Preprints
https://doi.org/10.5194/egusphere-2025-2073
https://doi.org/10.5194/egusphere-2025-2073
18 Jun 2025
 | 18 Jun 2025
Status: this preprint is open for discussion and under review for Solid Earth (SE).

Low-velocity and low-resistivity zone detected in the crust of the passive continental margin of south China

Shaoting Feng, Dikun Yang, Feng Jiang, Chunquan Yu, and Xianglong Liu

Abstract. Passive continental margin has long been regarded as a tectonically and geo-dynamically inactive region with few discoveries of crustal unconformity and hence lacks scientific attention. However, previous seismic studies have hinted the presence of isolated crustal weak zones characterized by low shear-wave velocities in Guangdong-Hong Kong-Macao Greater Bay Area (GBA), north rim of South China Sea. In order to confirm the crustal heterogeneity, a 100 km-long magnetotelluric (MT) survey (ZHMT) was conducted across Zhuhai and Jiangmen (Guangdong Province) to fill in the blank of resistivity property in the region and to validate the crustal low-velocity zone at the research region. 3D inversion of the ZHMT data reveals a striking low-resistivity anomaly below the township of Shuangshui at the depth of 10–15 km depth. As plausible evidence of on-going or past tectonic activities, the Shuangshui Low-resistivity Anomaly (SLRA) is in a good spatial agreement with the low-velocity feature from the ambient seismic noise tomography. Two geological models are proposed for its origin: a fluid-bearing shear zone associated with deep faulting and fluid migration, or partial melting of mid-crustal material, possibly linked to anomalous heat flow. These findings provide new insights into the tectonic evolution of the passive margin at the research region, revealing previously unrecognized mid-crustal activity.

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Shaoting Feng, Dikun Yang, Feng Jiang, Chunquan Yu, and Xianglong Liu

Status: open (until 09 Aug 2025)

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Shaoting Feng, Dikun Yang, Feng Jiang, Chunquan Yu, and Xianglong Liu
Shaoting Feng, Dikun Yang, Feng Jiang, Chunquan Yu, and Xianglong Liu

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Short summary
The coastal region of southern China is often assumed to be tectonically stable. However, recent studies suggest otherwise. Using magnetotellurics, we discovered a mid-crust conductive anomaly in the region, matching seismic data. This anomaly may represent fluids, fractures, or molten rock, indicating unexpected crustal activity. Our work challenges traditional views of passive margins and highlights the need to reassess geological hazards in this densely populated area.
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