Summary:
Local Project Geology
Minera Don Nicolás holds approximately 335,000 hectares of mining properties and projects, covering a sizable portion of the eastern sector of the Deseado Gold Silver Massif. Various portions of the property are currently at different levels of exploration.
Las Calandrias
Calandrias has been divided into three regions – Calandrias Sur, Calandrias Norte and El Nido. These deposits occur within the Jurassic-age rhyolite domes in the southeastern part of the Property (also referred to as “Dos Calandrias”) and, to a lesser extent, at the El Nido dome complex situated in the centre and west of the Property. El Nido Complex includes the El Nido Sur, El Nido Norte, El Nido Este, and El Nido Centro prospects.
Calandrias Sur and Calandrias Norte mineralised zones are part of a rhyolite dome complex within an approximate 3 x 3 km area that intrudes ignimbrite of the Jurassic Chon Aike Formation. Calandrias Sur and Calandrias Norte domes are centred on 1.5 x 1.3 km. An early polymictic breccia, interpreted to be a phreatic or phreatomagmatic vent fill (Sillitoe, 2009b), crops out on the lower ground around the dome margins. The rhyolite domes were emplaced into the breccia fill and exhibited flow banding and total devitrification. The Calandria Norte dome, cut by the Calandria Norte vein, is distinguished by delicate, highly contorted flow foliation. The Calandria Sur dome, containing the hydrothermal brecciahosted mineralisation at Calandria Sur, largely comprises clast-supported breccia at the surface. Overburden cover consists of volcanic ash and alluvium.
Martinetas
The Martinetas low-sulfidation epithermal deposits are hosted by the Jurassic Bahía Laura Volcanic Complex (BLVC; De Martino, 2021). The BLVC is locally represented by extensive pyroclastic (dilute and dense) and interbedded coherent silicic and meso-silicic volcanic units. This sequence is covered by massive ignimbrites and intruded by a swarm of rhyolitic dikes.
The main district host rock is Martinetas Ignimbrite, which is joint with related rhyolitic domes. Post-mineralisation, a phreatic brecciation stage, fractured and mixed much of the geology near the surface into the polymictic breccia unit. The project areas encompass the deposits of Armadillo, Cerro Oro, Chique, Coyote, Mara, and Zorro, ranging from early to advanced exploration stages.
Paloma North and Central Block
The Paloma district is in the northeastern sector of the Deseado Massif, Santa Cruz province, Argentina, and is in a very advanced exploration stage. It belongs 100% to Minera Don Nicolas and is located 45 km from the CIL process plant at the Martinetas flagship project.
The North Block of Paloma contains an andesitic sequence of volcanic breccias (sectors with large lithics), stratified tuffs, and porphyry andesites (laccolith-type intrusives and dykes that intrude the pyroclastic units). The veins exhibit colloform to massive textures of chalcedonic silica with primary NE-SW and N-S orientations. The main areas of interest include the Verde (N-S), Hermanas V (NE-SW), Arco Iris (NE-SW), Clara (N-S), Luisa (NE-SW), Reyna-Princesa (N-S), and Duquesa-Zaina-Maria Eugenia (E-W to ENE-WSW).
Mineralisation
Silicified structures and vein breccias host gold mineralisation in Calandrias Sur and Calandrias Norte. High-grade gold and silver veins (greater than 3 g/t Au and 50 g/t Ag), veinlets, stringers, and breccias are closely related to subaerial rhyolite flow domes that were emplaced at the junctions of northwest- and northeast-trending fractures.
The veins are composed of dense brown chalcedony at the surface, partly hydrothermally brecciated. This chalcedony is locally crustiform, and cavities within the veins are filled with massive kaolinite.
Calandrias Sur
The bulk of the mineralisation is centred in the core of the Calandrias Sur rhyolite dome. It consists of thick zones (up to 90 m) of disseminated sulphides, stockworks, and subordinate breccias. The highest gold and silver grades correlate with increased silicification intensity and stockwork veinlets' density.
Calandrias Norte
The Calandrias Norte rhyolite dome, located about 600 m north of Calandrias Sur, hosts northeast-trending veins and vein/breccia mineralisation entirely within the circular rhyolite dome. This vein and vein/breccia mineralisation lies within a broader area of weak stockwork to disseminated mineralisation. High-grade gold-silver mineralisation starts 50 to 60 m below the surface. At least three distinct vein systems are found within Calandrias Norte: the Calandria Norte vein, the Tongoril and the Morena in the northwest. At the discovery outcrop of the Calandria Norte Vein, where the mineralisation was initially identified by trenching, the vein-breccia is up to 0.7 m wide with multiple parallel veins; the vein breccia strikes northeast and dips steeply to the northwest.
Martinetas
The Martinetas region contains multiple mineralised structures occurring as large “vein swarms” with minor intervening stockwork. and by more discrete localisation of continuous veins. The area has been extensively explored for more than 25 years, and for the most part, all known large deposits in the project area have been mined.
Paloma Trend
The Paloma trend's primary orientation is NNW to NW and follows the architecture of preexisting faults cutting andesitic rocks. The Sulfuro Vein corridor, located in the southern part of the La Paloma district, constitutes a 1000 m long and up to 600 m wide block occupied by several segments of mineralised lodes between 0.3 and 6 m thick. To the north, this trend turns to a WNW and an ENE orientation that confers an arcuate shape. In the Sulfuro vein, the mineralisation has been defined for 850 m along strike and to a depth of 250 m, with an average width of 3 m.
Deposit Types
Las Calandrias Area
The Deseado Massif hosts numerous low- to intermediate-sulphidation, epithermal, precious metal quartz vein and vein-breccia deposits, of which Las Calandrias Sur and Las Calandrias Norte deposits are examples. Hydrothermal activity and formation of these deposits closely followed episodes of the Jurassic magmatism and extension in the Deseado Massif (Ristorcelli et al., 2018).
Martinetas and La Paloma Trend Area
The gold-silver deposits of the Deseado Massif are hosted in silicic volcanic and volcanic sedimentary Jurassic rocks related to arc or back-arc settings in Andean or extra-Andean settings. The ore geology, textures, mineralogy, restricted alteration, and geochemistry of these mineralised occurrences indicate they belong to the epithermal class of precious metal deposits. The deposits are mainly associated with quartz +/- calcite +/- adularia +/- illite alteration assemblages interpreted to represent low and intermediate sulphidation epithermal type deposits.