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Title: Rare earth elements in apatite: Uptake from H{sub 2}O-bearing phosphate-fluoride melts and the role of volatile components

Abstract

The partitioning of rare earth elements (REEs) between fluorapatite (FAp) and H{sub 2}O- bearing phosphate-fluoride melts has been studied at about 700 and 800{degrees}C and 0.10-0.15 GPa. REE uptake patterns, i.e., plots of D(REE:FAp/melt), are convex upwards and peak near Nd for single-REE substituted FAp at minor (0.03-0.25 wt% REE{sub 2}O{sub 3}) abundances, and binary (LREE + HREE)-substituted FAp, and hexa-REE-substituted FAp at minor to major (0.25-7.8 wt% REE{sub 2}O{sub 3}) abundances. Partition coefficients for minor abundances of REE and depolymerized phosphate melts are about 5, 8, and 1 for La, Nd, and Lu, respectively and broadly comparable to those for early fluorapatite in the fractionation of melts of basaltic composition. The Ca2 site exerts marked control on the selectivity of apatite for REE because it preferentially incorporates LREE and its effective size varies with substitution of the A-site volatile anion component (F, Cl, OH). Using simple crystal-chemical arguments, melt(or fluid)-normalized REE patterns are predicted to peak near Nd for fluorapatite and be more LREE-enriched for chlorapatite. These predictions are consistent with data from natural rocks and laboratory experiments. The wide variation in D(REE:apatite/melt) in nature (from <1 for whitlockite-bearing lunar rocks to about 100 for evolved alkalic rocks) ismore » attributed largely to the influence of the volatile components. 49 refs., 8 figs., 3 tabs.« less

Authors:
 [1];  [2]
  1. Univ. of Western Ontario, London, Ontario (Canada)
  2. Univ. of Saskatchewan, Saskatoon (Canada)
Publication Date:
OSTI Identifier:
585486
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 61; Journal Issue: 22; Other Information: PBD: Nov 1997
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; 58 GEOSCIENCES; RARE EARTHS; APATITES; MAGMA; CHEMICAL COMPOSITION; FRACTIONATION; GEOCHEMISTRY; PETROLOGY

Citation Formats

Fleet, M.E., and Pan, Yuanming. Rare earth elements in apatite: Uptake from H{sub 2}O-bearing phosphate-fluoride melts and the role of volatile components. United States: N. p., 1997. Web. doi:10.1016/S0016-7037(97)00292-5.
Fleet, M.E., & Pan, Yuanming. Rare earth elements in apatite: Uptake from H{sub 2}O-bearing phosphate-fluoride melts and the role of volatile components. United States. doi:10.1016/S0016-7037(97)00292-5.
Fleet, M.E., and Pan, Yuanming. Sat . "Rare earth elements in apatite: Uptake from H{sub 2}O-bearing phosphate-fluoride melts and the role of volatile components". United States. doi:10.1016/S0016-7037(97)00292-5.
@article{osti_585486,
title = {Rare earth elements in apatite: Uptake from H{sub 2}O-bearing phosphate-fluoride melts and the role of volatile components},
author = {Fleet, M.E. and Pan, Yuanming},
abstractNote = {The partitioning of rare earth elements (REEs) between fluorapatite (FAp) and H{sub 2}O- bearing phosphate-fluoride melts has been studied at about 700 and 800{degrees}C and 0.10-0.15 GPa. REE uptake patterns, i.e., plots of D(REE:FAp/melt), are convex upwards and peak near Nd for single-REE substituted FAp at minor (0.03-0.25 wt% REE{sub 2}O{sub 3}) abundances, and binary (LREE + HREE)-substituted FAp, and hexa-REE-substituted FAp at minor to major (0.25-7.8 wt% REE{sub 2}O{sub 3}) abundances. Partition coefficients for minor abundances of REE and depolymerized phosphate melts are about 5, 8, and 1 for La, Nd, and Lu, respectively and broadly comparable to those for early fluorapatite in the fractionation of melts of basaltic composition. The Ca2 site exerts marked control on the selectivity of apatite for REE because it preferentially incorporates LREE and its effective size varies with substitution of the A-site volatile anion component (F, Cl, OH). Using simple crystal-chemical arguments, melt(or fluid)-normalized REE patterns are predicted to peak near Nd for fluorapatite and be more LREE-enriched for chlorapatite. These predictions are consistent with data from natural rocks and laboratory experiments. The wide variation in D(REE:apatite/melt) in nature (from <1 for whitlockite-bearing lunar rocks to about 100 for evolved alkalic rocks) is attributed largely to the influence of the volatile components. 49 refs., 8 figs., 3 tabs.},
doi = {10.1016/S0016-7037(97)00292-5},
journal = {Geochimica et Cosmochimica Acta},
number = 22,
volume = 61,
place = {United States},
year = {1997},
month = {11}
}