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Mercury loss and isotope fractionation during high-pressure and high-temperature processing of sediments: Implication for the behaviors of mercury during metamorphism TEXT SIZE: A A A

Metamorphic rocks show much lower mercury (Hg) levels than sedimentary rocks, which may be due to the loss of Hg during high-pressure and high-temperature conditions during metamorphism. To test this hypothesis, we conduct high-pressure and high-temperature experiments on ancient and modern sediments (WH black shale and GSS-4 soil). Under 0.3 GPa, the Hg concentrations decrease while the delta Hg-202 values increase with rising temperatures (WH black shale: 333-89 ppb, -1.34 to -0.79 parts per thousand, 250-700 degrees C; GSS-4: 545-265 ppb, -1.39 to -1.01 parts per thousand, 400-700 degrees C), suggesting the loss of isotopically light Hg isotopes under high-temperature conditions. Under constant temperatures of both 200 degrees C and 500 degrees C, with increasing pressure (0.5-1.4 GPa), GSS-4 shows only a slight decrease in Hg concentration with no variation in delta Hg-202, suggesting that high-pressure conditions restrain the loss of isotopically lighter isotopes. Consistent delta Hg-199 and delta Hg-200 values were observed in both samples during our experiment, implying no Hg isotope mass-independent fractionation (Hg-MIF) under high-temperature and high-pressure conditions. While results of this imply that metamorphism may lead to the emission of isotopically lighter Hg from sedimentary rocks to the surface environment, the lack of Hg-MIF during metamorphism provides important support for the use of Hg isotopes for paleoenvironment reconstruction. (C) 2022 Elsevier Ltd. All rights reserved.

Publication name

 Geochimica Et Cosmochimica Acta, Volume 334, Page 231-240, DOI 10.1016/j.gca.2022.08.010, Published OCT 1 2022

Author(s)

 Chen, Di; Ren, Dongsheng; Deng, Changzhou; Tian, Zhendong; Yin, Runsheng

Corresponding author(s) 

 Yin, Runsheng
 yinrunsheng@mail.gyig.ac.cn 
 Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550081, Peoples R China

Author(s) from IGCAS   Yin, Runsheng; Chen, Di; Deng, Changzhou; Tian, Zhendong

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