The interaction of fluid inclusions and migrating grain boundaries in a rock analogue: deformation and annealing of polycrystalline camphor–ethanol mixtures



The results of deformation and annealing experiments using a rock analogue containing a liquid phase as observed in transmitted light microscopy are presented. Samples were made of camphor–ethanol mixtures, with the polycrystalline solid being a rhombohedral phase and the liquid a saturated solution of camphor in ethanol. Results show the in situ pore fluid morphology during grain boundary migration recrystallization. Samples were deformed at high homologous temperatures (Th ∼ 0.7) and strain rates of 1 × 10−6 to 9 × 10−4 s−1. For grain boundary migration rates ranging from 10−10 to 10−6 ms−1 Zener pinning, not only the drag and drop of fluid inclusions by migrating grain boundaries but also the passage of grain boundaries over fluid inclusions without noticeable interaction was observed. The drag-limiting migration rate is three times lower for post-kinematic annealing than for dynamic recrystallization and shows a weak dependence on fluid inclusion size. A detailed description is presented of fluid inclusion–grain boundary interaction with respect to fluid inclusion sizes and grain boundary migration rates. Fluid inclusions show up to 39% reduction in diameter after passage of a grain boundary, indicating fluid flow along the mobile grain boundary.