Barrick Mining Corporation (B) shares tumbled 5.36% in pre-market trading, as a plan by Chairman John Thornton to spin off the company's North American mines into a separate publicly traded entity ignited fierce opposition from its largest shareholders.

Portfolio managers at Van Eck Associates, Mackenzie Financial, and Franklin Equity Group have all voiced their opposition to the proposed IPO, arguing that it lacks clarity and would effectively sell off a portion of Barrick's best assets. The controversy has overshadowed the company's upcoming Q2 earnings report, with consensus estimates projecting significant year-over-year growth in revenue and adjusted EPS, driven by strong gold and copper prices.

The dispute is expected to be a focal point when Barrick reports its quarterly results, with investors concerned that the spinoff could dilute their stake in the company's premium operations and cede future value to new investors. The mounting pressure on Chairman Thornton, who has faced criticism for the company's prolonged share price underperformance, has further weighed on market sentiment.