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Quinchia District - La Cumbre, El Centro, Dos Quebradas, Miraflores |
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Colombia |
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Au Ag Cu
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Quinchia district contains the main La Cumbre porphyry gold-copper deposit, the similar but less significant El Centro and Dos Quebradas occurrences, and the Miraflores gold-silver rich, magmatic-hydrothermal epithermal breccia pipe. These deposits are located in the municipality of Quinchia, Department of Riseralda, Republic of Colombia, some 190 km WNW of Bogotá.
(#Location: La Cumbre - 5° 17' 43"N, 75° 42' 45"W; Miraflores - 5° 17' 34"N, 75° 41' 41'W).
Artisanal mining has taken place in the Quinchia district from Pre-Colombian to modern times, but was most intensive during the 1950s (Rodriguez et al., 2000). Interest was renewed in the late 1970's and culminated in the 1980's in the Miraflores area with the formation of the 'Associacion de Mineros de Miraflores', a local artisanal mining cooperative. In 2000, INGEOMINAS undertook a series of technical studies in the area including geological mapping, geochemical and geophysical surveying and prognostic resource estimations (Baldys and Anderson, 2010).
From May 2005, Kedahda, a Colombian private subsidiary of Anglogold Ashanti, investigated the area, including 18 drill holes on the the Dos Quebradas, La Cumbre, and El Centro targets at Quinchia and 4 holes at La Cruzada on the Miraflores prospect.
Kedahda concluded that the Miraflores property did not meet their target criteria, and in May, 2007, Kedahda optioned the project to B2Gold who undertook exploration, including a drilling program, until 2010 before withdrawing. Subsequently Miraflores was purchased by Seafield Resources Ltd. Similarly, in 2010, Kedahda sold the Quinchia property to Batero Gold Corp.
Regional Setting
The Quinchia mineralised district is located on the eastern margin of the Western Cordillera of the Colombian Andes, which is underlain by the Romeral Terrane of Cediel and Cáceres (2000) and Cediel et al. (2003). The Romeral Terrane is composed of late Jurassic(?) to Cretaceous oceanic plateau basalts and oceanic sedimentary rocks. This allochthonous terrane obliquely collided with, and was accreted to, the northern Andean palaeo-continental margin from the SW, during the Aptian to Albian (late Lower Cretaceous). The resultant suture, the dextral Romeral fault system, occurs as a broad, tectonic mélange that can be traced for over 1000 km along the northern Andes. The Romeral Fault mélange essentially comprises a >10 km wide series of north-south striking, vertically dipping dextral transcurrent faults that separate mega-scale interleaved slivers of the oceanic allochthon and autochthonous Palaeozoic crustal metamorphic rocks from the palaeo-continental margin. Virtually all lithologic contacts within the Romeral basement are structural, characterized by abundant shearing, mylonitisation and the formation of clay-rich fault gouge.
The structure of the Romeral Fault system is the result of the original collision and various post-Romeral tectonic events, including the successive oblique collision and accretion of the Dagua-Piñón to the western margin of the Romeral Terrane during the Paleogene, separated by the dextral Cauca Fault, and then the Gorgona Terrane and the Panama Microplate to the west of the combined collage during the Neogene.
For detail of the regional setting and geology, see the separate record for the North Andes and Panama copper-gold province.
Cenozoic transtension during these oblique collisional events resulted in the formation of the Cauca-Patia (or Inter-Andean) Graben/Depression (or Central Magmatic Belt) between the Romeral and Cauca faults and a series of pull-apart basins.
