Minera Santo Domingo SCM, a wholly owned Chilean subsidiary of Capstone Copper Corp., holds the Santo Domingo copper-iron-gold-cobalt development project.
- subscription is required.
Summary:
Santo Domingo is part of the iron oxide–copper–gold (IOCG) type deposits located within the Cretaceous Iron Belt (CIB), which extend approximately 630 km by 40 km in Chile´s coastal range.
Spatially, the project is divided into three large deposits, Santo Domingo, Iris Norte and Estrellita. Santo Domingo is made up of two areas, Santo Domingo Sur and Iris.
Hydrothermal alteration selectively affects the different lithologies and is characterized by sodic (-calcic), potassic, carbonate and calc-silicate skarn.
At the Santo Domingo Sur deposit drilling at 100 m centres or less has outlined a 150 m to 500 m thick copper-bearing, specular hematite–magnetite manto sequence covering an area of approximately 1,300 m by 800 m. The mantos are zoned from an outer rim of specular hematite toward a magnetite-rich core. The mantos consist of semi-massive to massive specularite and magnetite layers with clots and stringers of chalcopyrite, that range in thickness from approximately 4–20 m. Additionally, cobalt-bearing pyrite can be found mainly associated with magnetite mineralization. The upper parts of the manto sequence are frequently oxidized and contain various amounts of copper oxides and chalcocite. Drilling below a depth of 350 m is sparse and mineralization below that depth is not well defined at this time.
The Iris deposit is a narrow zone (100 m to 250 m wide) of copper-bearing iron mantos and breccias extending over 1,900 m that are hosted by andesitic tuffs and andesitic breccias. The dominating iron oxide at Iris is hematite and the main copper mineral is chalcopyrite. There are some old mine workings at the southern end of the deposit where copper oxides such as brochantite and chrysocolla were mined at surface.
Mineralization at Iris Norte is very similar to the Iris deposit. However, part of the mineralization appears to be hosted by volcaniclastic and andesitic flows. The deposit is approximately 500 m wide and has been tested over a strike length of 1,600 m. The Iris Norte deposit has been intruded by significant amounts of diorite dykes and sills that separate the deposit into two lenses. The main sulphides are pyrite and chalcopyrite, with the latter providing the copper content of the deposit.
Santo Domingo
Santo Domingo Sur
Mineralization occurs in the form of copper-bearing semi-massive to massive iron oxide mantos that have replaced the tuffaceous rocks, with minor veins and breccias. The mantos are zoned from an outer rim of specular hematite toward a magnetite-rich core.
Mineralization in the deposit is strongest in the southern part and in the upper levels. Copper grade and intensity of the mineralization weaken towards the northern part of the deposit as well as with depth. The high-grade core of the deposit is located along the southern margin and close to surface. The oxidized mineralization at surface becomes gradually less oxidized with depth and transitions through an enrichment zone of secondary sulphides (chalcocite) and lesser oxides into a sulphide zone where the main copper mineral is chalcopyrite.
A zone of hydrothermal brecciation has been recognized in the southeast of the area. The mineralized breccia consists of andesite and volcaniclastic rocks fragments in a fine-grained matrix of iron oxides sulphides and other gangue minerals. The most superficial part of the breccia contains mainly andesite fragments while at depth the fragments mainly correspond to rocks of mineralized volcaniclastic origin, which is consistent with the host rock. The upper part of the breccia is oxidized with both limonite, which is the dominant iron oxide and copper oxides. Native copper has also been observed. The lower part of the breccia contains regular sulphide mineralization. In the proximity of the major structures that have produced the brecciation, areas with copper oxides are observed even at depth, surrounded by an enrichment zone with a strong presence of secondary sulphides, passing in its most distal part to a zone of primary sulphides.
Iris
The Iris area footprint, when projected to surface, is approximately 500 m wide, has a strike length of 1,200 m and has been traced from surface to a depth of approximately 500 m below surface. When the dip and plunge of the zones is considered, the real width of the deposit is of the order of 200 m.
The deposit consists of iron oxide mantos and breccias developed along a north–northwest-striking fault zone. The dominant iron oxide at Iris is hematite and the main copper mineral is chalcopyrite.
Mineralization occurs close to surface at the southern end and plunges gently towards the north.
The oxide mineralization is hosted by a specularite manto that is cut by steeply dipping structures. The extent of oxide mineralization at surface is approximately 100 m by 60 m.
The Iris Mag zone is located between the Iris and the Santo Domingo Sur area. Mineralization in the zone consists of magnetite and chalcopyrite with a very high magnetite content (40% and more) and typically low copper content (approximately 0.1% Cu on average).
Iris Norte
The Iris Norte deposit is located 600 m to the north of the Santo Domingo deposit and is also blind, being entirely covered by a gravel sequence. The deposit is very similar in character to Iris. The deposit is approximately 1,000 m wide and has been tested over a strike length of 1,600 m and to a depth of 300 m below surface.
Mineralization is hosted within andesitic flows and volcaniclastics, which differs to the mainly tuff host rock at Santo Domingo. The deposit displays a north-easterly strike which is a rotation of approximately 55° clockwise versus the strike of the Santo Domingo deposit. The Iris Norte deposit has been intruded by significant numbers of diorite dykes and sills and presents an intercalation of andesitic lava flows with volcaniclastic andesitic rocks that make the mineralization more discontinuous, generating different mineralized levels.
Mineralization consists of mixed magnetite and hematite-rich mantos. The main sulphides in Iris Norte are cobalt-rich pyrite with lesser chalcopyrite, with the latter providing the copper content of the deposit. Iris Norte contains a higher proportion of magnetite than the Iris area and there are a higher proportion of intrusive rocks.
Estrellita
Mineralization is interpreted by Santo Domingo geologists to occur at a higher stratigraphic level than Santo Domingo and Iris Norte, which are hosted in tuff sequences below the level of mineralization at Estrellita.
Estrellita has been faulted into a series of four blocks which step downwards to the north, with displacement across the faults ranging up to approximately 75 m. The overall footprint of the zone measures 900 m long by 450 m wide and is up to 100 m thick.
The character of mineralization at the Estrellita deposit is a mixture of manto-style, iron oxide and structurally controlled, vein and breccia-style mineralization. The central part of the Estrellita deposit consists of a more or less horizontal tabular body of iron oxide manto that appears to have formed at the intersection of a flat-lying and a steeply dipping set of specularite structures.
Copper mineralization typically consists of copper oxides such as chrysocolla, malachite, Cu-limonite, black oxides, Cusulphates, and Cu-clays. In the same way as in Santo Domingo the oxidized mineralization at surface becomes gradually less oxidized with depth and transitions through a mixed and enrichment zone with oxides and secondary sulphides into a sulphide zone where the main copper mineral is chalcopyrite.
Production
The oxide material of 49 Mt is treated as waste in the mine plan. No economic process has been defined to treat this material. However, a stockpile area for the oxide material with copper content greater than 0.2% was set aside so that this material can be stockpiled for possible future processing.
| Commodity | Product | Units | Avg. Annual | LOM |
|
Copper
|
Payable metal
|
M lbs
| | 2,740 |
|
Copper
|
Metal in concentrate
|
M lbs
| 150 | 2,851 |
|
Copper
|
Concentrate
|
kt
| | 4,896 |
|
Gold
|
Payable metal
|
koz
| 20 | 370 |
|
Gold
|
Metal in concentrate
|
koz
| 22 | 412 |
|
Iron Ore
|
Concentrate
|
kt
| 3,600 | 68,398 |