8
SWIR Lithological Identification Index analysis
The above techniques have been reinforced with the indexes
defined by Ninomiya, therefore, the OHla index with rep-
resentative minerals muscovite – illite – montmorillonite
and the OHlb index with the representative mineral pyro-
phyllite indicate six areas of interest within the Cospan and
Asuncion districts. The Calcite Index (CLI) indicates areas
of presence of said mineral, where the southwest shows
more concentration than in the northeast. The Alunite
Index (ALI) and Kaolinite Index (KLI) indicate its presence
to the Northest with less frequency and in greater frequency
to the Southwest with respect to the Chamis district.
Spectral Mapping Results by the SAM Method
Pixels were generated that would indicate the presence of
different alteration minerals, which were corroborated by
comparing the USGS spectral signatures vs. the spectral
signatures of the processing.
The spectral signature of alunite is characterized by
its double absorption range in the range 1.44μm and
1.48μm, and its absorption peaks in the ranges 1.76μm,
2.16–2.17μm (Band 5) and 2.32μm, the absorption peak
in the range 2.16–2.17μm is typical when it is mixed with
pyrophyllite, kaolinite or dickite. Pyrophyllite has absorp-
tion peaks in the ranges 1.39μm (OH), 2.07μm, 2.16μm
(Band 5) and 2.31μm. The peaks in the ranges 2.07μm and
2.31μm are typical when it is mixed with another mineral.
Finally, kaolinite also has two double absorption features,
less marked than dickite, in the ranges 1.40–1.41μm and
2.16–2.20μm (Band 5), the peak at 1.830μm is typical
of kaolinites with a high degree of crystallinity and in the
range 2.38μm it occurs when it is mixed with another min-
eral (Caiza, 2018). In Figure 9 it can be observed that the
spectral signatures of the minerals described above, in the
case of the advanced argillic alteration, minerals such as alu-
nite were obtained in both absorption peaks at 2.18 µm of
the wavelength, in pyrophyllite 2.18 µm and in kaolinite
2.2 µm. The population centers where high concentrations
of these minerals (Figure 10) are found are in Suso, Huaten,
Payhual, El Progreso, Chilca, northeast of Huaycotito and
southeast of Limb.
Figure 8. Minerallogic Indices (a) (b) bearing altered minerals index -OHIa and OHIb (c) Kaolinite Index – KLY (d) Calcite
Index – CLI (e) Alunite Index (ALI)
SWIR Lithological Identification Index analysis
The above techniques have been reinforced with the indexes
defined by Ninomiya, therefore, the OHla index with rep-
resentative minerals muscovite – illite – montmorillonite
and the OHlb index with the representative mineral pyro-
phyllite indicate six areas of interest within the Cospan and
Asuncion districts. The Calcite Index (CLI) indicates areas
of presence of said mineral, where the southwest shows
more concentration than in the northeast. The Alunite
Index (ALI) and Kaolinite Index (KLI) indicate its presence
to the Northest with less frequency and in greater frequency
to the Southwest with respect to the Chamis district.
Spectral Mapping Results by the SAM Method
Pixels were generated that would indicate the presence of
different alteration minerals, which were corroborated by
comparing the USGS spectral signatures vs. the spectral
signatures of the processing.
The spectral signature of alunite is characterized by
its double absorption range in the range 1.44μm and
1.48μm, and its absorption peaks in the ranges 1.76μm,
2.16–2.17μm (Band 5) and 2.32μm, the absorption peak
in the range 2.16–2.17μm is typical when it is mixed with
pyrophyllite, kaolinite or dickite. Pyrophyllite has absorp-
tion peaks in the ranges 1.39μm (OH), 2.07μm, 2.16μm
(Band 5) and 2.31μm. The peaks in the ranges 2.07μm and
2.31μm are typical when it is mixed with another mineral.
Finally, kaolinite also has two double absorption features,
less marked than dickite, in the ranges 1.40–1.41μm and
2.16–2.20μm (Band 5), the peak at 1.830μm is typical
of kaolinites with a high degree of crystallinity and in the
range 2.38μm it occurs when it is mixed with another min-
eral (Caiza, 2018). In Figure 9 it can be observed that the
spectral signatures of the minerals described above, in the
case of the advanced argillic alteration, minerals such as alu-
nite were obtained in both absorption peaks at 2.18 µm of
the wavelength, in pyrophyllite 2.18 µm and in kaolinite
2.2 µm. The population centers where high concentrations
of these minerals (Figure 10) are found are in Suso, Huaten,
Payhual, El Progreso, Chilca, northeast of Huaycotito and
southeast of Limb.
Figure 8. Minerallogic Indices (a) (b) bearing altered minerals index -OHIa and OHIb (c) Kaolinite Index – KLY (d) Calcite
Index – CLI (e) Alunite Index (ALI)