Introduction

The Greenbushes Lithium Mine is a world-class hard rock lithium mine owned by the Chengdu Tianqi Industrial Group and is located approximately 250 kilometres south of Perth, near to the town of Greenbushes in Western Australia, see Figure 1 (Source: Talison Mining Limited).

The Greenbushes Mine is adjacent to the town of Greenbushes and 250 kilometres from Perth. It is located in a State Forest that adjoins agricultural land used for cattle and sheep grasing, vineyards and tree plantations.

Greenbushes Lithium Mine - Location Map
Figure 1: Greenbushes Lithium Mine – Location Map

History of the Greenbushes Mining Operations

Mining in the Greenbushes area first commenced with tin production in 1888 by the Bunbury Tin Mining Company and continued through to until 1930. In period of 1935 to 1943 the Greenbushes tin mine transitioned to a new owner – Vultan Mines which carried out sluicing operations of the weathered tin oxides. Later in 1945 to 1956 with the introduction of modern earth moving equipment, Vultan Mines commenced tin dredging. In 1964 a new corporation – Greenbushes Tin NL was formed and open cut mining of the softer oxidised rock commenced in 1969.

Tantalum Mining

Tantalum mining at Greenbushes commenced in 1992 with an ore processing capacity of up to 800,000 tonnes per annum. By the late 1990’s demand for tantalum reached all-time highs and the existing high grade Cornwall Pit was nearing completion. In order to meet increasing demand a decision was made to expand the mill capacity to 4 million tonnes per annum and develop an underground mine, to provide higher grade ore for blending with the lower grade ore from the Central Lode pits.

An underground operation was commenced at the base of the Cornwall Pit in April 2001 to access high-grade ore prior to the completion of the available open pit high-grade resource. In 2002, the tantalum market collapsed due to a slow-down in the electronics industry and subsequently the underground operation was placed on care and maintenance. The underground operation was restarted in 2004 due to increased demand but again placed on care and maintenance the following year. The lithium open pit operation has continued throughout recent times and mining is now focused on the Central Lode zone. Only lithium minerals are currently mined from the open pits. The tantalum mining operation and processing plants have been on care and maintenance since 2005.

Lithium Mining

The mining of lithium minerals is a relatively recent event in the history of mining at Greenbushes with Greenbushes Limited commencing production of lithium minerals in 1983 and commissioned a 30,000tpa lithium mineral concentrator two years later in 1984-1985. The lithium assets were acquired by Lithium Australia Ltd in 1987 and Sons of Gwalia in 1989. Production capacity was increased to 100,000tpa of lithium concentrate in the early 1990’s and to 150,000tpa of lithium concentrate by 1997, which included the capacity to produce a lithium concentrate for the lithium chemical converter market.

The Talison Minerals Group was incorporated in 2007 for the purpose of acquiring the assets of the Advanced Minerals Division of Sons of Gwalia by a consortium of US private equity companies led by Resource Capital Funds. The Talison Mineral Group’s assets included the Wodgina tantalum mine located about 1,500 kilometers north of Perth and 120 kilometers south of Port Hedland in the Pilbara region of WA as well as the Greenbushes Lithium Operations .

Upon completion of the reorganisation of the Talison Minerals Group in 2010, Talison acquired the Greenbushes Lithium Operations and the remainder of the assets were acquired by GAM.

There are two lithium processing plants that recover and upgrade the spodumene mineral using gravity, heavy media, flotation and magnetic processes into a range of products for bulk or bagged shipment. In the period 2005 to 2008, demand from the Chinese chemical producers was satisfied by using the Greenbushes primary tantalum plant which had been on care and maintenance. Products from that plant had a lower grade than preferred by the Chinese customers and were supplied as a temporary measure until Talison’s lithium concentrate production capacity was increased.

In 2009, Talison’s processing plants were upgraded to total nominal capacity of approximately 260,000tpa of lithium concentrates and in late 2010 capacity was further increased to the current nominal production capacity of approximately 700,000tpa of ore feed yielding approximately 315,000tpa of lithium concentrates. The lithium processing plants are currently operating at full production capacity and a further expansion is in progress to increase nominal production capacity to approximately 1,500,000tpa of ore feed yielding approximately 740,000tpa of lithium concentrates.

