Agnew Open Pit & Underground Gold Mine

Location: Agnew, Western Australia.

Products: Gold.

Owner: Gold Fields Limited.

Mineral Resources at 3.5 Moz.

Mineral Reserves at 1.2 Moz.

Life of Mine extends to 2019 (7 years).

Licence status and holdings

The agnew gold mining company proprietary limited (agmc), can 098-385-883, was Incorporated in australia in 2001 as the legal entity holding and conducting mining activity on the Agnew mineral leases. The gold field’s limited group holds 100% of the issued shares of AGMC Through its 100% holding in the issued shares of orogen holding (bvi) limited. Agnew controls Exploration and mineral rights over a total area of 57,836 hectares (total of granted tenements) and has security of tenure for all current exploration and mining leases that contribute to future Mineral reserves.

Operational infrastructure

One underground complex, mining from two separate ore bodies (kim south and main north) accessed via declines. Centralised administrative office, engineering workshops and one cip processing plant (1.3 mtpa capacity).

Deposit type

Orogenic greenstone gold deposits hosted in a number of different styles of lodes. Although all of the agnew deposits broadly occur at the intersections between structures and stratigraphy, there are subtle differences in alteration and mineralisation, that are controlled in part by the local host rock chemistry.

Reporting codes Gold Fields reports its Mineral resources and mineral reserves in accordance with the 2007 Samrec code, the south african codes for the reporting of mineral asset valuation (2009 Samval code) and other relevant international codes such as the united states securities and Exchange commission (sec) industry guide 7, the joint ore reserves committee (jorc 2012) Code and the national instrument (Ni) 43-101. The mineral resources and mineral reserves are underpinned by an appropriate mineral resource management process and protocol to ensure adequate corporate governance in respect of the sarbanes-oxley act.

Geological setting and mineralisation

Agnew is situated in the northern portion of the Norseman- Wiluna greenstone belt, which is part of the yilgarn craton, A 2.6 ga granite greenstone terrain in Western Australia.

The rock types in the belt comprise abundant tholeiitic and Komatiitic volcanic rocks, chert, sulphidic and albitic Sedimentary rocks, and a chain of discrete felsic volcanic Centres. The greenstones of the agnew area have been Metamorphosed to upper greenschist, lower amphibolite Metamorphic grades. Gold mineralisation is found in quartz Breccia lodes, quartz tensional veining and disseminated Arsenopyrite-pyrite-biotite mineralisation. This is developed along the lithological contact between a sandstone and ultramafic conglomerate and on other contacts within the ultramafic conglomerates package. High-grade ore shoots Plunge steeply to the north along these contacts. The controls on mineralisation are dilational zones at the intersection of steeply dipping north-south axial planar structures with the Stratigraphy. The stronger the contrast in rock competency in these zones, the greater the potential for mineralisation. Much of the yilgarn craton is deeply weathered and partially covered by tertiary and quaternary regolith. Pre-tertiary Lateritic horizons are variably exposed, stripped or buried by later deposits that have in turn been lateritised. The depth of Weathering is strongly controlled by original rock types, with mafic rocks generally being more susceptible to weathering than felsic rocks.

Although all of the Agnew deposits are broadly hosted by the intersections between structures and stratigraphy, there are subtle differences in alteration and mineralisation, controlled in part by the local host rock chemistry. Songvang is unusual in its relatively high lead, silver and fluorine content, possibly reflecting input from tonalite and porphyry intrusions. There also appears to have been a slight decline in mineralization temperatures from south to north through the Agnew area, associated with the north plunge of the Lawlers Anticline and resultant erosion of the overlying lower-temperature rocks to the south. This temperature change is reflected in the changing mineralisation styles from south to north, with biotite/garnet assemblages dominating to the south and quartz veining to the north. The stratigraphy of the Agnew-Wiluna belt appears to be broadly similar to the stratigraphy of the Kalgoorlie Region. The following section provides a detailed description of the general stratigraphy for the Agnew mining leases and the stratigraphic location of various ore bodies.