Deposition within this depression commenced with the Late Oligocene to Early Miocene siliciclastic sedimentary sequences of the Amaga Formation, including basal conglomerates, quartz sandstones, siltstones, shales and coal. In the Mid to Late Miocene, both the Romeral mélange and the Amaga Formation were overlain by mafic to intermediate volcanic flows and pyroclastics of the Combia Formation, associated with at least one Middle to Late Miocene volcanic arc emplaced into the Romeral Terrane basement. Also associated with late arc formation was the syntectonic emplacement of a series of 8 to 6 Ma (K-Ar whole rock) intrusives of dioritic, granodioritic and monzonitic composition, occurring as polyphase hypabyssal stocks, dykes and sills. These intrusives cut all of the above mentioned stratigraphic units (Cediel et al., 2003).
Structural reactivation during the Miocene resulted in orthogonal compression accompanied by mostly west-directed thrusting and high-angle reverse fault development in the basement rocks. The Amaga Formation was deformed into generally open, upright folds with tilting and near isoclinals folding being associated with generally localised, west-verging thrusting. The Combia Formation records tilting and open folding. Both the Amaga and Combia Formations exhibit moderate to strong diapiric doming where affected by the emplacement of the Mid to Late Miocene intrusive suite. North-south, NE, NW and east-west conjugate shearing and dilational fracturing affects all of the above geologic units. Some of these elements can be observed as structural lineaments traversing the region.
District and Deposit Geology
The Quinchia district is surrounded and underlain by four principal rock sequences, as follows:
• Romeral Terrane basement complex, which comprise a tectonically disrupted suite of mafic and ultramafic oceanic volcanic rocks and granitoid intrusive rocks of the Romeral Terrane that directly host the La Cumbre, Dos Quebradas and Miraflores breccias and associated mineralisation.
Where exposed, the host sequence occurs as fine grained packages of mafic oceanic igneous rocks, including basalt, dolerite and microgabbro of tholeiitic composition, locally interstratified with fine grained pelagic sediments. The mafic igneous rocks are dark grey, altered to dark green in colour, and are macroscopically aphanitic with isolated phenocrysts in a compound groundmass. Original textures are difficult to distinguish due to tectonic disruption, although pillow structures and auto brecciation are occasionally evident, as are amygdules containing zeolites, epidote and chlorite.
In the vicinity of porphyritic intrusive rocks, the mafic lithologies are variably hornfelsed, fractured, veined and hydrothermally altered. Intrusion related fracturing/veining forms as dense quartz-magnetite filled stockworks, accompanied by secondary (hydrothermal) biotite, to produce a potassic assemblage related to porphyry style mineralisation in the intrusions. These assemblages are commonly overprinted by late propylitic alteration, dominantly of chlorite and epidote.
The 97±10 Ma (K/Ar, biotite) Irra stock in the southern part of the Quinchia district is part of the Romeral Terrane. It has a calc-alkaline, granodioritic to monzonitic and locally syenitic composition and covers an area of ~32 km2 area. It is light grey to pink in colour, coarse grained and holocrystalline, and is dominated by andesine and orthoclase±quartz with augite and biotite forming the mafic phases. Contacts between this stock and Romeral basement are structurally modified, and it is unclear whether it was intruded before, during, or after Romeral accretion to the continental margin.
At Miraflores, the wall rock of the mineralised breccia pipe is composed of massive basalts and pillow lava basalts, which have been subjected to propylitic alteration with epidote, pyrite, calcite and chlorite. The wall rocks may have some stockwork veining locally, as on the southern margin of the pipe, with high grade clean breccias in cracks or open fractures inside the wall rock.
• Amaga Formation, which comprises Upper Oligocene to Lower Miocene (dated from pollen analyses) stratified clastic sedimentary rocks, which unconformably overlie Romeral Terrane basement rocks. The sequence is predominantly greyish green to cream coloured sandstones which form well stratified, thickly to moderately bedded packages containing intercalations of conglomerate and siltstone. The sandstones form coarse to medium grained, moderately to poorly sorted beds up to 6 m thick ranging in composition from quartz arenite to clay-rich wacke. The conglomerates occur as thin to moderate interbeds within the sandstones, and are generally matrix supported, with subrounded quartz pebbles ranging from 1 to 5 cm in diameter. The siltstones commonly contain organic partings, and occur as up to 10 m thick thick interbeds within the sandstones, and locally dominate exposures.
