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Condor Project - Chinapintza, Los Cuyes, Soledad, Santa Barbara, El Hito |
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Ecuador |
| Main commodities:
Au Ag Zn 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 gold-silver±zinc and copper±gold deposits of the Condor Project are located ~400 km SSE of Quito, and ~40 km east of the regional capital of Zamora, in the Province of Zamora-Chinchipe of southern Ecuador, close to the Peruvian border.
Three types of mineral systems are recognized at the Condor district, corresponding to the main deposits, as follows:
• Chinapintza - an intermediate sulphidation narrow-vein epithermal system;
• Los Cuyes and Soledad - intermediate sulphidation epithermal gold bearing diatremes, volcaniclastics and breccia pipes; and
• Santa Barbara Au-Cu porphyry and the El Hito Cu-Mo porphyry.
Chinapintza, Los Cuyes and Soledad are distributed in that order, from north to south in the north of the district, while El Hito is 6 km to the south, and Santa Barbara is 4 km further to the west.
Regional Setting
The Condor district is located within the Condor Cordillera, between the Andean Cordillera Real in the west and the Guyana Shield. It is part of a significant Jurassic to Cretaceous fold and thrust belt where Jurassic granitoid plutons intrude supracrustal sequences of Palaeozoic and Mesozoic sedimentary and arc-related igneous-volcanic rocks.
This district is part of the Zamora Copper-Gold Belt (previously known as the Corriente Copper Belt and the Pangui Belt) and is located ~60 km south of the Mirador and Mirador Norte porphyry copper deposits, and ~35 km south of the Fruta del Norte intermediate sulphidation epithermal gold deposit, while the Nambija gold skarn deposit is located 25 km to the west. All of these deposits are related to Late Jurassic magmatism (Drobe, 2013).
For details of the regional setting and geology, see the separate records for North Andes copper-gold province in Ecuador and the broader North Andes and Panama copper-gold province.
District Geology
The stratigraphic sequence in the district, is as follows, from the base:
Precambrian to Devonian
• Isimanchi, Pumbuiza and Macuma Formations - comprising slates, schist and quartzite that form the basement to the sequence of the district;
• Unconformity
Triassic to Lower Jurassic
• Piuntza Formation - quartzite, limestone/marbles, siltstones/slates and volcanic and volcaniclastic rocks.
Lower to Mid Jurassic
• Chapiza Formation - red bed sandstones, turbidite, mudstones and basaltic flows.
• Zamora Batholith, an I-type tonalitic to granodioritic intrusive complex that is a regionally extensive and NNE elongated, parallel to the Ecuadorian Andes. It is composed of hornblende-bearing diorite and granodiorite, plus lesser granite, tonalite and monzodiorite. The batholith was emplaced along a north-south structural feature as evidenced by contact relationships with roof pendants of Triassic to Jurassic volcano-sedimentary formations, and Early Jurassic marine sedimentary formations. Breccia zones within the batholith are important in the Mirador copper/gold porphyry and other copper deposits of the Zamora Copper-Gold Belt
Upper Jurassic
• Misahuallí Formation, which is interpreted to be coeval with the Zamora Batholith, comprises a mix of flows, breccias, pyroclastic, volcaniclastic epiclastics and intrusive rocks that range in composition from alkali basalt to dacite and are exposed as ~north-south aligned supra-crustal pendants within the Zamora Batholith, dated as Middle Jurassic 169 to 164 Ma (Drobe, 2013).
• Late Jurassic, 160 to 145 Ma, high level diorite porphyry dikes and stocks which preceded and/or accompanied early movement on regional fault zones within the batholith tend to be associated with the margins of the Zamora batholith, and are associated with mineralisation in the region. A volcanic event with accompanying near surface intrusive activity is associated with this Late Jurassic igneous activity. These younger intrusive rocks are spatially associated with mineralisation in the Chinapintza portion of the Santa Barbara epithermal gold-silver systems as well as the Nambija gold skarn district (Henderson, 2010).
Lower Cretaceous
• Hollin and Napo Formations, comprising transgressive marine sedimentary rocks, mainly sandstone, limestone and mudstone.
• Chinapintza Formation and intrusions - rhyodacite to dacite pyroclastic rocks.
