Intercrystalline stable isotope diffusion; a fast grain boundary model
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Authors:  Eiler, John M.; Baumgartner, Lukas P.; Valley, John W. 

Author Affiliations:  Primary: University of WisconsinMadison, Department of Geology and Geophysics, Madison, WI, United States 
Volume Title:  Contributions to Mineralogy and Petrology 
Source:  Contributions to Mineralogy and Petrology, 112(4), p.543557. Publisher: Springer International, HeidelbergNew York, International. ISSN: 00107999 
Publication Date:  1992 
Note:  In English. 59 refs.; illus. 
Summary:  A numerical model has been formulated for stable isotope interdiffusion which predicts the T recorded between two or more minerals, and the intragranular distribution of stable isotopes in each mineral, as functions of mineral grain sizes and shapes, diffusivities, modes, equilibrium isotopic fractionations, and the cooling rate of a rock. One of the principal assumptions of the model is that grain boundaries are regions of rapid transport of stable isotopes. This fast grain boundary (FGB) model describes interdiffusion between any number of mineral grains, assuming that local equilibrium and massbalance restrictions apply on the grain boundaries throughout the volume modelled. The model can be used for a rock containing any number of minerals, any number of grain sizes of each mineral, several grain shapes, and any thermal history or domain size desired. Previous models describing stable isotope interdiffusion upon cooling were based on an earlier worker's equation or an equivalent numerical analogue. The closure T in this analogue is the average, bulk T recorded between a mineral and an infinite reservoir. By using this equation, these models have treated the closure T as an innate characteristic of a given mineral, independent of the amounts and diffusion rates of other minerals. Such models do not accurately describe the mass balance of many stable isotope interdiffusion problems. Existing models for cation interdiffusion could be applied to stable isotopes with some modifications, but only describe exchange between two minerals under specific conditions. The results of FGB calculations differ considerably from the predictions of an earlier equation in many rock types of interest. Actual calculations using the FGB model indicate that closure T and diffusion profiles are as strongly functions of modal abundance and relative differences in diffusion coefficient as they are of functions of grain size and cooling rate. Closure T recorded by two minerals which exchanged stable isotopes by diffusion are a function of modal abundance and differences in diffusion coefficient and may differ from prediction by 100's of degrees C. [P.Br.] 
Subjects:  Amphibole group; Chain silicates; Clinoamphibole; Closed systems; Cooling; Diffusion; Feldspar group; Framework silicates; Geologic thermometry; Grain boundaries; Hornblende; Isotope ratios; Isotopes; Numerical models; O18/O16; Open systems; Oxygen; Quartz; Silica minerals; Silicates; Stable isotopes; Temperature 
Abstract Numbers:  93M/2781 
Record ID:  1993019861 
Copyright Information:  GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom 
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LEADER  04701naaaa2200565zu 4500  

001  1993019861  
003  ViAlAGI  
005  20190221171417.0  
008  190110e199212 vp a 0 0 eng d  
040  a ViAlAGI c ViAlAGI  
072  7  a 02D 2 georeft  
072  7  a 05A 2 georeft  
100  1  a Eiler, John M. e analytic author u University of WisconsinMadison, Department of Geology and Geophysics, Madison, WI  
245  1  0  a Intercrystalline stable isotope diffusion; a fast grain boundary model 
300  a p. 543557  
500  a In English. 59 refs.  
500  a Abstract number: 93M/2781  
500  a Abstractor: P.Br.  
500  a Affiliation: University of WisconsinMadison, Department of Geology and Geophysics; Madison, WI; USA; United States  
500  a Key title: Contributions to Mineralogy and Petrology  
500  a Source note: Contributions to Mineralogy and Petrology, 112(4), p.543557. Publisher: Springer International, HeidelbergNew York, International. ISSN: 00107999  
500  a Publication type: journal article  
504  b 59 refs.  
510  3  a GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom  
520  a A numerical model has been formulated for stable isotope interdiffusion which predicts the T recorded between two or more minerals, and the intragranular distribution of stable isotopes in each mineral, as functions of mineral grain sizes and shapes, diffusivities, modes, equilibrium isotopic fractionations, and the cooling rate of a rock. One of the principal assumptions of the model is that grain boundaries are regions of rapid transport of stable isotopes. This fast grain boundary (FGB) model describes interdiffusion between any number of mineral grains, assuming that local equilibrium and massbalance restrictions apply on the grain boundaries throughout the volume modelled. The model can be used for a rock containing any number of minerals, any number of grain sizes of each mineral, several grain shapes, and any thermal history or domain size desired. Previous models describing stable isotope interdiffusion upon cooling were based on an earlier worker's equation or an equivalent numerical analogue. The closure T in this analogue is the average, bulk T recorded between a mineral and an infinite reservoir. By using this equation, these models have treated the closure T as an innate characteristic of a given mineral, independent of the amounts and diffusion rates of other minerals. Such models do not accurately describe the mass balance of many stable isotope interdiffusion problems. Existing models for cation interdiffusion could be applied to stable isotopes with some modifications, but only describe exchange between two minerals under specific conditions. The results of FGB calculations differ considerably from the predictions of an earlier equation in many rock types of interest. Actual calculations using the FGB model indicate that closure T and diffusion profiles are as strongly functions of modal abundance and relative differences in diffusion coefficient as they are of functions of grain size and cooling rate. Closure T recorded by two minerals which exchanged stable isotopes by diffusion are a function of modal abundance and differences in diffusion coefficient and may differ from prediction by 100's of degrees C.  
650  7  a Amphibole group 2 georeft  
650  7  a Chain silicates 2 georeft  
650  7  a Clinoamphibole 2 georeft  
650  7  a Closed systems 2 georeft  
650  7  a Cooling 2 georeft  
650  7  a Diffusion 2 georeft  
650  7  a Feldspar group 2 georeft  
650  7  a Framework silicates 2 georeft  
650  7  a Geologic thermometry 2 georeft  
650  7  a Grain boundaries 2 georeft  
650  7  a Hornblende 2 georeft  
650  7  a Isotope ratios 2 georeft  
650  7  a Isotopes 2 georeft  
650  7  a Numerical models 2 georeft  
650  7  a O18/O16 2 georeft  
650  7  a Open systems 2 georeft  
650  7  a Oxygen 2 georeft  
650  7  a Quartz 2 georeft  
650  7  a Silica minerals 2 georeft  
650  7  a Silicates 2 georeft  
650  7  a Stable isotopes 2 georeft  
650  7  a Temperature 2 georeft  
700  1  a Baumgartner, Lukas P., e analytic author  
700  1  a Valley, John W., e analytic author  
773  0  t Contributions to Mineralogy and Petrology d HeidelbergNew York : Springer International, Dec. 1992 x 00107999 y CMPEAP n Contributions to Mineralogy and Petrology, 112(4), p.543557. Publisher: Springer International, HeidelbergNew York, International. ISSN: 00107999 Publication type: journal article g Vol. 112, no. 4 h illus. 