The Amaga Formation is considered to be of continental origin, having been deposited in trans-extensional (pull apart) basins along the Cauca-Patia, in response to transgression and uplift generated by post Romeral tectonics along the Pacific margin to the west. Structurally, it occurs as elongate NNE-SSW trending ridges, dipping moderately to steeply west.
The formation is locally intruded by a porphyry suite, in the vicinity of which it is domed, highly fractured and contains abundant disseminated hydrothermal pyrite and illite±sericite alteration.
• Combia Formation, a largely volcanic sequence that is widespread throughout the Quinchia district. It is predominantly composed of two main units, although the true thickness and temporal relationships is unclear. They are:
i). a lower sequence of massive, compact, dark grey-green, magnetic flow rocks and agglomeratic pyroclastics of basalt-andesite composition, which contains primary mafic phases, including hornblende and magnetite. These rocks are of tholeiitic composition and are interpreted to have formed in a back arc setting;
ii). a volumetrically dominant upper, fine to medium grained, interbedded tuffaceous to agglomeratic pyroclastic unit of intermediate to felsic composition, comprising mixed, coarse to fine grained crystal, lithic, ash and lapilli tuffs. The lithic fragments are up to 40% of the coarse grained pyroclastic rocks, and include fragments of basalt, basalt-andesite and hypabyssal porphyry. The volcanic rocks are of calc-alkaline volcanic arc affinity.
In proximity to the porphyritic intrusions, the Combia Formation is variably fractured, veined and hydrothermally altered. This fracturing and associated veining occurs as dense quartz and magnetite filled stockworks accompanied by a potassic porphyry style alteration assemblage directly linked to mineralisation. These assemblages are overprinted by late propylitic alteration.
The Combia Formation has not been accurately dated, although the lower unit ranges from ~14 to 11 Ma in age, and the upper is intruded by the 8 to 6 Ma mineralised porphyry suite.
• Porphyry Suite, which is both volumetrically and metallogenetically significant in the Quinchia district, occurring as various sub-tabular intrusive centres, including those directly associated with the mineralisation at Dos Quebradas, La Cumbre and El Centro. It is composed of multiple phases of fine- to medium-grained, light grey to greenish-grey porphyry that ranges in composition fromdacite to diorite to quartz-diorite. The older porphyries are light grey to reddish-grey dacites occurring as pre-mineralisation dykes, with phenocryst densities that vary from sparsely populated to crowded. At Miraflores, dacite porphyry dykes are found in the eastern part of the Miraflores breccia pipe, and predate breccia formation and mineralisation. The dykes have chilled margins at the basalt wall rock contacts, with up to 10% clasts of the dacite being common in the breccias.
Within the porphyries, plagioclase phenocrysts are ubiquitous, followed in abundance by biotite, hornblende and augite, with quartz occurring as bipyramidal eyes up to 8 mm across in the more felsic porphyry phases.
A fine grained biotite microdiorite phase occurs within the suite, locally appearing to be transitional to sparsely populated plagioclase porphyry. A matrix supported magmatic intrusive breccia is also associated with the suite, containing variable fragments of diorite, quartz-diorite and microdiorite as well as vein fragments in a dioritic matrix.
The porphyry suite in the Quinchia district is the southern section of a belt of porphyritic intrusive rocks, the Middle Cauca porphyry belt, which extends for >150 km, from south of Quinchia, to north of Buritica in the north. Where dated along this chain, similar porphyries generally return ages of from 9 to 6 Ma. Unpublished whole rock (K/Ar, biotite) dates from the Dos Quebradas porphyry returned 8.1±1 Ma, whilst geochronological studies indicate ages of 8.92±0.15 Ma (U/Pb zircon) and 8.94±0.13 Ma (U/Pb zircon) for the dioritic units that host the mineralization in the district (Richards, 2011).
