Andacollo Mine

Andacollo Mine

Andacollo Mine

Location: Elqui, Coquimbo, Chile.

Products: Copper & Gold.

Owner: Royal Gold,Inc.

Ore Type: Porphyry copper-gold deposit, hosted by altered andesitic and dacitic volcanic rocks, and small stocks and irregular dykes of potassium-rich tonalitic porphyry.

Overview

The Andacollo mining district is located in the Coquimbo region of Chile at 30°14’ south, 71°06’ west, some 55 km southeast of La Serena, at a mean elevation of 1030 m within a semi-arid hilly landscape. Current mining activity in the district is concentrated on copper and gold. These metals are mined, respectively, from a porphyry copper deposit and epithermal, manto and vein gold deposits of adularia–sericite type.11,13 Other types of mineralization include mercury veins hosted by carbonate rocks. The gold veins are controlled by a northwest-trending set of normal faults, whereas the manto-type mineralization is strata-bound and largely confined to andesite breccias, dacites and sites of strong fracturing. The lateral and vertical continuity of the mantos is strongly controlled by rock type, faulting and intensity of fracturing. The gold deposits have been the focus of a recent study,11 but comparable information on the Andacollo porphyry has not become available.

Andacollo’s operating profit from August 22 to December 31, 2007 was $27 million before the effects of the revaluation of copper inventory to fair value on acquisition and negative pricing adjustments. The revaluation established a higher value for copper inventories, based on market prices at the date of acquisition. This increased our cost of sales by $24 million and the subsequent decline in metal prices resulted in a loss on the sale of these inventories. In addition, the mine recorded negative pricing adjustments of $2 million since they acquired it in August 2007. After these adjustments, Andacollo’s operating profit was $1 million. Copper cathode production in 2008 is expected to be approximately 20,000 tonnes and capital expenditures are planned at US$190 million, including US$185 million on the hypogene development.

Geological setting and Mineralization

The Andacollo deposits are the products of a complex hydrothermal system and consist of a porphyry copper-gold deposit and peripheral strata-bound manto gold deposits and veins with minor associated base metals. The hydrothermal system was part of the Pacific porphyry copper belt which was generated during development of an Early Cretaceous magmatic arc displaying shoshonitic petrochemical affiliations. Rocks that crop out in the area include a volcanic sequence, the Arqueros and Quebrada Marquesa Formations, consisting of andesitc and dacite flows, volcanic breccias, and pyroclastic rocks of Early Cretaceous age. Intrusive rocks range from diorite to granodiorite in composition and date between 87 and 130 Ma. The porphyry copper-gold deposit is zoned vertically downward from a leached capping through a supergene enrichment blanket to a hypogene sulfide zone. Alteration is characterized by central potassic (K feldspar-biotite), phyllic, and peripheral propylitic zones. Abundant northwest-trending tensional fractures were superimposed on the porphyry copper-gold deposit and surrounding areas during the later stages of the evolving mineralized system. The fractures channeled mineralizing fluids from the central parts of the porphyry copper deposit outward for up to 5 km. Replacement by adularia and sericite took place together with deposition of gold-bearing pyrite and minor amounts of zinc and copper where these fluids encountered permeable dacite flows and andesite flow breccias. The alteration process caused remobilization of aluminum and alkalies and addition of K 2 O, which attains values of 12 to 13 wt percent. The Andacollo system is interpreted to be a porphyry copper-gold deposit that is transitional outward to distal epithermal, adularia-sericite-type contact metasomatic gold orebodies.

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Batu Hijau Copper, Gold Mine

Batu Hijau Gold Mine

Batu Hijau Gold Mine

Location: Sumbawa, West Nusa Tenggara, Indonesia.

Products: Copper & Gold.

Owner: P.T. Newmont Nusa Tenggara.

Ore Type: Porphory Copper deposits.

Reserves: the Batu Hijau included 2.77 million tonnes of copper with an average grade of 0.69g/t gold, which would allow mining to continue until 2025.

