Shares of Teck Resources Ltd (TECK) tumbled 5.70% in pre-market trading on Thursday after the company released its second-quarter earnings report. While adjusted earnings beat analyst expectations, revenue fell short of estimates and the company lowered its production guidance for its Quebrada Blanca (QB) copper mine.

Teck reported Q2 adjusted earnings of CA$0.38 per share, surpassing the FactSet analyst consensus of CA$0.23. However, revenue for the quarter came in at CA$2.02 billion, missing the analyst expectation of CA$2.17 billion. The company's copper business, a key focus for investors, generated a gross profit before depreciation and amortization of CA$673 million, slightly lower than a year ago.

Adding to investor concerns, Teck revised its 2025 annual copper production guidance for its QB operations downward to 210,000-230,000 tonnes from the previous 230,000-270,000 tonnes. The company cited ongoing tailings management facility development work and potential production impacts from external factors as reasons for the lowered guidance. Additionally, Teck increased its net cash unit cost guidance for QB, reflecting lower production and increased costs due to alternative shipping arrangements necessitated by a port facility outage.