A series of porphyry style Au-Cu occurrences are coincident with these porphyry suite intrusions in the Quinchia district (Sillitoe, 2000 and Sillitoe, 2006). These deposits and occurrences are enclosed within mineralised alteration envelopes that grade inwards to Au (±Cu) mineralised centres as follows:
- an outer kilometre scale propylitic halo, characterised by an assemblage of chlorite-epidote-carbonate-quartz-pyrite that intensifies inwards to;
- a shell of calcic-potassic alteration, containing A-veining, calcic-amphibole, disseminated magnetite and magnetite veining, with K feldspar±biotite, to;
- intensely fractured/stockwork 'phyllic' sericite-illite-pyrite alteration with 'D-veins', to;
- an upper core with an 'intermediate argillic' alteration assemblage of sericite-chlorite-clay (illite-smectite).
Unpublished radiometric dates from quartz-sulphide veinlets in the mineralised system of 8.81±0.04 Ma and 8.90±0.04 Ma (Re-Os, molybdenite) are consistent with the host rock age data (Richards, 2011).
Structure
The structural framework of the Quinchia district is dominated by the generally north-south striking, sub-vertical basement architecture of the Romeral Fault system, reflected in the regional structural lineaments and the general north-south trend of the Middle Cauca porphyry belt. Structural reactivation during various post-Romeral events is also evident, in primary and secondary faults in the Quinchia district such as the Amarilla Structural Corridor which strikes WNE-ESE separating the La Cumbre and El Centro deposits, whilst other fault systems trending NE-SW. The Miraflores fault, which passes to the east of the Miraflores deposit, in the eastern part of the district, strikes at 47° dips at ~45°NW, and appears to be an east-vergent thrust of undefined displacement which places Romeral terrane basalts over sandstones of the Amaga Formation. Its age is likely middle to late Miocene. Within the mineralised Miraflores breccia, numerous minor, high-angle NNW-SSE striking faults are recorded, and as indicated by their hydrothermal infillings, control the distribution of high-grade mineralisation within the breccia pipe. Based upon work completed by Sociedad Kedahda S.A. and B2Gold Corp., low-angle structures (<30° dip), also cut the Miraflores breccia and control the distribution of high-grade mineralisation.
Mineralisation, Brecciation and Alteration
The principal deposits in the Quinchia district comprise the La Cumbre, El Centro and Dos Quebradas cluster, which are aligned from the SSW to NNE respectively over a 2.5 km long trend, and the Miraflores deposit, ~2 km east of La Cumbre.
• La Cumbre, El Centro and Dos Quebradas
These three copper-poor, porphyry gold deposits are associated with three Miocene intrusive centres, each composed of dykes and stocks separated in three dioritic phases, namely: i). early intra-mineral; ii). late intra-mineral, and iii). post-mineral, all of which are emplaced into intermediate to felsic volcanic rocks of the Miocene Combia Formation and in Cretaceous basalts of the Romeral Terrane basement Barosso Formation. Masses of intrusive breccia separates the main La Cumbre and El Centro intrusions, while smaller zones occur on the eastern margins of the former intrusion.
The disposition of the three deposits may be summarised as follows:
La Cumbre, the largest and highest grade of the deposits. Mineralisation of >0.3 g/t Au covers a maximum 350 x 900 m, and persists to s depth of between 180 and 325 m below surface. The mineralised zone is elongated in a NW-SE direction and plunges at ~15 to 20°SE. This low grade envelope surrounds core of >0.7 g/t Au, the largest of which is 120 to 150 m wide, by ~500 m long, with a vertical extent of 200 to 500 m.
El Centro, a lower grade, more irregularly developed zone that contains a number of discontinuous and disconnected blocks >0.3 g/t Au, with smaller cores of >0.5 g/t and some >0.7 g/t Au, distributed over an area of ~800 x 350 m.
