Connecting Satellite Technology to Exploration:
Remote Identification of Iron Rich Minerals
Paul Budkewitsch and Steve Sharpe
Mineral Resources
Resource Management Directorate
Nunavut Regional Office
Aboriginal Affairs & Northern Development
16th Nunavut Mining Symposium, Iqaluit, Nunavut, 8-11
8
April 2013
Outline
1. Earth observation and satellite technology
2. Spectral properties of iron-oxides/hydroxides
oxides/hydroxides (gossans)
Detection from satellite data (example of results from Baffin Island)
3. Hall Peninsula (RapidEye)
4. Borden Basin (WorldView-2)
5. Conclusions: Outlook and benefits
1. Earth observation and satellite technology
Benefits of the new class of satellite technology
• High ground resolution = smaller target detection.
• Daily accessibility of any point on the globe; lower risk of collection
failure with constellations (larger number of orbiting systems).
systems
• Large area coverage and a rapidly growing archive:
Country-wide
wide remote areas destined for exploration could benefit.
Examples:
Australia (e.g. ASTER satellite based products)
Processed data into publicly accessible data products.
Afghanistan (e.g. airborne hyperspectral mineral mapping)
Effective and accurate, but surveys and processing costs are higher.
Australia: satellite geoscience maps
• ferric oxide content based on ASTER multispectral bands.
• produces maps sensitive to presence of iron oxide minerals.
http://portal.auscope.org/portal/gmap.html
Surface materials map of Afghanistan:
Iron-bearing
bearing minerals and other materials from an
hyperspectral airborne survey
T.V.V. King, R.F. Kokaly, T.M. Hoefen, K.B. Dudek and K.E. Livo, 2011. U.S. Geological Survey,
Scientific Investigations Map 3152-B,
B, http://pubs.usgs.gov/sim/3152/B
2. Spectral properties of iron-oxides/hydroxides
iron
USGS Spectral Library – Goethite and Hematite (fine grained)
50
Fe+3
geothite
Percent Reflectance
40
Fe+3
30
hematite
20
Two prominent Fe+3 absorption bands in the
visible (VIS) and near infrared (NIR) are
spectral properties used to identify the
presence of iron oxides/hydroxides
10
0
375
500
625
750
875
Visible to near-infrared
infrared wavelength range (nm)
1000
Optical satellite band response (Landsat-7)
(Landsat for spectra of typical
gossan exposures (iron hydroxides)
22
VIS-NIR range
20
5
Percent Reflectanance
18
7
16
Gossan spectra
band 1 (blue)
14
band 2 (green)
band 3 (red)
12
band 4 (NIR)
10
3
band 5 (SWIR1)
band 7 (SWIR2)
2
8
6
4
1
4
375 475 575 675 775 875 975 1075 1175 1275 1375 1475 1575 1675 1775 1875 1975 2075 2175 2275 2375
Wavelength (nm)
• Multispectral bands 1-5,7 shown for Landsat-TM
Landsat
and ETM.
• Window of VIS-NIR
NIR spectral sensitivity of bands for GeoEye,
IKONOS, QuickBird, RapidEye and Worldview.
Gray - Gossan spectra (northern Baffin)
Colors - Approximate Landsat-7 bands
Band characteristics of high resolution Earth
observation systems
First generation sensors
(e.g. QuickBird): a
panchromatic band and 4
multi-spectral bands
QB Pan
MS
Green
Red
Near-IR 1
WV1 Pan
panchromatic bands have
broad VIS-NIR sensitivity
WV2 Pan
MS
Near-IR 2
Coastal Blue
400
500
Green Yellow
600
Red
Red Edge
700
Near-IR 1
800
Wavelength (nm)
900
1000
1100
WorldView-2 has a
panchromatic band plus 8
multi-spectral bands
• Four multi-spectral VIS-NIR
NIR spectral bands has been the standard configuration of most high resolution
sensors such as QuickBird, IKONOS, and GeoEye (RapidEye
RapidEye has five bands in this range).
• The panchromatic band in many systems produce gray-scale
gray
images much like aerial photographs.
• Worldview-2 (WV-2)
2) is the latest generation with eight multi-spectral
multi
bands.
Source modified: courtesy DigitalGlobe
Blue
3. Hall Peninsula Geoscience Mapping Project:
RapidEye data coverage (July-September
(July
2012)
• image tiles are 25 x 25 km.
• approximately 28,000 km2 for eastern Hall Peninsula, Nunavut.
Example of Geological Mapping
Data processing of RapidEye satellite data identifies levels of iron concentratrion
Includes material © 2011, RapidEye AG.
subarea = 3.2 x 3.2 km
Satellite data processed to highlight
exposures concentrated with iron.
Satellite data displayed as a color
image.
Example of Geological Mapping
Data processing of RapidEye satellite data identifies large exposures of ultramafic rock.
Includes material © 2011, RapidEye AG.
subarea = 3.2 x 3.2 km
Satellite data processed to highlight
exposures concentrated with iron.
Satellite data displayed as a color
image.
Includes material © 2011, RapidEye AG.
80 metres
Small pods of ultramafic rock exposed on the Hall Peninsula also detected.