Mining methods

Access to the Waroonga underground mine is via a portal and decline, located in the previously mined Waroonga open pit. All primary infrastructures, including escape ways and ventilation shafts, are located in the competent sandstone of the hanging wall. The dimensions of the decline are 5.5 metres wide by 5.8 metres high, with arched backs to allow high-capacity trucks to operate.

The Rajah Lode was mined in 2012 using the modified Avoca Method. This is a variation of bench-stoping methodology where the fill typically consists of uncemented waste rock that is introduced to control wall stability at intervals from 20 to 30 metres. During 2012 the Main Lode North ore body was extracted using transverse stoping, with mining commencing at the footwall and retreating to the hangingwall. The stopes were accessed via a tramming drive developed in the hangingwall sandstone. The final northern cutback of the Songvang pit was completed in February 2012.

Mineral processing

The comminution circuit comprises a contractor-owned and operated three-stage crushing plant, feeding a fine ore stockpile, ahead of a two-stage closed circuit ball milling circuit. Milled ore proceeds to a three-stage leaching train feeding the six-stage carbon in pulp (CIP) circuit. Carbon elution is by pressure Zadra with gold being electro-won and smelted. In February 2003 a gravity circuit was retrofitted. It comprises a Knelson gravity concentrator and an intensive leach reactor (ILR) for intensive cyanidation of the gravity concentrate. The gravity circuit was upgraded and retrofitted in September 2011 to incorporate a second 26” Knelson gravity concentrator, an ILR 2000BA and two Magscreen 1000 units. The processing capacity at the plant is 1.3 Mtpa. Quantitative analysis of recovery improvements will be evaluated and included in future Mineral Resources and Mineral Reserve calculations in accordance with the grade/ recovery model currently adopted. Tailings disposal and impoundment have historically been to a conventional dam constructed using the upstream lift method sourcing wall material from dried tailings. The original tailing storage facility (TSF) was located in an area some 1.5 kilometres south-west of the Agnew plant. Deposition to this facility ceased in early 2004 and a large section of this decommissioned facility has been capped with waste rock.

The remaining exposed sections are being harvested for use as underground paste fill. Following completion of mining activities at the Redeemer Mine, the abandoned pit has been converted to a tailings storage impoundment for tailings arising from the Agnew plant (TSF3). Although situated seven kilometres south of the Agnew plant, the static head is negative, and pumping of the tailings material is therefore done at no additional cost from the previous deposition technique. The pontoon-mounted decant pump recovers water from the supernatant pond, which forms due to liberation of water from the tailings slurry as it settles and consolidates. TSF3 is projected to last until 2015, based on deposition rates of 1.3 million tonnes per annum and historical deposition levels from December 2004 to February 2011.

Mineral Resource classification

Mineral Reserve classification

Mine model of Agnew Waroonga ore body

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DeGrussa Copper-Gold Mine

Location: Perth in Western Australia.

Products:  high-grade copper mines and secondary Gold .

Owner: Sandfire Resources.

Brief Summery: 

The degrussa VHMS (volcanic-hosted massive sulphide) copper–gold deposit is located 900 kilometers north of perth and 150 kilometers north of meekatharra in the peak hill mineral field, on the peak hill 1:250 000 map sheet, sg 50-8. It lies on a major drainage divide between the gascoyne river catchment and the lake gregory to carnegie lake salinas internal drainage. The deposit lies beneath a mantle of scree and sheet wash deposits on gentle slopes mantling an upland area of exposed bedrock and relic duricrust.

The degrussa copper–gold massive sulphide deposit is hosted within the bryah basin, one of a number of separate palaeo-proterozoic depositional basins in the eastern part of the capricorn orogen, which is a major tectonic unit that lies between the archaean pilbara craton and the yilgarn craton. The bryah group is a succession of mafic rocks of mid-ocean ridge basalt to oceanic plateau affinity overlain by clastic and chemical sediments.