Dos Quebradas, which is exposed by the incised Dos Quebradas valley. Mineralisation within the >0.3 g/t Au contour covers a maximum area of ~350 x 400 m, trending NW-SE, enclosing areas of >0.7 g/t Au.
Within each deposit, intermediate argillic alteration locally overprints an early potassic assemblage and its associated quartz veinlet stockwork (Jahoda, 2007), with gold occurring within altered dioritic intrusions, and in the contact zone between diorite and both basalt and volcaniclastic rocks.
The highest gold and copper grades appear to occur in the early diorite phase, characterised by potassic (mainly biotite with subordinate K feldspar) and potassic-calcic alteration (characterised by traces of actinolite and garnet in the potassic assemblage). Grades reach a maximum where hydrothermal biotite and fine grained chalcopyrite are most strongly developed. Significant quantities of quartz±sulphide veinlets and >3% hydrothermal magnetite are also common in the high grade section of the early intra-mineral phase. Gold grades decline where potassic alteration is weaker, and there is a lower density of veinlets, with generally <1%, but locally up to 3% sulphides, mainly pyrite, with traces of chalcopyrite, bornite and molybdenite.
The late intra-mineral intrusive phase is devoid of potassic alteration and quartz veins, but has undergone moderate to strong intermediate argillic alteration with an average sulphide content of 3 to 5%, mainly of pyrite, and traces of molybdenite and chalcopyrite.
Post mineral dykes exhibit argillic alteration (kaolinite) with subordinate chlorite and epidote.
Gold and copper grades in basaltic wall rock are proportional to potassic biotite and potassic calcic (biotite-actinolite) alteration. A-veinlet densities are as high as 50 veinlets per metre.
Most artisanal mining activity in the Quinchia district follows centimetric fault gouge within tuffaceous volcanic rocks which have been subjected to strong intermediate argillic alteration, with gold being found in the gouge that contains fine grained pyrite.
The overlap of alteration and intrusion suggest telescoping of porphyry and epithermal systems.
The deposit is overlain by a saprolite blanket that is 20 to 70 m thick over the La Cumbre mineralisation and ~20 to 40 m thick at El Centro and Dos Quebradas. In general, the saprolite is thinner over areas with basalt and is thicker over diorite and breccias. The saprolite or oxide zone is underlain by a thick transition zone that contains ≤2% total sulphur that varies from being absent distal to the ore deposit, to as much as 250 m in the core of the deposit. Below this, is the primary sulphide zone with ≥2% total sulphur. Gold grades do not appear to be influenced by the oxidation state, with contours passing from primary sulphide to transition to oxide zone without deviation (Batero Gold Corp. website, 2016).
• Miraflores
The Miraflores deposit occurs within a sub-vertical cylindrical breccia-pipe, with surface dimensions of 250 x 280 m, and a known vertical extent of 500 to 600 m, but open to depth, with well defined contacts with the basalts of the Romeral Terrane Barosso Formation. Mineralisation is also found in the basalt wall rocks close to the breccia pipe contact. A NNW-SSE oriented fracture system appears to control the formation of the breccia. Four types of breccia have been distinguished:
- Grey Breccia - interpreted to represent the original breccia pipe infill, occurring as zones of milling in the upper part of the pipe, where there is a higher abundance of small rounded clasts in a rock flour matrix. They are mainly clast supported, although there are some occasional grey matrix supported rock flour breccia zones. These breccias are un-mineralised or only carry low grades.