Ore geology and Mineralization: The Batu Hijau porphyry Cu‐Au deposit is a world‐class island arc type porphyry deposit, located on the southwestern portion of Sumbawa Island, Nusa Tenggara Barat Province, Indonesia. This 12 km by 6 km district contains an estimated 914 million tonnes of ore at an average grade of 0.53% Cu and 0.40 g/t Au (Garwin, 2002; Arif and Baker, 2004), and is one of the largest and richest porphyry Cu‐Au deposits in Asia.

Ore fluids produced distinct quartz ± sulfide veins and veinlets that cross cut the tonalite intrusions and their surrounding host rocks. Within these veins, fluid inclusions trapped in quartz contain ore fluids, which represent fluids moving through the deposit during the time of its formation. The ore fluids in the fluid inclusions are key to defining the temperature and pressure conditions under which the deposit formed, and defining the geochemistry of the hydrothermal system, which was responsible for the distribution Cu and Au within the deposit.

Preliminary fluid inclusion studies have suggested that deposit formation temperatures ranged from 280 to over 700 °C. Based on the coexistence of magnetite‐bornite ,chalcocite, Garwin (2000) suggested that the earliest veins at Batu Hijau likely formed at > 500–700 °C (cf. Simon et al., 2000). A preliminary fluid inclusion study by Garwin (2000) on inclusions in halite‐bearing transitional veins produced homogenization temperatures that ranged from about 450 to 500 °C. These temperatures are consistent with phase equilibria temperature estimates based on a chalcopyrite , bornite vein mineralogy (Simon et al., 2000).

Homogenization temperatures of < 400 °C were obtained by Garwin (2000) for late pyrite‐bearing veins. A fluid inclusion study conducted by Imai and Ohno (2005) documented homogenization temperatures ranging from 280 to 454 °C, significantly lower than temperatures obtained by Garwin (2000). This temperature is similar to Au saturation temperatures for bornite (~300 °C) and chalcopyrite (250 °C) (Kesler et al., 2002; Arif & Baker, 2004).

A detailed fluid inclusion microthermometry study to clarify processes of ore formation is warranted. Microthermometric data on well‐characterized fluid inclusions with appropriate pressure corrections can provide the temperatures and pressures at which the deposit formed. Additional qualitative and quantitative data from synchrotron x‐ray fluorescence (SXRF) and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS), respectively, can document and quantify major and trace element concentrations. Such data will contribute to a model describing the transport of metals by hydrothermal fluids, and the precipitation of Cu‐ and Au‐bearing minerals.

Mining & Milling: Batu Hijau is an open-pit mine. Ore is removed from the mining face using P&H 4100 electric shovels (pictured) and loaded into Caterpillar 793C haul trucks. Each haul truck can move a payload 220 t (240 short tons) of ore. The trucks haul ore from the shovel to primary crushers. Crushed ore is sent by a conveyor 1.8 m (6 ft) wide and 6.8 km (4.2 mi) long to the mill. Daily production from the mine is an average of 600,000 t (660,000 short tons) ore and waste combined. Ore from the mine has an average copper grade of 0.49% and an average gold grade of 0.39g/t.

Crushed ore is further reduced in size by Semi-Autogenous Grinding and ball mills. Once milled it is sent through a flotation circuit which produces a concentrate with a grade of 32% copper and 19.9g/t gold. The mill realizes a copper recovery of 89%.[3] The concentrate is thickened into slurry and piped 17.6 km (10.9 mi) to the port at Benete where water is removed from the slurry. The concentrate storage at the port can hold 80,000 t (88,000 short tons) of copper-gold concentrate.

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The Goldstrike Mine.

Barrick Goldstrike Mine

It is owned and operated by the world's largest gold mining company, & it is the largest gold mine in North America.

The Goldstrike Mine.

Location: Eureka County, Nevada, United States.

Products: Gold , Silver.

Ore Type: Epithermal gold deposite in carbonate or silicate sedimentary rocks.

Owner: Barrick Gold.

