Porphyry copper deposit
Encyclopedia
Porphyry copper deposits are copper
ore
bodies which are associated with porphyritic
intrusive rocks and the fluids that accompany them during the transition and cooling from magma to rock. Circulating surface water or underground fluids may interact with the plutonic fluids. Successive envelopes of hydrothermal alteration typically enclose a core of ore minerals disseminated in often stockwork
-forming hairline fractures and veins. Porphyry orebodies typically contain between 0.4 and 1 % copper
with smaller amounts of other metals such as molybdenum
, silver
and gold
.
The first mining of low-grade copper porphyry deposits from large open pits coincided roughly with the introduction of steam shovels, the construction of railroads, and a surge in market demand near the start of the 20th century. Some mines exploit porphyry deposits that contain sufficient gold or molybdenum, but little or no copper.
Porphyry copper deposits are currently the largest source of copper ore. Most of the known porphyrys are concentrated in: western South and North America and Southeast Asia and Oceana - along the Pacific Ring of Fire
; the Caribbean; southern central Europe and the area around eastern Turkey; scattered areas in China, the Mideast, Russia, and the CIS states; and eastern Australia. Only a few are identified in Africa, in Namibia and Zambia; none are known in Antarctica. The greatest concentration of the largest copper porphyrys is in Chile. Almost all mines exploiting large porphyry deposits produce from open pits.
Porphyry copper deposits are typically mined by open-pit
methods.
, many of which contain very little copper. Examples of porphyry molybdenum deposits are the Climax
, Urad, and Henderson
deposits in central Colorado
, and the Questa
deposit in northern New Mexico
.
The US Geological Survey has classed the Chorolque and Catavi
tin deposits in Bolivia
as porphyry tin deposits.
Some porphyry copper deposits in oceanic crust environments, such as those in the Philippines
, Indonesia
, and Papua New Guinea
, are sufficiently rich in gold that they are called copper-gold porphyry deposits.
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
bodies which are associated with porphyritic
Porphyry (geology)
Porphyry is a variety of igneous rock consisting of large-grained crystals, such as feldspar or quartz, dispersed in a fine-grained feldspathic matrix or groundmass. The larger crystals are called phenocrysts...
intrusive rocks and the fluids that accompany them during the transition and cooling from magma to rock. Circulating surface water or underground fluids may interact with the plutonic fluids. Successive envelopes of hydrothermal alteration typically enclose a core of ore minerals disseminated in often stockwork
Stockwork
In geology, a stockwork is a complex system of structurally controlled or randomly oriented veins. Stockworks are common in many ore deposit types and especially notable in greisens. They are also referred to as stringer zones....
-forming hairline fractures and veins. Porphyry orebodies typically contain between 0.4 and 1 % copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
with smaller amounts of other metals such as molybdenum
Molybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
, silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
and gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
.
The first mining of low-grade copper porphyry deposits from large open pits coincided roughly with the introduction of steam shovels, the construction of railroads, and a surge in market demand near the start of the 20th century. Some mines exploit porphyry deposits that contain sufficient gold or molybdenum, but little or no copper.
Porphyry copper deposits are currently the largest source of copper ore. Most of the known porphyrys are concentrated in: western South and North America and Southeast Asia and Oceana - along the Pacific Ring of Fire
Ring of Fire
-Music:* Ring of Fire, a Johnny Cash song, written by his wife, June** Ring of Fire: The Best of Johnny Cash, an album by Johnny Cash** Ring of Fire , a musical theater production on the life of Johnny Cash...
; the Caribbean; southern central Europe and the area around eastern Turkey; scattered areas in China, the Mideast, Russia, and the CIS states; and eastern Australia. Only a few are identified in Africa, in Namibia and Zambia; none are known in Antarctica. The greatest concentration of the largest copper porphyrys is in Chile. Almost all mines exploiting large porphyry deposits produce from open pits.
Characteristics
Characteristics of porphyry copper deposits include:- The orebodies are associated with multiple intrusions and dikesDike (geology)A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...
of dioriteDioriteDiorite is a grey to dark grey intermediate intrusive igneous rock composed principally of plagioclase feldspar , biotite, hornblende, and/or pyroxene. It may contain small amounts of quartz, microcline and olivine. Zircon, apatite, sphene, magnetite, ilmenite and sulfides occur as accessory...
to quartz monzoniteQuartz monzoniteQuartz monzonite is an intrusive igneous rock that has an approximately equal proportion of orthoclase and plagioclase feldspars. The plagioclase is typically intermediate to sodic in composition, andesine to oligoclase. Quartz is present in significant amounts. Biotite and/or hornblende...
composition with porphyritic textures. - BrecciaBrecciaBreccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
zones with angular or locally rounded fragments are commonly associated with the intrusives. The sulfideSulfide mineralThe sulfide minerals are a class of minerals containing sulfide as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides, the arsenides, the antimonides, the bismuthinides, the sulfarsenides and the sulfosalts...
mineralization typically occurs between or within fragments. - The deposits typically have an outer epidoteEpidoteEpidote is a calcium aluminium iron sorosilicate mineral, Ca2Al2O, crystallizing in the monoclinic system. Well-developed crystals are of frequent occurrence: they are commonly prismatic in habit, the direction of elongation being perpendicular to the single plane of symmetry. The faces are often...
