Case study: joint seismic reflection and CSAMT data interpretation for mineral explorations in Fujian, China
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RESEARCH ARTICLE - APPLIED GEOPHYSICS
Case study: joint seismic reflection and CSAMT data interpretation for mineral explorations in Fujian, China Guofeng Liu1 · Xiaohong Meng1 · Handong Tan1 · Zhaoxi Chen1 · Jianhui Ni2 · Lanbo Liu3 Received: 21 February 2020 / Accepted: 28 August 2020 © Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences 2020
Abstract The Southwestern area of Fujian Province in China contains a major metallogenic belt. There have been three major tectonic movements since the Late Paleozoic, and the thrusts here are the main mineral deposits. These occurred between the Early Carboniferous and Late Permian eras. Due to dramatic undulations in the surface and associated complex underground structures, a single geophysical method cannot provide reliable imaging results. This is largely due to difficulties in data acquisition and processing. Seismic exploration provides one example. Using this method, raw shot gathers have a low signal-to-noise ratio because of the undulations in the topography. Furthermore, strong lateral velocity variation makes the migration process exceedingly difficult. This means that interpretations of the resulting reflection seismic profile give rise to uncertainty. For this reason, two-dimensional reflection seismology and controlled source audio-frequency magnetotellurics (CSAMT) electromagnetic sounding techniques were performed. After initially completing conventional processing on the seismic reflection data, subsequent pre-stack depth migration (PSDM) over the rugged topography yielded a much better image. It was able to identify thrust faults and magma intrusions. Then, using CSAMT, inversion was conducted with the same topography as the seismic reflection. By combining the migrated seismic profile, inverted resistivity profile, and borehole data, a vertical geological model was constructed. This proved the existence of an overlapped thrust, and it also indicated the possible presence of deeper mineralization. Keywords CSAMT · Joint interpretation · Mineral exploration · PSDM on rugged topography · Reflection seismic · Thrust
Introduction Southwestern Fujian, China, is a major metallogenic belt containing multiple mineral deposits. The main mineral deposits are found in the thrusts that occurred between the Early Carboniferous and Late Permian eras (Wu et al. 2000; Zhou 2006; Zhang et al. 2012). Over the past 40 years, most near-surface mineral resources have already been discovered, but there have also been many attempts at deep
* Guofeng Liu [email protected] * Xiaohong Meng [email protected] 1
School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China
2
The Eighth Geology Team of Fujian Province, Fujian, China
3
Integrative Geosciences Center, University of Connecticut, Mansfield, CT 06269, USA
mineral exploration as well (Zhang et al. 2011). Since 2002, more than 10 drill holes have been made in this region to a cumulative depth of 4300 m. All these drill holes discovered de
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