Fluid Geochemical Segmentation Along the Tan–Lu Fault Zone and Its Tectono-Fluid Implications

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Abstract
The Tan–Lu Fault Zone (TLFZ) is a lithosphere-scale fault system in eastern Asia with pronounced along-strike heterogeneity in structure and fluid activity. Previous geochemical studies have largely focused on individual segments, sample media, or single tracers, leaving the fault-zone-scale organization of fluid geochemical signals unresolved. Here, published helium-isotope data and cross-fault soil-gas CO2 and Rn observations are integrated within a common fault-parallel coordinate framework to compare source-sensitive proxies with those more responsive to transport and near-surface processes. The three proxy groups define contrasting spatial patterns. Mantle-derived He is strongest and spatially focused in Liaoning, intermediate but comparatively persistent in Anhui–Jiangsu, and generally subdued in the available Shandong dataset. Soil-gas CO2 and Rn anomalies, by contrast, are most continuous in Anhui–Jiangsu, locally enhanced in Liaoning, and subdued to intermediate in the available Shandong transects. Combining the mantle-derived He state with the soil-gas response identifies four proxy-association types. The most laterally continuous Type I interval extends for approximately 200 km in the Anhui–Jiangsu segment, whereas southern Liaoning is characterized by spatially focused, adjacent Type II and Type I intervals. These contrasting associations show that the near-surface expression of deep-derived fluids depends not only on volatile availability, but also on crustal pathway connectivity, groundwater circulation, and modification during transport and release. The integrated comparison reveals where deep-source and shallow-response signals are coupled or decoupled along the TLFZ, providing a basis for evaluating fault-zone fluid segmentation.
Funding Information
  • National Science and Technology Major Project (2024ZD1000404)
  • Natural Science Foundation of Liaoning Province (2025JH4/480000008)
  • Research Program of the Institute of Geology and Geophysics of the Chinese Academy of Sciences (IGGCAS-202204)

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