Open AccessEffect of aqueous and carbonic fluids on the dislocation creep strength of quartz
Author(s) -
Chernak Linda J.,
Hirth Greg,
Selverstone Jane,
Tullis Jan
Publication year - 2009
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008jb005884
Subject(s) - quartz , fugacity , creep , dislocation creep , mineral redox buffer , materials science , overburden pressure , dislocation , oxidizing agent , deformation (meteorology) , differential stress , graphite , geology , mineralogy , composite material , thermodynamics , chemistry , geotechnical engineering , geochemistry , physics , organic chemistry , mantle (geology)
Dislocation creep experiments conducted on quartzite indicate that the presence of CO 2 can cause strengthening or weakening depending on the oxygen fugacity of the deformation environment. Under oxidizing conditions (ferrosilite‐hematite‐quartz), the presence of CO 2 reduces the water fugacity and results in strengthening of the quartz. Under moderately reducing conditions (∼Ni‐NiO), CO 2 reacts with H 2 from the sample assembly to form graphite; the water produced by this reaction causes weakening. Under extremely reducing conditions (quartz‐fayalite‐iron), CO 2 is reduced to methane, a reaction that consumes original water, thereby increasing the strength of quartz. Our results show that increasing at constant confining pressure, by changing fluid composition, has a similar effect as increasing by increasing confining pressure. The exponent suggested by our data for the dislocation creep flow law is 0.375 to 1 (assuming a stress exponent of 3 to 4), which is on the low side of previously reported values. Differences in deformation behavior over small length scales may thus be related to local differences in the that effectively change the in the presence of CO 2 .