Regional Geology
The Property is part of a larger district, straddling the Chile/Argentina border at a latitude of approximately 28.5° S.
Regional modern day geology is the product of eastward directed sub-duction of the Pacific Plate with associated volcanism and deformation along the western margin of South American continent.
Basement rocks in the region include Late Paleozoic granites and rhyolites of the Choiyoi Group. These are overlain by Jurassic and Cretaceous sediments. Compressional episodes in the middle Cretaceous have resulted in the uplift of the Andes. Extensional periods within the arc, such as is in the Paleocene-Eocene, resulted in extensional faulting, basin development and subsequent infill with terrigenous sediments. Eocene dioritic intrusive complexes are associated with this period.
A compressional regime has dominated from the Late Oligocene to present day and, along with development of the Miocene volcanic arc, there has been inversion of the Paleocene-Eocene extensional faults and related basins. The Property lies on the northern edge of the Chilean Flat Slab subduction zone (Kay and Mpodozis, 2002; Kay et al., 2014). Many of the significant porphyry and epithermal deposits within this belt have formed during the process of slab flattening from 18-5 Ma (Bissig et al., 2001; Mpodozis and Kay, 2003; Y. Kapusta in Rode et al., 2015; Yoshie et al., 2015; Holley et al., 2016; Sillitoe et al., 2016; Astorga et al., 2017).
Several belts of Late Oligocene to Miocene intrusions and associated volcanic rocks are developed in the central Andes and are responsible for the porphyry Cu-Au and epithermal systems of the Maricunga Belt and the high-sulphidation epithermal systems, including the El Indio-Pascua-Lama District.
Mineralization in The Maricunga Belt is from Late Oligocene to Miocene (Vila and Sillitoe, 1991) whereas the more southerly El Indio-Pascua-Lama Belts is of Middle to Late Miocene age (Bissig et al 2002).
Up until the late 1990’s, the Maricunga and El Indio belts were the main focus of exploration in the region, but it was recognized that the area between these two districts was prospective for similar systems. This has been borne out by work undertaken over the last two decades with discoveries such as the Los Helados, Josemaría and the Filo del Sol deposits which are of Late Oligocene to Late Miocene in ages.
Intrusive activity in the region, along with associated hydrothermal alteration, has been dated at Mid-Miocene to Late Miocene and shows similarities to many of the Maricunga-style Au-porphyries. Movement on structures has often led to the juxtaposition, telescoping or overprinting of high-sulphidation epithermal mineralization on these porphyry systems.
The figure below shows the aerial relationship of the Late Oligocene to Miocene volcanic rocks and associated porphyry and epithermal deposits.