Rare earth resource

Materials World magazine
,
1 Jun 2010

Namibian rare earth resources could break the Chinese monopoly, says Don Burton, Vice-President Corporate Development of Canadian company Etruscan Resources. Michael Forrest reports

Rare earth elements, ranging from atomic number 57 to 71, have recently come to the attention of miners and speculators. These elements have applications in electric motors and batteries in hybrid and all-electric automotives, permanent magnets for wind powered-generators, and in catalysts in refineries and vehicles.

The American Recovery and Reinvestment Act plans to invest more than US$80bln in clean energy, including US$37bln by the US Department of Energy. The fund will be used to develop electric vehicles, batteries and advanced energy storage, a more efficient and reliable electric grid, and wind and solar technologies, among other areas.

The increasing demand for the heavy rare earths is reflected in price. Prices quoted by the US Geological Survey and UK publication Metal Pages show that lanthanum sells for US$9/kg with neodymium at US$20/kg. Heavy rare earth prices are factorially higher, europium is US$475/kg and dysprosium at US$115/kg.

In addition, political announcements have focused these trends. The first is China’s 2009 decision to reduce rare earth exports to 40% of previous levels. The country produces about 95% of world supply. The second is the move by Baotou Rare Earth, one of China’s major producers, to build 10 reserve facilities capable of storing more than 200,000t of rare earth oxides in Inner Mongolia.

Although some of them are far from rare and certainly not earths, these elements are classified as light rare earth elements (LREE), lanthanum to samarium and heavy rare earth elements (HREE) europium to lutetium. According to the United States Geological Survey global consumption of total contained rare earth oxides is 124,000t with the greater proportion being LREE.

China’s cache

The largest worked deposits are lateritic ores in Inner Mongolia and Sichuan Province that are enriched in HREE. This Chinese monopoly, and its reduced export quotas, have triggered a wave of new projects in the rare earth sector. In exploration terms, many projects are revisits of known deposits/projects, which look more promising as demand increases.

Some older mines have reopened including the Mountain Pass mine in California, USA. At present it treats stockpiles but plans are being made to mine fresh ore next year. Some are new discoveries, such as the Lofdal project of Canadian company Etruscan Resources. According to Don Burton, Vice-President Corporate Development at the company, the decision to enter the rare earth industry came from an opportunity that arose from an exploration project in Namibia.

He says, ‘Etruscan is a gold company focused on Africa, with several exploration plays and operating mines in west Africa. Our model expanded to look for iron oxide copper gold (IOCG) deposits, and the Proterozoic geology of Namibia became the focus of attention. Of particular interest were alkaline intrusives and known copper occurrences in the central region near Khorixas. Rare earths are indicator elements for IOCG deposits and our attention was drawn to a known REE occurrence at Lofdal Farm’.

Unfortunately no economic copper or gold deposits were discovered but early exploration results from Lofdal demonstrated the viability of a rare earth project. Previous mapping and exploration had delineated most of the intrusive complex at Lofdal as syenite, but remapping by the Namibia Geological Survey in 2007 confirmed the presence of a main carbonatite intrusion and a series of dykes enriched in heavy rare earth minerals. This was followed by the discovery of a second carbonatite intrusion in 2008.

Geological clues

The alkaline intrusive complex at Lofdal comprises carbonatites, syenites and nepheline syenites that have intruded highly metamorphosed gneisses and schists of the +/-1,700Ma Huab Metamorphic Basement Complex. The Complex is bounded by Damara Sequence metasediments to the north and south. The carbonatite dykes and intrusions clearly cross-cut all of the other rocks and represent the youngest intrusive event. Rare earth element mineralisation has been dated coeval with nepheline syenites at +/-764Ma. This is distinct from the younger (+/-135Ma) rift-related magmatism of other alkaline and carbonatite complexes in Namibia.

The Lofdal Carbonatite Complex shows up well on airborne geophysical surveys and particularly thorium radiometric surveys. Etruscan initially collected 1,426 rock grab samples over an area of 25km2, within the 125km2 of the intrusive complex. Upon analysis, 602 samples contained >0.5% total rare earth plus yttrium (TREE+Y) with an average concentration of 1.3%, while 292 samples reporting over one per cent had an average concentration of two per cent. The highest individual sample graded 8.9%.

Light rare earth minerals identified to date at Lofdal include bastnaesite, parisite, synchysite, monazite and allanite, with xenotime and aeschynite comprising the heavy rare earth minerals. ‘The next steps at Lofdal,’ says Burton, ‘are mapping and sampling the entire licence area and integration of the results with regional high resolution radiometric and magnetic surveys. The results will be compared with data from hyperspectral surveys recently flown by the Namibian Geological Survey as part of their ongoing research in the area. Fortunately there is a strong correlation between airborne radiometrics and rare earth element values enabling target selection.

‘The relative low values in the Lofdal and Emanya carbonatite plugs relative to the dykes require explanation. There must be a source for these elevated values and that may be a near-surface plug that as yet remains to be found’.

Future exploration on a local level will include detailed mapping, channel sampling and scintillation (radiometric) surveys to delineate HREE enriched zones. Between 5,000 and 10,000m of diamond core drilling is also planned to trace the values to depth. ‘The principal objective is to find a source carbonatite plug for the heavy rare earths, or the dykes we see at surface may well be of economic significance on their own,’ notes Burton.

Etruscan Resources has created a private company, Namibia Rare Earths Inc, to develop the Namibian assets. It intends to take this company public before the end of 2010.

‘If we are successful in discovering an economic ore body, particularly one enriched in the heavy rare earths, we may one day offer an alternative to the world’s current reliance on the Chinese monopoly,’ says Burton.