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El Teniente |
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Chile |
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Cu Mo
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Super Porphyry Cu and Au
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The El Teniente porphyry/breccia style copper-molybdenum ore deposit is located at Colon, some 80 km to the southeast of Santiago, and 35 km ENE of Rancagua in Chile (#Location: 34° 6' 2"S, 70° 27' 31"W).
The deposit supports the world's largest underground copper mine, which in 1999 produced 35 Mt of ore averaging 1.16% Cu, yielding 0.346 Mt of fine copper. In 2015, it produced 0.471 Mt of fine copper, and >22 Mt of copper since operations commenced 110 years ago. It is also possibly the largest copper deposit in the world containing more than 94 Mt of recoverable copper in ores with a grade in excess of 0.67% Cu.
For details of the tectonic, metallogenic and regional setting, see the Andean Cu-Au-base metals province - Central Andes and Bolivian Orocline record.
El Teniente is the southernmost of the Andean "super porphyries" and was emplaced in multiple telescoped Late Miocene to Pliocene magmatic-hydrothermal biotite, anhydrite and tourmaline breccias hosted by middle Miocene mafic intrusive and extrusive rocks within a semi-regional sequence of Cretaceous to Quaternary volcanics, continental sediments and felsic to intermediate intrusives.
Three distinct felsic intrusives cut both the breccias and the mafic intrusive hosts which were previously interpreted to have been altered andesites of the lower member of the surrounding Miocene Farellones Formation. Recent mapping has shown that in the mine area the mafic to intermediate hosts into which the felsic intrusives have been intruded belong to a pervasively biotite altered mafic intrusive complex of gabbros, dolerites (diabases), porphyritic basalts and basaltic andesites.
Regionally the Farellones Formation, which is cut by both the mafic complex and the felsic volcanics, comprises a Lower member of massive andesite flows overlain by the epidotised andesitic flows with intercalated reddish lacustrine sediments of the Middle member which are in turn unconformably followed by the basalt and andesite flows and intercalated pyroclastics of the Upper member.
The three felsic intrusives which were emplaced into the earlier mineralised mafic complex, comprise: i). The quartz-diorite to tonalite present in four stocks dated at 5.67 to 5.46±0.19 Ma. The main diorite, the Sewell Diorite, is present as irregular stocks with surface dimensions of around 200 m across, but increasing in size with depth, with a phaneritic core, an outer porphyritic crust and brecciated outer contacts. The stocks have been subjected to potassic (feldspar and biotite) alteration over printed by strong quartz-sericite-chlorite developed from the alteration halos of veinlets. Some apophyses have brecciated contacts characterised by strong silicification and sericitisation. ii). The northern dacite porphyry, the Teniente Porphyry, dated at 5.28±0.10 Ma, is represented as a north-south trending, tabular, sub-vertical 1500x200 m body intruding mafic rocks with sharp but irregular contacts. iii). Central 4.82±0.09 Ma latite ring dykes with a related cataclysmic explosive diatreme breccia pipe in the centre of the deposit, the Braden Breccia Pipe. At depth the latite occurs as a ring dyke complex centred on the breccia. The breccia was emplaced late in the mineralising sequence, truncating the Teniente Porphyry and containing mineralised clasts.
The majority of the high grade (>1% Cu) hypogene copper ore is found within and is encompassed by multiple magmatic-hydrothermal breccia pipes and breccia pipe complexes with vertical extents of more than 1.5 km. These breccias are developed within the mineralised and pervasively biotite-altered mafic complex and include copper and sulphide rich igneous, tourmaline, anhydrite, magnetite and rock flour breccias. They are surrounded by a dense stockwork of biotite veining that coalesces to form the pervasive biotite alteration. The copper mineralisation is characterised by dominant chalcopyrite with lesser bornite and pyrite.
Later veins with various amounts of quartz, anhydrite, sericite, chlorite, tourmaline, feldspars and copper sulphides accompanied the felsic intrusions, generating a sericitic zone in the upper parts of the deposit, and contributing additional copper, although in other places re-distributing pre-existing mineralisation. Alteration is related to a late magmatic, a main hydrothermal and a late hydrothermal phase. The late magmatic phase corresponds to the consolidation of the Sewell Diorite and the Teniente Porphyry, and is characterised by potassic alteration as K feldspar and biotite in both the intrusives and the wall rocks, with a propylitic fringe. Mineralisation associated with this stage occurs as veinlets and disseminations with a conspicuous zoning around the Teniente Porphyry, a bornite core, an intermediate chalcopyrite shell and a pyrite rich periphery in the propylitic zone. The main hydrothermal stage is superimposed on the late magmatic phase and is characterised by northeast and lesser northwest trending quartz-sericite-chlorite and anhydrite bearing veinlets and halos which do not pervasively alter the host rocks, except where the density of veining is such that the halos overlap. The main sulphides associated with this phase are chalcopyrite and pyrite as veinlet fillings and disseminated in the halos. The late hydrothermal stage is apparently related to the Marginal Breccia of the Braden Breccia Pipe and is represented by concentric and radial veins and veinlets filled by anhydrite, tourmaline, quartz, chlorite, calcite, siderite and gypsum. Sulphides are chalcopyrite, bornite, pyrite and tennantite-tetrahedrite.
