Caspiche
- Location
- The Property and Agreement
- Caspiche Porphyry Prospect
- Caspiche Property Regional Prospects
- Caspiche Porphyry Metallurgy
- Available 43-101 reports
Location
The Caspiche Project is located in the Maricunga Belt of Chile, between Barrick and Kinross Gold’s Cerro Casale gold-copper deposit 10 kilometres to the south and Kinross Gold’s Maricunga Mine 15 kilometres to the north. Andina Minerals new Volcan gold deposit lies 35 kilometres north northeast of Caspiche. (See Figure 1).
The endowments for these deposits shown below demonstrate the potential of the area to host world class orebodies and recent success marks the Maricunga as an emerging world class gold province;
- Cerro Casale Gold-Copper Deposit, 21.2 million ounces of gold at a grade of 0.61 grams per tonne (“g/t”) and 5,308 million pounds of copper grading 0.22% (Kinross NI 43-101 Report, December 31st 2008).
- Refugio Gold Mine, 5.4 million ounces of gold at a grade of 0.76 g/t (Kinross NI 43-101 Report, December 31st 2006)
- Volcan Deposit, Measured and Indicated resources of 9.8 million ounces gold at a grade of 0.62 g/t and a further 0.77 million ounces of gold at 0.65g/t (Andina 43-101 Report, September 2009)
Figure 1: Southern Maricunga Belt Mineral Deposits on Satellite Imagery.
View Caspiche on Google Earth (File opens with Google Earth)
The Property and Agreement
In October of 2005 Exeter signed an option agreement with Anglo American Chile Limitada and Mantos Blancos S.A. (collectively "Anglo American") over the Caspiche Project in the Maricunga metallogenic belt of Chile. Exeter has now met all the required commitments to exercise the option. It currently proposes to exercise the option for 100% ownership within 60 days from January 31, 2011 which will trigger advance annual payments of $250,000 deductible from future royalties. Anglo American will be entitled to a 3% net smelter return from production.
The Caspiche property has a combined area of 1262 hectares, with a total property holding in the area of 3311 hectares. Exeter has identified a number of drill targets on the property, of which the most advanced is the Caspiche Porphyry and the associated intrusive complex (Figure 2). Additional drilling as also been undertaken at Caspiche EPITHERMALS and several other regional targets.
Figure 2: Caspiche Property, Principal Prospects and Drill Hole collars. Accurate to March 2010.
Caspiche Porphyry Prospect
DISCOVERY
Following prior exploration and drilling of the property by Anglo during the 1980’s and Newcrest during the 1990’s the property lay dormant until Exeter undertook an option agreement over the area in December 2005.
Building on detailed mapping and geophysics, in May 2007 Exeter drilled CSR-013, the final hole of the 2006/2007 season and the first Exeter drill hole testing the porphyry potential of the Caspiche Porphyry. This discovery hole reached 344 meters which was the ultimate capacity of the drill rig and intersected 304 metres (1,003 ft) grading 0.9 grams/tonne (“g/t”) gold (0.026 oz/ton).
Additional drilling confirmed the existence of a large previously untested higher grade porphyry intrusion with intersections such as 792.5 m @ 0.96 g/t Au and 0.4% Cu from hole CSD-16 and 1,234 m grading 0.89 g/t Au and 0.33% Cu which included 708 m grading 1.22 g/t Au and 0.42% Cu from hole CSD-032.
Currently drilling is continuing on the property, aimed at increasing the confidence and classification of the current resource, to define additional mineralisation where zones have not been closed off, and to look for satellite deposits. A range of test programmes and preliminary development studies have commenced and are ongoing.
Geology
Gravels (Quaternary alluvium) cover over 90% of the Caspiche property.
Host (basement) rocks at Caspiche comprise Tertiary age volcanic sandstone and siltstone. In the vicinity of Caspiche Porphyry this unit is overlain by a 500 to 700 m thick sequence of homogeneous polymict, volcanic breccia coeval with volcanism.
Two main porphyry intrusions, early and early inter-mineral phases, constitute the well mineralised Caspiche stock, with a third, late inter-mineral phase abutting it to the west and south. The well-mineralized stock measures roughly 300 x 400 m in plan view, with a vertical extent of over 1,200m. The early porphyry is blind, being concealed beneath an average of 100 m of pre-mineral volcanic breccia.
A late stage diatreme breccia occurs on the western side of the Caspiche porphyry system, dipping westward at approximately 30º. The breccia extends for a distance of at least 1 km in a north-south orientation and has been drilled to a thickness of 280 m.
