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Portable Infrared Spectroscopy as a Tool for the Exploration of Gold Deposits in Tropical Terrains: A Case Study at the Damang Deposit, Ghana

By
Alistair J. R. White
Alistair J. R. White
1
Oxford Centre for Tectonics and Metallogenic Studies, Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3AN United Kingdom
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Vicki M. Robb
Vicki M. Robb
2
88 Manor Road, Woodstock, OX20 1XL United Kingdom
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Laurence J. Robb
Laurence J. Robb
1
Oxford Centre for Tectonics and Metallogenic Studies, Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3AN United Kingdom
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David J. Waters
David J. Waters
1
Oxford Centre for Tectonics and Metallogenic Studies, Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3AN United Kingdom
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Published:
January 01, 2010

Abstract

Gold mineralization at the Damang deposit is unique among known deposits in Ghana, comprising two distinct styles of mineralization. These include a stratigraphically controlled auriferous quartz-pebble metaconglomerate that is overprinted by later gold contained in a complex fault-fracture vein array with surrounding hydrothermal alteration. A systematic study using portable, field-based infrared reflectance spectroscopy has proven to be a valuable exploration tool at Damang. Spectral parameters such as the ferrous-iron response, the AlOH/H2O absorption depth ratio, and automated mineral identification successfully distinguish metasedimentary and metadoleritic lithologic units at Damang. Systematic variations in these parameters, together with the water/OH absorption depth, both downhole and in three-dimensional models, provide vectors to gold mineralization. The spectral parameters AlOH wavelength and MgOH wavelength are used to define the regolith profile at Damang, throughout which the ferrous-iron response parameter provides a reliable indicator of gold mineralization. All recorded changes in spectral parameters can be linked to sample petrography and are supported by mineral-chemical data. These results show that portable infrared spectroscopy can be used in a variety of roles, including regolith mapping, geologic mapping and logging, and recognition of hydrothermal alteration patterns, as each lithology and alteration style exhibit distinct and identifiable spectral characteristics. These spectrally derived alteration proxies indentify a broader zone of potential gold mineralization than gold grades alone, providing a larger target for exploration. The rapidity of data collection and ease of analysis of spectral data make infrared reflectance spectroscopy a useful methodology that can be readily incorporated into both preexisting and established exploration programs in other tropical terrains.

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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
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Erin E. Marsh
Erin E. Marsh
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Thomas Monecke
Thomas Monecke
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Society of Economic Geologists
Volume
15 (1)
ISBN electronic:
9781629490397
Publication date:
January 01, 2010

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