JOHANNESBURG (miningweekly.com) – Iron-ore explorer London Mining has cut its 2013 production guidance from its initially forecast output of between 3.6-million and 3.9-million wet metric tonnes to between 3.3-million and 3.4-million wet metric tonnes, as a result of a negative stockpile adjustment to fourth-quarter production, slower-than-expected completion of the processing plant upgrades and lower production owing to the wet season in Sierra Leone.

By November 30, production for the year had reached 3.1-million wet metric tonnes, with sales of 3.3-million wet metric tonnes.

The effects of the wet season at Marampa continued into the fourth quarter, with lower mining rates causing a full depletion of the run-of-mine (RoM) stockpile, which significantly impacted the miner’s ability to consistently feed the processing plant with the appropriate ore blend.

“RoM stocks have since been replenished. We will continue to improve our management of the issues arising from the wet season in 2014,” the Aim-listed company said in a statement on Thursday.

Owing to longer commissioning times experienced for mills and a delay in final completion of the spirals circuit, the contribution in the fourth quarter from the upgraded 5.4-million-wet-metric-tonne-a-year plant would be lower than previously expected.

The commissioning and ramp-up of the gravity circuit was taking place over the next few weeks.

Meanwhile, the depletion of the concentrate stockpiles following logistics upgrades had allowed a comprehensive reconciliation of production volumes with finished product stockpiles and exports, which had now resulted in a negative 100 000 t stockpile adjustment to fourth-quarter production volumes.

“To more accurately quantify finished stock in the future, we are upgrading our weight and moisture monitoring capability at the final plant conveyors, installing a truck weighbridge and have recalibrated stockpile survey assumptions,” said the company.

These factors had been incorporated into revised sales expectations of between 3.5-million and 3.6-million wet metric tonnes, down from between 3.9-million and 4.1-million wet metric tonnes.

Although impacting fourth-quarter production and sales, these factors were not expected to recur.

London Mining added that export operations had progressed well following the onset of the dry season, with record export volumes of 5.3-million wet metric tonnes a year achieved in November.