Three dominant alteration types are recognised being potassic, intermediate argillic and advanced argillic. Potassic alteration is overprinted by intermediate argillic and both these are affected by the advanced argillic alteration assemblage. Massive silica and vuggy residual silica ridges crop out in the south and north of the Caspiche Porphyry prospect.
Siliceous ridges outcrop on the northern and southern peripheries of the Caspiche Porphyry prospect and are the surficial expression of high sulphidation epithermal style mineralization that extends to depths up to 200 m.
Oxidation effects are notable in the upper 100 m to 150 m and occasionally down to 200 m. The contact between oxide and sulphide material is sharp.
Immediately to the west, underneath a west dipping barren breccia a new zone of mineralisation named the “MacNeill zone” has recently been identified. This appears to be a separate later pulse of gold rich, copper poor mineralisation. Its shape appears to be lenticular and thickest underneath the shallower portions of the overlying breccia.
Alteration and Mineralisation
Mineralisation at the Caspiche Porphyry is described as a stockwork-hosted, gold-copper porphyry. This large tonnage, relatively low grade style of deposit is host to some of the worlds largest orebodies and are often mined in a bulk tonnage scenario.
The bulk of the mineralisation is hosted in a dense stockwork of grey veins. Potassic alteration is the earliest alteration phase and is more pronounced at deeper levels.
Intermediate argillic alteration overprints much of the potassic alteration. The main effect of this overprint are to convert magnetite to hematite (martitization). Due to this the porphyry mineralization is non magnetic to depths of around 400-500 m.
There is a “telescoped high-sulphidation epithermal” gold system overprinting the upper portion of the porphyry system, which provides some local upgrading of the gold from this upper zone.
Copper has been almost totally leached from the relatively flat lying oxide zone making it suitable for heap leaching. Secondary copper is rarely observed on the oxide-sulphide contact, but there is no significant copper enrichment. Visually the contact is easy to pick and is geochemically sharp with depletion in copper in the oxide zone.
Dominant ore minerals at Caspiche include chalcopyrite, covelite with bornite becoming the dominant mineral species with depth. Advanced argillic altered zones contain a high-sulphidation sulphide assemblage in which pyrite is accompanied by typically fine-grained intergrowths of enargite, tennantite, chalcopyrite, chalcocite, covellite and minor bornite.
Gold is associated with sulphides within the veins and locally disseminated in the wallrocks outside the intrusions but still spatially associated with vein material.
The MacNeill zone is dominated by pyrite as the primary sulphide with subordinate chalcopyrite.
Drilling
Figure 3 shows the collar locations and provides an indication of the large ore body “footprint” outlined from drilling to April 2010. Results and modelling indicate an orebody footprint to the mineralised system at +0.3 g/t gold approximately 1 cubic kilometre (0.62 cubic miles) in dimension.
A six rig drilling program was completed during May, 2010. At the end of this 30km drilling programa further 20km of drilling was compleyed at the Caspiche porphyry since the data cut-off for the interim resource estimate. The current program has two objectives: firstly to continue expansion of deposit through step out drilling, and secondly to complete the upgrade of the higher grade central zone to “indicated resource” status or better. A final resource estimate for the 2009/2010 season is expected near the end of Q3, 2010.
Figure 3 Caspiche Porphyry prospect, Drill hole collars and traces projected to surface. Accurate to March, 2010
The nominal drill spacing at Caspiche is on the order of 200 by 200 metres on a local grid orientated 060 degrees for inferred (lower confidence) resource. This is now being reduced to a (staggered) 100m line spacing for indicated (higher confidence) resources. This broad spacing is typical for porphyry deposits with low variability such as Caspiche.
Resources
On April 5th, 2010 Exeter reported an updated National Instrument 43-101 (“NI 43-101”) compliant mineral resource estimate.
The indicated resource is 785 Mt (million metric tons) at a grade of 0.57 g/t gold (grams per metric ton) and 1.33 g/t silver including 690 Mt at a grade of 0.20% copper. This equates to in-situ indicated resources of14.3 million ounces of gold, 33.6 million ounces of silver and 3.5 billion pounds of copper (a total of 23.9 million gold equivalent ounces*). The new inferred resource which consists mostly of new material (not previously estimated) as a result of expansion drilling contains a further 10.0 million ounces of gold, 26.7 million ounces of silver and 2.9 billion pounds of copper (a total of 17.8 million gold equivalent ounces*). The resource estimate uses all available assay data up to Feb 6th, 2010.
