Application of multiscale magnetotelluric data to mineral exploration: an example from the east Tennant region, Northern Australia

Abstract

Summary The footprint of a mineral system is potentially detectable at a range of scales and lithospheric depths, reflecting the size and distribution of its components. Magnetotellurics is one of a few techniques that can provide multi-scale datasets to image and understand mineral systems. We have used long-period data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) as a first-order reconnaissance survey to resolve large-scale lithospheric architecture for mapping areas of mineral potential in northern Australia. The 3D resistivity model reveals a broad conductivity anomaly extending from the Tennant Creek district to the Murphy Province in the lower crust and upper mantle, representing a potential fertile source region for mineral systems. Results from a higher-resolution infill magnetotelluric survey reveal two prominent conductors in an otherwise resistive host whose combined responses result in the lithospheric-scale conductivity anomaly mapped in the AusLAMP model. Integration of the conductivity structure with deep seismic reflection data reveals a favourable crustal architecture linking the lower, fertile source regions with potential depositional sites in the upper crust. The enhanced conductivity likely resulted from the remnant (metallic) material deposited when fluids were present during the ‘ancient’ tectonic events. This observation strongly suggests that the deep-penetrating major faults potentially acted as pathways for transporting metalliferous fluids to the upper crust where they could form mineral deposits. This result and its integration with other geophysical and geochronological datasets suggest high prospectivity for major mineral deposits in the vicinity of these major faults i.e. Gulunguru Fault and Lamb Fault. In addition to these insights, interpretation of high-frequency magnetotelluric data acquired during the infill survey helps to characterise cover and assist with selecting targets for stratigraphic drilling which, in turn, can validate the models and improve our understanding of basement geology, cover sequences and mineral potential. This study demonstrates that integration of geophysical data from multi-scale surveys is an effective approach to scale reduction during mineral exploration in covered terranes with limited geological knowledge.

A Review of Relationship between the Metallogenic System of Metallic Mineral Deposits and Lithospheric Electrical Structure: Insight from Magnetotelluric Imaging

“…Other typical results include the Ning (Nanjing)-Wu (Wuhu) basin in eastern China [90], the Shihu-Xishimen gold-iron ore district in North China [91], the Middle-lower Yangtze Metallogenic Belt (including Ningwu, Luzong, Xuancheng, Anqing, Guichi, and Tongling areas) in East China [12,[92][93][94][95][96], the Jiaodong gold deposits in northern China [97], the Liaodong Qingchengzi orefield [98], the Yixingzhai gold deposits (Boqiang Cu-Mo-Au deposits and Nanling W-Sn ore district in China) [45,99,100], the northeastern Jiangxi metallogenic province in southeastern China [101], the Caosiyao porphyry Mo ore district in North China [43], the Beiya Cu ore district in southwestern China [46], the large-scale Hatu epithermal gold deposit in western Junggar, NW China [102], Zhaxikang in the Tethys-Himalaya area in southwestern China [103,104], the Baogutu porphyry copper-gold deposit, the Hongqiling Cu-Ni sulfide intrusions in the Central Asian Orogenic Belt [105], the Xiangshan volcanogenic uranium deposit [106,107], the Narusongduo Pb-Zn-Fe-Cu ore district, and the Qulong-Jima porphyry ore Cu deposit in southwestern China [41,42]. In the Olympic Dam mine and Tennant ore district in Australia [108], the Tsagaan Tsahir Uul Au deposit in southern Mongolia [109], the Norrbotten district in northern Sweden [110,111], and the orogenic gold district in the Red Lake greenstone belt, western Superior craton, Canada [51], the electrical resistivity models obtained by MT sounding provide better geophysical evidence of the metallogenic dynamics of metallic mineral deposits.…”

Application of Audio-Magnetotelluric and Dual-Frequency Induced Polarization Joint Inversion in a Pb-Zn Deposit Exploration in Inner Mongolia, China

“…The development of electromagnetic (EM) geophysical methods in the 1950s has played a crucial role in mapping the lateral and vertical 2 variations in subsurface resistivity. These methods, such as natural source audio magnetotelluric (AMT) and controlled source (CSAMT), have found wide-range of applications in metallic mineral exploration [5][6][7][8][9], groundwater studies [10], and geothermal system investigations [11][12][13][14]. Induced polarization (IP) also has a longstanding history in geophysics, initially employed in the field of mining geophysics to delineate and localize ore bodies [15,16].…”

An efficient spectral element method for two-dimensional magnetotelluric modeling

“…This electrical resistivity, measured by comparing the electric field's horizontal component to the magnetic field on the surface, can detect a depth of several tens of kilometers associated with the acquisition frequency. With the rapid advancement in magnetotelluric modeling and inversion, it has become one of the essential tools for recognizing deep geological structures (Unsworth, 2010;Avdeeva et al, 2012;Azeez et al, 2017;Nagarjuna et al, 2021) and geophysical investigations, such as geothermal exploration (Barcelona et al, 2013;Patro, 2017;Tarek et al, 2023), mineral deposit exploration (Benjamin et al, 2018;Jiang et al, 2022), and gas exploration (Zhang et al, 2014).…”