East (Benhamouda.F, 1989b). Its geology limit with syn- 
orogenic granite is less obvious in the channel of 
infrared thermal but lightly apparent in the channal of 
T.M5 
1.2.2 Oriental Hoggar 
In the Oriental Hoggar, other domain characterized by a 
strong contrast in a geological point of view, three 
characteristics units different by their lithology, their 
tectonic evolution and their metamorphism (Rapport 
Sonarem-Armines, 1977b). These are : 
- the early pan-africain granite, 
- the unit of Tirririne, (East of 8°30° fault 
conglomerate, arkose) 
- the diorites. 
The analysis of the fundamental criterias of the 
photointerpretation allow us to distinguish between 
them. 
BT 
"3 
og 
The difference in the interpretation between the 
formations of Tirririne series and the early pan-africain 
granite, of the different nature lithologic, resides in the 
spectral analysis and structural forms of these wholes. 
The granite presents a tonality relatively high and its 
frank rupture radiometric, less obvious in infrared 
thermal and middle infrared, permitted to delimit it well 
with regard of its environment. 
The Tiririne series is identified by sombre radio-facies 
and where we note a presence of particular lines very 
apparent in their North and which are distinctive to the 
set. 
The third whole is the unit of diorite, of weak extension 
and possesses a grey tonality to fine texture, flushes in 
benches of North East directions, cutting up certain set 
formations of Tiririne. 
  
  
   
Echelle: 1/2.352 564 
T "FiL'MII 
LEGEND 
Quaternary 
CDune Quaternary 
raClarbomferous 
-— EM Devomen 
j EE Sdunan 
El Cambro-Ordovicien 
EH Syn-Ürogenic granite + concordant 
and ther aurecle (prd) 
my Middle Proterozoic 
(amphibolite facies: Hoggar Central) 
Lower Proterozoic 
Metasediment undifferenciated 
(Arrechhoum senes) 
Djanet-Tafassasset Zone 
Trrmne Cham 
@ Tahaggart mdex 
    
  
  
mug l'irinne series 
(Green schiste facies) 
EE Pan-Afncam early granite 
  
  
#2 Dhontes 
t3 Discordance 
E^3 Geological limit 
CZ Fault 
Figure 1. An Analytic Geological Map of the Region of In -Azaoua 
by Remote Sensing from Thematic Mapper Data 
2. THE TACTIC LEVEL 
2.1 A put foward of alterations related 
with the mineralisation through the 
radiometric indices. 
2.1.1 A put foward of alteration profile by 
bands ratios 
The results of studies made over 200 specters at high 
spectral resolution, acquired on varied rocky terrains in 
arid regions, have permitted to show two spectral 
signatures in the band 0.5 to 0.9 um. The one of The 
ferric iron and the other rocks of the acid/basic character. 
These spectral signatures were indicated by indices for 
the S.P.O.T. and T.M. bands concerning our study. 
However, after statistical data processing for a 
correlation between the spectral data and the global 
chemical composition of the rocks, Cervelle et Al, 
1988a, propose two relatively reliable correlation and 
this using the medium reflectances of the rocky surfaces, 
simulated for the S.P.O.T XS spectral Bands which were 
extrapolated for our data Thematic Mapper. 
Fi 
ce