29-27 Experimental Determination of Lithium Diffusion Rate in Plagioclase to Aid in Eruption Forecasting

Session: Undergraduate Research, Part II (Posters)

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Abstract:

Understanding the timing of volcanic eruptions is very important for eruption forecasting. Diffusion naturally occurs within volcanic crystals as they move between regions of melts of varying compositions and/or during magma decompression. Lithium is a common trace element in most feldspars and diffuses very quickly relative to other elements. The diffusion of lithium in feldspar can be used to understand and quantify the timescales of rapid magmatic processes in silicic to intermediate composition volcanoes, which typically erupt explosively with little warning. We ran eight Li diffusion experiments in An-60, an intermediate composition feldspar, using powdered spodumene mixed with quartz as our Li source. Experiments were run at five different temperatures between 850 and 1100 degrees C in a 1 atm furnace. We fit each diffusion profile using two different programs to determine which model best describes the diffusive behavior of Li in feldspar: 1) a two-pathway model where diffusion occurs simultaneously on interstitial (fast) and vacant (slow) sites; and 2) a concentration-dependent (single-pathway) model, where Li diffusivity decreases as its concentration increases. We found that both numerical models show good fits for most of the experiments, but results from the two-pathway model best conform to expected temperature relationships. The interstitial path has a lower activation energy and is faster than the vacancy path by about 1-2 orders of magnitude at a given temperature. Our results can be used by volcanologists to aid in timing rapid magmatic events using extracted lithium diffusion profiles from crystals in nature.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

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