TABLE 1: Indicated and Inferred Mineral Resource Estimate for Open Pit Mining Combined with Underground Mining Scenario
| Category | Source Material | Gold Equivalent Cut-off (g/t) |
Million Metric Tonnes (Mt) |
Gold (g/t) |
Gold (Million Ounces) |
Copper (%) |
Copper (Billion pounds) |
Silver (g/t) |
Silver (Million Ounces) |
Gold Equivalent (g/t) |
Gold Equivalent* (Million Ounces) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Indicated | Open Pit Oxide | 0.2 | 95 | 0.46 | 1.4 | 0.01 | 0.0 | 1.84 | 5.6 | 0.46 | 1.4 |
| Indicated | Open Pit Sulphide | 0.3 | 482 | 0.58 | 9.0 | 0.20 | 2.2 | 1.24 | 19.1 | 0.97 | 15.0 |
| Indicated | Underground Sulphide** | NA* | 208 | 0.59 | 3.9 | 0.29 | 1.3 | 1.32 | 8.8 | 1.13 | 7.5 |
| TOTAL INDICATED | 785 | 0.57 | 14.3 | 0.20 | 3.5 | 1.33 | 33.6 | 0.95 | 23.9 | ||
| Inferred | Open Pit Oxide | 0.2 | 13 | 0.30 | 0.1 | 0.01 | 0.0 | 1.94 | 0.8 | 0.30 | 0.1 |
| Inferred | Open Pit Sulphide | 0.3 | 377 | 0.44 | 5.3 | 0.15 | 1.2 | 1.16 | 14.1 | 0.71 | 8.6 |
| Inferred | Underground Sulphide** | NA* | 298 | 0.47 | 4.5 | 0.25 | 1.6 | 1.23 | 11.8 | 0.95 | 9.1 |
| TOTAL INFERRED | 688 | 0.45 | 10.0 | 0.19 | 2.9 | 1.21 | 26.7 | 0.81 | 17.8 | ||
Metal endowment for this mining scenario is as follows:
INDICATED 14.3 Million Ounces of Gold, 3.5 Billion pounds of Copper and 33.6 Million ounces of silver
INFERRED 10.0 Million Ounces of Gold, 2.9 Billion pounds of Copper and 26.7 Million ounces of silver
Importantly the majority of this higher confidence, indicated resource is centred on the coherent higher grade central core to the system (shown in Table 2 as a discrete stand-alone mining scenario) which extends to the base of the oxide zone. In all likelihood this central higher grade zone will drive any future mining and/or economic models for the project.
Growth to the resource beyond the previous September 2009 estimate was aided by the discovery of new mineralised systems within the immediate vicinity of the Caspiche Porphyry including the recently identified MacNeill Zone to the west.
While primarily a gold rich porphyry system the base metal contribution at Caspiche continues to be significant with copper providing approximately 40% of the value of the project using AMEC’s internal long term price forecasts for gold and copper.
TABLE 2: Indicated and Inferred Mineral Resource Estimate for Open Pit Mining of the Oxide Resource Only Combined with Underground Mining of the Central Higher Grade Zone
| Category | Source Material | Gold Equivalent Cut-off> (g/t) |
Million Metric Tonnes (Mt) |
Gold (g/t) |
Gold (Million Ounces) |
Copper (%) |
Copper (Billion pounds) |
Silver (g/t) |
Silver (Million Ounces) |
Gold Equivalent (g/t) |
Gold Equivalent* (Million Ounces) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Indicated | Open Pit Oxide | 0.2 | 70 | 0.51 | 1.2 | 0.01 | 0.0 | 1.84 | 4.1 | 0.52 | 1.2 |
| Indicated | Underground Sulphide** | NA* | 398 | 0.73 | 9.4 | 0.29 | 2.6 | 1.37 | 17.6 | 1.28 | 16.4 |
| TOTAL INDICATED | 469 | 0.70 | 10.6 | 0.25 | 2.6 | 1.44 | 21.7 | 1.17 | 17.6 | ||
| Inferred | Open Pit Oxide | 0.2 | 5 | 0.37 | 0.1 | 0.01 | 0.0 | 1.94 | 0.3 | 0.37 | 0.1 |
| Inferred | Underground Sulphide** | NA* | 234 | 0.63 | 4.8 | 0.28 | 1.5 | 1.47 | 11.0 | 1.16 | 8.7 |
| TOTAL INFERRED | 239 | 0.63 | 4.8 | 0.28 | 1.5 | 1.48 | 11.3 | 1.15 | 8.8 | ||
Metal endowment for this mining scenario is as follows:
INDICATED 10.6 Million Ounces of Gold, 2.6 Billion pounds of Copper and 21.7 Million ounces of silver
INFERRED 4.8 Million Ounces of Gold, 1.5 Billion pounds of Copper and 11.3 Million ounces of silver
*AMEC chose to report the resource above a Au equivalent cutoff. For this they used prices of US$950/oz for Au and $2.30/lb for Cu. The formula used to calculate Au equivalents is Au(g/t) + Cu (%) * (Cu Price [$/lb]/Au Price [$/oz]) * (Rec Cu/Rec Au)*0.06857*10000. Where Rec = % recovery and 0.06857 = conversion g*lb/oz. Au and Cu are the block kriged Au and Cu grades. Projected metallurgical recoveries were 75% and 85% for Au and Cu respectively in sulphide material and 50% for Au in the oxide zone. Recoveries are based on benchmarking of similar deposits.
