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【Tectonophysics】Isotope geochemistry of mercury and its relation to earthquake in the Wenchuan Earthquake Fault Scientific Drilling Project Hole-1 (WFSD-1)

TectonophysicsIsotope geochemistry of mercury and its relation to earthquake in the Wenchuan Earthquake Fault Scientific Drilling Project Hole-1 (WFSD-1)

Lei Zhang, Yaowei Liu, Lishuang Guo, Duoxing Yang, Zhen Fang, Tao Chen, Hongwei Ren, Ben Yu

Based on the Wenchuan Earthquake Fault Scientific Drilling Project (WFSD), we first investigated the distribution of the total mercury (THg) from 600 m to 1035 m of WFSD Hole-1 core (WFSD-1). The concentrations of THg in the fault gouge are significantly higher than the sandstone, shale, siltstone, and cataclasite in WFSD-1. The THg concentrations in the main seismic fault zone range from 9.9 to 73.5 ng/g while those under the main fault range from 20.5 to 36 ng/g. To determine the source of Hg, typical rocks from different depths were chosen for Hg isotope analysis. The results show that δ202Hg in the main seismic fault zone ranges from -0.11 ‰ to -2.68 ‰, and, below the seismic fault zone, δ202Hg are from -0.64 ‰ to -1.33 ‰. The seismic fault rocks are more enriched in THg and have a larger variation of δ202Hg compared to the other rocks. Mercury has different isotopic compositions and fractionation mechanisms in the fault zone, which are mainly affected by the earthquake and the fluid. The mercury isotope compositions reflecte the fluid activities at the main fault zone. We demonstrate that mercury stable isotope ratios could serve as an effective tool for tracing mercury sources and monitoring and predicting earthquakes.

 

Zhang L, Liu Y, Guo L, Yang D, Fang Z, Chen T, Ren H, Yu B. 2014. Isotope geochemistry of mercury and its relation to earthquake in the Wenchuan Earthquake Fault Scientific Drilling Project Hole-1 (WFSD-1), Tectonophysics, 619-620: 79-85

https://doi.org/10.1016/j.tecto.2013.08.025

 

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Figure 1. Map of the 2008Wenchuan earthquake geological structures and geologic cross-section across theWFSD-1 drilling site

 

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Figure 2.  Variations of the total Hg concentrations and δ202Hg vs. depth in the rocks taken from WFSD-1 (a). δ202Hg vs. Δ199Hg of rocks samples from WFSD-1 (b), the three lines represent the

rough variations of the Hg isotope values. The combination of MDF/MIF signatures of the

rocks indicate a complex mixing Hg sources.


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