Jul 16, 2020

New approach for old stopes at Pajingo mine

New approach for old stopes at Pajingo mine

Minjar Gold is expanding on a novel mining method to revisit old stopes at North Queensland’s Pajingo gold mine in a move scheduled to increase tonnages for the balance of this year.

General manager Dale Oram said the team planned to target thin hangingwall skins of remnant ore perched against the old stopes in the Vera lode.

“To do this, we will adopt a method similar to a sub-level cave style of mining rather than the modified avoca method which is the predominant method now in play,” he said..

“One complicating factor is that this mineralisation is a skin resting against old stopes that have been backfilled with unconsolidated waste.

“These skins weren’t mined as part of the original Vera lens, so in our approach we will be ring-firing this mineralisation into the backfill and preferentially drawing down the ore with the backfill as drawpoints are opened as we move down the lens.

 “So, it’s technically and operationally challenging, but it’s do-able. And it certainly increases the tonnes we’re going to be able to mine from the underground in the latter half of this year.”

This ore improves the tonnage scheduled for the balance of the year to allow Pajngo to return its mill to full-time processing rather than the current campaign milling.

Minjar Gold Pajingo general manager Dale Oram.

“We’ve actually, from the first levels of sub-level caving we want to do, already got development ore from those areas up on surface now. So, it’s all happening,” Mr Oram said.

“This ‘entrepreneurial’ design, planning, and execution of extracting mineralisation that previous operators were not able to mine for various reasons is one of the reasons I believe sets the Pajingo teams apart.”

 It comes as work continues to develop a decline for a new underground mining area based on the Lynne ore body.

That project is expected to transition the Charters Towers district mine to what has been dubbed ‘Pajingo 2.0’ as it gains access to the Lynne ore body.

Mr Oram said work on the decline had progressed more slowly than expected due to difficult ground conditions.

“The ground has been a lot softer and more clay rich, and so it’s been really difficult with water creating weak and sloppy development work areas.” he said.

The decline, being developed by contractor Pit N Portal, has reached just under a kilometre from the portal entry and is expected to start delivering some ore for the mill by the end of the year.

Recent progress includes completion of a 1.8m diameter raise bore to provide an exit escapeway and a 4.3m diameter raise bore for ventilation, with a large extraction fan to be installed at surface within the next few weeks.

The raisebore head being extracted from the new ventilation shaft.