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Remote Sensing and Mineral Exploration

James Whittington

ES 771 Remote Sensing, Emporia State University, Fall 2005

Exploration drilling in the Canadian Rockies

core drilling


image acquired from:
http://66.113.204.26/mining/explore1.htm.

Abstract

The search for metals and materials needed to sustain our culture has been carried out since primitive man has searched for flint to craft hand tools. Today, the materials needed to drive our economic and technological growth are just as crucial. Most of the easily accessible metal ores were discovered decades ago; and thus the search has turned to more subtle deposits and more remote locations.
Since the inception of rudimentary aerial photography at the turn of the twentieth century, remote sensing has been used as a tool in the search for economic mineral deposits. As the level of technology has improved, the value of remotely sensed data has increased. The page will highlight the history and implementations of remote sensing on mineral exploration today.

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Introduction

The value of remote sensing data to mineral exploration has evolved and increased as technology has improved. In the early days of aerial photography, aerial photos were used when available to evaluate topography and plan prospecting and sampling forays. After World War II, the analysis of aerial photo data became much more sophisticated and actual geological data began to be extracted. The use of stereoscopic pairs enabled geologist to interpret subtle structural features. Nonetheless, the primary use of remotely gathered data was comparative. If a particular type of deposit was being mined in a district, aerial photos would be used to locate similar features elsewhere within the district.

This trends of comparative photography continued until well into the satellite age when satellite imagery became commercially available. The availability of multi-spectral, radar, and IR imaging, in variety of combinations allowed geologists to evaluate regions in much more detail then ever. In addition, the multiple flyovers allowed a prospect to be viewed in different light during different seasons. This greatly reduced the cost of regional exploration by precluding the need for repeated trips to a locale to reassess. Another advantage was the ability to gather data through cloud and surface cover with radar imagery. This allowed data to be collected from the tropics and arid regions that had previously been inhospitable to large regional field exploration. The computer age further enhanced the usefulness of data by allowing imagery to be digitally enhanced to highlight specific features. Now spectral studies can be done which allow the identification of specific minerals from space.

A Pegmatite hosted gem mine in California. Pegmatites can often be located within granite bodies due to differential vegetation growth and erosion patterns. This is prominent in aerial photos.
Toumaline Mine


image acquired from:
http://digforgems.com/.

The most elementary operation of remote sensing in mineral exploration is using aerial photographs to identify topographic surface features which may imply the subsurface geology. Such telling surface features as differential erosion, outcropping rock, drainage patterns, and folds/faults can be identified. These features can be compared to other potential targets in the region when looking for similar deposits. Faults fractures and contacts often provide a conduit or depositional environment for hydrothermal or magmatic fluids in regions of known mineralization, and thus make excellent targets for further investigation.

A fault trace near Moab Utah, that would be difficult to detect on the ground is easily seen in an aerial photograph.
Fault Trace


image acquired from: http://www.bdrg.esci.keele.ac.uk/Staff/Images/court.jpg.

An extension of simple air photo comparison is utilizing satellite imagery to locate structural features on a regional level. This can allow geologist to narrow a large field of targets to a more manageable group. The same basic parameters exist, the search for favorable structural trends, only on a regional level. Field teams can then prioritize their energy in a more effective and efficient manner.

The Ray Rock gold prospect, North West Territories, Canada. A large scale linear feature related to an ophiolite sequence developed during Precambrian tectonism.
Canadian Gold Prospect


image acquired from: http://www.ersi.ca/.

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As satellite image collection and data management improved a new kind of remote sensing application began being used by exploration geologists. Multispectral imaging and thematic mapping allowed surface mapping to be performed remotely in ways only dreamed about during the era of early photo interpretation. Different scanning spectrums enabled researchers to begin cataloguing various reflection and adsorption properties of soils, rock, and vegetation. These spectra could be utilized to interpret actual surface lithologies from remote images. With a field crew providing ground truth data, large areas could be geologically mapped in a short time at a fraction of the cost of traditional geologic mapping.

The Pogo district granitics, as seen from LandSat 5. These granites are clearly seen in this enhanced false color image. The Pogo district deposits are among the richest mineral locals in the world.

Satellite Mineral Mapping, Alaska


image acquired from: http://www.ersi.ca/.

Among the most valuable data collected is the weathering and alteration products of mineral deposits, especially clays. Clays and oxides can be readily differentiated by the spectra utilized for remote sensing. By correlating the alteration products to parent materials, potentially valuable ores may by distinguished without the need for extensive soil sampling programs. Another valuable component of spectral analysis is differentiating various types of vegetation. Changes in plant cover may indicate a change in lithologies.

This image and the associated spectral analysis of different clay alteration was crucial in the location of a set of copper prospects for Norandal.
Noranda Copper Prospects


image acquired from: http://www.space.gc.ca/asc/eng/satellites/hyper_geo logy.asp.
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Today, there are a variety of remote sensing tools available to the exploration geologist. The synthesis of the various forms of imagery, digital image processing, spectral analysis, remote mapping, and field work has come together with the help of GIS technology. Now a comprehensive program can manage data collected in the field with satellite images. Potential drill targets or known drilling results can be integrated with topographic maps, air photos, structural maps, and ore grade data to assist the geologist in the most effective use of exploration details. In addition, GIS allows project planners to use exploration information to get a head start on mine planning and environmental compliance.

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This is a stock image of a remote image combined with drill data and surface mapping to extrapolate subsurface geology.
GIS and 3D, Rockworks


image acquired from: http://www.mpassociates.gr/softw are/distrib/science/rock/rockworks2002.html.

Summary

As population increases and more nations industrialize the demand for natural resources continues to increase. Growing pressure for environmental sustainability and the spread of population centers has driven the search for economically viable mineral deposits into more remote and desolate regions. Increased competitiveness and price consciousness from investors has produced intense pressure to maximize the return on exploration capital expenses. These are among the many factors contributing to the increased use of remote sensing in geologic mineral exploration. As technology improves, so will geologists ability to gather even more detailed data information from remotely sensed data.


References

Bio-Geo-Recon, World Wide Web homepage URL:
http://www.biogeorecon.com/

The Canadian Space Agency, World Wide Web homepage URL:
http://www.space.gc.ca/asc/eng/satellites/hyper_geology.asp.

The Mineral Industry Exploration Workshop, World Wide Web homepage URL:
http://www.crestech.ca/archives/MET/METworkshop%20Presentations%20as%20PDF%27s/6-2.%20Greg%20Lipton%20RemoteSensing.pdf.

ERSI Mineral Deposits, World Wide Web homepage URL:
http://www.ersi.ca/mineral.html.

Mine-Engineer.com, World Wide Web homepage URL:
http://www.mine-engineer.com.

Evans, Anthony M., 1995; Introduction To mineral Exploration, Blackwell Science

Guilbert, John M. and Park, Charles F., 1986; The Geology of Ore Deposits, W H Freeman Company

McPherson, Roger. 2003; Modern Prospecting, Gem Guides Book Company

Hartman, H.L. (editor), 1992; Mine Engineering Handbook, SME press

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This web page was created to fulfill the requirements for Remote Sensing at Emporia State University.

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