Ounces of gold produced in 2014 >> 902,000

Ounces of proven and probable gold reserves >> 9,614,000

Overview: The Goldstrike mine, one of the top five gold-producing mines in the world, is Barrick Gold’s largest producing mine. The mine consists of both the Betze-Post open-pit and the Meikle and Rodeo underground mines (the “Goldstrike Mine”). Barrick, which is also the biggest gold producer in the world, has operated the mine for over 20 years (since 1987). The mine is located on the Carlin Trend in north-central Nevada, USA, about 40 kilometers northwest of the city of Elko. In 2007, the Goldstrike operation produced 1.63 million ounces of gold at average total cash costs of $373 per ounce. The Goldstrike property comprises approximately 4,197 hectares of surface rights ownership and approximately 3,535 hectares of mineral rights ownership on the Carlin Trend, a prolific gold producing region of North America. The northwestsoutheast trend is an 80 km long, 8 km wide belt that contains more than 20 major gold deposits. The operation employs approximately 1,600 employees.

Geological settings & Mineralization : The Goldstrike mine complex (including the Betze-Post-Screamer and Meikle Rodeo deposits). 

Betze-Post Open Pit

After Barrick took over the operation, two sulphide ore zones were identified as the Betze and Deep Post deposits in 1987. Since it entered production in 1993, the Betze-Post pit has been a truck-and-shovel operation using large electric shovels. The Betze-Post ore zones extend for 1,829 meters northwest and average 183 to 244 meters in width and 122 to 183 meters in thickness. The Post oxide orebody occurs in the siliceous siltstones, mudstones, argillites and minor limestones of the Rodeo Creek Formation. The Betze and Post oxide deposits are hosted in sedimentary rocks of Silurian to Devonian age. The mineralization of the Betze-Post pit was captured by structural traps developed by Mesozoic folding and thrust faults. Volcanic and sedimentary rocks filled ranges and basins formed by Tertiary faulting. The Tertiary volcanism initialized gold mineralization approximately 39 million years ago.

In 2007, the open pit mine produced 1,215,000 ounces of gold from 136.9 million tons mined and 10.5 million tons processed. The average grade processed is 0.136 oz/ton with a recovery rate of 85.5%. The average total cash cost was $355 per ounce. The open pit mine has proven and probable reserves totaling 12.19 million ounces from 94.9 million tons grading 0.128 oz/ton. The mine is expected to sustain the current production level for approximately 8 years, based on existing reserves. Most of the open pit mine is subject to a net smelter return of up to 4% and a net profits interest of up to 6%. 

Meikle Rodeo deposits

The Meikle deposit occurs in hydrothermal and solution collapse breccias in the Bootstrap Limestone of the Roberts Mountains Formation. The gold at Goldstrike was carried into the various orebodies by hot hydrothermal fluids, and deposited with very fine pyrite and silica. Over time, the pyrite oxidized, freeing the gold and making its extraction relatively easy, as in the Post Oxide deposit. In the deeper deposits – Betze, Rodeo and Meikle – the gold is still locked up with the iron sulphide and an additional processing step (autoclaving or roasting) is required to free the gold. Two haulage drifts connect the Meikle and Rodeo orebodies.

The drifts are accessed from two shafts and by a decline at the bottom of the open pit mine. In the year ended December 31, 2007, the underground mine produced 413,186 ounces of gold at an average total cash cost of $431 per ounce. Proven and probable reserves underground are estimated at 7.42 million tons at 0.364 oz/ton, containing 2.7 million ounces. The Goldstrike’s total (open pit and underground) proven and probable mineral reserves as of December 31, 2007 are estimated at 14.9 million ounces of gold. The underground mine, which originally produced at a rate of approximately 2,000 tons of ore per day, averaged 3,562 tons per day in 2007. Based on current reserves and production capacity, the expected mine life is 9 years. The maximum royalties payable on the Meikle deposit are a 4% net smelter return and a 5% net profits interest.

Mining Processing & operations: The Goldstrike complex consist of three distinct mines: the large Betze-Post open pit mine, and the Meikle and Rodeo underground mines. The ore from all three mines is milled and leached by the cyanide process. Carlin-type gold deposits host gold mainly as microscopically fine grains. Refractory non-carbonaceous sulphide ore is treated in an autoclave followed by a carbon-in-leach (CIL) cyanidation circuit. Carbonaceous ore, also refractory, is treated with a roaster followed by a CIL circuit. The two treatment facilities treat ores from both the open pit and underground mines. Recovered gold is processed into doré on-site and shipped to outside refineries for processing into gold bullion.