- chloriteChlorite groupThe chlorites are a group of phyllosilicate minerals. Chlorites can be described by the following four endmembers based on their chemistry via substitution of the following four elements in the silicate lattice; Mg, Fe, Ni, and Mn....
mineral alteration zone. - A quartzQuartzQuartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
- sericiteSericiteSericite is a fine grained mica, similar to muscovite, illite, or paragonite. Sericite is a common alteration mineral of orthoclase or plagioclase feldspars in areas that have been subjected to hydrothermal alteration typically associated with copper, tin, or other hydrothermal ore deposits...
alteration zone typically occurs closer to the center and may overprint. - A central potassic zone of secondary biotiteBiotiteBiotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
and orthoclaseOrthoclaseOrthoclase is an important tectosilicate mineral which forms igneous rock. The name is from the Greek for "straight fracture," because its two cleavage planes are at right angles to each other. Alternate names are alkali feldspar and potassium feldspar...
alteration is commonly associated with most of the ore. - Fractures are often filled or coated by sulfides, or by quartz veinsVein (geology)In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation...
with sulfides. Closely spaced fractures of several orientations are usually associated with the highest grade ore. - The upper portions of porphyry copper deposits may be subjected to supergeneSupergene (geology)In ore deposit geology, supergene processes or enrichment occur relatively near the surface. Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering. The descending meteoric waters oxidize the primary sulfide ore minerals and...
enrichment. This involves the metals in the upper portion being dissolved and carried down to below the water table, where they precipitate.
Porphyry copper deposits are typically mined by open-pit
Open-pit mining
Open-pit mining or opencast mining refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow....
methods.
Examples of porphyry copper deposits
- La CaridadLa CaridadLa Caridad is one of eight parishes in the El Franco municipality, within the province and autonomous community of Asturias, in northern Spain.The population is 1,796 .-Villages:* Arboces* Llóngara...
, SonoraSonoraSonora officially Estado Libre y Soberano de Sonora is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided into 72 municipalities; the capital city is Hermosillo....
, Mexico - Dizon, PhilippinesPhilippinesThe Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
Chile
- Cerro Colorado
- ChuquicamataChuquicamataChuquicamata, or "Chuqui" as it is more familiarly known, is by digged volume the biggest open pit copper mine in the world, located in the north of Chile, 215 km northeast of Antofagasta and 1,240 km north of the capital, Santiago...
- Collahuasi
- EscondidaEscondidaMinera Escondida, which means 'hidden' in Spanish, is a mining company that operates two open pit copper mines in the Atacama Desert, 170 km southeast of Antofagasta in northern Chile. It is currently the highest producing copper mine in the world...
- El Abra
- El Salvador
- El TenienteEl TenienteEl Teniente is an underground copper mine in the Chilean commune of Machalí in Cachapoal Province, O'Higgins Region, near the town of Sewell, above mean sea level in the Andes. Mining at El Teniente is reported to have started as early as 1819...
- Los Pelambres
- Radomiro TomićRadomiro Tomic (mine)The Radomiro Tomić mine is open pit mine that extracts oxide minerals at above sea level in the Andes mountains near to Chuquicamata mine and Calama in northern Chile's Antofagasta Region....
United States
- Ajo, ArizonaAjo, ArizonaAjo is a census-designated place in Pima County, Arizona, United States. The population was 3,705 at the 2000 census. Ajo is located on State Route 85 just from the Mexican border. It is the closest community to Organ Pipe Cactus National Monument....
- Bagdad, ArizonaBagdad, ArizonaBagdad is a copper mining community and census-designated place in Yavapai County, Arizona, United States, in the western part of the state. It is one of only two remaining company towns in Arizona...
- Lavender PitLavender PitThe Lavender Pit is a former open pit copper mine near Bisbee in Cochise County, Arizona, United States. It is located near the famous Copper Queen Mine. The Lavender Pit was named in honor ofHarrison M...
, Bisbee, ArizonaBisbee, ArizonaBisbee is a city in Cochise County, Arizona, United States, 82 miles southeast of Tucson. According to 2005 Census Bureau estimates, the population of the city was 6,177... - Morenci, ArizonaMorenci, ArizonaMorenci is a census-designated place in Greenlee County, Arizona, United States. The population was 1,879 at the 2000 census. It is part of the Safford Micropolitan Statistical Area...
- Pebble MinePebble MinePebble Mine is the common name of an advanced mineral exploration project investigating a very large porphyry copper, gold, and molybdenum mineral deposit in the Bristol Bay region of Southwest Alaska, near Lake Iliamna and Lake Clark. The proposal to mine the ore deposit, using large-scale...
, AlaskaAlaskaAlaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait... - Safford MineSafford MineThe Safford Mine is an open-pit copper mine located in Graham County, Arizona, eight miles north of the city of Safford. The mine is owned and operated by Freeport-McMoran Copper & Gold....
