposits have been classified as high-sulphidication type deposits. The style and distribution of the mineralization and alteration has many similarities to high-sulphidication gold systems around the world including Pueblo Viejo in the Dominican Republic, El Indio in Chile, and Lepanto in the Philippines.

The Golden Hills Au oxide deposits are underlaid by a large mineralized system hosting Au and Cu enriched sulphide bodies. Wide intersections of blind, massive, semi-massive, and disseminated sulphide mineralization with Au and Cu occur within the area, and the potential to define large Au and Cu sulphide resources is excellent.”

Major Target

The Golden Hills deposit represents a major target for Antilles Gold which is planning an aggressive exploration program of the property in 2022-24. The Company will establish a regional office in Camaguey in south east Cuba to conduct the program under the control of Antilles Gold’s Exploration Manager. Exploration costs will be reimbursed to Antilles Gold if the deposit is developed.

Interpreted Longitudinal Section through Little Golden Hill

Mined oxide deposits at Golden Hills underlaid by an outcropping interconnected sulphide deposit

Florencia & Maclama Project

The Florencia and Maclama gold deposits near Golden Hills, are low sulphide, near surface deposits which have been explored by Russian companies, and MacDonald Mines from Canada

Geological data from 17,000m of cored drill holes (237 holes), and an 80m shaft at Florencia with 1200m of drifts and cross cuts, has been made available to Antilles Gold.

Metallurgical test work on Florencia ore by SGS Lakefield in Canada indicated concentrate grades could be up to 120 g/t Au and 90 g/t Ag with a very low arsenic content (0.05% As).

The deposits are approximately 7km apart and the plan is to develop two small mines with ore being transported to a central plant for the production of concentrate.

It is anticipated that if the development proceeds, the capital costs for the two relatively small mines will be able to be met from surplus cash flow generated by the La Demajagua mine.

Annual concentrate production of only 15,000 tonne from each mine at a conservative grade of 50g/t Au would result in the production of approximately 50,000 oz Au per year plus silver credits.

Concentrate Processing Facility

Antilles Gold intends to review the technical and commercial viability of constructing a plant at a suitable location in Latin America, to process refractory concentrate sourced from the joint venture’s mines in Cuba, and possibly from other regional mines, to produce significantly higher value doré.

The oxidation process that would be utilised in conjunction with standard cyanide-in -leach (“CIL”) technology could be either pressure oxidization (“POX”), or Glencore’s patented Albion process (refer TECHNOLOGY section) with which the Company has had considerable experience.

The Company’s 200tpd VSPA oxygen plant which is currently stored in the Dominican Republic and is being well maintained, would, if utilised in a new plant, be the major determinant in the capacity of the concentrate processing facility.

This oxygen plant would satisfy the demands of either a mini 70,000 tpa POX plant, which equates to the proposed annual concentrate production from La Demajagua, or an Albion oxidation circuit with the capacity for two trains of 60,000 tpa each.

Based on metallurgical test work to date, the La Demajagua concentrate appears to be more amenable to the POX process.

Las Lagunas Oxygen Plant

ANTILLES GOLD LIMITED
ASX CODE AAU
OTCQB:ANTMF
55 Kirkham Road
Bowral NSW 2576
Australia
+ 61 2 4861 1740
ANTILLES GOLD LIMITED
ASX CODE AAU
55 Kirkham Road
Bowral NSW 2576
Australia
+ 61 2 4861 1740