In 2008 the Betze-Post open-pit mine produced 1,281,450 oz (36,328 kg) of gold and 152,886 oz (4,334.2 kg) of silver, while the Meikle-Rodeo underground operations yielded 424,687 oz (12,039.7 kg) of gold and 51,438 oz (1,458.2 kg) of silver. This was 30% of the total 5,698,000 oz (161,500 kg) output of all gold mining operations in Nevada.

Non-carbonaceous sulphide (refractory) ore is treated at an autoclave and carbon-in-leach (CIL) cyanidization circuit. Carbonaceous ore is treated at the roaster and CIL circuit, since the active carbon content in carbonaceous ore responds poorly to autoclaving. The two facilities treat ores from both the open pit and underground mines and, when combined, have a design capacity of 33,000 to 35,000 tons per day. Recovered gold is processed into doré on-site and shipped to outside refineries for processing into gold bullion. A modified pressure leach technology was successfully tested last year and it will be used to process ores that would otherwise have been treated at the roaster facility, consequently extending the life of the autoclave. The property also has a 115 megawatt natural gas-fired power plant, providing a significant portion of the operation’s power requirements off-grid.

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Golden Sunlight Mine

Golden Sunlight Mine 

Location: Jefferson County, Montana, United States.

Products: Gold.

Owner: Barrick Gold Corporation.

Ore Type: Breccia pipe.

Reserves: Golden Sunlight produced 86,000 ounces of gold in 2014 at all in sustaining costs of $1,181 per ounce1. Proven and probable mineral reserves as at December 31, 2014, were 127,000 ounces of gold2.

In 2015, gold production is expected to be 90,000-105,000 ounces at all-in sustaining costs of $1,000-$1,025 per ounce.

Geological setting & Mineralization

The Golden Sunlight gold-silver deposit is hosted by a breccia pipe that cuts sedimentary rocks of the Middle Proterozoic Belt Supergroup and sills of a Late Cretaceous rhyolite porphyry (Porter and Ripley, 1985; Foster, 1991a, 1991b). At depth, rhyolite porphyry forms the matrix for fragments of the pipe. Creation of the pipe appears to be related to emplacement of an underlying hypabyssal stock related to the sills. Crosscutting the breccia pipe are hydrothermally altered lamprophyre dikes that postdate the gold-silver ore; locally, these dikes may have created areas of high-grade ore in the breccia pipe near their margins. The timing of emplacement of various igneous rocks and the hydrothermal alteration related to mineralization at the deposit.

Gold and silver in the region was concentrated along northeast-striking, high-angle faults and shear zones, some of which cut the breccia pipe and along which lamprophyre dikes have been emplaced (Porter and Ripley, 1985). These structures are thought to be part of a regional, northeast-striking zone of crustal weakness that has been intermittently active from the Proterozoic to the present (Foster and Chadwick, 1990; Foster 1991a). Because some hydrothermally altered and mineralized lamprophyre dikes are preferentially emplaced along structures that cross-cut the breccia pipe, their relationship to mineralization of the breccia pipe has been ambiguous. Certainly their emplacement is later than that of the pipe, and the simplest interpretation is that lamprophyre emplacement postdates mineralization. But, because the northeast-striking shear zones, veins, and dikes contain high-grade ore in places, a mineralizing process was obviously continuing during emplacement of the lamprophyre bodies.

 

Geologic cross section of the Golden Sunlight breccia pipe.

Mine Life

Since its beginnings in 1982, Golden Sunlight Mine has continued to add resources to extend the life of the mine. Currently, the Montana DEQ is conducting the environmental review necessary to grant permission for mining additional resources referred to as the North Area Pit and South Area Layback, which would extend the mine life into 2016. Additional exploration is ongoing north of the Mineral Hill pit site with drilling activity in the Bonnie/Microwave area. 2013 will bring its own mix of success and challenge, so it is important that we remain intently focused on continuous improvement. As we work to deliver safe and profitable gold production, we cannot lose sight of our long-range goals—community partnership, environmental stewardship and most importantly, the safety and health of our people. I thank everyone again for the warm reception and look forward to getting to know you better in the coming months.

