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RESEARCH PRODUCT

Deformation of melt-bearing systems—insight from in situ grain-scale analogue experiments

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Abstract The deformation behaviour of partially molten rocks was investigated using in situ analogue experiments with norcamphor+ethanol, as well as partially molten KNO 3 +LiNO 3 . Three general deformation regimes could be distinguished during bulk pure shear deformation. In regime I, above ca. 8–10 vol.% liquid (melt) fraction ( ϕ bulk ), deformation is by compaction, distributed granular flow, and grain boundary sliding (GBS). At ϕ bulk ϕ bulk (regime III), grains form a coherent framework that deforms by grain boundary migration accommodated dislocation creep, associated with efficient segregation of remaining liquid. The transition liquid fraction between regimes I and II ( ϕ LT ) depends mainly on the grain geometry and is therefore comparable in both analogue systems. The transition liquid fraction between regimes II and III ( ϕ GBS-L ) varies between 4–7 vol.% for norcamphor–ethanol and ca. 1 vol.% for KNO 3 +LiNO 3 and depends on system specific parameters. Regime II behaviour in our experiments can explain the frequently observed small melt-bearing shear zones in partially molten rocks and in HT experiments.