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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Boddington Gold Mine

Boddington Gold Mine

Boddington Gold Mine

Location: Boddington ,Western Australia. 

Ore Type: Lode Deposits.

Products: Gold. Secondary Copper.

Owner: Newmont Mining.

Reserves: By the end of 2011, proven ore reserves at Boddington were 20.3 million ounce (moz) of gold and 2.26 billion pounds (blbs) of copper.

Overview: Boddington Gold Mine (BGM) is located about 130km south-east of Perth in Western Australia. The largest gold mine in the country, it is poised to become the highest producing mine once production ramps up over the next few years. The $2.4bn project was initially a three-way joint venture between Newmont Mining, AngloGold Ashanti and Newcrest Mining. In 2006 Newmont bought Newcrest's 22.22% share, bringing its interest to 66.67% and ending any Australian ownership. AngloGold owned the remaining 33.33%. In June 2009, Newmont became the sole owner of the mine by acquiring the 33.3% interest of AngloGold. The original, mainly oxide open-pit mine was closed at the end of 2001.

The project has an attributable capital budget of between A$0.8bn and A$0.9bn. On 23 July 2009, the project, including the construction of the treatment plant, was completed. Production began in the third quarter of 2009. The first gold and copper concentrate was produced in August 2009.

Approximately 100,000t of ore was processed by mid-August. Gold production began on 30 September 2009. By 19 November 2009, the mine achieved commercial production. The mine was officially inaugurated in February 2010. The project had an attributable capital budget of between A$0.8bn and A$0.9bn. It employs 900 workers.

Based on the current plan, mine life is estimated to be more than 20 years, with attributable life-of-mine gold production expected to be greater than 5.7Moz.

In May 2012, Newmont decided to seek the expansion of mine life to 2052 by combining the north and south Wandoo open pits. It also plans to expand the waste rock facility to two billion metric tons.

Newmont and Anglo had focused their exploration activities on the poorly explored areas of the greenstone belt outside the already identified Boddington Expansion resource. The exploration strategy was to identify the resource potential of the remainder of the greenstone belt, with the emphasis on high-grade lode-type deposits.

Geological settings & Mineralization:

The Boddington gold mine is hosted in Archean volcanic, volcaniclastic, and shallow-level intrusive rocks that form the northern part of the Saddleback greenstone belt, a fault-bounded sliver of greenstones located in the southwestern corner of the Yilgarn craton, Western Australia. Total Au content of the Boddington gold mine (past production plus in situ resource) exceeds 400 metric tons, making the Boddington gold mine one of the largest Au mines currently operating in Australia.Geologic mapping and radiometric dating indicate that five phases of igneous activity occurred during development of the Saddleback greenstone belt. Basaltic, intermediate, and minor felsic volcanism occurred between approximately 2714 and 2696 Ma and again at approximately 2675 Ma. An older suite of ultramafic dikes was emplaced between approximately 2696 and 2675 Ma and a younger suite was emplaced between approximately 2675 and 2611 Ma. Granitoid plutons crystallized at approximately 2611 Ma and cut all the other Archean rocks in the Saddleback greenstone belt.Regional upper greenschist facies metamorphism accompanied the earliest phase of ductile deformation (D 1 ). Sericite-quartz + or - arsenopyrite-altered shear zones developed during subsequent ductile deformation (D 2 ). Crosscutting relationships indicate that D 1 and D 2 predate approximately 2675 Ma. Further ductile shear zones characterized by quartz-albite-sericite + or - pyrite alteration developed during D 3 , after approximately 2675 Ma. Narrow brittle faults (D 4 ) with biotite + or - clinozoisite alteration halos, active between approximately 2675 and 2611 Ma, cut the three generations of ductile shear zones.Rare quartz-albite-fluorite-molybdenite + or - chalcopyrite + or - pyrrhotite veins developed prior to D 1 and the regional metamorphism. These veins are not associated with any Au mineralization or significant Cu. Quartz + or - pyrite + or - molybdenite + or - Au veins and crosscutting clinozoisite-biotite + or - actinolite + or - quartz-chalcopyrite-pyrrhotite + or - galena + or - molybdenite + or - scheelite Au veins developed during movement on the D 4 faults between approximately 2675 and 2611 Ma. Mineralized veins crosscut the three generations of ductile shear zones but are not foliated. Movement on the D 4 faults controlled the location of mineralization within the Boddington gold mine. Higher grade mineralization occurs along the D 4 faults and coplanar pyroxenite dikes and where the faults intersect older shear zones, and quartz veins. Widespread lower grade stockwork mineralization is concentrated in the general vicinity of the D 4 faults. The orientation of veins within stockworks is consistent with vein development during sinistral strike-slip movement on the D 4 faults. Au-Cu + or - Mo + or - W mineralization at the Boddington gold mine, therefore, occurred late in the tectonic evolution of the Saddleback greenstone belt.The timing of mineralization at the Boddington gold mine is analogous to many other structurally late Au deposits in the Yilgarn craton, e.g., Mount Magnet, Mount Charlotte, and Wiluna. Movement on the D 4 faults and mineralization may have been coeval with the emplacement of granitoid intrusions at approximately 2611 Ma. Whereas these granitoids are unaltered and therefore unlikely to have been the source of significant volumes of hydrothermal fluids, they may have provided the thermal energy necessary to drive circulation of auriferous hydrothermal fluids through D 4 faults that may also have accommodated their intrusion.Previous workers at the Boddington gold mine have inferred that mineralization is genetically linked to subvolcanic intrusions emplaced between approximately 2714 and 2696 Ma. However, this inference is inconsistent with the crosscutting relationships of structures and mineralized veins which indicate that mineralization occurred between approximately 30 and 80 Ma after emplacement of these rocks.