“For block model level plans, and sections”, click here.
For further information on the Caspiche Porphyry discovery, geology, mineralisation and resources:
Download the latest 43-101 on Caspiche 3.5 MB PDF
Link to March 2010 resource announcement press release
Link to Caspiche Discovery history paper
Engineering and Infrastructure
Caspiche is a green field discovery, and thus existing site infrastructure is limited to an exploration camp and roads. However the Cerro Casale is located to the immediate south, and the operating Maricunga mine is located 15 kilometres to the north providing generally good infrastructure in the area.
In 2009 Exeter commissioned Santiago based NCL Ingenieria y Construccionto (NCL) to undertake an Initial Mine Development and Infrastructure Study for internal purposes only. NCL reviewed a number of mining options based on the then current resource.
Early conclusions based on their preliminary work appear to support those from AMEC international that the Property is large enough to host an open pit and/or underground mining operation, including a reasonably-sized open pit, mill, tailings facilities, waste dumps, and leach pads. Currently the preferred extraction option by NCL is a hybrid scenario with a 600 metre deep open pit to extract the oxide and shallow sulfide material followed by an underground block cave to mine the sulfide material below 600m. New studies will be conducted by NCL following the issue of the April and thence the September resource estimates.
The mining concession owner in Chile typically has the right to establish an occupation easement over the surface as required for the comfortable exploration or exploitation of the concession. In January, 2008, Exeter made formal application to the Ministry of Public Land of the Chilean government (Bienes Nacionales) for the surface rights to the Caspiche property area and the application is currently being processed.
In May 2009, Exeter contracted Inversiones Ambiental Ltda. (IAL) from Santiago, Chile to perform baseline environmental studies. IAL will be investigating the following topics as part of the study:
- Physical aspects, including climatology, geology, geomorphology, and hydrology
- Biological aspects, including seasonal monitoring of flora and fauna.
- Human aspects, including socioeconomics and demography
- Construction aspects, including economic activities and infrastructure
- Use of the soil
- Archaeology
- Anthropology
- Landscapes
- Natural risks, including flood and landslide
The study will focus on about 20,000 hectares surrounding the Caspiche project area. However, the human, construction, and anthropology studies will incorporate the local communities well beyond this area. The duration of the baseline study activities is anticipated to be about 14 months, with a final report anticipated in mid 2010.
Power and Water
Power for the existing projects in the Maricunga region is normally sourced from near Copiapó and carried to the mines by private power lines owned by the operating companies. At Caspiche, two areas of relatively level ground are already under mineral concessions over which Exeter maintains rights, and the process for obtaining permits for easements is straightforward in Chile.
Exeter contracted the engineering company, Hatch Engineering to perform a power supply overview study for electrical power in Chile, with specific focus on Region III. Hatch reported new investment in power generation in Chile, particularly for coal-fired power plants. Power costs in the area are expected to decrease in 2009, and continue decreasing through 2014, thence to remain stable for several years.
Currently Exeter is in the early stages of a preliminary study into the high voltage power supply and distribution specifically to Caspiche.
Exeter contracted the engineering company, Knight Piesold, to complete a preliminary water supply study that included a review of previous water studies in the Caspiche area, descriptions of applicable regulations, a compilation of existing hydrologic data and water rights for the area, an analysis of the social impact of water demands in the area, and recommendations of water sources potentially available to the Caspiche project.
Exeter is compiling a survey of the subterranean and surface water use rights held by third parties located within the area of influence of the Caspiche project area. Exeter is currently implementing a water acquisition strategy as part of which the company has requested three permits for the exploration of underground water, covering a total area of 69,125 ha. These exploration permits remain in process.
Caspiche Metallurgy
Preliminary metallurgical testwork has been carried out by Exeter on six oxide composites from prior drilling campaigns. Column leach results from the two composite samples from this material returned 84% recovery from the andesite composite with a calculated head grade of 0.50 g/t gold, and 77.5% recovery from the diorite composite with a calculated head grade of 0.40 g/t gold.