The region is strongly structurally controlled by through going north–northeast to north-south trending lineaments cross-cut by younger, northeast and northwest sets. Jurassic magmatism and volcanism was partly controlled by the former regional lineaments which remain active.
Deposits
Within the Condor district, there are three distinct and different geologic settings, as listed above, and as follows: the Chinapintza vein district; the Los Cuyes and Soledad epithermal gold complex; and the Santa Barbara Au-Cu and El Hito Cu-Mo porphyry systems to the south.
The Chinapintza Veins
This veining is located in the northernmost part of the district, occurring as a series of narrow, parallel, high-grade, intermediate sulphidation epithermal sulphide and carbonate-rich quartz veins, predominantly hosted by granodiorite intrusive. The veins trends vary from north-south to NW-SE with a less well defined NE-SW set of low amplitude sinusoidal anastomosing brittle to semi-brittle structures with dips from sub-horizontal to near vertical.
These silica rich veins, with variable manganese carbonate content, commonly follow pre-existing faults that were subsequently modified to produce deformed brecciated to cataclastic or gouge-like mineralised material. This vein set has a strike length of at least 6 km within a zone that is 4 to 5 km wide. The Chinapintza veining is considered to be truncated to the south by the east-west La Pangui Fault on the margin of a postulated graben. South of the fault, the main lithologies are volcaniclastic tuffs, rhyolites and granite porphyry.
The dominant host is a dacitic quartz-feldspar porphyry mass that is exposed over an area in excess of 1 km in diameter. This is intruded by smaller, NW oriented plugs and dykes of andesite porphyry and by breccias. To the west, the dacite porphyry is bounded by a thin strip of basement schist sandwiched between it and the main Zamora Batholith, while to the east, a breccia separates it from further dacites.
The host rocks are commonly variable sericite-clay-chlorite altered quartz or feldspar porphyritic dacite of either intrusive or effusive origin. The sulphide assemblage is mainly pyrite, with sphalerite and lesser galena, pyrrhotite and arsenopyrite, which may be either disseminated, vein-type, replacement or banded and locally semi-massive. Some open space infill has been noted.
Los Cuyes and Soledad Epithermal Gold
These occurrences are found in the northern part of the district, from <1 km south of the Chinapintza Veins, and are underlain by intrusive and volcanic rocks of the Chapiza and Chinapintza formations, bounded to the west principally by granodioritic rocks of the Zamora Batholith. Amphibolite schists, representing metamorphosed Misahualli Formation volcanic rocks are found bounding dacite porphyry to the NW of the main area of mineralisation. The surrounding rocks are predominantly Cretaceous rhyodacite to dacite intrusions and effusive rocks, overlying the Zamora Batholith, with lesser Cretaceous volcanogenic sedimentary rocks and superficial cover.
The immediate host to mineralisation comprise dacite to rhyodacite or simply quartz porphyritic volcanic units proximal to one or more eruptive vents, as well as related hydrothermal phreatomagmatic breccias associated with the Late Jurassic shallow intrusions and volcanic event. The volcanic material includes lapilli and coarser breccia deposits with pumice, accretionary lapilli and fragments of fresh and altered rock from numerous sources. Multiple intrusive bodies of stocks and dykes are spatially associated with the volcanic units. Mineralisation is centered on rhyolite plugs and associated breccia bodies.
Tuff beds are common, varying from fine ash with thin laminations to more coarse bedding with large fragments. The laminated tuffs are frequently tilted to angles greater than the original bedding, implying post-depositional tilting, either due to slumping, listric faulting into a crater, or local deformation caused by shallow intrusion. Common strike-slip post-mineral faulting is considered another cause of tilting.
A number of diatreme bodies and intrusions and/or diatreme related breccias are known within and around these deposits, as well as intrusive plugs. The principal mineralisation controlling structures in this area generally trends northwesterly.
In addition, there are also intrusive breccias with a soft, dark, muddy matrix, known as Brechas Negras, which are spatially associated with high gold grades in structures and related breccias. These Brechas Negras contain fresh and altered wall rock, including black sedimentary shale fragments. In addition to the depositional, hydrothermal and sedimentary diapiric breccias, there is also evidence of phreatomagmatic breccias.
