Gondwana Research, V 4, No. 2, pp. 212-214. 0 2001 International Association for Gondwana Research, Japan. ISSN: 1342-937X

Delineation of Tectonic Features Utilizing Satellite Remote Sensing Data: I1 - The Northern-Half of the Arabian Shield

F.A. Zakirl and R.S. Divi2

Faculty of Earth Sciences, King Abdulaziz University, Jeddah, Saudi Arabia Department of Earth and Environmental Sciences, Kuwait University, Kuwait

The entire Arabian Shield is mapped (58 Quadrangle Sheets) at 1:250000 scale and some parts in the shield are mapped at a more detailed scale of 1:lOOOOO. The two compilations, one for the lithofacies (Johnson, 1983) and the other for the plutonic rocks (Stoeser et al., 1985) form good geological base maps at 1: 500000 scale for developing regional models - metallogenic, geochronologic, tectonic and other (Agar, 1992; Pallister et al., 1987; Stoeser and Camp, 1985; Johnson et al., 1987). However, a regional map ( e.g. at 1:500000 scale) of the structural features in the Arabian Shield is not available, and understandably so, in view of the enormous time needed for field-based structural mapping. As an alternative, satellite remote sensing data-based, and with limited field verified, delineation of the structural features was performed for the entire shield at 1:250000 scale (Zakir et al., 1983). The procedures used for the enhancement, delineation and analysis of the structures from the satellite images was given elsewhere (Divi et al., 1986). The structural features delineated are compiled at 1: 500000 scale and displayed in two map sheets, divided along the 23ON latitude to correspond with the two geological map sheets of Johnson (1983) and Stoeser et al. (1985). The structures in the southern sheet are discussed elsewhere (Divi and Zakir, 2001), and those in the northern map sheet are presented here.

Ttventy six Landsat-scenes that lie within the paths 178 - 187 and rows 040 - 044 cover the northern half of the Arabian Shield. As an example, one of the enhanced scenes (path 185 and row 042) that includes the Al-Wajh area in the southwestern part of the scene and the delineated structures (originally at 1:250000 scale) in this scene are shown in figures 1 and 2, respectively. The southwestern diagonal half adjoining the Red Sea in figure 1 displays a

general northwesterly tectonic fabric in the region with narrow high strain zones, separating plutonic complexes (Imdan, Baladiya and Abu Saur) and more competent layered rocks. In detail, discordant foliation trends, some of which showing drag features, fold hinges disrupted along later foliations and shear zones in figure 2 indicate polyphase deformational structures. Isoclinal folding and concentration of closely spaced fold hinges close to the Red Sea margin indicate areas of intense deformation, which coincide with the areas occupied by the Zaam Group of rocks. The regionally occurring and northwest

Fig. 1. Enhanced Landsat image for the A1 Wajh scene (Path 185, Row 042) in the northern part of the Arabian Shield. Width of the scene is approximately 185 km. Red Sea is in the southwestern part of the scene.

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STRUCTURE MAP - AL WAJH IMAGE ( 185 -042 1 FIG. 8

1 0 I S E I L C

- --r ---- m m

I L E O C N P I

Fig. 2. Structural features delineated from the enhanced Landsat image in figure 1.

trending Ajjaj shear zone passing through an area near Jabal A1 Wasil, is not so clearly visible in figure 1.

References

However in figure 2, discordance bemeen axial planes of possibly reflect the

Agar, R*A* (1992) The tectono-metallogenic

Divi, R.S., Chagarlamudi, p, ZaKr, E and Mwash, M.A. (1986)

Of the Arabian Shield. Precamb. Res., v. 58, pp. 169-194.

Procedures for enhancement, delineation and analysis of structures from satellite images. Saudi Arabian center for Science and Technology Project AT-6-91 Technical Report TR-4/ST 691, Riyadh, Saudi Arabia, 144p.

and later in these existence of a shear zone in these areas. A third phase of folding in the area is indicated by the northeast trending cross folds in an area northeast of Jabal Knashab (Fig. 2).

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Divi, R.S. and Zakir, F.A. (2001) Delineation of tectonic features utilizing satellite remote sensing data: I - The northern-half of the Arabian Shield. Gond. Res., v. 4 (this issue).

Johnson, P.R. (1983) A preliminary lithofacies map of the Arabian Shield. Deputy Ministry of Mineral Resources, Jeddah, Saudi Arabia, Technical Record RF-TR-03-2, 72p.

Johnson, P.R., Scheibner, E. and Smith, E.A. (1987) Basement fragments, accreted tectonostratigraphic terranes, and overlap sequences: elements in the tectonic evolution of the Arabian Shield. In: Kroner, A. (Ed.), Proterozoic lithospheric evolution. Amer. Geophy Union, Geodyn. Series, v. 17, pp.

Pallister, J.S., Stacey, J.S., Fischer, L.B. and Premo, W.R. (1987) 323-343.

Arabian Shield ophiolites and late Proterozoic microplate accretion. Geology, v. 15, pp. 320-323.

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Stoeser, D.B., Jackson, N.J., Ramsay, C.R., Drysdale, A.R., du Bray, E.A. and Douch, C.J. (1985) Map of plutonic rocks in the Arabian Shield, Kingdom of Saudi Arabia (Northern Sheet and Southern Sheet). Deputy Ministry for Mineral Resources, Saudi Arabia.

Zakir, FA., Chagarlamudi, P., Alwash, M.A. and Divi, R.S. (1983) Delineation of tectonic features using remote sensing for mineral potential. King Abdulaziz City for Science and Technology (KACST), Saudi Arabia, Project AT-6-91, 81p.

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