The age of the bryah group is poorly constrained between 2.0 ga and 1.8 ga. It is younger than 2.65 ga and older than 1785 ±11 ma (u-pb zircon age), the age of the uncomformably overlying mount leake formation.

The bryah basin has undergone two episodes of deformation. The 1.96 ga glenburgh orogeny (d1) accreted the narracoota oceanic plateau onto the yilgarn craton. Folding, faulting and shearing attributed to this orogeny have been largely overprinted by the 1.8 ga capricorn orogeny (d2) that was the result of the oblique collision between the pilbara and yilgarn cratons. During deformation the volcano-sedimentary succession was metamorphosed to greenschist facies.

The copper–gold rich-massive sulphide lenses are vhms-style based on the host rock package, mineralisation style, mineral composition and alteration.

The host rocks are submarine basalts, mafic volcaniclastic rocks and debris flows with sub-volcanic dolerite/gabbro sills of the de grussa formation.

Sulphide mineralisation consists of massive sulphide, semi-massive sulphide and stringer zone mineralisation. The transition from massive sulphide to an underlying stringer zone is not always present because of dolerite intrusion close to or at the base of the massive sulphide. Primary sulphide minerals present are pyrite, chalcopyrite, pyrrhotite, and sphalerite together with magnetite. The base of the massive sulphide is chalcopyrite rich with magnetite, passing upwards into iron sulphides with decreasing copper content and increasing zinc content higher up. Gold is associated with the chalcopyrite-rich zones and occurs as a high-silver electrum.

The oxide mineralisation is located vertically above conductor 1 and degrussa. The grade and width of the oxide mineralisation is highest proximal to the main lenses and then forms enriched plumes that transgress lithological boundaries as the mineralisation disperses and dissipates. Close to the main lenses there is significant native copper and elevated gold. As the plumes disperse away from the ore zones the grade dissipates and mineralisation transitions through chrysocolla, cuprite, azurite and malachite.

Alteration associated with the massive sulphide is chlorite + sericite + quartz + pyrite which is typical for vhms deposits. Stringers in the stringer zone are chalcopyrite rich.

The massive sulphide lenses are deformed and often exhibit a strong foliation. The harder pyrite and pyrrhotite tends to fracture, while the softer chalcopyrite and sphalerite are easily remobilized and recrystallised.

Beneath a hardpan cap there is about 80 metres of weathering over the sulphide lenses. Within the weathering profile is an upper, residual, gold-oxide zone overlying an oxide-copper zone. The oxide- copper zone contains the minerals malachite, chrysocolla, native copper and minor cuprite. A secondary supergene chalcocite blanket lies beneath the oxide-copper zone and immediately above fresh primary sulphides.

Four lenses of copper-rich massive sulphides have been discovered to date as shown in figure 3. Degrussa has a strike length of 180m, is some 20m thick on average and dips near vertically to the south. It has a vertical extent of 300m.

“Commencing with an initial 2-year open pit mining operation which was completed in April 2013, the DeGrussa Operation is based on a long-term underground mine delivering sulphide ore to an on-site 1.5Mtpa concentrator.”

The mine will produce up to 300,000 tonnes of high-grade copper concentrate annually.

Based on the figures published in the Western Australian Mineral and Petroleum Statistics Digest, this would make DeGrussa the largest copper producer in Western Australia.

In addition to the 1.5Mtpa DeGrussa Concentrator, other infrastructure and services on site include a Tailings Storage Facility (TSF), power station, paste plant for the underground mine, a sealed airstrip capable of accommodating small jets, a state-of-the-art 400-room mine village, a Next G mobile phone service and fibre optic communications, office buildings, assay laboratory and sealed access roads.

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Grasberg Gold Mine

Grasberg Gold & Copper Mine

It is the largest gold mine and the third largest copper mine in the

world

Location: Papua, Indonesia.

Products: Gold & Copper.

Owner: Freeport-McMoRan.

