Iron and water losses from hydrous basalts contained in Au80Pd20 capsules at high pressure and temperature

Journal article

We have performed experiments to determine the extents to which Fe and H2O are lost from hydrous basaltic melts contained in Au80Pd20 and graphite-lined Pt capsules at 0.7-1 GPa and 1300-1350°C. All experiments were performed in the piston-cylinder apparatus. In order to minimize the possibility of rupture of the AuPd capsule and to control H2O loss we used a double-capsule method. The inner welded 2 mm diameter Au8Pd20 capsule was placed inside a welded 3 mm diameter Pt capsule, the intervening space being packed with hydrous sample. Loss of FeO* from the sample was found to be ≤4% relative in both the Au80Pd20 and graphite-lined Pt capsules in experiments of up to 24 h duration. Loss of H2O is greater and it depends on the oxidation state of the starting materials and the nature of the capsule. For starting mixes fired at 1 log fO2 unit above the quartz-fayalite-magnetite (QFM) buffer at 1 atm, H2O loss from AU80Pd20 capsules averaged 9% relative. Starting mixes fired at 1 log fO2 unit below the QFM buffer at 1 atm lost, on average, 32% of their H2O when run in Au80Pd20 capsules at high pressure. All samples run in graphite-lined Pt capsules experienced dramatic H2O loss, averaging 52% relative, irrespective of initial oxidation state. We conclude that Au80Pd20 capsules are suitable for high-pressure hydrous melting experiments and that the sample loses very little Fe. In order to minimize H2O loss, however, it is important that the starting materials be relatively oxidized. © 2004 The Mineralogical Society.

Authors: Hall, L; Brodie, J; Wood, B; Carroll, MR

• Publication status: Published
• Journal: MINERALOGICAL MAGAZINE
• Volume: 68
• Issue: 1
• Pages: 75-81
• Publication date: 2004-02-01
• DOI: 10.1180/0026461046810172
• EISSN: 1471-8022
• ISSN: 0026-461X
• Keywords: AuPd capsules; water; hydrous basalt; iron loss