Li diffusion in zircon

摘要: Diffusion of Li under anhydrous conditions at 1 atm and fluid-present elevated pressure (1.0–1.2 GPa) has been measured in natural zircon. The source diffusant for 1-atm experiments was ground spodumene, which sealed vacuum silica glass capsules with polished slabs An experiment using a Dy-bearing also conducted to evaluate possible rate-limiting effects on diffusion slow-diffusing REE+3 that might provide charge balance. performed the presence H2O–CO2 fluid were run piston–cylinder apparatus, consisting powdered mixture quartz zircon oxalic acid added produce fluid. Nuclear reaction analysis (NRA) resonant nuclear 7Li(p,γ)8Be used measure profiles experiments. following Arrhenius parameters obtained normal c-axis over temperature range 703–1.151°C spodumene source: $$ D_{\text{Li}} = 7.17 \times 10^{ - 7} { \exp }( 275 \pm 11\,{\text{kJmol}}^{ 1} /{\text{RT}}){\text{m}}^{2} {\text{s}}^{ 1}.$$ Diffusivities are similar transport parallel c-axis, indicating little anisotropy Similar diffusivities found source. is considerably faster than other cations zircon, smaller activation energy diffusion. Although comparatively rapid, zircons will be moderately retentive signatures mid-crustal metamorphic temperatures, but they unlikely retain this information geologically significant times high-grade metamorphism.