Valuation and Prioritization of Early-Stage Exploration Projects: a Case Study of Cu–Ag and Au-Mineralized Systems in the Tiltil Mining District, Chile

Abstract

A problem for mining districts, for example those with small to medium operations, is the uncertainty with respect to the valuation of exploration targets. In cases where a mining district has been only partially developed, geological uncertainty likely represents a substantial part of resource valuation risk. To address this problem, we developed a method for valuing exploration targets in the early stage of exploration based on four variables: (1) risks associated with exploration; (2) geological uncertainty; (3) economic potential; and (4) exploration costs. The new method presented offers a simple and replicable means to value mineralized bodies and prioritize mining activities based on quantitative geoscientific information and can additionally be adapted to analyze other exploration projects, such as those located in areas without mining activity. In this work, we studied a series of Cu–Ag and Au veins located in the Tiltil Mining District in the Coastal Cordillera of the Chilean Central Andes. We performed four steps in order to characterize the level of uncertainty in the resource exploration and valuation: (1) we acquired district-level data on the geology in and around Tiltil and the activity of 39 small mining operations; (2) we designed a preliminary conceptual exploration campaign; (3) we applied and adapted a new method for the valuation of mineral resources; and (4) we estimated the economic value of the studied mineral targets. The valuation method uses the product of three mutually independent variables: potential value, exploration risk, and geological uncertainty. The estimated value of minerals, at Tiltil, without discounting cash flows is 50.2 billion CLP, while a discount rate of 15.62% returns an estimate of 26.7 billion CLP. When adjusting these values for the level of geological uncertainty discerned in our method, the resulting values are approximately 56% less. We additionally applied the valuation method to seven potential mining targets, considering both potential exploration resources and inferred resources, and found values ranging from 21.8 billion and 11.8 billion CLP (32.3 million and 17.5 million USD with an exchange rate of 675.48 CLP per USD) without discounting cash flows and with a discount rate of 15.62%. We encourage the use of this new method in the early-stage development of small mining operations in order to characterize correctly potential profitability.