Deposit Type: Porphyry deposits associated with the 3.2 to 2.7 Ma Grasberg Igneous Complex, porphyry ores of the 4.4 to 3.0 Ma Ertsberg Diorite 2.5 km to the south, and a series of skarns deposits.Together these deposits account for near 80 Mt of copper and around 3900 tonnes of gold (including inferred resources).

Mineralization: Mineralisation associated with the Ertsberg intrusive includes: The Ertsberg stockwork which contained a resource of 122 Mt @ 0.54% Cu, 0.90 g/t Au in 2005.The skarn mineralisation, which includes the: i). GB (Gunung Bijah) - 33 Mt @ 2.5% Cu, 0.8 g/t Au (the original reserve on which mining in the district was commenced), which is surrounded by Ertsberg Diorite near its NW margin; ii). GBT Complex (the vertically stacked GBT, IOZ & DOZ), 1.5 km east of GB on the northern contact, with reserves of >230 Mt @ 1% Cu, 0.8 g/t Au, iii). Dom Skarn, 0.5 km south of GBT, partially enclosed by the intrusive near its SE margin, with >70 Mt @ 1.4% Cu, 0.4 g/t Au, iv). Big Gossan within a fault zone cutting sediments to the west of the Ertsberg Diorite with 33 Mt @ 2.81% Cu, 1 g/t Au, v). Kucing Liar (dated at 3.42 Ma, the oldest mineralisation in the district, predating the Dalam Diorite) is associated with a fault zone between the two intrusive complexes, but close to the Grasberg complex, contains >225 Mt @ 1.42% Cu, 1.57 g/t Au.

Block diagram showing the Grasberg Igneous Complex and zoned alteration. Weak stockwork and potassic alteration associated with South Kali Dikes are not shown.

Mining:

The workings comprise an open pit mine, an underground mine and four concentrators. The open pit mine – which forms a mile-wide crater at the surface – is a high-volume low-cost operation, producing more than 67 million tonnes of ore and providing over 75% of the mill feed in 2006.

Designed to be fully mechanised, using 6.2m3 Caterpillar R1700 load-haul-dump vehicles (LHDs) at the extraction level with a truck haulage level to the gyratory crusher, the Deep Ore Zone (DOZ) block cave mine is one of the largest underground operations in the world.

After 2004, when the DOZ mine averaged 43,600 tonnes/day a second underground crusher and additional ventilation were installed to increase daily capacity to 50,000 tonnes.

Ore from both operations is transported by conveyor to centralized mine facilities, feeding a combined daily average total of some 225,000t of ore to the mill and 135,000t to the stockpiles.

Production equipment includes 30m3–42m3 buckets, a 170-strong fleet of 70t–330t haul trucks, together with 65 dozers and graders, with radar, GPS and robotics used in the mine’s state-of-the-art slope-monitoring system.

PROCESSING

Ore undergoes primary crushing at the mine, before being delivered by ore passes to the mill complex for further crushing, grinding and flotation. Grasberg’s milling and concentrating complex is the largest in the world, with four crushers and two giant semi-autogenous grinding (SAG) units processing a daily average of 240,000t of ore.

“This is a high-grade resource, with averages of 1.5% copper and 2 g/t gold.”

A flotation reagent is used to separate concentrate from the ore. Slurry containing 60-40 copper concentrate is drawn along three pipelines to the seaport of Amamapare, over 70 miles away, where it is dewatered. Once filtered and dried, the concentrate – containing copper, gold and silver – is shipped to smelters around the world.

The facilities at the port also include the PT Puncak Jaya coal-fired power station, which supplies the Grasberg operations.

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Gwalia Gold Mine

Location: Gwalia, Western Australia

TENEMENT: M37/25, M37/333

OWNER: St Barbara Ltd 100%

OPERATOR: St Barbara Ltd (ACN 009 165 066) Level 10, 432 St Kilda Road, MELBOURNE,VIC 3000

COMMODITIES: Gold

Brief History of the Gwalia Gold Mine:

The Gwalia Deeps underground Gold Mine is located 3km south of Leonora in the north-eastern goldfields of Western Australia. Gwalia Deeps is the name given to the down plunge extension of the Sons of Gwalia ore body from 1,075 metres below surface. The Gwalia mine has produced in excess of 4,580,000 ounces of gold via open pit and underground mining since its discovery in 1896.

