TY - JOUR

T1 - Cocrystallization of isomorphic components in solutions and crystal zoning

T2 - An example of the (Ba,Pb)(NO3)2 series

AU - Franke, V. D.

AU - Glikin, A. E.

AU - Kryuchkova, L. Yu

AU - Tabuns, E. V.

N1 - Funding Information: This study was supported by the Russian Foundation for Basic Research (project no. 04-05-64416) and the DAAD (325-A/05/05316).

PY - 2007/12

Y1 - 2007/12

N2 - The phase equilibrium and growth of mixed (Ba,Pb)(NO3) 2 crystals in aqueous solutions were investigated. The microcrystallization method was adapted to systems with isomorphic components, where crystal composition deviates from the thermodynamic equilibrium even at a low supercooling. The solid phase is characterized by continuous miscibility of the components within the analyzed ranges of temperature and solution composition. The diagram is characterized by substantial nonlinearity of the solubility isotherms and nonuniformity of the solid isocomposite location. Quasiequilibrium paths change their slope depending on solution enrichment in Ba(NO3)2 and depletion in Pb(NO3)2. The area of curvature of quasiequilibrium paths is coordinated with the area of the changing isotherm slope, i.e., the area of "remarkable" points, where the behavior of the system changes drastically. Examples of theoretical zoning of a crystal approximated to a sphere were calculated for paths at a temperature decreasing from 50 to 15°C. The content of the Ba component decreases toward the periphery with the consecutive overgrowing of zones. Each zone corresponds to one gram of (Ba,Pb)(NO3)2. Crystals grown from different initial solutions consist of different numbers of zones owing to the nonlinearity of solubility isotherms. Specific features of mixed crystal formation should be taken into account in genetic interpretation of natural minerals of mixed composition.

AB - The phase equilibrium and growth of mixed (Ba,Pb)(NO3) 2 crystals in aqueous solutions were investigated. The microcrystallization method was adapted to systems with isomorphic components, where crystal composition deviates from the thermodynamic equilibrium even at a low supercooling. The solid phase is characterized by continuous miscibility of the components within the analyzed ranges of temperature and solution composition. The diagram is characterized by substantial nonlinearity of the solubility isotherms and nonuniformity of the solid isocomposite location. Quasiequilibrium paths change their slope depending on solution enrichment in Ba(NO3)2 and depletion in Pb(NO3)2. The area of curvature of quasiequilibrium paths is coordinated with the area of the changing isotherm slope, i.e., the area of "remarkable" points, where the behavior of the system changes drastically. Examples of theoretical zoning of a crystal approximated to a sphere were calculated for paths at a temperature decreasing from 50 to 15°C. The content of the Ba component decreases toward the periphery with the consecutive overgrowing of zones. Each zone corresponds to one gram of (Ba,Pb)(NO3)2. Crystals grown from different initial solutions consist of different numbers of zones owing to the nonlinearity of solubility isotherms. Specific features of mixed crystal formation should be taken into account in genetic interpretation of natural minerals of mixed composition.

UR - http://www.scopus.com/inward/record.url?scp=38049128920&partnerID=8YFLogxK

U2 - 10.1134/S1075701507070239

DO - 10.1134/S1075701507070239

M3 - Article

AN - SCOPUS:38049128920

VL - 49

SP - 641

EP - 647

JO - Geology of Ore Deposits

JF - Geology of Ore Deposits

SN - 1075-7015

IS - 7

ER -