The Braden Breccia Pipe, the dominant litho-structural unit of the deposit is a breccia complex that takes the form of an upward expanding cone with a generally circular surface diameter of around 1200 m and vertical extent of more than 1800 m. The eastern margin is sub-vertical while the western flank dips at 60 to 70 degrees to the east. The breccias is composed of a series of concentric zones, commencing with the outer 50 to 150 m wide Marginal Breccia which encircles the structure, thinning with depth. This zone is characterised by angular to subangular clasts which are variably altered and are lithologically similar to the units the breccia cuts, set in a quartz-tourmaline cement, with lesser anhydrite, copper/iron sulphides (bornite > chalcopyrite) and sulphosalts. In contrast the breccia pipe core is composed of rounded to subangular heterolithic clasts with alteration and mineralisation typical of the clasts' origin, set in a matrix of rock flour cemented by sericite and lesser tourmaline, calcite and sulphides (mainly pyrite). There are a variety of breccias within the pipe, grouped by the predominant clast type, clast size and cement, as well as clasts of breccia, suggesting a complex multiple formation. In places the breccia has a flow lineation imposing a pseudo bedding affect. The dominant breccia is light grey in colour, with poorly sorted subrounded fragments. A posthumous stage accompanies the late stages of the Braden Breccia and comprises an association of sericite, calcite and pyrite in the breccia cement, and altered clasts, with low temperature minerals in cavities, such as gypsum, ankerite, siderite, barite, sphalerite, galena and quartz with chalcopyrite, pyrite, anhydrite, and tourmaline.
Overall the orebody has a gross triangular shape in plan view, elongated to the north where it is centred on the Teniente Porphyry and extending to the south into the Sewell Diorite, while the central zone consists of a low grade zone centred on the Braden Breccia Pipe. The Teniente Porphyry and the central rock flour core of the Braden Breccia are relatively copper poor and are interpreted to have been emplaced at a late stage creating the low grade core.
Post ore amphibole rich andesite dykes have been dated at 3.85±0.18 Ma. These and other latite, lamprophyre and pebble dykes, which average 0.5 to 2 m in thickness and are all un-mineralised, generally dip towards and cut the pipe, forming a conic envelope.
Molybdenite is found in association with all three felsic intrusive phases and in the Braden Breccia matrix. Dating of molybdenite has produced ages of 5.6±0.02 Ma, 4.87±0.03 Ma and 4.42±0.02 Ma, while systematic dating of biotite and sericite alteration produced dates in the range 4.81±0.05 to 4.37±0.05 Ma. It is implied that the deposit was formed by at least three main phases of mineralisation and alteration spanning a period of approximately 1.3 Ma from 5.6 to 4.3 Ma, with the earlier mafic hosted breccias being emplaced from before 6.4 Ma towards the end of a 10 m.y. episode of Miocene and Pliocene magmatic activity.
Vertically the orebody comprises an around 100 m thick oxidation-leaching zone, a supergene enrichment interval that extends to a depth of 500 m in the north with hypogene mineralisation below this to as deep as 1600 m below the surface.
The total reserve + resource at El Teniente has been estimated at (USGS Porphyry copper database, viewed 2014):
20.731 Gt @ 0.62% Cu, 0.019% Mo, 0.52 g/t Ag, 0.005 g/t Au.
Published in situ geological mineral resources at the end of 2014 (Codelco, 2015) at a 0.2% Cu cut-off, were:
Measured resource - 2.704 Gt @ 0.86% Cu;
Indicated resource - 2.819 Gt @ 0.57% Cu;
Inferred resource - 9.948 Gt @ 0.48% Cu;
TOTAL resource - 15.471 Gt @ 0.56% Cu for 87.3 Mt of contained copper.
