Cation diffusion in aluminosilicate garnets: experimental determination in pyrope-almandine diffusion couples

Article Abstract:

The self-diffusion coefficients of Fe and Mg in Mn-poor ferromagnesian garnets were determined by employing diffusion couples made from natural pyrope and almandine garnet crystals. Results showed that the self-diffusion of Fe and Mn are substantially improved with the increase in Mn/Mg ratio. However, the improvement effect on the diffusion coefficient of Mg is relatively small. Proper use of the self-diffusion data to compute interdiffusion coefficient or diffusion matrix elements for modeling diffusion processes in natural garnets must consider these compositional effects on self-diffusion.

Analysis

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Mg tracer diffusion in aluminosilicate garnets at 750-850 degrees celsius, 1 atm. and 1300 degrees celsius, 8.5 GPa

Article Abstract:

Measurements of Mg tracer diffusion coefficients in aluminosilicate garnets confirm that the diffusion mechanism does not change from extrinsic to intrinsic between 750-1475 degree celsius and confirm the reliability of the tracer diffusion coefficients discovered in chemical coefficient profiles. The pressure dependence of Mg tracer diffusion coefficients in garnets is much larger than that in forsterite, another orthosilicate. This difference may be due to different geometries and site compressibilities of Mg in the minerals.

Diffusion processes

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Cation diffusion in aluminosilicate garnets: experimental determination in spessartine-almadine diffusion couples, evaluation of effective binary diffusion coefficients, and applications

Article Abstract:

Experimental data on cation diffusion are presented. The data covers almandine-spessartine diffusion couples in graphite capsules which fall in the P-T range of 14-35kb, 1100-1200 degrees celsius. It is shown that effective binary diffusion coefficients (EBDC) can always be defined regardless of D matrix variables. The similarity of EBDCs of Fe, Mg, Mn and Ca allows for the inclusion of these components' diffusion profiles into a concentrated range.

Cations, Diffusion, Diffusion (Physics)

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