Discovery of the Silver-Rich Juanicipio-Valdecañas Vein Zone, Western Fresnillo District, Zacatecas, Mexico
Peter K. M. Megaw, 2010. "Discovery of the Silver-Rich Juanicipio-Valdecañas Vein Zone, Western Fresnillo District, Zacatecas, Mexico", The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries, Richard J. Goldfarb, Erin E. Marsh, Thomas Monecke
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The 2003 to 2006 discovery of the important Juanicipio-Valdecañas vein zone in the western part of the famous Fresnillo silver district was the result of 10 years of research and geologic fieldwork predicated on the idea that the Fresnillo district was much larger than conventionally believed. High levels of vein exposure, extensive cover, and weak surface geochemical signatures have historically hampered exploration in the district and arguably resulted in a limited perception of the overall system. Nevertheless, new exploration success was the consequence of a continuation of discovery history in the district, just with a wider application of established concepts and broader scope of vision.
Information from published studies and reconnaissance field observations from the district were combined with improved academic understanding of the importance of variations in boiling levels in low-sulfidation epithermal vein systems to generate the concept that the extensive alteration zone, 5 km west of the Fresnillo mine, concealed additional veins. However, detailed geologic mapping, geochemical sampling, and geophysical surveys were required to convince investors that the concept was worth pursuing. The spectacular successes validate the work and demonstrate that several mineralization centers, with different boiling depths, were active in different places at various times in the district. This creates new exploration possibilities for the Fresnillo district and suggests that seeking vertically and laterally shifting mineralization centers in any large epithermal vein camp may be fruitful, particularly where mining and exploration have been confined to relatively limited areas or within vertically restricted zones.
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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.