Safety and Health

We made great strides in improving our safety record, an achievement we celebrated in March, when we received Barrick’s Excellence Award for Best Safety Performance. As of first quarter 2013, GSM has gone five and a half years, and 2.7 million employee hours, without a lost-time incident, and over a year without a medical aid treatment incident. We still have more work to do in order to achieve our goal of zero incidents. As with most things, safety starts and ends with leadership. I expect all of our employees to be leaders when it comes to ensuring safety and continuing to send all GSM employees and contractors home safe and healthy every day.

Environment

Golden Sunlight Mine was the recipient of the prestigious Bureau of Land Management (BLM) 2012 Mineral Environmental Award for our third-party ore processing and reclamation initiatives. Golden Sunlight Mine initiated the program to assist small miners to mill outside “ores” and to assist with legacy mine materials containing reasonable concentrations of precious metals. In presenting the award, the BLM stated: “The Golden Sunlight Mine has turned liabilities into environmental and economic benefit—greatly enhancing the quality of the environment, saving taxpayer dollars, and creating local jobs.”

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Grasberg Gold & Copper Mine

Grasberg Gold & Copper Mine

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

Grasberg Gold & Copper Mine

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.

 

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Yanacocha Gold Mine

Yanacocha Gold Mine

Yanacocha Gold Mine

Location: Cajamarca, Peru.

Products: Gold.

It is the largest gold mine in Latin America, and The second largest gold mine in the world, producing over US$7 billion worth of gold to date.

Deposit Type: High sulfidation- type epithermal gold deposits.

Geological Settings & Mineralization: 

The high-sulfidation epithermal gold deposits are hosted by volcanic rocks that occur at the southern terminus of the northern Peruvian volcanic belt, a continuous sequence of a north-northwest trending Miocene-Pliocene suite of bimodal andesite to rhyolite volcanic rocks that extend into southern Ecuador. In the Yanacocha district, the volcanic pile has been subdivided into three groups: (1) the lower andesite sequence, consisting of an intercalated sequence of block and ash flow tuffs, flow sequences with rare, associated flow domes, and an upper zone dominated by ignimbrites and fine-grained, laminated epiclastic sequences that show a transition into the overlying Yanacocha pyroclastic sequence; (2) the Yanacocha pyroclastic sequence, a variable sequence of lithic to lithic crystal tuffs, extensively altered in the central portion of the district and primary host to the majority of gold deposits within the district; (3) the upper andesite-dacite sequence, consisting of intercalated units of andesite to dacite flows, dominated by multiple flow dome complexes in its upper portion. Ar-Ar age dating within the district has yielded ages ranging from 19 Ma (basal lower andesite) to >12 Ma (upper andesite sequence). The entire volcanic pile has been crosscut by multiple phases of phreatic (vapor phase dominant), phreatomagmatic (intrusive component) and hydrothermal breccias, and intruded by multiple late-stage phases of andesite dikes and dacite to quartz dacite plugs, dikes and stocks (10–8 Ma), the latter of which are associated with shallow Au-Cu porphyry-style mineralization that underlies the high-sulfidation epithermal deposits.

Schematic map showing the geology of western Peru and general location of the Yanacocha mining district.

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Sunrise Dam Gold Mine

Sunrise Dam Gold Mine

Sunrise Dam Gold Mine

Location: Laverton, Western Australia.

Product: Gold.

Geological Settings: The deposit is hosted by the Archaean Norseman-Wilunabelt, in the Eastern Goldfields Province of the YilgarnCraton. The deposit falls within the structurally complex LavertonDomain, which is characterized by tight folding and thrusting. A number of other Au deposits lie within or near the margins of the LavertonDomain, including Laverton, Granny Smith (this volume), Red October (this volume), Childe Harold, Lancefield and Keringal. Most of these deposits are hosted by metasedimentary rocks, a distinctive feature of the Lavertonregion relative to other parts of the YilgarnCraton.