Figure 2: The Greenbushes lithium mine in WA

Greenbushes Lithium Mine: Production History

Year Lithium Ore Mined (tonnes) Lithium Products (tonnes) Lithium Carbonate Equivalent  (tonnes)
2005 367,000 146,000 21,000
2006 390,000 183,000 25,000
2007 390,000 271,000 25,000
2008 572,000 235,000 33,000
2009 507,000 209,000 31,000
2010 639,000 262,000 39,000
2011 569,000 252,000 38,000

Table 1: Greenbushes Lithium Mine: Production History

Greenbushes Lithium Mine: Geology

The Greenbushes pegmatites belong to the Lithium-Caesium-Tantalum family. The Greenbushes pegmatite deposit intrudes along a major northwest regional fault zone. It is approximately 2,525 million years old. The pegmatite consists of a large main zone over 3 kilometers long and up to 300 meters wide with numerous smaller pegmatite dykes and pods flanking the main body. The Greenbushes pegmatites are mineralogically zoned in a lenticular inter-fingering style along strike and down dip. The lithium zone is over 2 kilometers long and enriched in the lithium-bearing mineral spodumene which often makes up 50% of the rock.

The Greenbushes pegmatite has unique features that distinguish it from many other rare-metal pegmatites. Lithium ore (spodumene) at Greenbushes is mined from the fresh, unweathered zones in the pegmatite that are exposed in the open pits.

Mining is traditional drill and blast method with ore graded and stockpiled according to its mineralogical characteristics and grade. Waste material is trucked to designated areas within the site where it is contoured and replanted as part of an ongoing rehabilitation plan.

The Greenbushes Lithium Operations has two processing plants, one producing technical-grade lithium concentrates and one producing chemical-grade lithium concentrate. Ore containing 3.0% to 4.5% Li2O is fed into the processing plants which upgrade the lithium mineral, using gravity, heavy media, flotation and magnetic processes, into a range of lithium concentrates for bulk or bagged shipment. Various operating modes are used in the processing plants to produce a variety of different lithium concentrates to meet specific customer requirements (Source: Talison Mining Ltd).

Regional Geology

The Greenbushes pegmatite intrudes rocks of the BMB which forms the southern portion of the Western Gneiss Province, one of four divisions of the Yilgarn Craton in WA (Figure 3). The BMB has limited exposure, being largely obscured by Tertiary sediments and laterite. It is bounded to the west by the Darling Fault and Phanerozoic rocks of the Perth Basin, to the south by the Proterozoic Albany-Fraser Mobile Belt, and to the east by the Hester Lineament. The BMB extends as far north as the Loguebrook Granite, where it is truncated by intrusions of the Darling Range Batholith.

The Greenbushes pegmatite lies within a 15-20km wide, north to north-west trending lineament known as the Donnybrook-Bridgetown Shear Zone. A sequence of sheared gneiss, orthogneiss, amphibolite and migmatite outcrops along the trace of the lineament. A series of syn-tectonic granitoid intrusives occur within the BMB, elongated along the Donnybrook-Bridgetown Shear Zone.

The Greenbushes pegmatites have been dated at approximately 2,525 million years (“Ma”) and appear to have been intruded during shearing, thereby accounting for the fine grain size and internal deformation (Jacobson et al, 2007). However, the pegmatites have been affected by subsequent deformation and/or hydrothermal re-crystallisation, the last episode dated at around 1,100Ma (Partington et al, 1995).

Greenbushes Lithium Mine - Regional Geology
Figure 3: Greenbushes Lithium Mine – Regional Geology

Local Geology

The Greenbushes deposit consists of a main, rare-metal zoned pegmatite with numerous smaller pegmatite dykes and pods in the footwall to the main body. The main pegmatite and its subsidiary dykes and pods are concentrated within shear zones which form along the boundary between sequences of granofels and amphibolite. The pegmatite body strikes in a north to north-westerly direction and dips moderately to steeply towards the west-southwest.

The syn-tectonic development of the pegmatite has given rise to well-developed mylonitic fabrics, particularly along host rock contacts.

