Capricorn Metals breathes life into Newman gold exploration

Image source - Capricorn Metals - Birdseye view of Capricorn Metals’ Karlawinda gold project.
Image source – Capricorn Metals – Birdseye view of Capricorn Metals’ Karlawinda gold project.

Located in a largely unexplored and recently recognised belt of Archaean- aged greenstone rocks lies the Karlawinda gold project (KGP).

Situated approximately 65km south of Newman in the Pilbara province of WA, gold mineralisation at Karlawinda lies underneath laterite gold mineralisation in clays rich in kaolin and smectite.

Over its 12-year mine life, the advanced gold project is expected to produce about 1.2moz of gold.

Project background

After acquiring 100% of the project in 2016, Capricorn Metals (ASX:CMM) began construction of Karlawinda in December 2019 with work completed in June 2021. First gold was poured a few weeks later with a 12kg (386oz) bar produced.

With a strike length of 2.5km and a downdip length of 2.5km, the main gold production at Karlawinda comes from the Bibra gold deposit.

Karlawinda also contains several other exploration targets including the Francopan prospect, the Vedas prospect, the Carnoustie prospect and the Berwick prospect.

Due to its location in the Pilbara, very little modern and thorough gold exploration has been completed outside of the Bibra deposit.

Autonomous vehicles

To demonstrate and evaluate the capabilities of autonomous vehicles, Capricorn and mining and civil construction company MACA completed a stage one proof of concept trial of driverless trucks in March 2022. The trial was undertaken in a cleared and safe area away from active operations. The technology was installed on a Hitachi EH3500 model 180T dump truck on a haulage cycle route. Given the results of the proof of concept, a non-binding memorandum of understanding was signed between both companies.

“The autonomous haulage trials that MACA and its technology partners have completed at Karlawinda are a very exciting first step in innovation that could be a step change opportunity for the mid-tier open pit mining space,” Capricorn executive chairman Mark Clark said at the time.

“Capricorn is proud to have facilitated the trials and is impressed by the proof of concept that has been achieved to date.”

If Capricorn chooses to go autonomous, it will improve operating efficiency and availability which could deliver cost savings and improve the safety outcomes of workers in the active mine.

The autonomous vehicles would also lower fuel consumption and reduce maintenance and tyre wear.

Capricorn remains in discussions regarding its future using autonomous vehicles.
Production

Open-pit mining from a single large multistage open pit is used to mine Bibra while other methods, including grade control reverse circulation drilling, blasting and load and haul activities, were chosen to suit the orebody and reduce dilution and ore loss.

The mining fleet consists of four 100t haul trucks, eight 130t haul trucks, and other equipment including excavators, dozers, graders and loaders.

In Q3 2023, Karlawinda produced 30,841oz of gold — an increase on the 29,310oz produced in Q2 2023 — and keeping Capricorn in line with its annual guidance range of 115,000 – 125,000oz.

This result was achieved despite operating challenges late in Q3 which included 230mm of rain in the last week and a two day mill shutdown to repair a plant electrical fault.

Mining and processing

Consisting of a crushing circuit, gravity recovery, crushed ore stockpile, grinding, adsorption, electrowinning and smelting qualities, the process plant has a throughput capacity of up to 5mtpa.

Image source - Capricorn Metals - Decant water from the tailings storage facility runs into the process water pond.
Image source – Capricorn Metals – Decant water from the tailings storage facility runs into the process water pond.

The run of mine ore is firstly passed through a primary crusher before it is stockpiled and passed through a semi-autogenous ball mill crusher. The ore is then grinded further.
Gold is recovered through conventional cyanide leaching and carbon-in-leach recovery processes.

Once the process is completed, the tailings are deposited in either a tailings storage facility or an integrated waste landform.

The water is recovered using recycling techniques.

Process water pond

Decant water from the tailings storage facility and general overflow is removed by a submersible decant pump and pumped directly into a process water pond.
Able to hold up to 10,000m3 of water, water from the process pond will be distributed to various end use points in the process plant.

Water that has been contaminated by hydrogen and carbon from the vehicle washdown bay and workshop is treated through an oil-water separator.

Treated water is then reused at the washdown bay and in dust suppression around the site.

 

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