首页|Significance of H-2 and CO release during thermal treatment of natural phyllosilicate-rich rocks
Significance of H-2 and CO release during thermal treatment of natural phyllosilicate-rich rocks
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NSTL
Elsevier
Phyllosilicates may trap hydrogen (H-2) in the crust, but they may also produce it through various processes, including oxidative dehydrogenation. The dehydrogenation temperature depends on the type and composition of the phyllosilicates considered, but it may be as low as 300 degrees C. Here, we document the release of H-2 and CO during thermal treatment of chloritite (300 degrees C) and talc (500 degrees C) from the Trimouns deposits (Eastern Pyrenees, France). Thermal release of gases coupled to stable isotope analysis has been used to recover and characterize H-2 and CO, the two detected gases. Hydrogen content may be as high as 7 ppm with delta D-H2 values ranging from -258 parts per thousand to - 224 parts per thousand for sub-pure chloritite and - 140%0 for pure talc. CO content ranges between 3 ppm and 35.3 ppm with very homogeneous delta C-13(CO) values between -27.6 parts per thousand and - 25.7 parts per thousand. This study supports the idea that H-2 was produced during experiments by dehydrogenation. The origin of CO remains enigmatic, but its carbon isotope composition suggests a link to the few amounts of graphite documented in chloritite and talc from the deposit. This work also reports extensive hydrogen isotope fractionation between H-2 produced by dehydrogenation and both talc and chloritite. Dehydrogenation of phyllosilicates is a potential source term of H-2 in numerous magmatic-hydrothermal settings and must thus be accounted for in the budget of the H-2 geochemical cycle.
Quesnel, Benoit、Truche, Laurent、Boiron, Marie-Christine、Lempart-Drozd, Malgorzata、Rigaudier, Thomas、Derkowski, Arkadiusz、Gaucher, Eric C.、Cathelineau, Michel
NSTL
Elsevier
