Application of CSAMT Method for Gold-copper Deposits, Chinkuashih Area, Northern Taiwan

Abstract

This paper deals with the Controlled Source Audiofrequency Magneotelluric method (CSAMT) applied to gold-copper deposits, in the Chinkuashih area, northern Taiwan. This is the very first time CSAMT has been used for precious metals exploration. Theoretically, the CSAMT method is used to receive the E-field and the orthogonal H-field which is produced by the magnetic field induced by transmitting the step current source into the subsurface by grounded bipole. For calculating the apparent resistivity, the Cagniard resistivity formula was employed. Finally the resistivity layers of each station will be obtained by means of matching the field apparent resistivity curve with the model one.
Because of the considerable advantages of CSAMT sounding, such as: great depth of detection, excellent lateral resolution, flexible survey design, and little topographic effect, it was applied in the Chinkuashih area to un­derstand more of the extent of the gold-cop r deposits. Based on the CSAMT founding data in this survey, a total of three contour maps as well as three profiles were made. According to the geologic interpretation, the main factors governing the localization of the ore bodies are rock contacts, such as dacite contacts, faults, bedding planes, joints, etc. The hydrothermal solutions and sulfur which were derived from the igneous intrusions would precipitate the ore minerals. The contacts acted as channelways for magmatic water at the Chinkuashih area. This deposit model extends to the south, where concealed gold deposits might exist.

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