The mine sequence has been intruded by Proterozoic dolerite dykes and sills. The dykes trend east-west and vary in width from a few centimetres to tens of metres.

The pegmatite bodies of the Greenbushes deposit are mineralogically zoned, but these do not conform to the conventional concentric zonation models of other pegmatite bodies. Rather, zones are generally lenticular in nature and interfinger along strike and down dip. The primary ore minerals are found in specific mineral assemblages displaying complex mineralogical zoning. The Lithium or Spodumene Zone is enriched in the lithium-bearing silicate mineral spodumene. Tantalite and cassiterite mineralization are concentrated in the Sodium or Albite Zone which is characterized by albite (Na-plagioclase), tourmaline and muscovite. A third zone, of lesser commercial importance, contains concentrations of the potassium feldspar microcline. Other accessory minerals present in the pegmatite are phosphates such as apatite, minor beryl and garnet.

Greenbushes Mine Geology
Figure 4: Greenbushes Mine Geology

Mineralisation

The Greenbushes lithium deposits belong to the Spodumene sub-class of the LCT pegmatite deposit class. The pegmatites are hosted in a major regional structure and represent a late stage product of cooling granite magma.

Early crystallisation of the pegmatite formed albite-tourmaline zones, followed by albite, cassiterite and tantalite crystallisation. Spodumene-quartz assemblages crystallised at slightly lower temperatures, followed by formation of a potassium feldspar-rich zone in the hanging wall.

Lithium-rich zones are spatially related to tantalite-bearing zones which have been mined and processed in the recent past. In places pegmatite may contain economically recoverable levels of both lithium and tantalum, although more typically lithium ore is low in tantalum (<100 parts per million tantalum oxide (“Ta2O5”)).

The Greenbushes pegmatite is distinguished from many other rare-metal pegmatites by:

  • not being symmetrically or truly asymmetrically zoned, and not having a quartz core;
  • having no indication of a parental granitoid at depth or in close proximity; and
  • being formed at higher pressure/temperature, under synkinematic conditions.

Mineral Resource Estimate

The Greenbushes Lithium Mine has a measured and indicated mineral resource estimate of 118.5 million tonnes of spodumene ore grading at 2.4% lithium, containing approximately 7.13 million tonnes of Lithium Carbonate Equivalent (Source: Talison Mining Ltd: NI 43-101 Technical Report 2012).

Category Tonnes (Mt) Li2O Grade (%) LCE (Mt)
Measured Resource Estimate 0.6 3.2 0.04
Indicated Resource Estimate 117.9 2.4 7.08
Inferred Resource Estimate 2.1 2.0 0.10

Figure 5: Greenbushes Lithium Mine: Mineral Resource Estimate (Source: Talison Mining Ltd)

The Greenbushes Lithium Mine has a proven and probable mineral reserve estimate of 61.5 million tonnes of spodumene ore grading at 2.8% lithium, containing approximately 4.3 million tonnes of Lithium Carbonate Equivalent (Source: Talison Mining Ltd: NI 43-101 Technical Report 2012).

Category Tonnes (Mt) Li2O Grade (%) LCE (Mt)
Proven Reserves 0.6 3.2 0.04
Probable Reserves 61.0 2.8 4.3

Figure 6: Greenbushes Lithium Mine: Mineral Reserve Estimate (Source: Talison Mining Ltd)

Lithium Hard Rock Deposit: Comparison

World lithium hard rock deposits
Figure 7: World Lithium Hard Rock Deposits (Source: Company Reports)

For more information about the Tianqi Group

Chengdu Tianqi Industrial Group is a part of the Sichuan Tianqi Lithium Industries, Inc. which is the world largest lithium chemical producer that converts from hard rock lithium concentrates. Tianqi Lithium has been focussing on the development, production and sales of lithium chemical products for more than 10 years.The product portfolio of Tianqi Lithium includes lithium carbonate technical and battery grade, lithium carbonate high purity, lithium chloride anhydrous battery grade, lithium hydroxide monohydrate battery grade, lithium dihydrogen phosphatea, lithium metal, etc.The China Nonferrous Metals Industry Association concludes according to statistics that Tianqi Lithium leads the lithium chemical industry in China in terms of technology, scale and competitiveness (Source: Tianqi Group).

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