The low-temperature shift of antigorite dehydration in the presence of sodium chloride: In situ diffraction study up to 3 GPa and 700 °C.

At 1.5-3 GPa, the HT <math xmlns="http://www.w3.org/1998/Math/MathML"><msubsup><mi>T</mi><mtext>deh </mtext><mtext>o</mtext></msubsup></math> ht is in the range of 540-570 °C in the presence of the NaCl-H SB 2 sb O fluid, whereas the minimal temperature of the Atg degradation is 700 °C in the NaCl-free system (run 2d, Fig. Regarding antigorite, the calculations based on an empirical equation of state for NaCl-H SB 2 sb O fluids predict the suppression of the dehydration temperature by about 70 °C at 2-3 GPa even in a relatively diluted NaCl-H SB 2 sb O solution ([18]). Keywords: Antigorite; decomposition; subduction zone; NaCl aqueous fluid; H2O activity; high pressure; high temperature; in situ X-ray diffraction EN Antigorite decomposition subduction zone NaCl aqueous fluid H2O activity high pressure high temperature in situ X-ray diffraction 1074 1079 6 06/01/22 20220601 NES 220601 Introduction The serpentine group minerals, phyllosilicates with the ideal formula Mg SB 3 sb Si SB 2 sb O SB 5 sb (OH) SB 4 sb , are major constituents of hydrated ultramafic rocks of the oceanic lithosphere. Antigorite decomposition in the presence of halite The HP-HT diffraction patterns collected on antigorite mixed with the NaCl-H SB 2 sb O fluid (runs 1s-3s, Table 1) are presented in Figures 3 to 5. [Extracted from the article]