By Agnieszka Olenska and Jesus Calero

Oct 29 (Reuters) - Swedish miner Boliden reported a roughly 77% jump in third-quarter adjusted operating profit on Thursday as higher copper and zinc prices outweighed operational disruptions and rising costs.

Operating profit excluding the revaluation of process inventory rose to about 4.90 billion crowns ($494.4 million), up from 2.75 billion crowns a year earlier.

Supply constraints have helped drive copper and zinc prices higher, boosting profitability at Boliden's mines even as lower treatment charges weighed on its smelting business.

"There is a growing consensus that the copper price has a new floor," CEO Mikael Staffas said in a statement.

Boliden cut its full-year copper-grade guidance for its flagship Aitik mine after more waste rock was mixed with ore, although it raised the site's ore-processing target to 42 million tonnes.

Problems with a new roaster slowed expansion at one of Boliden's smelters earlier this year, but performance improved toward the end of the quarter, supporting expectations for a faster ramp-up.

Smelter operating profit excluding inventory revaluation more than doubled to 1.48 billion crowns as higher metal and sulphuric-acid prices offset lower processing fees.

The company maintained its 2026 capital-expenditure forecast of 15.5 billion crowns and its target for Garpenberg to process 1.5 million tonnes of ore.

Garpenberg's zinc and silver production was disrupted by an earthquake in March, though Staffas said recovery remained on track.

Zinc prices have also surged on tight supply, reaching a four-year high in September as inventories and mined-material availability remained constrained.

($1 = 9.9106 Swedish crowns)

(Reporting by Agnieszka Olenska and Jesus Calero in Gdansk, editing by Milla Nissi-Prussak and Matt Scuffham)

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