TORONTO (miningweekly.com) – Canadian miner Centerra Gold has increased its total reserve base by 9% to 8.4-million ounces of contained gold as at the end of December, up from 7.7-million ounces reported in the previous year.

At the end of 2015, Centerra’s estimated proven and probable gold reserves increased by 666 000 contained ounces, after accounting for the processing of 658 000 contained ounces in 2015.

The reserve increase was mainly a result of the positive feasibility study on the Öksüt project, in Turkey, where resources were upgraded to reserves in June 2015.

The 2015 year-end reserves had been verified and estimated using a gold price of $1 200/oz.

At Kumtor mine, in Kyrgyzstan, proven and probable gold reserves decreased by 495 000 contained ounces, after accounting for processing of 658 000 contained ounces in 2015.

Centerra advised that the KS2014YE resource model for Kumtor continued to overestimate tonnage in the +3 g/t fraction and underestimate tonnage in the 1.1 g/t to 3 g/t fraction. For this reason, a new resource model, KS2015YE was developed for 2015 year-end reserve estimation, which incorporated additional in-fill drilling that had been completed during the year.

As a result, 164 000 contained ounces were added, and Kumtor’s proven and probable reserves now totalled an estimated 5.6-million ounces of contained gold (69.2-million tonnes grading 2.5 g/t gold), including 4.1-million contained ounces of gold (44.3-million tonnes grading 2.8 g/t gold) in the Central pit at the end of December 2015. This was 500 000 oz less than when compared with the previous total of proven and probable reserves at Kumtor of 6.1-million ounces, as at December 31, 2014.

Centerra had booked an $111-million, or $0.47 a share, goodwill impairment charge on the Kumtor mine in February last year, as a result of decreasing the reserves and resources at the mine following negative production reconciliation in 2014, developing a new resource model for the Kumtor central pit and design changes to the Central pit, resulting from a new resource model and flattening certain of the pit slopes.

In Mongolia, at the Boroo mine, the 16 226 oz of gold produced in 2015 came from secondary leaching of the heap leach pad and from the Boroo mill clean out. Centerra advised that the Boroo heap-leach operation was transitioning into closure and the mill was on care and maintenance awaiting a positive decision on the nearby Gatsuurt project, which received governmental approval last week.

At the Gatsuurt project, proven and probable reserves remained unchanged from 2014 and totalled more than 1.6-million contained ounces of gold (17.1-million tonnes grading 2.9 g/t gold).

In Turkey, at the Öksüt project, the proven and probable reserves also remained unchanged from the June 30, 2015 reserve and resource summary and contained 1.2-million ounces of gold (26.1-million tonnes grading 1.4 g/t gold). The company was currently working on updating the resource model with further drill results obtained in 2015.

For 2016, Centerra estimated gold output to be in the range of 480 000 oz to 530 000 oz.