Publication Date:
2017-01-12
Description:
While is it accepted that silica-rich melts behave anomalously with a decrease of their viscosity at increased pressures ( P ), the viscosity of silica-poor melts is much less constrained. However, modeling of mantle melts dynamics throughout Earth's history, including the magma ocean era, requires precise knowledge of the viscous properties of silica-poor magmas. We extend here our previous measurements on fayalite melt to natural end-members pyroxenite melts (MgSiO 3 , CaSiO 3 ) using in situ x-ray radiography up to 8 GPa. For all compositions, viscosity decreases with P , rapidly below 5 GPa and slowly above. The magnitude of the viscosity decrease is larger for pyroxene melts than for fayalite melt, and larger for the Ca end-member within pyroxene melts. The anomalous viscosity decrease appears to be a universal behaviour for magmas up to 13 GPa, while the P -dependence of viscosity beyond this remains to be measured. These results imply that mantle melts are very pervasive at depth.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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