You are using an outdated browser that does not fully support the intranda viewer.
As a result, some pages may not be displayed correctly.

We recommend you use one of the following browsers:

Full text

International cooperation and technology transfer
Mussio, Luigi

ances of the
/ the values
: variations
nponent, it
; difference
th maximal
; very dark
tracks was
le extreme
ice of the
1 from the
al absolute
it has to be
put bands,
■esence of
the fourth
1, 5, and 7,
nted out in
1 with the
i limonite
:d for each
I. Thus, a
:nts can be
al fourth
iges were
y, a new
1 between
lit will be
Vith this
>nent was
were the
;hows the
where the
s the the
ig to the
fom CP2,
>xile and
, and low
concentrations imply darker colors for both
Table 4: Covariances of the eigenvector for
the principal components of hydoxides and
It can be concluded, that three virtual images
were created, one formed by the component H,
other by the F component and the third one by a
combination of the former ones. To illustrate
them graphically, the RGB technique constitute
an efficient technique to create maps, using the
following channel assignation:
Red = component H
Green = Second principal component of the
components H and F
Blue = component F
As a result, a map was obtained, where the
abundance of clay minerals such as caolinite,
illite and other hydroxide silicates appears in
redish tones.
The principal result was the reconnaissance of
all hydrothermal alteration zones with evidences
in the field. On the other hand, many clayey
zones got included without hydrothermal origin,
especially recently reworked agricultural soils.
A segmentation of the image was realized to
distinguish between hydrothermal and not
hydrothermal clays, using exclusively pixels
recognized as “alteration zones”. The result is a
notable reduction of the detected alteration
zones; the majority of them are accommodated
along faults and along the caldera borders,
which occurs in the majority of the geothermal
fields with this structural type.
1. The Acoculco Caldera forms part of a
hydrothermal activity stage, causing zones
of surface alteration.
2. The presence of quartz, calcite, limonite,
illite, smectite and caolinite stands out in the
mineralogy of the surface alteration.
3. The analysis of remote sensing images was
proved as a numerical tool for the
reconnaissance and mapping of mineral
groups, such as iron oxides and aluminium
hydroxides. These two groups form part of
the typical hydrothermal alteration
mineralogy of the Acoculco Caldera.
4. The principal component technique was
shown to be appropriate to recognize iron
oxides (limonite) and aluminium
hydroxides (clays).
Características geológicas de la zona termal de
Chignahuapan-Zacatlán, Puebla. Comisión
Federalde Electricidad, Reporte GG 4/86. 8 p.
CHÁVEZ L. (1975). Atmosferic, solar and MTF
corrections of ERTS digital imagery.
Proceedings of American Society of
Photogrammetry Fall Convention, Phoenix, 69
CROSTA A.P. & MOORE McM. (1989).
Enhancement of Landsat Thematic Mapper
Imagery for residual soil mapping in SW
Mináis Gerais State, Brazil: prospecting case
history in greenstone belt terrain. Proceedings
of the b7th (ER1M) Thematic
Conference:Remote Sensing for Exploration
Geology, Calgary, 2-6 Oct, pp. 1 173-1187.
HUNT G.R. & SALISBURY J.W. (1970) Visible
and near-infrared spectra of minerals and rocks:
I Silicate minerals. Modern Geology, 1, 283-
FTUNT G.R. (1977). Spectral signatures of
particulate minerals in visible and near infrared.
Geophysics, 42, 501 -513.
QUIJANO L.J.L. (1983). Reconocimiento y
evaluación geoquímica de zonas termales del
estado de Puebla. Comisión Federal de
Electricidad, Informe Interno 01/83, 12 p.