Application of tensor CSAMT with high-power orthogonal signal sources in Jiama porphyry copper deposit, South Tibet

Abstract

The Jiama porphyry copper deposit in Tibet is one of the proven supergiant copper deposits in the Qinghai-Tibet Plateau at present, with the reserves of geological resources equivalent to nearly 20×10⁶ t. However, it features wavy and steep terrain, leading to extremely difficult field operation and heavy interference. This study attempts to determine the effects of the tensor controlled-source audio-magnetotellurics (CSAMT) with high-power orthogonal signal sources (also referred to as the high-power tensor CSAMT) when it is applied to the deep geophysical exploration in plateaus with complex terrain and mining areas with strong interference. The test results show that the high current provided by the high-power tensor CSAMT not only greatly improved the signal-to-noise ratio but also guaranteed that effective signals were received in the case of a long transmitter-receiver distance. Meanwhile, the tensor data better described the anisotropy of deep geologic bodies. In addition, the tests also show that when the transmitting current reaches 60 A, it is still guaranteed that strong enough signals can be received in the case of the transmitter-receiver distance of about 25 km, sounding curves show no near field effect, and effective exploration depth can reach 3 km. The 2D inversion results are roughly consistent with drilling results, indicating that the high-power tensor CSAMT can be used to achieve nearly actual characteristics of underground electrical structures. Therefore, this method has great potential for application in deep geophysical exploration in plateaus and mining areas with complex terrain and strong interference, respectively. This study not only serves as important guidance on the prospecting in the Qinghai-Tibet Plateau but also can be used as positive references for deep mineral exploration in other areas.

Keywords

Jiama porphyry copper deposit / Supergiant copper polymetallic deposit / Tensor CSAMT of 150 kw High power / 2D inversion / Deep prospecting / Mineral exploration engineering / Xizang (Tibet)

CRediT authorship contribution statement

Peng-liang Yu and Ting Qu completed the study of section inversion and comparative analysis. Ri-zheng He conceived and planned the study and oversaw its implementation and compiled all of figures. Jian-li Liu gave theoretical guidance and verification to the research results. Su-fen Wang and Xiao-long Chen completed the parameter test and physical property statistics. Peng-liang Yu wrote the manuscript with the support of Ri-zheng He, Ting Qu, Jian-li Liu, Su-fen Wang and Xiao-long Chen. All authors discussed the results and contributed to the final manuscript.

Declaration of competing interest

The authors declare no conflict of interest.

Acknowledgment

The authors would like to extend their sincere gratitude to Professor Ju-xing Tang and Dr. Pan Tang from the Institute of Mineral Resources, Chinese Academy of Geological Sciences, Professor Deng-hai Bai from the Institute of Geology and Geophysics, Chinese Academy of Science, Professor Jing-tian Tang from the Central South University, and Professor Jian-en Jing from the China University of Geosciences for their guidance and assistance during field data collection and indoor data processing in this study. This work was together supported by the National Key Research and Development Program of China (2018YFC0604102), and the project of China Geological Survey (DD20190015). Owing to the limitation on the authors' knowledge and paper length, this paper only introduced the actual application of the high-power tensor CSAMT in the Jiama porphyry copper deposit. The authors will appreciate any comments and corrections to any omissions and errors.

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