, Safford, ArizonaSafford, Arizona- History :Safford was founded by Joshua Eaton Bailey, Hiram Kennedy and Edward Tuttle, who came from Gila Bend, in southwestern Arizona. They left Gila Bend in the winter of 1873-74; their work on canals and dams having been destroyed by high water the previous summer... - San Manuel, ArizonaSan Manuel, ArizonaSan Manuel is a census-designated place in Pinal County, Arizona, United States. The population was 4,375 at the 2000 census.San Manuel was built in 1953 as a company town to serve the then-new San Manuel copper mine, mill and smelter complex. The mine and smelter were permanently closed in...
- Sierrita, Arizona
- Resolution CopperResolution copperResolution Copper, , is a joint venture owned by Rio Tinto and BHP, formed to develop and operate an underground copper mine on deeded, unpatented and land removed from mining by executive order at Superior, Arizona, U.S. The project targets a deep-seated porphyry copper deposit located under the...
, Superior, Arizona - El ChinoEl Chino MineThe Chino Mine , also known as the Santa Rita mine, is an open-pit copper mine located in the town of Santa Rita, New Mexico east of Silver City. The mine was started as the Chino Copper Company in 1909 by mining engineer John M. Sully, and is currently owned and operated by Freeport-McMoRan...
, Santa Rita, New MexicoSanta Rita, New MexicoSanta Rita is a ghost town in Grant County in the U.S. state of New Mexico. The site of El Chino copper mine, Santa Rita was located fifteen miles east of Silver City.-History:... - Ely, NevadaEly, NevadaEly is the largest city and county seat of White Pine County, Nevada, United States. Ely was founded as a stagecoach station along the Pony Express and Central Overland Route. Ely's mining boom came later than the other towns along US 50, with the discovery of copper in 1906...
- Bingham Canyon MineBingham Canyon MineThe Bingham Canyon Mine, also known as the Kennecott Copper Mine, is an open-pit mining operation extracting a large porphyry copper deposit southwest of Salt Lake City, Utah, USA, in the Oquirrh Mountains. It is the deepest open-pit mine in the world. The mine is owned by Rio Tinto Group, an...
, UtahUtahUtah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the... - Ray Mine, Arizona
Australia
- Cadia-Ridgeway Mine, New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, copper-gold deposit mined by open pit and block caving. - NorthparkesNorthparkesNorthparkes is a copper and gold mine located in central New South Wales, Australia, approximately 27 kilometers north-northwest of the town of Parkes....
copper porphyry deposit, New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, with 63 million tonnes at 1.1% Cu and 0.5 ppmPPM- Culture :*Peter, Paul and Mary, a 1960s folk music trio*Picture Postcard Monthly, a magazine for collectors of postcards*Please Please Me, the first album by The Beatles- Health :*Permanent pacemaker or artificial pacemaker...
Au. - Boddington, Western AustraliaBoddington, Western AustraliaBoddington is a town and shire in the Peel region of Western Australia, located south-east of Perth. The town sits on the road from Pinjarra to Williams on the Hotham River...
, one of the largest Archaean gold porphyry deposits in Australia
Indonesia
- Grasberg mineGrasberg mineThe Grasberg Mine is the largest gold mine and the third largest copper mine in the world. It is located in the province of Papua in Indonesia near Puncak Jaya, the highest mountain in Papua, and it has 19,500 employees...
, at >3 billion tonnes at 1 ppm Au, is one of the world's largest and richest porphyry deposits of any type
Porphyry-type ore deposits for metals other than copper
Copper is not the only metal that occurs in porphyry deposits. There are also porphyry ore deposits mined primarily for molybdenumMolybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
, many of which contain very little copper. Examples of porphyry molybdenum deposits are the Climax
Climax mine
The Climax mine, located in Climax, Colorado, United States, was a major molybdenum mine in Lake and Summit counties, Colorado. In its heyday, the Climax mine was the largest molybdenum mine in the world, and for many years it supplied three-fourths of the world's supply of molbdenum...
, Urad, and Henderson
Henderson molybdenum mine
The Henderson molybdenum mine is a large underground molybdenum mine west of the town of Empire in Clear Creek County, Colorado, USA. The Henderson mine, which has produced molybdenum since 1976, is owned by Freeport-McMoRan....
deposits in central Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
, and the Questa
Questa, New Mexico
Questa is a village in Taos County, New Mexico, United States. The population was 1,864 at the 2000 census. Located on the Enchanted Circle scenic highway, near the confluence of the Rio Grande and the Red River, Questa is the least tourist-oriented town on the route...
deposit in northern New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
.
The US Geological Survey has classed the Chorolque and Catavi
Catavi
Catavi is a tin mine in Bolivia, near the city of Llallagua in the province of Bustillos, Potosí Department. Along with the Siglo XX mine, it is part of a mining complex in the area.-History:...
tin deposits in Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
as porphyry tin deposits.
Some porphyry copper deposits in oceanic crust environments, such as those in the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, and Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
, are sufficiently rich in gold that they are called copper-gold porphyry deposits.