Los Cuyes represents a complex intrusive phreatomagmatic breccia with associated hydrothermal alteration hosted by magmatic and effusive volcanic lithologies. Fragment textures in these breccias as deep as 400 m in drill core, as well as at the surface, are interpreted to indicate juvenile characteristics of magma intruded into aqueous saturated rock with subsequent brecciation.
• Soledad - The Soledad complex is a large hydrothermal breccia pipe system containing small, discrete pipe-shaped bodies of higher grade mineralisation. Individual bodies include the original Soledad San Jose I and II, Bonanza and Guayas breccias, with the smaller original bodies being distributed around the margins of the main intrusive complex, at the contact between Zamora granodiorite and the rhyolite plug. Drilling, suggests the mineralised zone is elongated north-south, flaring slightly upwards. The felsic porphyry contacts are generally sharp, steep, with a faulted and brecciated SE contact. Vein-type and replacement mineralisation within quartz feldspar porphyry intrusion hosted breccia is underlain by a rhyolitic plug 600 m in diameter with marginal intrusive or hydrothermal breccias, all of which are, in turn, hosted by granodiorite and feldspar porphyry.
Shallow, higher grade mineralisation occurs as a combination of patchy replacement, irregular veinlets and grain scale replacement of feldspars by sphalerite and pyrite. Associated alteration is typically quartz-sericite-pyrite, with replacement silicification. There is a gradation from near surface gold-silver±sphalerite, to more pyritic, low grade gold mineralisation at depth, especially below a depth of 150 m, with values of ~0.2 g/t Au below 250 m. Higher grades of generally >1.0 g/t Au occur above 100 m depth within a NE to east striking structure with plan dimensions of 80 x 90 m, persisting to depths of 300 m. Au and Zn grades generally drop off below 200 to 300 m vertical depth, gradually replaced by pyrite from 100 m below surface.
The small San Jose I breccia is located in the north of the main Soledad intrusive complex at the contact between a rhyolite plug and the batholith granodiorite. The mineralisation within the breccias is found as Au-sphalerite rich veins containing fragments of basement, rhyolite and rare effusive rocks, and is more pyritic with fewer veins and corresponding lower gold grades at depth. The similarly small San Jose II breccia occurs in the east of the Soledad complex and is essentially a remnant breccia on the east side of a rhyolite plug. It is rhyolitic with fragments of the larger rhyolite plug, pyroclastic and shale material. The grade of the associate mineralisation appears to taper to the NW but continues down-plunge to the SE where it may become contiguous with the north-western margin of the Bonanza breccia mineralisation.
Mineralisation in the Guayas breccia covers an area of ~50 x 20 m, to a depth of 50 m, and is hosted by a steeply SE plunging quartz phyric rhyodacite, with dominant kaolinised alkali feldspar. Mineralisation is composed of veins of pyrite±sphalerite and Ag-Pb fine free gold, occurring in two main sets, generally trending NW, with NE dips. Contacts with the rhyodacite porphyry and granodiorite basement country rocks are typically steep, commonly faulted, brecciated and mineralised, with the breccia at the contact being polymict with a 'shearing' component. The contact zone is overprinted by variable hydrothermal alteration characterised by quartz-sericite with sub-ordinate kaolin-carbonate. Overall, stockwork veining is broader at the surface with weak associated sphalerite. Mineralisation weakens with depth and the breccias become coarser and predominates, where it is typically dark with variable argillic alteration, chlorite and sulphides, but is strongly pyritic, with variable rhodochrosite, calcite and minor ankerite-calcite.
• Los Cuyes represents a complex phreatomagmatic intrusive breccia with associated hydrothermal alteration within magmatic and effusive volcanic lithologies. Associated fragmental textures have been encountered as deep as 400 m in drill core, whilst intrusive breccias with a soft, dark matrix, as described above, are also found at Los Cuyes. Accretionary lapilli and related textures and the near vertical attitude of some beds are interpreted to reflect the slumping of beds into a crater.
