Skip to Main Content
Book Chapter

The Role of Geochemistry in Andean Copper Discoveries

By
David L. Kelley
David L. Kelley
1
MMG, 390 Union Blvd, Suite 200, Lakewood, Colorado 80228
Search for other works by this author on:
Chris Benn
Chris Benn
2
Gold Fields Exploration, #400-1155 Robson Street, Vancouver, British Columbia, Canada V6E 1B5
Search for other works by this author on:
K. Brock Riedell
K. Brock Riedell
3
Consulting Geologist, 4732 Willow Creek Road, West Vancouver, British Columbia, Canada V7W 1C4
Search for other works by this author on:
Teresa Johnson
Teresa Johnson
1
MMG, 390 Union Blvd, Suite 200, Lakewood, Colorado 80228
Search for other works by this author on:
Published:
January 01, 2010

Abstract

A review of the record of copper discovery in the Andes over the past four decades reveals that discoveries peaked in the 1990s when 14 discoveries were made. The 1980s and 1990s were the most important decades in terms of amount of copper discovered, accounting for 115 million metric tons (Mt) of copper. During the most recent decade, discoveries have dropped by 57 percent due to exploration maturity in well-exposed terrain, lack of effective exploration methods in concealed terrain, and a greater focus of exploration expenditures on known resources rather than new discovery. The first concealed deposit was recognized in 1986 at Candelaria, and since then nine additional concealed deposits have been discovered, accounting for 47.8 Mt of copper.

Geochemistry played an important role in several of these copper discoveries, but unfortunately the published record on these case histories is sparse. In the late 1960s, recently developed geochemical exploration methods using field-based analytical techniques were applied for the first time in South America. Although crude, these early applications were effective in aiding discoveries at Santa Clara, Argentina, and Los Pelambres, Chile. At Los Pelambres, the rugged topography and extensive talus deposits led to testing the use of finegrain talus as a sample medium. A subsequent talus survey effectively outlined the extent of mineralization. Reconnaissance stream-sediment geochemistry and leached cap geochemistry were instrumental in the discovery of Escondida and later Zaldivar-Escondida Norte. Although the discovery of the completely gravelcovered Spence deposit is mainly attributed to systematic grid-based drilling of vast covered regions, base-ofgravel copper geochemistry did provide a vector to nearby mineralization. The use of panned-concentrate geochemistry in southern Ecuador, initially designed for gold exploration, highlighted several areas of base metal mineralization, leading to the discovery of the San Carlos deposit. The discovery of the Haquira oxide mineralization in southern Peru, and subsequent discovery of primary mineralization, resulted from follow-up of anomalous molybdenum and copper in stream sediments. The Haquira deposit is hosted in nonreactive siliciclastic rocks and does not show visual signs of alteration, despite the fact that the deposit subcrops. The use of unconventional geochemical methods, such as partial extraction geochemistry and ground-water geochemistry, has not yet resulted in a copper discovery in the Andes.

Future discoveries in the Andes are likely to be in covered regions, deeper settings in outcropping areas where subtle signs of mineralization and alteration are present, and in poorly explored regions due to remoteness or political, social, or security concerns. An improved understanding of supergene enrichment processes in northern Chile, involving leaching and enrichment under semiarid conditions, and subsequent saline metasomatism under hyperarid conditions, help clarify secondary geochemical dispersion processes. Geochemical methods optimized to detect this dispersion should lead to greater success in exploring covered areas in this environment. The discovery of deep, high-grade hypogene mineralization at Los Sulfatos demonstrates the importance of this target type. Improved three-dimensional vectoring methods and zoning models are needed to aid in defining these targets. Other methods, such as ground-water geochemistry and the use of porphyry copper indicator minerals, are exciting developments that should contribute to future copper discoveries in the Andes.

You do not currently have access to this article.

Figures & Tables

Contents

Special Publications of the Society of Economic Geologists

The Challenge of Finding New Mineral Resources: Global Metallogeny, Innovative Exploration, and New Discoveries

Richard J. Goldfarb
Richard J. Goldfarb
Search for other works by this author on:
Erin E. Marsh
Erin E. Marsh
Search for other works by this author on:
Thomas Monecke
Thomas Monecke
Search for other works by this author on:
Society of Economic Geologists
Volume
15 (1)
ISBN electronic:
9781629490397
Publication date:
January 01, 2010

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal