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La Candelaria

Chile

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The La Candelaria deposit is located some 20 km south of Copiapo. Like Mantoverde and Mantos Blancos it is localised near the Atacama Fault Zone within the Central Andean Coastal Cordillera (or Central Andean Coastal Belt) of northern Chile, and the Chilean Iron Belt (#Location: 27° 30' 55"S, 70° 17' 19"W).

The Central Andean Coastal Belt comprises a Late Jurassic to Early Cretaceous volcano-plutonic belt (Sillitoe, 2003) that is is characterised by voluminous tholeiitic to calc-alkaline volcanic piles and plutonic complexes of primitive mantle origin gabbro to granodiorite. It is associated with an extensional to transtensional event when the underlying crust was attenuated and subjected to high heat flow. All of the intrusive rocks are oxidised and belong to the magnetite series (Charrier et al., 2007; Sillitoe, 2003 and sources cited therin). This belt contains a series of IOCG sensu stricto Cu-Au and other iron oxide-alkali altered mineralisation, such as magnetite-apatite deposits, distributed over a north-south interval of >500 km, with related manto deposits further to the north and south.
  The Candelaria deposit lies within the almost continuously altered, but discontinuously mineralised, Punta del Cobre district, which occupies an area of ~20 × 5 km along the eastern margin of the 120 to 97 Ma Copiapó batholith (Williams et al., 2005; Arévalo, 2006). This batholith, which lies immediately to the east of older Jurassic to Early Cretaceous (>125 Ma) granitoids, comprises the larger ~119 Ma La Brea pluton and ~110 Ma San Gregorio plutonic complex close to Candelaria, one of a group of smaller, similarly aged (111 to 106 Ma) intrusions on the eastern margin of the Copiapó batholith (Arévalo et al., 2006).
  The district is characterised by a ~12 × 5 km envelope of sodic±calcic alteration, superimposed upon volcanic, sedimentary and intrusive rocks. This alteration is manifested as either (1) albite or sodic-plagioclase, and/ or (2) scapolite, with or without calcic amphibole (mainly actinolite, ferro-actinolite, or actinolitic hornblende), pyroxene and/or epidote. Voluminous sodic scapolite-rich assemblages, commonly (but not always) associated with calcic-amphibole and/or pyroxene±epidote±andradite, are usually stratabound, and within the Abundancia and upper Punta del Cobre formations, largely above the ore zone, possibly representing metamorphosed evaporitic beds in these Early Cretaceous units. These rocks also host small magnetite±chalcopyrite-pyrite mantos.
  In contrast, where sodic alteration is predominantly albitisation, it is more commonly discordant and pervasive, occurring in igneous rocks, locally with associated minor pyrite±trace chalcopyrite and/or veinlets and disseminations of hematite (Marschik and Fontboté, 2001). Some of the early albite may be due to spilitisation of volcanics, rather than alteration (Ullrich and Clark, 1999). The overall sodic-calcic zone is enveloped by rocks that were affected by propylitisation, and/or contact thermal metamorphic skarn/hornfels alteration related to the Copiapó batholith (Marschik et al., 2003). The contact between the sodic and thermal metamorphism is gradational (Marschik and Fontboté, 2001).
  The more extensive thermal metamorphic aureole of the batholith, extends over a length of >20 km and width of 2 to 5 km from the contact, producing hornfels and skarns with mineralogies that are dependent upon the host rock, and distance from the contact. Skarn minerals in the thermal aureole include proximal diopsidic-hedenbergite, pyroxenescapolite±andraditic garnet, to distal biotite/quartz/pyroxene±epidote±K feldspar hornfels (Marschik et al., 2000). Early pervasive albitisation accompanied the introduction of widespread specularite, occurring in dilational fractures and open spaces. It preceded, and encloses cores of potassic alteration in the district, and occurs below and peripheral to the 116 to 114 Ma pervasive, brown biotite-quartzmagnetite stage (Mathur et al., 2002), and associated almandine±cordierite alteration that accompanied early barren, more intense magnetite mineralisation. This early magnetite was mainly composed of mushketovite after hematite, indicating a shift to more reducing conditions and/or higher temperatures (Marschik and Fontboté, 2001), and more than one pulse and source of iron oxide alteration (Mathur et al., 2002).
  The deposit lies near the core of the district wide Tierra Amarilla antiform, part of the Paipote fold and thrust system, 20 km to the east of the main Atacama Fault Zone (AFZ). The ore zone is relatively flat lying, broadly concordant with the host sequence of coarse-grained volcaniclastics and massive volcanic flows, breccias and tuffaceous rocks, and a broad, similarly flat-dipping shear zone, with hanging wall evaporite-bearing -limestone, shale and epiclastic rocks.
  The deposit is capped by the base of the 2 km thick Chañarcillo Group (comprising the Abundancia, Nantoco, Totoralilio and Pabellón formations) that was laid down immediately prior to the mineralisation, and hence the depth of formation is assumed to correspond to the thickness of that unit.
  The early pre-ore alteration described thus far, is overprinted by a younger (112 to 110 Ma; Mathur et al., 2002), more areally restricted, ore-related intense potassic±calcic alteration (K feldspar-biotite-amphibole) phase, although Re-Os ages of 115 to 114 Ma for molybdenite (Mathur et al., 2002) and two ~111 Ma dates for amphibole and biotite associated with chalcopyrite (Ullrich and Clark, 1999; Arévalo 1999), could represent the main sulphide phase. Fluids associated with the main stage sulphide mineralisation are hypersaline and CO2-bearing (Marschik and Fontboté, 2001).
  The ore at Candelaria is associated with a complex, multistage event, and occurs: (1) as bodies that are roughly concordant with stratification and comprise replacements and pore filling (mantos); (2) in the matrix to hydrothermal breccias and pseudobreccias; (3) superimposed on massive magnetite replacement bodies; (4) as discontinuous veinlets and stringers in altered host rock; and (5) as massive veins (Marschik et al., 2000; Marschik and Fontboté 2001). The breccia ores represent intervals of high copper grade.
  They generally occur as irregular zones, and sometimes lens-shaped bodies, 1 to 3 m thick, which are concordant with stratification. They comprise a chalcopyrite-pyrite-magnetite matrix between brecciated, biotite altered, metavolcanic rock clasts. Clasts are very angular to locally rounded, from a few to tens of cm across. The margins of breccia bodies are diffuse and defined by a decrease in the amount of sulphide matrix. Individual clast borders are sharp and form jigsaw patterns, indicating limited transport and rotation after fragmentation, although some may represent replacive pseudo-breccia. The concordant lens-like replacement and pore-infill manto bodies resemble breccias where sulphides fill pore spaces between angular to rounded volcanic and sedimentary breccia clasts. Networks of veins as they are enlarged also form a pseudo-breccia texture (Arévalo et al., 2006).

Candelaria Setting

The geology and superimposed alteration of the Candelaria-Punta del Cobre district of northern Chile (a). All of the known deposits lie within the Paipote fold and thrust system (which includes the steeply dipping Ojancos-Florida Shear Zone separating the Copiapó Batholith from the host Punta del Cobre Formation west of the Candelaria mine; as well as the Paipote, Ladrillos and Cerrillos thrusts and Tierra Amarilla anticline). This structural corridor is part of the regional Chivato fault system, which is ~20 km east of the main Atacama Fault Zone (top-left). The largest deposits, Candelaria and Carola are associated with potassic alteration within the broader sodic-calcic zone. Note the potassic core surrounding the Candelaria deposit is the exposure within the open pit mine, not an original pre-mine outcrop. The sodic-calcic alteration includes both stratabound alteration within the overlying Abundancia and Nantoco formations (possibly related to hydrothermal modification of evaporite-bearing beds within those units), and pervasive, discordant alteration within the volcanic and volcaniclastic rocks of the Punta del Cobre Formation (after Marschik et al., 2000; Marschik and Fontboté, 2001; Arévalo et al., 2006).
East-west cross section through the Candelaria mine (b). The diagram illustrates the distribution of the manto-like early magnetite and the outline of the overprinting +0.4% Cu orebody, both of which are largely confined to the coarse stratified volcaniclastic breccias and interlayered massive andesites of the Lower Andesites, and the flat-lying Candelaria Shear that caps this unit and the ore deposit. Note the concentration of steep faults near the core of the deposit. Distribution of alteration within the section comprises albite/sodic plagioclase-quartz-biotite-magnetite±K feldspar minor Ca amphibole below the orebody; biotite-quartz-magnetite±K feldspar and abundant Ca amphibole (largely actinolite) within the ore zone; biotite-quartz- almandine±cordierite and common Ca amphibole within the upper Candelaria Shear; biotite-amphibole with K or Na feldspar in the tuffs and volcaniclastic sediments and Upper Andesites above the shear; and scapolite±quartz±pyroxene±Ca amphibole within the overlying Abundancia Formation (after Marschik et al., 2000; Marschik and Fontboté, 2001; Arévalo et al., 2006).



  Copper ore is associated with magnetite and/or hematite and is dominantly composed of chalcopyrite and pyrite, with gold occurring as small inclusions in the chalcopyrite, within micro-fractures in pyrite and as a mercury-goldsilver alloy (Williams et al., 2005).
  At the deeper levels in the mineralised system, chalcopyrite has a close spatial association with calcic amphibole (mainly actinolite) in an assemblage that also includes biotite, K feldspar±epidote±sodic plagioclase. Magnetite is ubiquitous, occurring as massive bodies, with or without superimposed sulphide mineralisation, although hematite is rare. Intermediate levels, are characterised by potassic alteration (biotite and/or K feldspar), with or without local developments of calcic amphibole±epidote, sodic plagioclase, and/or local anhydrite. In shallower and distal parts of the system, chlorite is developed at the expense of biotite and amphibole, and albite, chlorite and carbonate alteration increases in intensity. Peripheral to the mineralisation, hematite becomes the dominant iron oxide (Williams et al., 2005). This alteration pattern is complicated by the influence of contact metamorphism related to components of the 120 to 97 Ma Copiapó batholith, as described above. The increasing sodiccalcic alteration in the upper levels of the Candelaria pit area, above the potassic and chloritic zones, may reflect the overlying evaporite-bearing Abundancia Formation (Marschik and Fontboté, 2001).
  Marschik and Fontboté (2001), describe a paragenetic sequence over-printing the early, district scale stage of iron metasomatism and associated pervasive albite alteration, comprising:
  1) a high temperature (600 to 500°C), pre-ore iron oxide stage, comprising pervasive magnetite (mushketovite)-quartz-biotite;
  2) the main sulphide ore stage at 500 to 300°C, represented by chalcopyrite and pyrite; and
  3) the late stage at <250°C, with hematite-calcite and locally minor sulphides.
  Sulphides from Candelaria and some other occurrences in the Punta del Cobre district yielded δ
34SCDT values largely between -3.2 and +3.1‰, with some as high as 7.2‰ for late stage mineralisation, or up to 6.8‰ in the marginal parts of the system (Rabbia et al., 1996; Ullrich and Clark, 1999; Marschik and Fontboté 2001). Marschik and Fontboté (2001) interpret these isotopic data to be consistent with a dominantly magmatic source for sulphur, with a minor contribution during their stage 2, but definite influence in stage 3, from a peripheral evaporite-bearing sedimentary host sequence (e.g., Mathur et al., 2002; Marschik and Fontboté 2001; Ullrich and Clark, 1999).
  Barton et al. (2005) reported that unpublished Sr isotope data for altered and host rocks in Candelaria-Punta del Cobre district, during both early sodic-calcic and late potassic stages of hydrothermal activity imply there are large contributions of non-igneous Sr, implying the ore systems involved influx of fluids from outside the local batholithic granitoids.
  Arévalo et al. (2006) note that the sulphide ages quoted above, corresponds closely to that of the San Gregorio plutonic complex of the Copiapó batholith, supporting a magmatic origin for the main sulphide mineralisation. They interpret the sulphide mineralisation to have been the product of magmatic fluids of a cooling hydrothermal system, emplaced during synplutonic deformation and dilation at the ductile-brittle transition, in the thermal aureole of the San Gregorio plutonic complex.
  An isochron calculated by Re/Os ratios from hydrothermal magnetite and sulphides at Candelaria and the small satellite deposit Bronce, constrains initial
187Os/188Os ratios of 0.36±0.10 and 0.33±0.01 respectively. These values are broadly similar to the calculated initial 187Os/188Os ratio for magmatic magnetite in nearby batholithic rocks that range from 0.20 to 0.41. These relatively radiogenic ratios also represent a mixture of mantle and crustal components in both the ores and batholitic rocks (Mathur et al., 2002).

