Assuming a US$1650 per ounce gold price, the mining minnow has ascribed a $218 million net present value and 43.7% internal rate of return to the project, which could rise to above $300 million and 54% at current prices.
Total development costs have been estimated by Cube Consulting at $75 million.
Antilles expects to contribute just A$18 million, together with contributions from Cuba's GeoMinera, a US$46 million project loan, and $16 million in supplier credit from China Exim Bank.
Financing is challenging with US sanctions in place against Cuba, so Antilles' options are more limited, but it is talking with groups not affected by the sanctions. It has also flagged deferred payment terms from preferred Chinese suppliers.
Antilles' payback is put at eight months from commissioning, with a A$221 million cash surplus, assuming an annual profit of $35 million over the six-year life of mine for the open pit.
The La Demajagua preliminary mine plan assumes recovery of both gold and silver refractory ore from an open pit, processed into 100,600 gold equivalent ounces per annum of a bulk concentrate for export.
Antilles executive chairman Brian Johnson described the scoping study as being particularly encouraging given the potential for "excellent returns" for the company given its relatively low equity contribution to the project.
He said cashflow should increase further once the 10-year underground phase commences at the end of surface mining.
Antilles' vision is to use La Demajagua as ‘proof of concept' for the development a series of mines in Cuba with GeoMinera, with around two dozen targets being assessed, including the large Golden Hills VMS deposit, and the adjacent Florencia and Maclama sulphide gold deposits.
Antilles completed almost 21,700m of drilling last year and is planning a further 6000m next quarter in support of its definitive feasibility study, which is scheduled for completion before the end of the year.
First production is targeted for early 2024.
La Demajagua previously operated as an underground gold mine until 1959. Antilles has been pursuing the project for several years.
Earlier this month Antilles set a production target of 4.8 million tonnes grading 3.27 grams per tonne gold and 40.5gpt silver of sulphide ore, plus 850,000t of oxide and transitional ore grading 2.7gpt gold and 36gpt silver.
Metallurgical test work has indicated high recoveries.
The company recently raised $5 million at 7.75c.
Its shares bucked the wider Europe-inspired market malaise today, rising 7.5% to 8.6c, valuing it at $24 million.
The stock has traded between 6c and 11.3c over the past year.
