Total copper production for three quarters of the year decreased by 10 per cent to 1,112 kt. Guidance for the 2022 financial year has been lowered to between 1,570 and 1,620 kt, from between 1,590 and 1,760 kt, which reflects lowered production guidance for Escondida.
Our Chilean assets experienced a challenging operating environment in the March 2022 quarter due to a reduction in our operational workforce as a result of a significant increase in COVID-19 cases in Chile, particularly the Omicron variant, and the mitigation measures implemented. This is despite high COVID-19 vaccination rates and continued use of control measures at our operating sites.
Escondida copper production decreased by 13 per cent to 715 kt primarily due to grade decline in the current mining area, the impact of a reduced operational workforce from COVID-19 and public road blockades associated with social unrest affecting access to site for both workers and supplies. Escondida achieved record material mined for the nine months to March 2022 despite these challenges. Production guidance for the 2022 financial year has been lowered to between 1,000 and 1,030 kt, from between 1,020 and 1,080 kt, reflecting the impact of increased COVID-19 cases and related supply constraints, as well as the road blockades.
Concentrator feed grade decline in the current mining area remains forecast at approximately 2 per cent for the year. Medium term guidance of an annual average of 1.2 Mt of copper production over the next five years remains unchanged, with production expected to be weighted towards the latter years.
Pampa Norte copper production increased by 37 per cent to 204 kt, reflecting the continued ramp up of the Spence Growth Option (SGO), partially offset by the impact of lower cathode production as a result of grade decline and the public road blockades.
Ore stacking grade for cathodes is now expected to decline by approximately 15 per cent for the 2022 financial year due to a change in mine sequencing. Production guidance for the 2022 financial year remains unchanged at between 260 and 300 kt.
BHP continues to progress the plant design modifications required at SGO to achieve planned copper production levels. The Spence guidance to average 300 ktpa (including cathodes) in the first four years of production will be subject to the timing of these modifications being completed.
Olympic Dam copper production decreased by 46 per cent to 83 kt as a result of the execution of the major smelter maintenance campaign which was completed in January 2022. The subsequent smelter ramp up to full capacity was achieved in April 2022, and has delivered 17 per cent higher smelted tonnes compared to the ramp up after the prior maintenance campaign in 2017.
Production for the 2022 financial year is expected to be at the lower end of the guidance range of between 140 and 150 kt primarily as a result of COVID-19 related impacts to the completion of the smelter maintenance campaign.
Antamina copper production increased by two per cent to 110 kt, reflecting higher copper head grades. Zinc production decreased by 13 per cent to 96 kt reflecting lower zinc head grades. Production guidance remains unchanged, with copper production expected to be at the upper end of the 120 to 140 kt guidance range, and zinc production between 115 and 130 kt.