Subsurface Geophysical Investigation in Aqiq Ghamed Ancient Mine.

B.Sc. Research project.

By

Ahmad Al-Oufi¹ and Saleh Al-Amry¹, B.Sc., (1999)

Supervisor: Dr. Hamdy El Sayed¹

Summary

The goal of this research is to study the subsurface of the mineralized zone for the gold-bearing quartz veins and identify their extensions and depths in the tonalite rocks and quartz porphyry by using geophysical techniques in Aqiq Ghamed area at the southern part of Saudi Arabia.

The geophysical techniques were conducted perfect work by USGS in 1998 at Aqiq Ghamed ancient gold mine working, south of Saudi Arabia. To knowledge subsurface for the gold-bearing quartz veins, a survey grid and three geophysical techniques were carried out successfully in the study area. These techniques included gravity, magnetic, and electrical resistivity (Wenner and Induced Polarization (IP)) methods along the survey grid of about 900 x 500 to 600 meters from south to north direction with totally 19 lines. The electrical resistivity data were collected and processed, and IP data were also processed and filtering by using Fraser techniques to yield resistivity contour maps and pseudo-sections profiling.

The interpretation of resistivity map indicates that the gold-bearing quartz veins have high resistivity anomalies with values greater than of (542 Ohm-m) that appears in the central and western parts of the area at a depth 26 m (Fig. 1). These anomalies are correlated to the interpretation of the IP resistivity pseudo-sections profiles, which have been characterized by increasing in the metal factor along of the chargeability and slightly resistivity anomaly that reflects a good content of the mineralized zones in the gold-bearing quartz veins between depths from 37 m and extend to depths of at least 87 m and 160 m.

The anomalies related to gold-bearing quartz veins extend from north to south and have been trending towards the northwest structural direction according to the interpretation of the electrical resistivity map, which may suggest these the veins formed as a result of the movement on Aqiq structural zone as suggested by previous geological studies. The locations of these anomalies for the gold-bearing quartz veins are considered important for mineral exploration purposes.

Funding:

Geophysics Department, Faculty of Earth Sciences, King Abdulaziz University, Jeddah- Saudi Arabia.

U. S. of Geological survey mission, Jeddah-Saudi Arabia.