Additional column leach testwork on oxide mineralization from 2009-2010 PQ diameter core is ongoing with several tonnes of material currently being tested at a range of different crush sizes to determine the optimum size-recovery relationships.
Test work on the sulphide component of the deposit is currently underway with 20 composite samples currently being analyzed covering a range of grades, rock and alteration types.
Basic flotation testwork on a nominal grind of 140 µm K80 on the sulphide composites shows that about 85% of the copper and between 40% and 70% of the gold was recovered in the concentrate. Work in 2009 and 2010 continues to focus on optimizing the grind and flotation conditions to improve metallurgical performance.
Gravity concentration from the rougher tailings stream is being investigated to investigate its potential to increase gold recovery. Ongoing testwork will focus on grouping the 20 drillhole metallurgical samples into true composites based around pyrite and arsenic content, to begin flow sheet optimization. Including ore hardness tests, flotation tests to optimize regrind requirements and additional gravity concentration tests, and locked cycle tests to provide reliable metallurgical performance values.
Caspiche, like many of the Chilean and the global copper porphyry projects has elevated arsenic which was identified early by the company. In August 2009, Exeter commissioned SNC-Lavalin (SNCL) to review and compare eight nominated processes for the treatment of enargite-rich concentrates in the context of the known Caspiche mineralization and geographical location. Capital and operating cost estimates were developed for a treatment rate of 1620 tonnes/day of concentrate. The treatment rate is based on a concentrator throughput of 50 million tonnes/year. The SNCL study was completed in February 2010 and, because of the proprietary nature of many of the technologies, the detailed outcomes will remain confidential. However the capital investments required (including a 25% contingency) ranged from approximately US$200M to US$700M. These estimates can be considered in the context of recent estimates for equivalent projects of the order of US$4,000M. The operating costs of the processes (including a 15% contingency) ranged from US$ 0.27/lb of copper to US$0.44/lb of copper.
Our intention is to start some testwork on the two preferred techniques later this year after we have carried out a first flotation pilot plant campaign on some Caspiche samples.
Proposed Schedule
The following figure shows the development schedule for progress and key milestones at the Caspiche project.
Available 43-101 Reports
This webpage is provided as a general summary of current activities and should not be considered definitive nor complete by nature. Additional technical information on all aspects discussed above are contained in our most recent NI43-101 report which is linked from this page or available on www.sedar.com.
12 March, 2010 (Details 7.8 MB - PDF)
19 October, 2009 (Details 3.5 MB - PDF)
14 September, 2009 (Details 3.5 MB - PDF)
14 September, 2009 (Details 3.5 MB - PDF)
27 March, 2009 (Details 4.9 MB - PDF)
9 February, 2009 (Details 8.1 MB - PDF)
26 April, 2008 (Details 6.23 MB - PDF)
24 December, 2007 (Details 6.72 MB - PDF)
Caspiche Property Regional Prospects
Exeter has identified a number of additional drill targets on the property beyond the immediate vicinity of the Caspiche Porphyry, of which the most advanced is the Caspiche epithermal prospect. Exeter commenced first pass drilling early in 2007 which confirmed the presence of an epithermal gold system at Caspiche Epithermals. Subsequent holes intersected significant widths of gold ± silver mineralisation. The best result to date was the most recent hole drilled near the end of the previous season which intersected 10 metres at 3.5ppm Gold and 33ppm Silver. Follow up drilling is being planned for both epithermal mineralisation and to explore the possibility for a Caspiche look alike system at depth.
| Hole | From (m) |
To (m) |
Width (m) |
Gold g/t |
Silver g/t |
|---|---|---|---|---|---|
| CSR-002 | 52 | 76 | 24 | 1.1 | 23 |
| CSR-002 | 172 | 178 | 6 | 1.7 | 16 |
| CSR-006 | 144 | 166 | 22 | 1.5 | 1.6 |
| CSR-008 | 42 | 58 | 16 | 1.3 | 5 |
| CSR-010 | 166 | 202 | 36 | 1.3 | 26 |
| CSR-011 | 96 | 108 | 12 | 1.2 | 4 |
| CSR-012 | 94 | 110 | 16 | 2.1 | 2 |
| CSD0040a | 232 | 242 | 10 | 3.5 | 32.6 |
Table 4: Significant Exeter Drill Intercepts from the Caspiche Epithermals Epithermal Gold + Silver Target
A number of additional regional targets have been identified from detailed mapping, geochemistry and geophysics. These have been ranked according to priority and will be tested progressively as the project evolves.
The potential for additional discoveries is considered good.