The PFS defines a 14-year mine life with average production of 135,000 ounces a year through the processing of 19.7 million tonnes of ore at an average all-in sustaining cost of US$872/oz following an initial capital cost of $269.4 million. The project is calculated to yield an after tax net present value of $263.9 million at a 5% discount rate and an internal rate of return of 20.1% at a gold price of $1,400/oz.

"The study affirms the economic viability of the project and the strength and potential for upside," said Caldas chair and CEO Serafino Iacono.

"With a continuation of our drilling programmes in the deeps mineralisation, we are confident that we will be able to continue to expand mineral resources at Marmato and add to the mine life."

Drilling in 2019 upgraded mineral resources from the inferred to measured and indicated categories. The updated measured and indicated resource is 39.4Mt grading 3.2g/t gold and 8.7g/t silver for 4.1Moz gold and 11.1Moz silver, a 100% increase over the 2019 estimate. The inferred resources increased 34% to 26.4Mt grading 2.6g/t gold and 4.4g/t silver for 2.2Moz gold and 3.7Moz silver.

Caldas outlined a package of potential capital raises totalling just shy of US$300 million in June, including a $110 million streaming agreement with Wheaton Precious Metals, to fund the Marmato development.

It aims to raise $150 million through the issuance of new senior secured gold-linked notes with warrants, which will have a nine-year term and 7.50% annual coupon.

The PFS outlines two distinct operations: the existing upper mine and the new MDZ operation which sits directly below the upper mine vein system.

The upper mine currently has six production levels and uses conventional cut and fill stope mining to supply 1,000 tonnes per day of material to a 1,200tpd mill. Caldas plans to expand the capacity of the mill to 1,500tpd over the next two years. Additional material will be mined from the wider porphyry area or transition zone, using a modified longhole stoping method.

In the PFS, it is envisioned to produce 5.1Mt grading 4.16g/t over a 13-year life for 600,000oz. This will be accomplished through the immediate implementation of an optimised mine plan and the mill expansion to increase production from about 26,000oz in 2019 to about 50,000oz/y from 2021 following an investment of $24.5 million over the next two years.

The MDZ area has not been developed and will be accessed by a decline drift with mineralisation transported via truck to an underground crusher and then to surface by conveyor. A new 4,000tpd plant facility using gravity concentration and cyanidation of the gravity tailings will be constructed. A dry stack tailings storage facility will be constructed to receive about 55% of the tailings with the other 45% to be returned underground as cemented paste backfill. In the PFS, the MDZ is envisioned to produce 14.6Mt grading 2.85g/t for 11 years from 2023 for production of 1.3Moz.

Shares in Caldas Gold are trading at C$2.79, valuing the company at $197 million.