Analysis of experimental data on the diffusion coefficients of Fe, Mn, Mg, and Ca in garnets

Abstract

Experimental data on the diffusion coefficients of Fe, Mn, Mg, and Ca in garnets are generalized. Frequency factors (cm2/s), activation energies (cal/mole), and activation volumes (cm3/mole) are optimized. Based on the compensation law, the dependences of diffusion coefficients on pressure (kbar) and temperature (K) have been derived:

Compensation of the Meyer‐Neldel Compensation Law for H diffusion in minerals

“…For diffusion in minerals, numerous workers have shown that the MNR is upheld for many diffusing species in individual minerals, with the first study being that of Hart []. Examples include oxygen diffusion in diopside [ Jaoul and Bejina , ], in perovskite [ Berenov et al ., ], and in a wide variety of minerals [ Zheng and Fu , ], silicon diffusion in silicate minerals [ Bejina and Jaoul , ], Fe, Mn, Mg, and Ca diffusion in garnets [ Korolyuk and Lepezin , ] (where Fe, Mn, and Mg are fit as one diffusing species), argon diffusion in sericites [ Batyrmurzaev , ], Fe/Mg interdiffusion in olivines and garnet [ Jaoul and Sautter , ], and Ar, H, Pb, and Sr diffusion in a wide array of minerals [ Zhao and Zheng , ]. Proton diffusion has been studied the most of all diffusing species, and adherence to the MNR has been reported for perovskites [ Kreuer , ], as well as other crustal and upper mantle minerals discussed below.…”

Magmatic garnet in the Triassic (215 Ma) Dehnow pluton of NE Iran and its petrogenetic significance

“…At a higher temperature (650°C), the process will take 1 × 10 7 , 5 × 10 7 , 1 × 10 9 , and 1.5 × 10 9 years, respectively. However, the actual D c of elements in natural garnet must be higher than these experimental values (Korolyuk and Lepezin 2008). Considering the possible cooling rate and magmatic time scale of the DTG pluton (<10 7 years), the large size of garnet (~10-20 mm), and Ca and Mg zoning, it seems that diffusion had no significant effects on garnet composition.…”

“…The timescale of magmatic processes in granite genesis, from melting to crystallization, rarely exceeds 10 5 years (Villaros et al 2009 and references therein). The experiments of Korolyuk and Lepezin (2008) show that the diffusion coefficients (D c ) of Ca, Mg, Fe, and Mn are in the order D Mn >D Fe >D Mg >D Ca . Diffusion coefficients are pressure-independent, but temperature-dependent.…”

“…Diffusion coefficients are pressure-independent, but temperature-dependent. Korolyuk and Lepezin (2008) indicate that at 500°C, the homogenization of a garnet grain of 1 mm radius, with an extremely inhomogeneous distribution of major components, will take 1 × 10 9 , 1.5 × 10 9 , 2 × 10 9 , and 3 × 10 9 years for Mn, Fe, Mg, and Ca, respectively. At a higher temperature (650°C), the process will take 1 × 10 7 , 5 × 10 7 , 1 × 10 9 , and 1.5 × 10 9 years, respectively.…”