Barrick said on Tuesday it had "concluded
that certain assumptions made by Acacia were not appropriately risked or supportable and that adjustments should be made" and said it expected to record a material impairment to its carrying value of Acacia in the current quarter.
It referred to resource uncertainty at Bulyanhulu and made adjustments for "more realistic" costs at North Mara, among its comments, and said it believed its proposal reflected the fair value of Acacia.
Acacia said it was "surprised" by the circumstances and timing of the announcement and urged shareholders to take no action.
"The company strongly disagrees with a number of statements made in the announcement," Acacia said yesterday, adding it would provide a detailed response in due course.
For its part, Barrick reiterated comments reported in a Bloomberg article that it was planning to "engage intensively with Acacia's minority shareholders" in coming weeks.
However it said it the article should not be considered a "no increase statement".
Barrick added it reserved the right to vary its proposal or offer less favourable terms than an exchange ratio of 0.153 Barrick shares for every Acacia share.
Barrick has said the government of Tanzania would not negotiate with Acacia to resolve its issues in the country, including a concentrate export ban and tax bill, and that Barrick's proposed solution was "the only credible option" to preserve the value of Acacia's assets.
Barrick, which owns 63.9% of Acacia and is trading close to a 12-month high, closed 0.1% lower in Toronto yesterday.
Acacia closed 2.25% lower in London.