•1897 to 1963 -Underground mining of the Sons of Gwalia gold deposit with shaft access to depths of 1.08 km

•1984 to 1999 –Mined as an open pit

•1998 to 2003 –Remnant underground mining of upper levels using hanging wall decline access

•2007 to present –Mine decline development recommenced and is now below 1.1 km.

Gold mineralisation occurs as a number of en echelon, moderately east dipping foliation parallel lodes within strongly potassic altered mafic rocks and extends over a strike length of approximately 500m and to a vertical depth of at least 2,000m. Five lodes have been identified and the lode names and geometries are summarised in Figure 1 below. Further detail on the geology and estimation techniques can be found in the St Barbara Limited Mineral Resource Report.

FIGURE 1 PLAN VIEW OF GWALIA LODES

The primary mining method since resumption of underground production in 2008 is a Longhole Open Stoping method with paste fill. Stoping configurations are predominantly double lift (40m vertical interval) however single lift stoping (20m vertical interval) is used in some areas. The Double Lift stoping method (as illustrated in Figure 2) involves concurrently mining the uphole (part DL3.1) and downhole (part DL3.2) sections of the stope. The upper and lower portions of the stope are drawn back and bogged at the same time. Parts 2 and 3 are then paste filled, followed by the delayed extraction of the DL3 part 3 wedge (part DL3.3).

FIGURE 2 SECTIONS OF DL3 STOPES WITH SEQUENCE MARKED

The delayed extraction of the part 3 wedge serves to reduce the hanging wall dip length in the primary stopes and thus preserve HW stability despite the 40m vertical lift. The installation of HW cables and the use of a concurrent strike retreat blasting sequence of the part 1 and 2 sections, also assist in controlling HW stability.

Gwalia is operated on a fly-in-fly-out (FIFO) basis with personnel residing in camp facilities in Leonora. The FIFO roster for most personnel is 8 days on site, with 6 days off site.

The Gwalia mine is one of the world’s deepest trucking mines. The Hoover decline is currently at the 1500 level which is about a 10km journey to the portal. Combined ore and waste production of around 1 Mtpa is trucked to surface using a fleet of six DAT 60 and three Atlas Copco MT 6020 trucks. The truck fleet is matched with a fleet of one Sandvik LH621 and three Caterpillar R2900 loaders operating on a combination of tele-remote and manual control. Normal drilling fleet includes two Jumbos and three production rigs.

The operating depth and relatively high diesel loading at Gwalia requires chilled air intake. Chilling is via a 4MW bulk air cooler using direct contact chilled water located on a raise-bored intake shaft at the edge of the open pit. Primary ventilation is supplied by two Howden WB Model B Size 3300 single inlet centrifugal fans.

All Gwalia ore is trucked to the Gwalia processing plant. The processing plant is located at St Barbara’s Leonora Operations and consists of a three stage crushing circuit, single stage milling circuit and hybrid CIL circuit with one designated leach tank and 7 adsorption tanks. Gold is recovered from activated carbon into concentrated solution via a split AARL type elution circuit. Electrowinning and smelting are conducted in an adjacent secure gold room. The tailings from the process are thickened and pumped to a paddock type tailings storage facility with multi-spigot distribution (Zimmerman 2013). Gold doré bars are transported by armoured trucks to the Perth Mint for refining.

The declared Reserve is based on the current Life of Mine plan for the Gwalia Deeps deposit. Figure 3 shows the Life of Mine design colour coded by the reserve classification.

FIGURE 3 GWALIA LIFE OF MINE DESIGN BY RESERVE CLASSIFICATION.

The mineral ore reserves declared for the Gwalia Deeps deposit in lines with the requirements of the 2012 Edition of the “Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves”.

