Regulators argue the undisclosed liabilities increase the probability that the state will be left with claims under the surface-mining and other environmental laws.
The miner said the decision applies to the entire 3,000 square kilometer Lulo site, a project that has bored some massive gems, including the largest diamond ever found in Angola.
Slowing power demand growth and low carbon capacity targets in China's latest five-year plan are found to be squeezing coal generation out of the power mix.