- White breccia - has a cement of epidote, quartz, adularia and calcite with sulphides and occasional visible gold. The clean breccia has a clast supported texture and has no rock flour matrix, or only minor relicts. The breccia matrix has a consistent paragenesis of epidote coating the clasts, followed by quartz, and finally calcite, which may not always be present. Adularia may occur with quartz, although it has only been observed in surface outcrops and not in drill core. The cement frequently has a drusy open space texture, but can also completely fill the breccia. Sulphide minerals are found throughout the quartz and calcite stages, and are often concentrated on epidote at the start of the quartz phase, and also occur in quartz vugs. The sulphides are euhedral and coarse grained (2 to 4 mm). The percentage of sulphides is low, and comprise pyrite, chalcopyrite, molybdenite, galena and sphalerite (honey colored, Zn-rich). Rare visible gold can occur in vugs. Polymictic breccia was further brecciated, broken and invaded by the quartz-calcite infill (Tobey, 2012).
- Green Breccia - green, epidotised, clast supported, with some occasional matrix supported rock flour breccias. The clasts are mainly heterolithic or more rarely monolithic adjacent to the wall rock. From the wall rock to the centre of the breccia pip, there is a transition from quartz stockworks in the basalt wall rock, to jigsaw breccias with quartz cement, to monolithic clast breccias, and then to heterolithic clast breccias. This matrix and cement composition does not vary with the style of breccia. The bulk of the clasts are angular to sub-angular in polymictic breccias, whilst zones of rounded to sub-rounded clasts are rare. This breccia contains medium gold grades.
- Red Breccia - hematised, mostly clast-supported, with some matrix‐supported rock flour (comminuted particles of pre-existing rock) breccias. Clasts are predominantly heterolithic or more rarely monolithic adjacent to the wall rock. This breccia type is late stage, crosscutting all the other types of breccia, and may be a late oxidised overprint of the early breccias (Tobey, 2012). It has medium to very high gold grades, with fault-vein zones containing 3 to 429 g/t Au.
The contacts between the various breccias types are gradational. The white breccia occurs in irregular, elongated vertical zones or pockets, surrounded by green or grey breccias. The white breccia is interpreted to have formed later than the dirty breccias and the hydrothermal fluid appears to have washed out the rock flour matrix or replaced it, with deposition of gangue and sulphide minerals.
Multiple brecciation phases are indicated by samples of rock flour matrix breccia containing clasts of earlier silicified rock flour matrix breccia, polymictic epidotised breccia with open space quartz-calcite-sulphide and another, older silica-sericite-pyrite breccia containing mineralised fragments (Tobey, 2012).
Petrographic studies suggest at least three older mineralising events prior to the formation of the epithermal breccia. Locally, basalt clasts within a breccia can be observed to contain a quartz 'B' veinlet (comb-quartz without an alteration halo) cut by pyrite-epidote cracks. Also in the same sample, there is a fragment of silicified breccia with strong pyritic alteration. This has been taken as evidence of possible porphyry style mineralisation events preceding formation of the breccia pipe (Tobey, 2012).
Mineralisation primarily occurs as disseminations in the hydrothermal cement between the breccia fragments, and in late, spaced, high-grade fault-controlled vein structures, which cut the breccia. The hydrothermal breccia cement, which varies from 25 to 75% of composite breccia mass, is characterised by coarse grained, euhedral infillings of abundant calcite, quartz and epidote, with pyrite, galena, sphalerite, chalcopyrite and native gold. Hydrothermal matrix varies from 25 to 75% of composite breccia body.
Much of the upper breccia pipe falls within the >0.3 g/t Au envelope which embraces substantial >0.5 g/t Au zones with cores of >1 g/t Au. The 0.3 g/t Au envelope tapers to a depth of ~600 m, where irregular, elongate, isolated zones of mineralisation persist.
Low grade gold mineralisation occurs in a halo surrounding the breccia pipe hosted by the basalts, and is characterised by quartz-calcite veinlets with low sulphide contents, primarily pyrite, galena and sphalerite, controlled by the density of fracturing created by the brecciation. The mineralisation in both the breccias and basalt generally has low contents of chalcopyrite, sphalerite and galena, occurring as fine (<100 µm) grains.
