@article{PAR00007719,
  title = {{I}ncorporation mechanisms of {T}a and {N}b in zircon and implications for pegmatitic systems},
  author = {{V}an {L}ichtervelde, {M}arieke and {H}oltz, {F}. and {D}ziony, {W}. and {L}udwig, {T}. and {M}eyer, {H}. {P}.},
  abstract = {{T}o investigate the processes that control {T}a incorporation in zircon, two types of synthesis experiments were performed: (1) crystallization of zircon from an {L}i-{M}o flux at 1 atm. and (2) crystallization of zircon (with or without coexisting tantalite) from a highly fluxed pegmatitic melt at 200 {MP}a and nearly water-saturated conditions. {T}he first type of experiment is used to identify the influence of various doping elements ({H}f, {P}, {A}l, and {M}n) on {T}a incorporation in zircon. {T}hese experiments reveal that {P} hinders the incorporation of {T}a, whereas {A}l enhances {T}a incorporation via charge balancing, and that {T}a can be incorporated in the absence of any other doping element via the creation of vacancies in the zircon structure. {H}afnium does not affect significantly {T}a incorporation. {M}anganese and lithium do not enter the structure of zircon, except in the presence of {P}. {E}xperiments with {N}b show that the concentration of this element in zircon is nearly one order of magnitude lower than {T}a (for similar {T}a and {N}b concentrations in the flux). {T}he second type of experiments show how {T}a is incorporated in zircon in natural granite and pegmatite systems. {I}n those systems, {P} and {A}l have elevated concentrations, and {P} is preferentially incorporated in zircon via {A}l substitution to maintain charge balance. {B}elow a {P}/{T}a atomic ratio of similar to 10 in the melt, {T}a competes with {P} for {A}l, and {P} is involved in a coupled substitution with {M}n for charge balancing. {C}oncentrations up to 3.7 wt% {T}a2{O}5 (0.03 apfu calculated to four atoms of oxygen) were measured in these zircon samples. {T}he partition coefficients of {T}a between melt and zircon are around 1 at 800-900 degrees {C} at conditions close to tantalite saturation. {T}hese results show that zircon incorporates significant amounts of {T}a from the melt in {P}-poor peraluminous granites with a {P}/{T}a atomic ratio lower than similar to 10, which may ultimately affect the precipitation of {T}a minerals. {S}uch interactions between cations both in melts and in mineral structures are important to constrain in order to understand rare-metal enrichment in granitic systems.},
  keywords = {{Z}ircon ; tantalum ; pegmatitic systems ; crystallization experiments},
  journal = {{A}merican {M}ineralogist},
  volume = {96},
  numero = {7},
  pages = {1079--1089},
  ISSN = {0003-004{X}},
  year = {2011},
  DOI = {10.2138/am.2011.3650},
  URL = {http://www.documentation.ird.fr/hor/{PAR}00007719},
}