期刊
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
卷 122, 期 12, 页码 9862-9880出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2017JB014510
关键词
subduction zones; hydrous defects; olivine; deepwater cycle; rheology; titanium
资金
- HISLa-DR
- EU [PIOF-GA-2010-273017, ANR-16-TERC-0013-01 TREMPLIN ERC]
The pressure and temperature sensitivity of the two most important point hydrous defects in mantle olivine involving Si vacancies (associated to trace amounts of titanium [TiChu-PD] or exclusively to Si vacancies [Si]) was investigated at subsolidus conditions in a fluid-saturated natural peridotite from 0.5 to 6GPa (approximately 20-200km depth) at 750 to 1050 degrees C. Water contents in olivine were monitored in sandwich experiments with a fertile serpentine layer in the middle and olivine and pyroxene sensor layers at the border. Textures and mineral compositions provide evidence that olivine completely recrystallized during the weeklong experiments, whereas pyroxenes displayed only partial equilibration. A site-specific water solubility law for olivine has been formulated based on the experiments reconciling previous contradictory results from low- and high-pressure experiments. The site-specific solubility laws permit to constrain water incorporation into olivine in the subducting slab and the mantle wedge, as these are rare locations on Earth where fluid-present conditions exist. Chlorite dehydration in the hydrated slab is roughly parallel to the isopleth of 5020ppmwt H2O in olivine, a value which is independent of the pressure and temperature trajectory followed by the slab. Hydrous defects are dominated by [Si] under the relevant conditions for the mantle wedge affected by fluids coming from the slab dehydration (slab-adjacent low viscosity/seismic low-velocity channel, P>3GPa). In cold subduction zones at 5.5km from the slab surface the storage capacity of the mantle wedge at depths of 100-250km ranges from 400 to 2,000ppmwt H2O.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据