Lineaments Analysis for Structural Geology and Mineral Occurrences in Loei Area, NE Thailand: Determined from Landsat Data By Kachentra Neawsuparp, Economic Geology Div., DMR Punya Charusiri, Chulalongkorn University

Purpose : An attempt to relate lineaments visible on TM Landast image for structural interpretation and mineral occurrences in northern part of Loei province. Material : Digital data of TM5 Landsat band 7 (NRCT), Geological map (DMR), Mineral occurrences (DMR), Computer and IDRISI, MapIfo, and Geosoft Programs

Selected Area Features All type of rock distributions, Intrusive and extrusive igneous rocks, Silurian-Quaternary Periods, Complex structural geology, Fold and thrust fault belt (Chairangsee, 1990; Bunopas, 1988) A lot of mineral occurrences (Jacobson,1969; DMR,1988) Plate tectonic feature, Loei suture zone ( Charusiri et al.,1990)

Fig 1 Location of the study area covering northern part of Loei province LOEI Tha Li Wang Saphung Pak Chom Dan Sai LAOS

Geological map of the study area Geological map of the study area (DMR, 1992)

Methodology

Enhancements for this study Edge enhancement is the process of increasing the contrast between adjacent areas with the different tone on an image. Directional filter is a spatial- frequency filter, which enhances features in an image in selected direction. Contrast stretching is the expanding a measured rang of digital number in an image to a larger range, to improve the contrast of the image and its component parts.)

What is a lineament? Satellite lineaments are linear features on the Earth’s surface, usually related to the sub- surface phenomena. Generally lineaments are related to a large fractures and faults. Their orientation and number give an idea of fracture pattern of rocks. (Arlegui ans Soriano,1998; Cortes et al., 1998).

Landsat TM5 (band 7) image of study area

Fig. 2 a.Lineaments by edge- enhanced filter

Fig. 2 b. Lineaments by directional filter in NE direction

Fig.2 c. Lineaments by directional filter in N direction

Fig 2 d. Lineament map by combination of a,b and c.

Fig. 3 Lineaments overlay on geological map

Fig. 4 lineament analysis Lineament map Selected N-lineament Selected NW-lineament Selected NE-lineament

a.Showing selected major lineamentsb.Structural data from geologic map c.Integrated map from a. and bd. Complied lineaments with geology and strain ellipsoid Fig.5 Lineaments related to the structural geology

Updated structural geological map

Fig.6 Lineaments related to mineral occurrences a.with circular feature b.with NE &NW lineament c.with density of lineaments d.with total length of lineaments

New target areas

CONCLUSION Digital image processing is a very useful tool to help analyzing Landsat data Combination of major lineament from Landsat data and structures from geological map can delineate updating structural geology of the area The lineaments related with the mineral occurrences by using lineament analysis show suitable area for future exploration