The pre-mining mineable reserve comprised 470 Mt @ 0.95% Cu, 0.22 g/t Au, 3.1 g/t Ag within a geological resource of 600 Mt at a similar grade.

The mine is operated by the Freeport subsidiary Compania Contractual Minera Candelaria.

The most recent source geological information used to prepare this summary was dated: 2001.    
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.


Candelaria

  References & Additional Information
   Selected References:
Arevalo C, Grocott G, Martin W, Pringle M and Taylor G,  2006 - Structural Setting of the Candelaria Fe Oxide Cu-Au Deposit, Chilean Andes: in    Econ. Geol.   v101 pp 819-841
Chen H,  2010 - Mesozoic IOCG Mineralisation in the Central Andes: an Updated Review: in Porter T M, (Ed),  2010 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective PGC Publishing, Adelaide   v.3 pp. 259-272
Chen H, Cooke D R and Baker M J,  2013 - Mesozoic Iron Oxide Copper-Gold Mineralization in the Central Andes and the Gondwana Supercontinent Breakup: in    Econ. Geol.   v.108 pp. 37-44
del Real, I., Thompson, J.F.H., Simon, A.C. and Reich, M.,  2020 - Geochemical and Isotopic Signature of Pyrite as a Proxy for Fluid Source and Evolution in the Candelaria-Punta del Cobre Iron Oxide Copper-Gold District, Chile: in    Econ. Geol.   v.115, pp. 1493-1518.
Huang, X.-W. and Beaudoin, G.,  2019 - Textures and Chemical Compositions of Magnetite from Iron Oxide Copper-Gold (IOCG) and Kiruna-Type Iron Oxide-Apatite (IOA) Deposits and Their Implications for Ore Genesis and Magnetite Classification Schemes: in    Econ. Geol.   v.114, pp. 953-979.
Marschik R and Fontbote L,  2001 - The Punta del Cobre Formation, Punta del Cobre-Candelaria area, Chile: in    J. of South American Earth Sciences   v14 pp 401-433
Marschik R and Sollner F,   2006 - Early Cretaceous U-Pb zircon ages for the Copiapo plutonic complex and implications for the IOCG mineralization at Candelaria, Atacama Region, Chile : in    Mineralium Deposita   v41 pp 785-801
Marschik R, Chiaradia M, Fontbote L  2003 - Implications of Pb isotope signatures of rocks and iron oxide Cu-Au ores in the Candelaria-Punta del Cobre district, Chile: in    Mineralium Deposita   v38 pp 900-912
Marschik R, Fontbote L  2001 - The Candelaria-Punta del Cobre Iron Oxide Cu-Au(-Zn-Ag) deposits, Chile: in    Econ. Geol.   v96 pp 1799-1826
Marschik R, Fontbote L  1996 - Copper (-iron) mineralization and superposition of alteration events in the Punta del Cobre Belt, Northern Chile: in Camus E, Sillitoe R H, Peterson R (Eds), 1996 Andean Copper Deposits: New Discoveries, Mineralisation, Styles and Metallogeny Soc. Econ. Geol.   Spec Pub no. 5 pp 171-190
Marschik R, Leveille R A, Martin W  2000 - La Candelaria and the Punta del Cobre district, Chile: Early Cretaceous iron oxide Cu-Au(Zn-Ag) mineralisation: in Porter T M (Ed), 2000 Hydrothermal Iron Oxide Copper-Gold & Related Deposits: A Global Perspective PGC Publishing, Adelaide   v1 pp. 163-175
Marschik, R, and Kendrick, M.A.,  2015 - Noble gas and halogen constraints on fluid sources in iron oxide-copper-gold mineralization: Mantoverde and La Candelaria, Northern Chile: in    Mineralium Deposita   v.50 pp. 357-371
Mathur R, Marschik R, Ruiz J, Munizaga F, Leveille R A, Martin W  2002 - Age of mineralization of the Candelaria Fe oxide Cu-Au deposit and the origin of the Chilean Iron Belt, based on Re-Os isotopes: in    Econ. Geol.   v97 pp 59-71