Published mineral resources in the business and development plan at the end of 2015 (Codelco, 2015) to the mining plan cut-off, were:
Measured resource - 1.445 Gt @ 0.97% Cu;
Indicated resource - 714 Mt @ 0.80% Cu;
Inferred resource - 1.879 Gt @ 0.75% Cu;
TOTAL resource - 4.038 Gt @ 0.84% Cu for 33.8 Mt of contained copper.
Published ore reserves at the end of 2015 (Codelco, 2015), were:
Proved reserves - 649 Mt @ 1.06% Cu;
Probable reserves - 1.024 Gt @ 0.84% Cu;
TOTAL reserve - 1.673 Gt @ 0.93% Cu for 15.5 Mt of contained copper.
For detail consult the reference(s) listed below.
For more detail consult the reference(s) listed below which were the principal source of the information on which this summary was based.
The most recent source geological information used to prepare this decription was dated: 2002.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
El Teniente
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Selected References:
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Astudillo, N., Roperch, P., Townley, B., Arriagada, C. and Chauvin, A., 2010 - Magnetic polarity zonation within the El Teniente copper-molybdenum porphyry deposit, central Chile: in Mineralium Deposita v.45. pp. 23-41,
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Camus F 1975 - Geology of the El Teniente orebody with emphasis on wall-rock alteration: in Econ. Geol. v70 pp 1341-1372
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Cannell, J., Cooke, D.R., Walshe, J.L. and Stein, H. 2005 - Geology, Mineralization, Alteration, and Structural Evolution of the El Teniente Porphyry Cu-Mo Deposit: in Econ. Geol. v.100, pp. 979-1003.
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Cooke, D.R., Agnew, P., Hollings, P., Baker, M., Chang, Z., Wilkinson, J.J., Ahmed, A., White, N.C., Zhang, L., Thompson, J., Gemmell, J.B., Danyushevsky, L. and Chen, H., 2020 - Recent advances in the application of mineral chemistry to exploration for porphyry copper-gold-molybdenum deposits: detecting the geochemical fingerprints and footprints of hypogene mineralization and alteration: in Geochemistry: Exploration, Environment, Analysis, v.20, pp. 176-188.
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Cooke, D.R., Agnew, P., Hollings, P., Baker, M., Chang, Z., Wilkinson, J.J., White, N.C., Zhang, L., Thompson, J., Gemmell, J.B., Fox, N., Chen, H. and Wilkinson, C.C., 2017 - Porphyry Indicator Minerals (PIMS) and Porphyry Vectoring and Fertility Tools (PVFTS) - Indicators of Mineralization Styles and Recorders of Hypogene Geochemical Dispersion Halos: in Tschirhart, V. and Thomas, M.D., (Eds.), 2017 Exploration 17: Sixth Decennial International Conference on Mineral Exploration, Toronto, Canada, October 22 to 25, 2017, Proceedings, Geochemistry, Paper 32, pp. 457-470.
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Hollings, P., Cooke, D. and Clark, A., 2005 - Regional Geochemistry of Tertiary Igneous Rocks in Central Chile: Implications for the Geodynamic Environment of Giant Porphyry Copper and Epithermal Gold Mineralization: in Econ. Geol. v.100, pp. 887-904.
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Klemm L M, Pettke T, Heinrich C A and Campos E, 2007 - Hydrothermal Evolution of the El Teniente Deposit, Chile: Porphyry Cu-Mo Ore Deposition from Low-Salinity Magmatic Fluids: in Econ. Geol. v102 pp 1021-1045
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Maksaev V, Munizaga F, McWilliams M, Fanning M, Mathur R, Ruiz J and Zentilli M, 2004 - New chronology for El Teniente, Chilean Andes, from U=Pb 40Ar/39Ar, Re-Os and fission track dating; Implications for the evolution of a supergiant porphyry Cu-Mo deposit: in Sillitoe R H, Perello J and Vidal C E 2004 Andean Metallogeny: New Discoveries, Concepts and Updates Society of Economic Geologists, Denver, SEG Special Publication 11 pp 15-54
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McInnes B I A, Evans N J, Fu F Q, Garwin S, Belousova E, Griffin W L, Bertens A, Sukarna D, Permanadewi S, Andrew R L and Deckart K, 2005 - Thermal History Analysis of Selected Chilean, Indonesian and Iranian Porphyry Cu-Mo-Au Deposits: in Porter T M (Ed), 2005 Super Porphyry Copper & Gold Deposits - A Global Perspective, PGC Publishing, Adelaide, v.1 pp. 27-42
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McKinnon, S.D. and Barra, I.G., 2003 - Stress field analysis at the El Teniente Mine: evidence for N-S compression in the modern Andes: in J. of Structural Geology v.25, pp. 2125-2139.
