Study at Porgera gold mine shows benefits of treating tailings with lime

Study co-author Joshua Fisher (lower right) collecting water samples from treated mine tailings. (Image courtesy Joshua Fisher – Columbia University).

A study conducted at the Porgera gold mine in Papua New Guinea showed that treating mine tailings with lime helped stabilize arsenic in soil and sediments around the mine, therefore preventing the toxic chemical from remaining dissolved in water and affecting people and ecosystems.

To understand how this sequestration process works, researchers from Australia and the US examined how pH and climate patterns, specifically wetting and drying cycles, impact arsenic capture and storage.

Given the tropical climate of the Porgera Watershed, the study also tested the impacts of wetting and drying the mine tailings that had been treated with lime. These tests indicated that the treated mine wastes rapidly released arsenic during rewetting, but the amount of arsenic released from the wastes decreased over time following repeated wetting and drying cycles. 

The Porgera Joint Venture owns the Porgera Mine, which is operated by Barrick (Niugini) Limited

The results of this scientific work were published in the journal Applied Geochemistry and they state that the Porgera Joint Venture should continue to treat tailings with lime to reduce arsenic mobility in the watershed. 

Located in the north-central Enga province at an altitude of 2,200 – 2,700 metres, the lime for neutralization at Porgera comes from a lime plant located 7 kilometres away from the mine site. Water, on the other hand, is supplied from a reservoir at the Waile Creek containing 7 million cubic meters of water.

The findings in the study are considered timely, as just two months ago Porgera was allowed to re-open after the James Marape administration and Barrick Gold reached a deal, which followed months of debates and legal battles.

The Porgera mine in Papua New Guinea. (Image courtesy of Barrick Gold.)

Operations at Porgera had been suspended since April when its mining lease expired and was not renewed by the government, whose top figure was demanding a greater share of Papua New Guinea’s resources wealth.

Since its first gold pour in 1990, Porgera has seen more than 143 million tonnes of ore being mined in both the open pit and the underground operations, for a total output of over 20 million ounces in gold reported to date. 

The Porgera Joint Venture owns the Porgera Mine which is operated by Barrick (Niugini) Limited which, in turn, owns 95% of the PJV while the remaining 5% is owned by Mineral Resource Enga, which is a consortium between the Enga Provincial Government (2.5%) and the Porgera landowners (2.5%).

Incorporated as an independently managed company in Papua New Guinea,  Barrick (Niugini) Limited is jointly owned through an equal partnership between Barrick Gold Corporation (47.5%) and Zijin Mining Group (47.5%). 

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