General Geological Map of Boddington Gold Mine

Note From Dr. Walter L. Pohl

"Lateritic gold deposits as a class are a relatively recent discovery. One of the largest representatives of this group was the Boddington bauxite mine in Western Australia, which until closure in 2001 was the biggest gold mine in Australia with an annual gold production of 2500 kg. Premining resources amounted to 60 Mt of ore at 1.6 ppm Au, apart from bauxite with gold contents <1 ppm. Exploitable gold was located in near-surface, iron-alumina hard crusts that reached a thickness of 5 m and in additional 8 m thick lumpy Fe-Al laterite of the B-horizon. Sources of the gold in soil at Boddington are quartz veins and hydrothermally altered bodies of Archaean greenstone bedrock. Since 2009, resources of 400 Mt of this primary ore with a grade of 0.9 g/t Au and 0.12% Cu are exploited in a new mine. Worldwide, numerous lateritic gold deposits are worked. They are attractive because exploration, extraction and processing of soil is less costly compared with hard rock mining."

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Bingham Canyon (Kennecott) Copper Mine

Bingham Canyon (Kennecott) Copper Mine

It is the world's deepest man-made open pit excavation.

Bingham Canyon (Kennecott) Copper Mine

Location: Salt Lake County, Utah, United States.

Products: Copper.

Owner: Rio Tinto Group.

Ore Type : Porphyry copper deposit.

The history of the Mine:

Bingham Canyon was settled in 1848 by the Bingham brothers, Thomas and Sanford, who were ranchers with no mining experience. In 1863, soldiers stationed at Fort Douglas in Salt Lake City explored the canyon and discovered lead ore. Utah’s first mining district was created in the Bingham Canyon area that same year. In 1893, Daniel Jackling, a metallurgical engineer, and Robert Gemmell, a mining engineer, studied the deposit and recommended developing the ore body through a revolutionary open-pit mining method and processing the ore on a large, industrial scale. The miners and their families lived near Bingham Canyon in places called Highland Boy, Copper Heights, Copperfield, Carr Fork, Heaston Heights, Telegraph, Dinkeyville, Terrace Heights, Greek Camp and Frog Town. At one point, the population in the area approached 20,000 people. In 1903, the Utah Copper Company was formed to develop the mine, based on the recommendations of Mr. Jackling and Mr. Gemmell. In 1906, the first steam shovels began mining away the waste rock that covered the ore body. The ore was found in a part of the mountain that divided the main canyon.

Geology of the Mine:

Every deposit of ore in the world is unique. There are no two ore bodies that are alike. Geologic forces were at work in the Oquirrh Mountains between 260 and 320 million years ago (Late Paleozoic Period). About 30 to 40 million years ago, molten, metal-bearing rock deep within the earth’s crust began to push toward the surface and formed Bingham’s ore deposit. Volcanoes erupted above the evolving ore body. This particular ore body contains primarily copper, gold, silver and molybdenum.

Tiny grains of ore minerals, mostly copper and iron sulfides, are scattered within what is called “host rock.” Because there is far more host rock than there are minerals, it is known as a low-grade ore deposit. Because this is a low-grade deposit, a ton of ore contains only about 10.6 pounds of copper. For every ton of ore removed, about two tons of overburden must first be removed to gain access to the ore.

