The Caspiche gold-copper property is located 120 kilometres
southeast of the city of Copiapó in northern Chile, South America. It is
situated at the southern end of the Maricunga Belt between Cerro Casale (a
large undeveloped gold-copper project 12 kilometres to the south) and the
operating Refugio Gold Mine (15 kilometres to the north). Erosion of Miocene
volcanoes in the Maricunga Belt has exposed many subvolcanic porphyry stocks,
resulting in the identification of numerous copper-gold porphyry deposits
within the belt. The Maricunga belt also hosts several high-sulphidation
epithermal deposits.
Main rock types at the Caspiche property comprise pre to
syn-mineralisation felsic volcanics that are partially intruded by a
microdiorite unit. Both these units have been intruded by a series of five syn-mineral porphyritic stocks and contain
related intrusion breccias. Post mineral volcanics cover much of the area in
the north of the property. Quaternary colluvium overlies most of the property.
The Caspiche deposit was identified in 2007 with surface
assays revealing a zone of elevated gold and copper partially overlapping a
halo of sub-economic molybdenum. Subsequent drilling has revealed a proven and probable mineral reserve
of 1,091 Mt averaging 0.55 g/t Au, all but 124 Mt of which also contain 0.23%
Cu, for a total of 19.3 Moz of contained gold and 2.1 Mt of copper.
Mineralisation at Caspiche is related
to a series of five phases of diorite to quartz-diorite porphyry emplacement. The earliest of
these porphyries is dioritic in composition and hosts the highest grades of
gold and copper, while the later four are quartz-dioritic and host
progressively lower grades of mineralisation. The lower portions of
mineralisation at Caspiche occur within quartz ± magnetite veined rocks subject
to potassic alteration, while the upper portions are hosted within a
quartz-kaolinite dominated advanced argyllic alteration zone. A ‘silica cap’
associated with partial epithermal overprinting is associated with higher gold
grades and lower copper grades.
(Source: Sillitoe, et al., Society of Economic Geologists, Inc. Economic Geology, v. 108, pp. 585–604,
2013)
(Source: Exeter Resource Technical Report, www.exeterresource.com,
2008)
