Wednesday 29th May 2019
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Lithium resources in the Taupo volcanic zone are potentially economic but may require conventional open-cast mining techniques if they are to be developed, delegates at the New Zealand Minerals Forum heard.
The presence of lithium – a core element in electric vehicle batteries - in local geothermal brine has long been understood. But studies by government-owned GNS Science show it is also present in the broader basin.
Reviewing existing data, including almost 200 core samples from geothermal wells and drilling from epithermal gold exploration, the study identified 31 sites where lithium was present at more than 200 parts per million, with the high of 3,500 ppm reported at Ohaaki.
Lithium previously hadn’t been identified at more than 450 ppm in New Zealand.
“That really clearly demonstrates that we do have economic grades in the Taupo volcanic zone for Lithium,” Rob Smillie, earth resources and materials manager at GNS, told the forum in Dunedin yesterday. “It’s a really big finding for us.”
GNS and New Zealand Petroleum & Minerals have been looking harder at the country’s minerals endowment to better understand the potential to develop so called “green minerals” - including lithium and cobalt - increasingly in demand for batteries, high-performance metals and other new technologies.
Smillie said that with the push toward renewables and other low-emission technologies, New Zealand needs to decide whether it is better to develop its own minerals to make that happen, import the technology, or import the minerals from places like the Congo.
The World Bank is projecting an almost 10-fold increase in lithium demand by 2050 on the back of greater electrification of transport and the use of batteries and solar. The world’s lightest metal is highly reactive, and is also an important treatment for depression. It sells for about US$20,000 a tonne, having jumped to about US$30,000 in 2015.
More than 40 percent of the world’s lithium is extracted from brines in South America, particular in Chile. The next largest supplier is Australia, where it tends to be mined from hard rock.
The US, which declared lithium a critical mineral in 2017, is developing its own resources. The largest is in Thacker Pass in Nevada where historic volcanic activity has built up high concentrations - more than 2,000 PPM - of lithium in thick claystones.
Smillie said investigations of lithium in geothermal brine remains an important area of research for New Zealand.
But GNS suspects the elevated levels of lithium it has discovered around the Wairakei, Tauhara, Ngatamariki and Ohaaki geothermal fields may have been laid down in a similar process to that in Nevada.
A lot more work will be needed to understand the area’s minerology and where potential deposits may be hosted, Smillie said.
And he noted that at the relatively lower grades seen locally, large, open cast mining could be required to extract it.
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