Tesoro Mining Chile SpA (95% owned by Tesoro Gold Ltd) has increased its ownership of the El Zorro Gold Project to 95.4% through a capital contribution of approximately CLP5.2 billion (approximately US$5.4 million) to El Zorro SCM, covering capitalised expenditure at the project. As a result, Tesoro Gold Ltd’s effective ownership of El Zorro has risen to approximately 90.6%.
El Zorro Joint Venture partner, Wanaco SpA (Wanaco).
The proceedings, filed in 2021 against Tesoro’s Chilean subsidiary, Tesoro Mining Chile SpA (TMC) and its officers, related to the valuation and the procedure followed for a capital increase approved at the Shareholders Meeting of El Zorro SCM held on 11 February 2021. Wanaco alleged breaches of the Mining Code, Corporations Law, and Civil Code.
The 7th Civil Court de Santiago de Chile has now confirmed that these claims and associated damages were without merit, awarding costs to TMC. Other ancillary proceedings filed by Wanaco remain before the courts.
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Summary:
The El Zorro Project is located within the Coastal Cordillera of Chile. At Ternera, gold mineralisation is predominately hosted within numerous intermediate intrusions and associated quartz and sulphide veins, veinlets, and alteration, within faulted and strongly altered tonalitic intrusions (El Zorro Tonalite or EZT). The EZT intrusions have intruded Permian aged basement sedimentary sequences. Gold mineralisation at Ternera has been classified as an Intrusive Related Gold System (IRGS) and Tesoro has discovered additional gold targets in the El Zorro District which exhibit similar styles of gold mineralisation.
Gold mineralisation is interpreted to be related to regional scale north-south striking fault zones and associated local north-west striking strike slip faults. Mineralisation is interpreted to occur as discontinuous shoots, controlled by a combination of the intersection of the structures with the preferred host rock tonalite, and locally developed intersections of fracture populations that developed during strike-slip deformation.
The project area is in an early Cretaceous volcanic arc containing structurally controlled batholitic intrusions. During this period extensional tectonic activity included the formation of the intra-arc, sinistral, strike-slip Atacama Fault System along the Coastal Cordillera. The metallogenesis during the evolution of the Chilean Andes was dominated by copper-gold mineralisation characterised by several Late Jurassic and Early Cretaceous volcanic-hosted Cu-Ag manto-type deposits, mesothermal Cu-AuAg veins and iron oxide copper-gold (IOCG) deposits. Although the El Zorro mineralisation is located within a belt characterised by IOCG-type mineralisation, the El Zorro mineralisation is more typical of an intrusive related gold deposit type with gold mineralisation closely associated with a suite of felsic to intermediate intrusive rocks of Late Triassic age.
The oldest rocks in the project area are Palaeozoic sediments of probable Devonian to Lower Carboniferous age. These have been intruded by a Jurassic granodiorite body of the Coastal Batholith Series which has thermally metamorphosed the sediments around the intrusion contact. Fine-grained sediments have been metamorphosed to phyllites and massive fine grained dark hornfels and the more arenaceous sediments to quartzites.
In the El Zorro Project, the main mineralised intrusions are underlain by a Devonian age sedimentary rock sequence consisting of interbedded siltstone, volcaniclastics, and minor quartzite, all of which has been variably metamorphosed and folded.
The sediments have been intruded by multiple mineralised tonalite to diorite intrusions interpreted as a possible late stage differentiate of a larger granodiorite body, which have been emplaced as dykes and sills. The granodiorite intrusion has thermally metamorphosed the sediments within several hundred metres of the contact resulting in highly resistant phyllite, dark fine grained hornfels and quartzite. The phyllite is a very fine grained, foliated, black, dense rock.
The later stage intrusive tonalites occur as south-west to north-east striking bodies dipping toward the south-east.
The mineralisation model is considered to be an intrusive related gold deposit. The key characteristics that are consistent with this style deposit include:
• Low sulphide content, (typically <5%); reduced ore mineral assemblage that typically comprises pyrite and lacks primary magnetite or hematite;
• Mineralisation occurs as sheeted vein deposits or stockwork assemblages and often combine gold with variably elevated Bi, W, As, Mo, Te, and/or Sb but low concentrations of base metals as seen in the initial four holes by Tesoro at El Zorro;
• Restricted and commonly weak proximal hydrothermal alteration;
• Intrusions of intermediate to felsic composition.
Dimensions
The mineralisation extends over a strike length of 1000 m and a width of 600m.
Mineralisation extends up to 600m below the topographic surface.