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Monecke, T., Monecke, J., Reynolds, T.J., Tsuruoka, S., Bennett, M.M., Skewes, W.B and Palin, R.M., 2018 - Quartz Solubility in the H2O-NaCl System: A Framework for Understanding Vein Formation in Porphyry Copper Deposits: in Econ. Geol. v.113, pp.1007-1046.
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Mpodozis, C. and Cornejo, P., 2012 - Cenozoic Tectonics and Porphyry Copper Systems of the Chilean Andes: in Hedenquist J W, Harris M and Camus F, 2012 Geology and Genesis of Major Copper Deposits and Districts of the World - A tribute to Richard H Sillitoe, Society of Economic Geologists, Denver, Special Publication 16, pp. 329-360
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Rabbia, O.M., Hernandez, L.B., French, D.H., King, R.W. and Ayers, J.C., 2009 - The El Teniente porphyry Cu-Mo deposit from a hydrothermal rutile perspective: in Mineralium Deposita v.44, pp. 849-866.
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Skewes, M.A., Arevalo, A., Floody, R., Zuniga, P. H. and Stern, C.R., 2002 - The giant El Teniente breccia deposit: Hypogene copper distribution and emplacement: in Goldfarb R J, Nielsen R L, (Eds) 2002 Integrated Methods for Discovery: Global Exploration in the 21st Century Soc of Econ. Geologists, Denver Spec. Publ. No. 9, pp. 299-332.
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Skewes, M.A., Arevalo, A., Floody, R., Zuniga, P.H. and Stern, C.R., 2005 - The El Teniente Megabreccia Deposit, the Worlds Largest Copper Deposit: in Porter, T.M. (Ed), 2005 Super Porphyry Copper & Gold Deposits - A Global Perspective, PGC Publishing, Adelaide, v.1, pp. 83-113.
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Stern C R and Skewes M A, 2005 - Origin of Giant Miocene and Pliocene Cu-Mo Deposits in Central Chile: Role of Ridge Subduction, Decreased Subduction Angle, Subduction Erosion, Crustal Thickening, and Long-Lived, Batholith-Size, Open-System Magma Chambers: in Porter, T.M. (Ed), 2005 Super Porphyry Copper & Gold Deposits - A Global Perspective, PGC Publishing, Adelaide, v.1 pp. 65-82
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Stern, C.R., Funk, J.A., Skewes, M.A. and Arevalo, A., 2007 - Magmatic Anhydrite in Plutonic Rocks at the El Teniente Cu-Mo Deposit, Chile, and the Role of Sulfur- and Copper-Rich Magmas in Its Formation: in Econ. Geol. v.102, pp. 1335-1344.
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Vry V H, WilkinsonJ J J, Seguel J and Millan J, 2010 - Multistage Intrusion, Brecciation, and Veining at El Teniente, Chile: Evolution of a Nested Porphyry System : in Econ. Geol. v105 pp 119-153
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Wilkinson, J.J., Baker, M.J., Cooke, D.R. and Wilkinson, C.C., 2020 - Exploration Targeting in Porphyry Cu Systems Using Propylitic Mineral Chemistry: A Case Study of the El Teniente Deposit, Chile: in Econ. Geol. v.115, pp. 771-791.
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| References in PGC Publishing Books: | |
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Stern C R and Skewe M A, 2005 - Origin of Giant Miocene and Pliocene Cu-Mo Deposits in Central Chile: Role of Ridge Subduction, Decreased Subduction Angle, Subduction Erosion, Crustal Thickening, and Long-Lived, Batholith-Size, Open-System Magma Chambers, in Porter T M, (Ed), Super Porphyry Copper and Gold Deposits: A Global Perspective, v1 pp 65-82
 Abstract
Skewes M A, Arevalo A, Floody R, Zuniga P H and Stern C R, 2005 - The El Teniente Megabreccia Deposit, the World’s Largest Copper Deposit, in Porter T M, (Ed), Super Porphyry Copper and Gold Deposits: A Global Perspective, v1 pp 83-112
Abstract
McInnes B I A, Evans N J, Fu F Q, Garwin S, Belousova E, Griffin W L, Bertens A, Djadjang Sukarna, Permanadewi S, Andrew R J and Deckart K, 2005 - Thermal History Analysis of Selected Chilean, Indonesian and Iranian Porphyry Cu-Mo-Au Deposits, in Porter T M, (Ed), Super Porphyry Copper and Gold Deposits: A Global Perspective, v1 pp 27-42
Abstract
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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