Mining company Orosur Mining announced in March that its geology teams have mobilised to Santa Cruz province, Argentina, to start the company’s first field exploration programme at the El Pantano gold/ silver project.
The field programme is expected to last about two weeks and will involve extensive mapping and surface sampling (soils and rock chip) programmes over the two most attractive prospects that have been identified following examination of historical data and previous due diligence visits.
The El Pantano project is subject to an exploration and joint venture (JV) agreement with private Argentinean company Deseado Dorado SAS and its shareholders, the details of which were announced on February 15, earlier this year.
The general terms of the agreement allow for the company to earn 100% equity in the project by investing $3-million over five years in two phases.
Phase 1 will earn 51% by investing $1-million over an initial three-year period.
Phase 2 will move to 100% ownership by investing an additional $2-million over a subsequent two-year period, granting Deseado a residual 2% net smelter return royalty on the project.
Location and Geology
The agreement covers nine contiguous licences owned by Deseado, that combined, total 607 km2 in the prolific Deseado Massif region of Santa Cruz province in southern Argentina, about 45 km from AngloGold Ashanti’s Cerro Vanguardia mining camp.
Access to the project is by paved road several hours drive south from the regional city of Comodoro Rivadavia, and then about 50 km travel on “good quality” dirt roads west from the Tres Cerros Roadhouse.
The region is barren and sparsely populated, largely as a result of the near complete devastation of the region’s agricultural industry by ashfall from the 1991 eruption of Mt Hudson. Several large and widely spaced ranches exist across the project area, which will provide accommodation for field teams, eliminating the need for development of dedicated camps.
The company has carried out extensive technical due diligence of the prospectivity of the project, including literature searches, field visits and detailed examination of previous company work.
Government provided airborne geophysical data demonstrates that the proect area is bisected by a major south-east to north-east trending crustal scale structure, which is the primary orientation known to control emplacement of gold and silver mineralisation across the Deseado Massif.
The company notes that preliminary field inspections concentrated on this structural corridor have demonstrated positive indications that a major epithermal system exists here and as such two initial prospects have been identified and will be the subject of this initial phase of exploration.
The San Antonio prospect lies within the south-east of the project area and was explored in a cursory fashion by Minsud Resources Corporation for several years until 2016.
Minsud carried out some low-level mapping and sampling of epithermal veins along the main structure that were the north-west continuation of high-grade veins that had been previously identified by other local companies outside the project area. A series of small resistivity and induced polarisation (IP) surveys were also undertaken.
Work by Minsud demonstrated a highly prospective and potentially large epithermal system associated with the eruption of dacitic domes, and evidence of pervasive silicification and argillic alternation.
During Minsud’s tenure, however, San Antonio would appear to have been its third-tier project, with most of its efforts concentrated on resource drilling elsewhere in Argentina and Chile, with little attention directed toward San Antonio.
La Esfinge (The Sphinx)
La Esfinge prospect lies about 5 km along strike from San Antonio to the north-west, located directly on the primary regional structure. This prospect is characterised by a large (8 km strike length) silicified hill within a large erosional window whereby the overlying basalts have been removed.
The prospect shows evidence of massive silica flooding and the development of alteration and other features that suggest La Esfinge is part of the same epithermal system as San Antonio, but slightly higher in that system.
No evidence of historical modern exploration has been uncovered, and it is possible then the prospect is untouched.
Exploration Plans and Logistics
El Pantano is well located, with good access, in a flat and open environment, and therefore, in general, is reasonably easy to explore.
The winter months (mid-May to mid-July) in Patagonia, however, in addition to being very cold, are characterised by very short days, making fieldwork logistically inefficient.
In light of the imminent winter, the company has decided to undertake a small sampling programme now, such that if results are positive, sufficient time may remain for a second follow-up programme before the winter break.
“With the handover of Anzá, and the freeing up of financial and technical capacity, our attention now turns to our new projects. El Pantano represents an exciting project in that it demonstrates all of the early-stage geological signs of a major epithermal system – but is largely untouched by modern exploration,” Orosur CEO Brad George said at the time.