In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
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EXTRACTING OLIVINE-RICH PORTIONS OF ULTRAMAFIC ROCKS USING 
ASTER TIR DATA 
O. B. Gurcay 
MTA General Directorate, RS&GIS Department, 06520 Cankaya-Ankara, Turkey (gurbora@yahoo.com) 
ISPRS Commission VII Symposium 
KEY WORDS: Geology, Mapping, Extraction, Satellite, Multispectral, Optical, Thermal 
ABSTRACT: 
There are several studies for extracting ophiolitic rocks using thermal properties. The algorithms developed to discriminate olivine-rich 
rocks among ophiolite units, even altered to serpentinite. 
Within this study, it was objected to recognize peridotite group rich in olivine minerals among ophiolitic rocks or mélange, and to map 
them with distinct boundaries. Besides, these results may point to the chromite occurrences related to dunite rocks as well. 
These algorithms were applied to ophiolitic units around Cankiri region. Various rock types exist within the area and were mapped 
during previous studies. Target ophiolitic rocks have extensive outcrops in Eldivan Mountain. The ophiolitic rocks cover most of 
ophiolitic sequence around the study area. 
The purpose is to discriminate olivine-rich portions of ultramafic lithologies with their thermal infrared properties. Olivine-rich 
ultramafic rocks have intense reflection near 10.58 and 11.92 micrometers and absorption around 8.86. Those can be identical for 
extracting dunite or olivine-rich units using ASTER data. Band ratio algorithms were developed by comparing olivine reference 
spectra with ASTER TIR bands 12, 13, and 14. Consequently, olivine-rich lithologies were clearly identified, and were checked during 
ground truth in 15 different locations. Petrographical determinations indicate that 13 of 15 samples are mostly serpentinized but still 
contain olivine, less orthopyroxene and clinopyroxene as relicts. Additionally, target unit’s boundaries were distinctly mapped among 
ophiolitic mélange within the area. 
1. INTRODUCTION 
Ophiolitic units include various types of lithologies such as 
peridotite, pyroxenite, gabbro, diabase, spilitic basalt, radiolarite, 
cherty limestone. In some cases, it can be easy to map with their 
composition and texture in the field. However, altered portions 
of ultramafic rocks are sometimes rather difficult to distinguish 
from each other. Various researches and algorithms concerning 
to the evaluation or identification of ultramafic rocks or related 
mineralizations have been conducted by using multispectral or 
hyperspectral satellite data analysis and reflectance or emittance 
portions of electromagnetic spectrum (Hunt and Wynn, 1979; 
Ninomiya, 2002, 2003; Chellaiah, 2003; Swayze et al, 2004; 
Rowan et al, 2004, 2005; Hook et al, 2005). 
The aim of this study is to detect olivine-rich bodies of 
ultramafic rock units belong to ophiolite or mélange with 
multispectral thermal infrared portion of ASTER image data. 
1.1 Thermal Spectral Properties of Ultramafic Rocks and 
Minerals 
The spectral reflectance, absorption or emittance interactions of 
surface materials responding to the electromagnetic solar energy 
have been commonly used in remote sensing studies (Chabrillat 
et al., 2000; Ninomiya, 2002, 2003; Saldanha, 2004; Swayze et 
al., 2004; Hook et al., 2005; Rowan et al., 2005) 
The reflection and absorption behaviors with respect to VNIR- 
SWIR and TIR wavelength of electromagnetic energy regions of 
common minerals constituting ultramafic rocks are given in 
figure 1A and IB. The pyroxene group has typical reflection in 
0.54 and 2.37 micrometers and has an absorption in 2.32 
micrometers according to figure 1A. Mg-rich olivine mineral, 
forsterite, in VNIR-SWIR region has absorptions in 0.62 and 
1.06 micrometers, and reflection in 0.58, 0.67 micrometers and 
the reflection increases to the longer wavelengths in SWIR 
region. The alteration product of those minerals, serpentine, has 
absorptions in 0.72, 1.39 and 2.36 micrometers and the 
characteristic reflection features in 0.51, 2.20 and 2.37 
micrometers. 
The electromagnetic energy is absorbed in 8.40, 10.09 and 10.73 
micrometers, and reflected in 8.85, 10.41 and 10.89 micrometers 
when the one of clinopyroxene minerals, like augite, is observed. 
If the spectral properties of other orthopyroxene group mineral 
has examined, the hyperstene mineral has absorptions in 8.49, 
9.89, 10.37 and 11.03 micrometers, and reflections in 8.22, 9.34, 
10.19, 10.45 and 11.34 micrometers. Similarly, besides having 
unique absorptions in 8.86, 10.05 and 10.39 micrometers, and 
the olivine mineral has also the reflections in 9.84, 10.19 and 
10.49 micrometers, then the reflection is getting decreased to the 
longer TIR wavelengths. 
Reflection and absorption properties of common ultramafic minerals 
in VN1R, SWIR and TIR regions are given in Figure 1.