 GWALIA ORE RESERVE SUMMARY - JUNE 2013

References

Browne, C. & Love, R. 2013, ‘SBM Gwalia Deeps Resource Report’, Internal St Barbara Report.

de Vries, J, Zimmerman, J & Beswick, M. 2013 ‘Gwalia Mine’ Australasian Mining and Metallurgical Operating Practices 3rd edition.

Wilson, L. Beswick, M and de Vries, J., 2013., St Barbara Limited Ore Reserve Report - Gwalia June 2013, SBM Report. June, 2013

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Veladero Gold Mine

Location: The Veladero mine is located in the San Juan province of Argentina, immediately to the south of the Pascua-Lama property, in the highly prospective Frontera district.

Controlling Company: Barrick Gold (100%).

Brief History: The deposits at Veladero mine were discovered in 1997. However, development of the mine only started in 2002, with production beginning in 2005.

Brief Overview: Barrick’s Veladero mine has helped trigger a remarkable economic turnaround in Argentina’s San Juan province, according to a recent study. Between 2004 and 2011, the province’s unemployment rate fell 36 percent, and per capita income surged 177 percent to $5,260 from $1,900. Exports jumped 12-fold to $2.5 billion from $211 million, and the province’s manufacturing sector grew at an average annual rate of 13.5 percent, twice the national average.

“Veladero has made an enormous economic contribution in San Juan,” says Alfredo Lasalvia, lead author of a study by the Universidad Tecnológica Nacional (UTN) that measured Veladero’s socioeconomic impact on San Juan. “Economic growth in San Juan outpaced every other province in Argentina between 2007 and 2010, and Veladero played a big part in that. We estimate the mine contributes about 34 percent to San Juan’s GDP.”

Veladero is located in northeast San Juan more than 4,000 meters above sea level. It is the second largest private sector employer in the province (Barrick’s Pascua-Lama project is the largest) with about 3,500 workers, 85 percent of whom are from San Juan. The mine, which went operational in 2005, produced 766,000 ounces of gold in 2012.

The economic impact of Veladero has manifested itself in a myriad of ways, including payment of taxes and royalties, hiring of local residents, and procurement of goods and services in San Juan and other parts of Argentina. In 2005, Veladero paid just $513,000 in royalties to the San Juan government, according to the UTN study. By 2011, royalty payments totaled $48 million and accounted for 86 percent of all royalties collected by the San Juan government.

In 2011, Veladero spent $428 million on goods and services in Argentina, including $190 million in San Juan alone. “veladero generates numerous opportunities for suppliers in San Juan, which leads to the creation of new companies and the growth of existing ones,” Lasalvia says. “That means more jobs are being created, which puts more money in peoples’ pockets, which drives economic activity in the province.”

Brief Description: The Veladero mine currently produces ore from two pits, with an expected minimum mine life of 16 years. Geology/Mineralisation: The Veladero mine property contains several large deposits of gold and silver mineralisation in altered, silicified volcanic rock, and various types of silicified breccia.

Main-stage mineralisation is superimposed on the Miocene volcanic vent complex of diatreme breccias, associated pyroclastic rocks, flow domes, and porphyry intrusions.

Reserves: Proven and probable mineral reserves as at December 31, 2013, were 5.1-million ounces of gold.

Products: Gold.

Mining Method: Veladero is a conventional openpit operation. Major Infrastructure and Equipment: Ore is crushed using a two-stage crushing process and transported by overland conveyor and trucks to the leach pad area. Run-of-mine ore is trucked directly to the valley-fill leach pad.

Prospects: Gold production in 2014 is expected to be 650 000 oz to 700 000 oz, reflecting increased recovery of leached ounces and higher grades from the Argenta and Filo Federico pits.

Take a virtual tour of the mine

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Kalgoorlie Superpit Gold Mine

The Australia's largest open cut gold mine

Location: Kalgoorlie, Western Australia.

Products: Gold.

Owner: Kalgoorlie Consolidated Gold Mines Pty Ltd.

