Copper miner First Quantum Minerals Ltd. launched a shareholder rights plan that allows shareholders to buy more First Quantum shares at a "substantial" discount if any investor acquires 20% or more of the company

In adopting the shareholder rights plan, First Quantum said it wants to ensure shareholders "are treated fairly in connection with any takeover bid for the company."

Under the plan, shareholders get one share-purchase right for each issued and outstanding share of First Quantum they own. The rights do not apply to the investor or group of related investors with a 20% or more stake, First Quantum said.

The shareholder rights plan, effective Jan. 6, 2020, also requires ratification of First Quantum shareholders at its annual and special meeting, scheduled for the spring, according to the company.

The move comes after Jiangxi Copper Co. Ltd. acquired a 17.7% stake in First Quantum late in 2019 and speculation that Rio Tinto may have been interested in buying the copper miner, according to media reports. In December 2019, First Quantum President Clive Newall said Chinese miner Jiangxi was already subject to a nondisclosure agreement restricting it from buying 20% or more of First Quantum.

First Quantum's assets include mines in Zambia and the Cobre Panama copper mine in Panama.