Host Rocks: The host rocks are shallow-dipping interbedded Archaean metasedimentary, metavolcaniclasticand felsic to intermediate metavolcanicrocks (Newton et al., 1998). The metavolcaniclasticrocks are interbedded with BIF. In general, they are thick, bedded to massive and fine upwards. The BIF units are typically 2-10 m thick and commonly grade into magnetite-rich tuffs. A 20-40 m thick mafic intrusive postdates the metavolcaniclasticsequence on the western side of Cleo. Quartzfeldsparporphyries also intrude the sequence at both Cleo and Sunrise and, at Cleo, post-date the mafic intrusive.

Mineralization: The Sunrise Shear, within the Archaean rocks, controls geometry of the mineralization and is thought to have been the main conduit for Au-bearing hydrothermal fluids (Newton et al., 1998). Pyrite replacement of BIF accounts for most of the primary mineralization and is well developed where the shear zones, parallel to bedding, follow the contact of BIF with less competent units. Gold is also associated with quartzankerite- pyrite veins and pervasive ankerite-silica-sericite-pyrite alteration of intermediate volcaniclastichost rocks. Thin quartz-carbonate veins also host Au, but are mostly located in the Sunrise part of the deposit. Supergene mineralization has developed in the weathered bedrock and in transported cover in the eastern part of the study area.

Regional geology and setting of the Sunrise-Cleo Au deposit

(after Newton et al., 1998)

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Bonikro Gold Mine

Bonikro Gold Mine

Bonikro Gold Mine

Location: Bonikro, Côte d’Ivoire.

Product: Gold.

Ore Type: Disseminated.  

Geological Settings & Mineralization: The Bonikro deposit is hosted primarily within a small granodiroite intrusion. Mineralisation extends into surrounding basalts to the south, and is controlled along a moderately dipping shear zone. Gold occurs associated with quartz and pyrite, with the highest gold grades occurring around the intersection of the shear and the granodiorite. Overall, the deposit has an average grade below 2g/t gold.

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Cadia-Ridgeway Mine

Cadia-Ridgeway Mine

Cadia-Ridgeway Mine

Location: Orange, New South Wales,is one of three gold mines Newcrest currently operates in Australia.

Products: Copper & Gold. A series of large underground and open-cut gold and copper mines

Ore Minerals: Ore minerals are native gold, chalcopyrite and bornite, mostly occurring within veins, but also disseminated.  Magnetite is a major accessory mineral in veins. Hydrothermal alteration associated with the strongest mineralisation is potassic: orthoclase, albite, actinolite, magnetite, biotite.  This is overprinted by later propylitic assemblages: epidote, chlorite, Fe-carbonate, calcite, hematite dusting. 

Geological setting: The Cadiadeposits are part of a Late Ordovician – Early Silurian porphyry alteration-mineralisationsystem that extends over an area of at least 6 X 2 km within the Ordovician MolongVolcanic Belt of the PalaeozoicLachlan Fold Belt (Newcrest Mining Staff, 1997).  The MolongVolcanic Belt comprises a suite of intermediate to basic volcanics, volcaniclastics, comagmaticintrusions, and limestones.  The suite is probably part of a subduction-related island arc disrupted by later tectonism (Glen et al, 1997).  In the Cadiaarea the volcanicsand intrusions are shoshonitic(Blevin, 1998).

Mineralization: Sheeted quartz vein, stockwork quartz vein, disseminated and skarn, all of which are genetically related to a relatively small (3 X 1.5 km in outcrop) composite intrusion of predominantly monzonitic composition, with a monzodioritic to dioritic rind (Cadia Hill Monzonite).  The Cadia Hill Monzonite intruded Forest Reefs Volcanics (volcaniclastics, lavas, subvolcanic intrusions, and minor limestone) and Weemalla Formation (siltstone, mudstone, minor volcaniclastics).  Emplacement of the Cadia Hill Monzonite was probably facilitated and localised by the development of a major north-west (NW) to south-east (SE) trending dilational structural zone, which is well evident in magnetic data.

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