Overview: The Super Pit is located off the Goldfields Highway on the south-east edge of Kalgoorlie, Western Australia. The pit is oblong in shape and is approximately 3.5 kilometres long, 1.5 kilometres wide and 570 metres deep. At these dimensions, it is large enough to be seen from space.

The Super Pit is owned by Kalgoorlie Consolidated Gold Mines Pty Ltd, a company owned 50/50 by Barrick Gold Corporation and Newmont Mining Corporation. The mine produces 850,000 ounces (28 tonnes) of gold per year, and employs around 550 employees directly on site.

Originally consisting of a number of small underground mines, consolidation into a single open pit mine was attempted by Alan Bond, but he was unable to complete the takeover. The Super Pit was eventually created in 1989 by Kalgoorlie Consolidated Gold Mines Pty Ltd.

Barrick Gold acquired its share of the mine in December 2001, when it took over Homestake Mining Company. Newmont became part-owner of the mine three months later, when it acquired Normandy Mining in February 2002.

Geological Setting: Most of the good gold mined in the Super Pit occurs within ore lodes formed by ancient shears in a rock unit called the Golden Mile Dolerite. The gold mining area of Kalgoorlie-Boulder-Fimiston has long been called the Golden Mile because of the geographical concentration of rich mines in that area, even though the lodes occur in an area over 2 km in width and 1 km in depth.

Kalgoorlie Terrane.

1. Pre- to syn-D, granitoids were emplaced as broadly conformable sheet-like bodies at the base of, or within, the greenstone succession, probably during

2. Post-D, to syn-D, granitoids were diapirically emplaced, and are concentrated in a zone along the western side of the Kalgoorlie Terrane.

3. Late-tectonic to post-tectonic granitoids were emplaced late in the history of the Terrane. Limited geochronological data suggest the granitoids were emplaced at 2690-2680 Ma (group I), 2665-2660 Ma (group 2) and 2650-2600 Ma (group 3) (Hill ef al.,

1992). Small porphyry intrusions, including lamprophyres

(Rock et aL, 1989), are widespread and petrologically diverse; they may be genetically related to some of the I-type granitoid suites (Witt, 1992). They are common in and near regional deformation zones, and are associated with many gold deposits (Perring et al., 1988,1989).

GOLD MINERALIZATION:

All rock types in the Kalgoorlie Terrane host gold mineralization, but most production has come from fractionated quartz-dolerite zones of mafic-ultramafic sills and from tholeiitic basalt.

The dominance of quartz-dolerite and tholeiitic basalt remains even if bias introduced by the "giant" Kalgoorlie deposits (Golden

Mile, Mount Charlotte) is eliminated. A similar picture emerges when host rocks to gold mineralization throughout the Yilgarn Craton are considered (.1B; Groves & Barley, 1988). Quartz-dolerite and tholeiitic basalt host rocks are characterized by high FeO* contents and FeO*/(FeO*+MgO) (Tables II.1,11.2), where FeO* is total iron expressed as FeO. Although mafic rocks are the dominant hosts, other rock types (e.g., granitoids, porphyry, ultramafic rocks) host important deposits, and can even be the dominant host rock on a camp scale (e.g., porphyries at New Celebration). All rock types in the Kalgoorlie Terrane host gold mineralization, but most production has come from fractionated quartz-dolerite zones of mafic-ultramafic sills and from tholeiitic basalt .

Production:

Mining is via conventional drill and blast mining via face shovels and dump trucks. Around 15 million tonnes of rock is moved in any given year, consisting primarily of waste rock.

Gold within the Golden Mile lode system is unusual in that it is present as telluride minerals within pyrite. In order to recover the gold, the ore must be crushed, passed through a gravity circuit to recover the free gold present in some of the higher-grade lodes, and then subjected to flotation to produce an auriferous pyrite concentrate. This is then roasted at a small smelter outside Kalgoorlie-Boulder to liberate the gold from the tellurides, with doré bars poured.

More information and resources 

http://wa.gsa.org.au/publications/guidebook8.pdf

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