Some aspects of the role of intergranular fluids in the compositional evolution of metamorphic rocks

Journal of Earth system science

Sumit Chakraborty1¹  Ralf Dohmen1¹ 

[1] Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.$$

关键词: Intergranular fluid;    metamorphism;    diffusion;    geothermometry;    closure temperature.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

Minerals that react with each other during the progressive evolution of metamorphic terranes are not always in physical contact. As such, an "intergranular fluid" could play a major role in element transfer and chemical evolution. However, the nature of this uid and its specific role remains somewhat elusive. Recent experiments in our laboratory shed some light on the behavior of such a uid. Here we present a simple mathematical model which accounts for diffusion within crystals and fluid, solubility in the fluid and mass balance between the various reservoirs. The model elucidates the nature of element exchange between two minerals via the mediation of an intergranular fluid. It is shown that a coupling of thermodynamics and kinetics controls the evolution of the system and the concentration of an element in the intergranular fluid is a key parameter of interest.The results have important implications for standard tools of metamorphic petrology such as geothermometers and barometers, geospeedometry and the closure of isotopic systems. For example, homogeneity of mineral grains may be a poor criterion for equilibrium and the rim compositions of minerals showing diffusion zoning may be out of equilibrium with distant exchange partners, even in the presence of a uid in which transport is fast.

【 授权许可】

Unknown