How big is the Bingham Canyon Mine?

Kennecott Utah Copper’s (KUC) Bingham Canyon Mine has produced more copper than any mine in history— about 18.1 million tons.

The mine is 2¾ miles across at the top and ¾ of a mile deep. You could stack two Sears Towers (now known as the Willis building), on top of each other and still not reach the top of the mine. The mine is so big it can be seen by space shuttle astronauts as they pass over the United States. By 2015, the mine will be more than 500 feet deeper than it is now. If you stretched out all the roads in the open-pit mine— some 500 miles of roadway — you’d have enough distance to reach from Salt Lake City to Denver. KUC mines about 55,000,000 tons of copper ore and 120,000,000 tons of overburden per year.

The mining process:

Bingham Canyon Mine This is where the mining process begins. Every day, Kennecott Utah Copper mines about 150,000 tons of copper ore and 330,000 tons of overburden. The ore containing copper, gold, silver and molybdenum is hauled and deposited in the in-pit crusher and sent to the Copperton Concentrator.

Copperton Concentrator From the mine, ore is transported on a five-mile conveyor and stockpiled at the Copperton Concentrator. There the ore is ground into fine particles. The smaller pieces are then combined with air, water and chemical reagents to separate the valuable minerals from the waste rock. The mineral bearing concentrate is then transported to the smelter through a pipeline.

Tailings: Are the leftover rock material that have had most of the valuable metals removed. Tailings are sent through a pipeline from the Copperton Concentrator to the tailings impoundment north of the town of Magna where they are stored.

Smelter: At the smelter, the copper concentrate is transformed into liquid copper through a flash smelting process. The copper matte is processed in the furnace to produce 98.6 percent blister copper. From there, the 720 pound copper plates, called anodes, are sent to the refinery.

Refinery:  At the refinery, anodes are lowered into electrolytic cells containing a stainless steel blank and acidic solution. For 10 days, an electric current is sent between the anode and the cathode, causing the copper ions to migrate to the steel sheet. The other impurities, including gold and silver, fall into the bottom of the cell and are recovered in the Precious Metals plant. This process forms a plate of 99.99% pure copper. The copper is separated from the steel sheet and sent to market.

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Kidd Creek Mine

Kidd Creek Mine

It is the world's deepest copper/zinc mine.

Figure 1. Kidd Creek Mine

Location: Timmins, Ontario, Canada.

Products: Copper & Zinc.

Owner: Xstrata Copper.

Deposit Type: The Kidd deposit is one of the largest volcanogenic massive sulfide ore deposits in the world, and one of the world's largest base metal deposits.

Ore Geology: Kidd Creek is based on a rich, steeply dipping volcanogenic sulphide deposit located in the Archaean Abitibi greenstone belt. There are two major orebodies, with associated smaller lenses. The ore is hosted in felsic rocks of the Kidd Volcanic Complex and is cut by mafic sills and dykes. Structural deformation resulting from several phases of folding and faulting affects the distribution of sulphide lenses.

Three ore types predominate: massive, banded and bedded (MBB) ores (pyrite, sphalerite, chalcopyrite, galena and pyrrhotite); breccia ores containing fragments of the MBB ores; and stringer ores consisting of irregular chalcopyrite stringers cutting a siliceous volcaniclastic host.

Geological setting & Stratigraphic section of the mine:

The Kidd Creek Volcanic Complex is interpreted to have formed within a proto-arc geodynamic setting, with the high silica FIII rhyolites a product of crustal extension during rifting and melting of the lithosphere (Wyman et al., 1999; Prior et al., 1999). A graben interpreted to contain the Kidd VMS deposit is consistent with this geodynamic setting and a recent volcanic reconstruction of the North Rhyolite by DeWolfe et al. (2003), suggest a minimum graben width of 5 to 7 km (Gibson and Kerr, 1993; Bleeker, 1999). Fissures that controlled the eruption and emplacement of the Footwall and QP rhyolites may be graben-parallel structures (Prior, 1996).

The simplified stratigraphic column in Figure 3 provides a general overview of the Kidd Mine stratigraphy and location of massive sulfide deposits. Komatiitic flows and intrusions constitute the base of the known stratigraphic sequence and likely formed a broad, low-relief lava plain upon which the Kidd Creek rhyolitic dome and ridge complex was constructed. The minimum thickness of the komatiitic unit is estimated at 500 metres.

