Relative strength of the pyrope–majorite solid solution and the flow-law of majorite containing garnets

• Published in: Physics of the earth and planetary interiors Vol. 179; no. 1; pp. 87 - 95
• Main Authors: Hunt, Simon A., Dobson, David P., Li, Li, Weidner, Donald J., Brodholt, John P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01.03.2010; Elsevier
• Subjects: Flow-law; GARNETS; GEOSCIENCES; High-pressure; High-temperature; Majorite rheology; national synchrotron light source; SOLID SOLUTIONS; STRAIN RATE; STRESS RELAXATION; Transition-zone; Majorite rheology; Flow-law; High-temperature; Garnets; Transition-zone; High-pressure; transition-zone; majorite rheology; flow-law; high-pressure; high-temperature; garnets
• ISSN: 0031-9201; 1872-7395; 0031-9201
• DOI: 10.1016/j.pepi.2009.12.001

Even though the garnet phase is the second most abundant phase in the upper-mantle and transition-zone, no previous studies have directly measured the effect of majorite content on the strength of garnet under mantle conditions. Here we report the results of constant strain-rate and stress-relaxation experiments on garnets in the pyrope–majorite solid solution which constrain the strength of majoritic containing garnets relative to pyrope as a function of majorite content and temperature. We find that at temperatures below 650 ° C both pure pyrope and majoritic garnets have the same strength. Conversely, above 650 ° C we find that majoritic garnets are initially stronger than pure pyrope but weaken with increasing temperature and majorite content and with significant majorite contents are weaker than pyrope above approximately 800 ° C. We develop a flow law for the entire pyrope–majorite solid solution as a function of temperature and majorite content.