The Los Cuyes portion of the large breccia complex is ~400 m east-west x 250 m north-south. Most of the mineralisation and alteration occurs within hydrothermal breccias above and flanking the diatreme breccia complex. The breccia complex is pipe-like and south-dipping, divided into several internal mineralised zones, specifically: i). an upper zone, which dips steeply southwards from the surface to ~150 m; ii). a second zone, roughly parallel to the topography; iii). a deeper more cylindrical, 200 x 100 to 150 m diameter breccia, deeper than 200 m below surface, and; iv). a central zone, with intersections of 68 m @ 1.0g/t Au from 188m and 47 m @ 3.13 g/t Au from 223 m depth.
High-grade Au-Ag mineralisation is commonly related to pyrite-sphalerite veins (±minor chalcopyrite and galena). Rhodochrosite occurs in the selvages of sulphide veins and replacing surrounding wall rocks, accompanied by alteration that is characterised by illite grading outward or downward to chlorite-epidote. Quartz veins are rare or absent, but moderate silicification of wall rocks and breccia clasts is common.
At least two pulses of mineralisation are indicated at Los Cuyes, the first gold-rich with silver, the other zinc-rich, each occurring in similar structural pathways and permeable units, resulting in areas that are rich in gold with low zinc, and vice versa, as well as zones that are anomalous in both. Similar zoning is also evident at Soledad.
Three main styles of alteration are observed, namely, i). propylitic, typically composed of chlorite-quartz-sericite ±carbonate; ii). phyllic, comprising sericite-silica-pyrite-carbonate, with pervasive or vein silica, plus silicified fragments and cement; and iii). silica-alunite-kaolinite, with kaolinite mainly occurring as a late replacement feature.
Finely crystalline illite is found within the lapilli tuff units, accompanied by disseminated pyrite and sphalerite. This style of alteration forms a halo to the quartz/silicification-adularia alteration. The sulphide paragenesis is pyrrhotite → pyrite → chalcopyrite → sphalerite → galena. Gold may occur at higher elevations within the system, including fine free gold grains, with sphalerite, galena ±manganese. Morrison (2007) reported a good correlation between Pb and Cu rather than with Pb-Zn, although there are some high grade Zn intersections with corresponding higher Au grades. Mineralisation has been encountered over true widths of from 20 to 80 m, to depths of 300 m, with intersections such as 44 m @ 1.26 g/t, 9 m @ 1.98 g/t, 12 m @ 3.64 g/t and 9 m @ 12.28 g/t Au.
Santa Barbara Porphyry Au-Cu Deposit
The deposit is dominantly underlain by fine-grained green basaltic andesitic volcanic rocks of the Upper Jurassic Misahualli Formation, partially intercalated with and overlain by a sedimentary sequence of conglomerate, quartz sandstone, limestone and local garnet skarn. These rocks have been intruded by at least two types of diorite porphyry intrusions: i). DP1 - a relatively feldspar phenocryst-rich variety, apparently directly associated with mineralisation, occurring as a swarm of 2 to 30 m wide, NW trending, diorite porphyry dykes in the NE of the deposit area, and ii). DP2 - a post-mineral hornblende phenocryst-rich variety which also forms dykes, as well as a stock in the NW section of the deposit area, where it apparently truncates the DP1 dykes. An alternative interpretation is that the DP2 stock is the primary porphyry intrusion with of mineralised dyke-like apophyses. Other porphyry dykes have also been recognised.
The principal hosts to gold-copper mineralisation are the basaltic-andesite volcanic suite of the Misahualli Formation, often in proximity to diorite porphyry dykes, although mineralisation is also found in other rocks. Two separate mineralised zones have been defined:
• Santa Barbara South, the main mineralised body, which extends over an area of >700 x ~300 m and is elongated in a north to northwest direction following the trend of interpreted faulting. The western margin of the deposit side is steep, while to the east it consistently dips 40 to 50°E.
• Santa Barbara North, which is located to the east in contact with the DP2 diorite porphyry stock, and comprises a small gold-copper resource. Mineralisation closely coincides with B-type quartz veins within an envelope of fine-grained secondary biotite alteration. Best gold grades correlate closely with chalcopyrite.
High gold grades are closely associated with chalcopyrite and B-type quartz veins which often carry sulphides, biotite alteration and disseminated pyrite. Pyrrhotite is also present, serving as a negative indicator, tending to occur outboard of the gold-copper zone. At least two types of quartz veins occur in the system; the first a massive deformed quartz vein suggesting high temperature ductile deformation, and a later straight B-type vein set with white to banded and coliform quartz.