Figure 2. Kidd Mine ore-bodies looking east from surface to 10,200 ft

Figure 3. Kidd Mine stratigraphic column.

Mining operation and reserves :

The mine started production in 1966 from an open pit. The orebody is now mined at depth through three shafts as the No.1, No.2 and No.3 Mines. Phase 2 of No.3 Mine is currently being developed. Mine D will extend Kidd Creek below No 3, from a depth of 2,100m to 3,100m.

Blasthole stoping with cemented backfill is used to extract the ore underground, Kidd Creek being the world’s second-largest user of cemented backfill (after Mt Isa in Australia). Blastholes are drilled using Ingersoll Rand, Mission and Cubex drills and broken ore is hauled underground by Tamrock load-haul-dump units. The hoisting shafts are equipped with an ABB Hoist Automation System, which has significantly increased the efficiency of raising ore from depth.

At the end of 2005, Kidd Creek’s proven and probable reserves were stated as being 19Mt grading 1.8% copper, 5.5% zinc, 0.18% lead and 53g/t silver. Measured and indicated resources totalled 2.6Mt at 2.2% copper, 6.3% zinc, 0.2% lead and 48 g/t silver, with a further 11.9Mt in inferred resources at 2.7% copper, 4.8% zinc, 0.3% lead and 81g/t silver.

Note

REFERENCES

Barrie, C.T., 1999. Komatiitic flows of the Kidd Creek footwall,

Abitibi Subprovince, Canada: In Hannington, M.D., and

Barrie, C.T., eds. The Giant Kidd Creek Volcanogenic Massive

Sulfide Deposit, Western Abitibi Subprovince, Canada. Economic

Geology, Monograph 10, p. 143-162.

Beaty, D.W., Taylor, H.P., & Coad, P.R., 1988. An oxygen

isotope study of the Kidd Creek, Ontario, volcanogenic massive

sulfide deposit: Evidence for high heat 18O ore fluid. Economic

Geology, v. 83, p. 1-18.

Bleeker, W., 1999. Structure, stratigraphy, and primary setting

of the late Archean Kidd Creek Volcanogenic massive sulfide

deposit: A semi-quantitative reconstruction: In Hannington,

M.D., and Barrie, C.T., eds. 

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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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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 Cadia deposits are part of a Late Ordovician – Early Silurian porphyry alteration-mineralisation system that extends over an area of at least 6 X 2 km within the Ordovician Molong Volcanic Belt of the Palaeozoic Lachlan Fold Belt (Newcrest Mining Staff, 1997).  The Molong Volcanic Belt comprises a suite of intermediate to basic volcanics, volcaniclastics, comagmatic intrusions, and limestones.  The suite is probably part of a subduction-related island arc disrupted by later tectonism (Glen et al, 1997).  In the Cadia area the volcanics and 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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El Chino Copper Mine

El Chino Copper Mine

El Chino CopperMine

Location: Santa Rita, New Mexico, United States.

Products: Copper Deposit.

Ore Type:  Porphyry copper deposit with adjacent copper skarn deposits.

Host rocks: The predominant oxide copper mineral is chrysocolla. Chalcocite is the most important secondary copper sulfide mineral, and chalcopyrite and molybdenite the dominant primary sulfides.

Geological setting: The Cobre Mountains are composed of Proterozoic metamorphic and igneous rocks covered by about 3800 to 4800 feet of Paleozoic to Mesozoic sedimentary rocks. Cretaceous diorite to quartz diorite sills subsequently intruded these older rocks. Shortly thereafter, mafic to intermediate composition dikes and other intrusive bodies were emplaced and 2000 feet of intermediate composition lavas and breccias were erupted onto the surface. Next, the large granodioritic plutons at Chino and at Hanover-Fierro to the north were intruded. The last stage of intrusive activity in this area was the emplacement of rhyolitic dikes. The multiple intrusions locally domed and folded the older Paleozoic and Cretaceous strata.

Mineralization: Porphyry copper deposit are low-grade (<0.8%) disseminated deposits of copper found in and around small intrusive bodies composed of porhyritic diorite, granodiorite, monzonite or quartz monzonite (McLemore, 2008). The small plutons (also called stocks) are often shallowly emplaced at depth within 1 to 6 km of the earth's surface. The copper occurs within breccia or in networks of fractures, both in the porphyritic intrusion and in the adjoining country rocks.

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