"The mine has not yet received any supporting reports, findings or testing data in relation to the matters set out in the EPO [environmental protection order] and is currently assessing the technical basis of the alleged non-compliances," Acacia said in a statement.
It believed the National Environment Management Council's reported findings regarding discharges of a hazardous substance were related to "a longstanding seepage issue" at the base of North Mara's tailings storage facility.
It said the seepage was returned by pumps to the TSF, did not present a risk of contamination to any public water source and it was not aware of the discharge alleged by the NEMC.
Acacia acknowledged it had been "verbally instructed" to build a new TSF at North Mara.
However it said it had not received any written notice or directive from the government, and did not have detailed or fully costed plans for a new facility, although it expected a new TSF was likely an economically viable alternative to further expansions.
The miner said its North Mara operations remained unaffected.
The fine comes just days after the country appointed another new mining minister and as the newly enlarged Barrick is keen for Acacia's issues in Tanzania to be resolved.
Acacia's operations have been hampered since the company was hit with a $190 billion tax bill in 2017 and several past and present employees were arrested in October, facing charges including tax evasion, corruption and money laundering.
Acacia shares closed down 1.46% on Friday to £1.951, around the same levels of a year ago, having dropped below £1 in September.
The miner is capitalised close to £812 million.