Alteration is patchy to pervasive, occurring as very fine-grained secondary biotite or phlogopite of the potassic alteration phase, often accompanied by finely disseminated magnetite. Propylitic alteration as represented by chlorite-epidote and actinolite forming a halo around the potassic alteration. There is also an illite alteration overprint imposed on the potassic alteration. Late stage alteration includes minor prehnite, calcite and zeolite veins (Hedenquist, 2007).
Hito Porphyry Cu-Mo Deposit
This mineralised system is associated with a Late Jurassic, fine- to medium-grained, sub-equigranular dioritic intrusive complex within the earlier Jurassic plutonic rocks of the Zamora batholith, represented by a Middle Jurassic coarse-grained foliated granodiorite. Two major structural orientations are defined by steeply dipping intrusive contacts, quartz veins, sulphide veinlets and faults that strike north, dipping steeply to both the west and east, and northwest striking, which dip steeply to the southwest.
The bulk of the diorite complex is moderately to strongly quartz-sericite-pyrite and illite-sericite-pyrite phyllic-argillic, overprinting potassic alteration at depth. The latter is characterised by fine-grained secondary biotite and K feldspar, where copper and molybdenum mineralisation is hosted by a quartz stockwork developed in the diorite complex. This zone includes a coherent zone of B-veining, chalcopyrite and potassic alteration. The principal sulphides are pyrite, chalcopyrite, bornite and molybdenite associated with three phases of quartz-feldspar, quartz-biotite and quartz-sericite-pyrite stockwork veining and flooding. The pyrite content overall is <5%. Copper-molybdenite mineralisation has been defined over a north-south elongated area of ~2.5 x 1.0 km enclosing enclosing the main 1400 x 400 m deposit that extends to a depth of ~600 m. The alteration increases towards the south of the intrusive complex, where massive to poorly banded, sulphide-bearing white quartz veins are hosted in muscovite altered diorite (Garwin, 2012).
Mineral Resources
Published NI 43-101 Mineral Resources are as follows (Maynard et al., 2014 and Short et al., 2015):
Chinapintza
Measured resource - 0.147 Mt @ 11.37 g/t Au, 70 g/t Ag, 2.4% Zn;
Indicated resource - 0.117 Mt @ 10.92 g/t Au, 70 g/t Ag, 0.1% Cu, 2.5% Zn;
Inferred resource - 2.423 Mt @ 5.9 g/t Au, 44 g/t Ag, 2.0% Zn.
Soledad
Measured resource - 34.9 Mt @ 0.63 g/t Au, 7.21 g/t Ag;
Indicated resource - 20.0 Mt @ 0.5 g/t Au, 6.9 g/t Ag.
Los Cuyes
Indicated resource - 46.80 Mt @ 0.82 g/t Au, 6.19 g/t Ag.
Santa Barbara
Indicated resource - 364.6 Mt @ 0.51 g/t Au, 0.85 g/t Ag, 0.1% Cu;
Inferred resource - 177.6 Mt @ 0.4 g/t Au, 0.8 g/t Ag, 0.1% Cu.
El Hito
Inferred resource - 161.0 Mt @ 0.31% Cu.
This summary is drawn from "Maynard, A.J. and Jones, P.A., 2011 - The Condor Gold Project, Located in Zamora, Ecuador; an NI 43-101 Technical Report prepared for Enterprise Capital Corporation by Al Maynard and Associates; 118p."
"Maynard, A.J., Jones, P.A. and Suda, R.U., 2014 - The Condor Gold Project, Located in Zamora, Ecuador; an NI 43-101 Technical Report prepared for Ecuador Gold and Copper Corporation by Al Maynard and Associates; 130p."
"Short, M., Maynard, A.J. and Jones, P.A., 2015 - Preliminary Economic Assessment of the Santa Barbara Gold and Copper Project in Zamora, Ecuador; an NI 43-101 Technical Report prepared for Ecuador Gold and Copper Corporation by Al Maynard and Associates; 188p."
The most recent source geological information used to prepare this decription was dated: 2015.
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.
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