The breccia is cross-cut by younger SSE-NNW and NW-SE veins that dip at 75 to 90° and are characterised by argillised material that contains important amounts of sulphides, mainly pyrite, chalcopyrite, sphalerite and galena, and some visible gold. These sulphides occur as coarse particles ranging from 100 to >200 µm. The persistence of the SSE-NNW structures is evident in artisanal workings, where high gold grade mineralisation may be followed for horizontal distances of >150 m and >80 m vertically, with almost no displacement of the structures. Structures/vein intersections form high gold grade shoots of variable dimensions that can be observed in the artisanal workings.
Resources
Published mineral resource estimates are as follows:
Quinchia - La Cumbre, El Centro and Dos Quebradas deposits combined, as at June, 2013, at a 0.3 g/t Au cut-off
(Batero Gold Corp. website, 2016)
Measured resource - 26.1 Mt @ 0.67 g/t Au, 1.8 g/t Ag, 0.11% Cu (=17.5 t Au);
Indicated resource - 105.6 Mt @ 0.57 g/t Au, 1.8 g/t Ag, 0.10% Cu (=60 t Au);
TOTAL measured + indicated resource - 131.8 Mt @ 0.59 g/t Au, 1.8 g/t Ag, 0.10% Cu (=78 t Au);
Inferred resource - 33.5 Mt @ 0.50 g/t Au, 1.6 g/t Ag, 0.06% Cu (=16.8 t Au);
Miraflores deposit, as at June, 2013, at a 0.27 g/t Au cut-off (Seafield Resources Ltd. website, 2016)
Measured resource - 38.75 Mt @ 0.68 g/t Au, 1.4 g/t Ag (=26 t Au);
Indicated resource - 33.88 Mt @ 0.89 g/t Au, 1.7 g/t Ag (=30 t Au);
TOTAL measured + indicated resource - 72.62 Mt @ 0.78 g/t Au, 1.5 g/t Ag (=56 t Au);
Inferred resource - 3.76 Mt @ 0.51 g/t Au, 2.3 g/t Ag, 0.06% Cu (=1.8 t Au);
At a 0.5 g/t Au cut-off (Seafield Resources Ltd. website, 2016), the resource becomes
TOTAL measured + indicated resource - 30.62 Mt @ 1.35 g/t Au, 2 g/t Ag (=41 t Au);
Inferred resource - 1.64 Mt @ 0.74 g/t Au, 3.2 g/t Ag, 0.06% Cu (=1.2 t Au).
This summary is largely drawn from:
• Evans, L., Ehasoo, G. and Altman, K.A., 2013 - Technical Report on the Batero-Quinchia Project, Department of Risaralda, Colombia; an NI 43-101 Report, prepared by Roscoe Postle Associates Inc. for Batero Gold Corp., 269p.
• Baldys, C. and Anderson, D., 2009 - Technical Report on the Quinchia Concession, Department of Risaralda, Colombia; a technical report, prepared for Angus Resources Inc., 100p.
• Wilson, S., Olin, E., Tinucci, J., Swanson, B., Poeck, J. and Willow, M., 2013 - Preliminary Economic Assessment, Miraflores Property, Quinchía District, Colombia; an NI 43-101 Report, prepared by SRK Consulting (U.S.), Inc., for Seafield Resources, Ltd., 296p.
• Gorham, J., 2007 - Summary Report on the Miraflores Property, Department of Risaralda, Colombia; a Technical Report prepared by Dahrouge Geological Consulting Ltd. for B2Gold Corp., 107p.
The most recent source geological information used to prepare this decription was dated: 2013.
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.
La Cumbre Miraflores
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Bissig, T., Leal-Mejia, H., Stevens, R.B. and Hart, C.J.R., 2017 - High Sr/Y Magma Petrogenesis and the Link to Porphyry Mineralization as Revealed by Garnet-Bearing I-Type Granodiorite Porphyries of the Middle Cauca Au-Cu Belt, Colombia: in Econ. Geol. v.112, pp. 551-568.
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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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