Visible in RapidEye image data and derived iron index maps (5
( m pixels).
12
4. Borden Basin: Zn-Pb mineralization
Northern Baffin Island
Nanisivik Mine
Regional Geological Setting – Borden Basin
Location of
Hawker Creek
site examined
(map and stratigraphy from Turner et al., 2012)
Hawker Creek
Nanisivik Mines Ltd. (Strathcona)
Assessment Report #83073
map of ground geophysics grid
and DDH collar location.
Integrated and georeferenced
with Worldview-2 (WV-2)
remote sensing data.
This area was previously
investigated with airborne
hyperspectral (Probe-1) data and
more recently with high
resolution (WV-2) satellite data
to evaluate exploration target
identification in gossanous zones.
A comparison of analysis results
is presented from the two data
sets and the relationship to
assessment work filed.
Line work illustrated: AR #83073. Satellite image © 2011, DigitalGlobe.
Spectral properties of iron-oxides/hydroxides
iron
USGS Spectral Library – Goethite and Hematite (fine grained)
50
Fe+3
geothite
Percent Reflectance
40
Fe+3
30
hematite
20
Two prominent Fe+3 absorption bands
in the visible to near infrared (VIS-NIR)
(VIS
are spectral properties used to identify
the presence of iron oxides/hydroxides
10
0
375
500
625
750
wavelength (nm)
875
1000
Results from 1999 CCRS airborne hyperspectral survey :
Probe-1 data, July 1999, Canada Centre for Remote Sensing (NRCan)
Mineral mapping results produces
exploration targets
1 km
goethite concentration map
1
High
0
Low
Field validation of mineralised
outcrop (goethite-limonite)
WV-2 Satellite Image (2011) and Probe--1 airborne hyperspectral results (1999)
with Assessment Report #83073 map, geophysical grid and drill holes (1991)
2011
1 km
1991
1999
2011
Satellite image © 2011, DigitalGlobe.
1991
Satellite image © 2011, DigitalGlobe.
Hawker Creek
Anomalously high goethite concentrations are difficult to recognize in the color satellite image, but are well identified in
the hyperspectral results. Drill hole locations (black dots) and geophysical grid (line work) do not appear to have
examined the gossan spectral target (AR #83073).
Spectral properties of iron-oxides/hydroxides
iron
Fe+3
Fe+3
6
goethite
Relative or Percent Reflectance
7
5
4
3
1
8
Worldview-2
2 VIS-NIR
VIS
band response functions
2
0.35
0.45
0.55
0.65
0.75
0.85
wavelength range (nm)
Field spectra of gossan is similar to goethite.
0.95
1.05 (µm)
Gossan spectra location: northern Baffin
Goethite spectra – USGS Spectral Library
Coloured bars are WV-2
2 bands, sampled according to the gossan spectra.
 Bands 5 and 8 are suitably located to detect characteristic Fe+3 absorption features.
1
High
Hawker Creek
WV-2 gossan (goethite) concentration map
1
Iron hydroxide (gossan) intensity
map derived by spectral matching
using WV-2 multi-spectral data
yields similar results to
hyperspectral data analysis with
few false positives.
Target areas of interest detected
(red pixels) represents 0.007% of
the total satellite image processed
(196 km2).
0
High
Low
Location0of theLow
gossanous target
identified in Probe-1
hyperspectral data
also detected from
the spectral bands
of Worldview-2.
1
High
0
Low
Hawker Creek
hyperspectral goethite (iron) concentration map
stacked above
WV-2 goethite (iron) concentration map
• WV-2 satellite image covers a
larger area than the hyperspectral
flight track.
• results appear to be similar.
• satellite data source approach
is cost effective.
gossanous
exploration
targets of
interest were
identified
outside the
hyperspectral
coverage.
21
5. Concluding Remarks
mineral mapping applications from multi-band
multi
sensors
• Distribution and intensity of ferruginous mineral soil and weathered
sulfide horizons were successfully identified from RapidEye data
sets and validated in the field.
• Iron oxide-hydroxide
hydroxide concentrations identified in satellite data proved
successful for identifying gossans and altered ultramafic rock.
 assisted geological mapping since ultramafic pods are often quite
small and therefore missed during field work.
Concluding Remarks
advanced, high resolution multi-band
band sensors
• Narrow-band multi-spectral
spectral sensors, such as Worldview-2,
Worldview are able to
accurately identify gossan occurrences (goethite / iron hydroxide)
with similar confidence to results obtained from analysis of
hyperspectral data with few false positives.
 a very cost-effective
effective application of this technology.
• Prospective areas for exploration identified from Earth observation
data can assist with reducing areas of interest to much less than 1%,
accelerating exploration programs and reducing risk.
• Integration with legacy geoscience data (e.g. NUMIN database,
Assessment Reports) adds value and helps to improve the contextual
knowledge of mineral mapping results obtained from satellite data
sources.
Thank you
●
Qujannamiik
●
Merci
Awaken the value of previous
work with new insights from
satellite data
Connecting the past to the
present may lead to new
discovery
www.aandc--aadnc.gc.ca
[email protected]
visit nunavutgeoscience.ca
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