Discovery History of the Navidad Silver Deposits, Chubut, Argentina: One Thousand Years in the Waiting
Paul G. Lhotka, 2010. "Discovery History of the Navidad Silver Deposits, Chubut, Argentina: One Thousand Years in the Waiting", The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries, Richard J. Goldfarb, Erin E. Marsh, Thomas Monecke
Download citation file:
The Navidad silver deposits in the Somuncura Massif of Patagonia in the province of Chubut, Argentina, were discovered in 2002 by following up results of a geochemical stream-sediment survey. The multisample Ag-Pb-Zn anomaly was recognized by the company that undertook and interpreted the survey, but it recommended that the anomaly not be staked. The anomaly was rediscovered in data passed to another company on November 28, 2002, and this led to a field examination on December 10, 2002. This quickly confirmed the source of the anomaly in outcropping and subcropping mineralization hosted in Jurassic volcanic and sedimentary rocks. Unlike most other silver occurrences in the region, the Navidad deposits contain no significant gold values and are not vein deposits.
Once the initial discovery was made, Navidad was quickly shown to host one of the world’s largest silver resources. It is now recognized to contain 23,359 metric tons (t; 751 Moz) Ag and 1.59 Mt Pb in 201.1Mt of mineralized rock at a grade of 117 g/t Ag and 0.79 percent Pb.
Navidad should easily have been found at an earlier date using only simple technology because it is easily accessible and outcropping. However, over the last 1,000 years different groups including indigenous peoples, European settlers, government mineral exploration programs, and finally modern exploration companies, failed to make the discovery due to cultural, not technological, factors. The cultural factors that impeded discovery are varied ranging from the general lack of interest in metallic minerals by early European settlers of Patagonia to the incomplete investigations of the government exploration programs and relatively inaccessible nature of the data they generated. Later corporate explorers emphasized gold, and ignored silver, or focused on remote sensing alteration mineral anomalies which are not well developed at Navidad. Finally, corporate culture including dogmatic model-, and/or commodity specific-, driven exploration instead of a more pragmatic react-to-the-data approach, may have also been a factor.
Figures & Tables
The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries
There seems to be general consensus throughout much of the global mining industry that the supply of base and precious metals and some other commodities (e.g., ferrous metals, uranium) is reasonably well assured into the oreseeable future because increases in total resources continue to keep pace with or outstrip global consumption. The basic assumption is that market forces and technological advances will combine to promote and perpetuate this trend (e.g., Tilton, 2003; Crowson, 2008). Others disagree, however, andpredict that shortages are inevitable if metal consumption continues to escalate (Beaty, 2010).
It is already becoming clear that many known resources seem unlikely to be mined, irrespective of commodity prices, because of their low grade and/or quality. Hence, many mineral resources that were uneconomic in the early 2000s are likely to remain so, both today and into the foreseeable future because of increases in both the direct (e.g., energy, labor) and indirect (e.g., environmental, social) production costs. This situation is being further exacerbated by the perceived decrease, over at least the past decade, in the discovery rate of base and precious metal resources measured in terms of both the number of major discoveries made and the exploration dollars spent per discovery (e.g., Dummett, 2000; Horn, 2002; Schodde, 2004). There is also a suggestion that the discoveries made are, on average, becoming both smaller and lower grade. Therefore, it seems reasonable to ask whether current exploration practices and success rates are going to be adequate to provide for the massive increases in metal consumption that world population growth, rising living standards, and rapid industrialization and urbanization in China, India, and other emerging markets appear to portend. For example, Rio Tinto's projections suggest that "by 2030 the additional supplyrequired will be equivalent to replicating the iron ore output of the Pilbara region of Australia every five years, adding another aluminium production complex the size of Canada's Saguenay every nine months, and developing another copper mine the size of Escondida in Chile each year. Future energrequirements are such that an entire Hunter Valley coal supply chain needs to be created each year plus a uranium mine the size of Ranger every four years" (Albanese, 2010, p. 7). Clearly, the exploration business has to become increasingly effective if it is to rise to the challenge of finding mineral resources of the right caliber to assure that this burgeoning demand can be adequately satisfied.