Mineral Exploration Using Modern Remote Sensing Techniques

1
Mineral Exploration Using Modern Remote Sensing
Techniques

• by
• John L. Berry

2

• ASTER DEM Draped Image

ASTER DEM with Contours
Bands 1,2,3 Composite
ASTER DEM
Oblique View of Band 1,2,3 composite draped over
DEM
3

• Comparison of ASTER Bands (bottom) with TM bands
  (top). Note multiple narrow ASTER bands where TM
  has one broad band in SWIR and TIR.

4
Landsat TM and ASTER SWIR Band Coverage of Clay
Mineral Spectra. ASTER can resolve Kaolinite,
Alunite, Illite, etc..
5
(No Transcript)
6
Standard USGS reference spectra for Na-Sericite,
K-sericite, phengite and Mg/Fe phengite in the
SWIR region, showing the progressive shift of the
absorption band position to longer wavelengths
(left). The same spectra convolved to the ASTER
band configuration showing the variation in the
shape of the 2209 nm absorption band for the same
minerals (right) (Courtesy AD, Inc., website)
7
Emissivity Spectra of Common Rocks showing shift
in emissivity low from 8.6 um (ASTER Band 11) for
granite to 10.7 um (ASTER Band 13) for dunite.
This shift forms the basis for using the
thermal bands of ASTER to map lithology
8
Thermal emissivity spectra of some important
minerals convolved with the ASTER thermal
bands, superimposed on each other by
normal- izing to a value of 1.0 at 8.0 um (Band
10). The spectral curves differ even more than
those for rocks. Thus alteration zones
char- acterized by these minerals can be
map- ped using ASTER TIR.
9
Green
Red
Minerals are widely separated on this plot, and
would show up as green (Dunite) to orange
(Albite) if Band 13 were assigned to Greeen and
Band 12 to Red.
10
The linear distribution shows that there is a
strong correlation between the emisssivity
spectra of different minerals in bands 13 and
14, a phen- omenon that is also seen in the SWIR
region, but for vegetation spectra. This means
that in an image, dunite (olivine) would be dark
and quartz would be bright, but they would have
the same color. This is therefore NOT a good
band combination Using ratio composites (next
slide) helps to spread the data points out in
color space, giving better discrimination
11
This is actually an enlarged section of a ternary
diagram, but Excel will not display it as such.
It shows that good separation of the minerals in
color space can be achieved using Thermal band
ratios.
12

• This image shows different ages of lava flow -
  the youngest being the whitest. The overall
  variation in the image is from red to green, with
  little blue this reflects the linearity of the
  distribution of points on the previous slide.
  The N-S dark line on the east edge appears to be
  a fault in alluvium.

Ethiopian Rift Valley Thermal image
13
(No Transcript)
14

• Khoy Ophiolite, NW Iran.
• ASTER Bands 3,2,1 draped over DEM
• Ophiolite nappes are at left

15
Bands 7,3,1, ASTER Composite
Khoy Area 7-3-1 ASTER composite compared to
Geological Map. Note the greater amount of
detail on the image in the Ultramafics at lower
left
16
3 NW-trending Nappes
John Berry Assocs. 5000 Beverly Hills
Dr. AUSTIN, TX 78731 1- 512 - 452 -
8068 jlbassoc_at_flash.net
17

• Left 7,3,1 Composite. Red Box outlines
  area of next 2 slides. Blue Box outlines the
  slide after that
• Right 4/7-3/4-2/1 Abram Band Ratio Composite

18
KHOY, IRAN 7-3-1 Composite, showing Tectonic
Windows and Related Folds
19
KHOY, IRAN ASTER Band Ratios, showing
Tectonic winows and related Folds
20
OIB
Band Ratio 4/7-3/4-2/1 composite distinguishes
Ocean Island Basalt (OIB) from mid-Ocean Ridge
(MORB) Basalt
E-MORB