Oyarzun R, Rodrguez M, PincheiraM, Doblas M, Helle S  1999 - The Candelaria (Cu-Fe-Au) and Punta del Cobre (Cu-Fe) deposits (Copiapo, Chile): a case for extension-related granitoid emplacement and mineralization processes?: in    Mineralium Deposita   v34 pp 799-801
Porter T M,  2010 - Current Understanding of Iron Oxide Associated-Alkali Altered Mineralised Systems: Part II, A Review: in Porter T M, (Ed),  2010 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective, PGC Publishing, Adelaide   v.3 pp. 33-106
Richards, J.P., Lopez, G.P., Zhu, J-.J., Creaser, R.A., Locock, A.J. and Mumin, A.H.,  2017 - Contrasting Tectonic Settings and Sulfur Contents of Magmas Associated with Cretaceous Porphyry Cu ± Mo ± Au and Intrusion-Related Iron Oxide Cu-Au Deposits in Northern Chile: in    Econ. Geol.   v.112, pp. 295-318.
Rodriguez-Mustafa, M.A., Simon, A.C., del Real, I., Thompson, J.F.H., Bilenker, L.D., Barra, F,. Bindeman, I. and Cadwell, D.,  2020 - A Continuum from Iron Oxide Copper-Gold to Iron Oxide-Apatite Deposits: Evidence from Fe and O Stable Isotopes and Trace Element Chemistry of Magnetite: in    Econ. Geol.   v.115, pp. 1443-1459.
Ryan P J, Lawrence A L, Jenkins R A, Matthews J P, Zamora J C, Marino E, Diaz I U  1995 - The Candelaria copper-gold deposit, Chile: in Pierce F W, Bolm J G, (Eds),  Porphyry Copper Deposits of the American Cordillera Arizona Geological Society    Digest 20 pp 625-645.
Sillitoe R H  2003 - Iron oxide-copper-gold deposits: an Andean view: in    Mineralium Deposita   v38 pp 787-812
Tornos F, Wiedenbeck M and Velasco F,  2012 - The boron isotope geochemistry of tourmaline-rich alteration in the IOCG systems of northern Chile: implications for a magmatic-hydrothermal origin: in  2012  Mineralium Deposita   v.47 pp. 483-499
Ullrich T D, Clark A H  1999 - The Candelaria copper-gold deposit, Region III, Chile: Paragenesis, geochronology and fluid composition: in Stanley, et. al., (Eds),  Mineral Deposits: Processes to Processing Balkema, Rotterdam    pp 201-204
Williams P J, Barton M D, Johnson D A, Fontbote L, de Haller A, Mark G, Oliver N H S and Marschik R,  2005 - Iron oxide copper-gold deposits: Geology, space-time distribution and possible modes of origin: in Hedenquist J W, Thompson J F H, Goldfarb R J and Richards J P (Eds.), 2005 Economic Geology 100th Anniversary Volume, Society of Economic Geologists, Denver,    pp 371-405
Williams, P. J., Kendrick, M.A. and Xavier, R.P.,  2010 - Sources of Ore Fluid Components in IOCG Deposits: in Porter T M, (Ed), 2010 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective PGC Publishing, Adelaide   v.3, pp. 107-116.
Zhu, Z.,  2016 - Gold in iron oxide copper-gold deposits: in    Ore Geology Reviews   v.72, pp. 37-42.

   References in PGC Publishing Books: Want any of our books ? Pricelist
Marschik R, Leveille R A, 2000 - La Candelaria and the Punta del Cobre District: Early Cretaceous Iron-Oxide Cu-Au(-Zn-Ag) Mineralization,   in  Porter T M, (Ed.),  Hydrothermal Iron Oxide Copper-Gold & Related Deposits: A Global Perspective,  v1  pp 163-175
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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 takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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