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Stability constants and formation of Cu(II) and Zn(II) phosphate minerals in the oxidized zone of base metal orebodies

Published online by Cambridge University Press:  05 July 2018

M. Clara ,
F. Magalhães ,
Julio Pedrosa de Jesus  and
Peter A. Williams
M. Clara
Affiliation:
Department of Chemistry, University of Aveiro, Aveiro, Portugal
F. Magalhães
Affiliation:
Department of Chemistry, University of Aveiro, Aveiro, Portugal
Julio Pedrosa de Jesus
Affiliation:
Department of Chemistry, University of Aveiro, Aveiro, Portugal
Peter A. Williams
Affiliation:
Department of Chemistry, University College, PO Box 78, Cardiff CF1 1XL, Wales, UK
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Abstract

The free energies of formation of the minerals libethenite, Cu2PO4OH, pseudomalachite, Cu5(PO4)2(OH)4, cornetite, Cu3PO4(OH)3, tarbuttite, Zn2PO4OH, spencerite, Zn2PO4OH · 1.5H2O, and scholzite, CaZn2(PO4)2 · 2H2O, have been determined at 298.2 K using solution techniques. The values of ΔfG° (298.2 K) for the above minerals are, respectively, −1228.8±3.0, −2840.3±4.2, −1600.9±5.9, −1632.1±4.0, −1982.4±3.1, and −3556.7±7.6 kJ mol−1. These results, together with others from the literature concerning hopeite, Zn3(PO4)2·4H2O, hydroxyapatite, Ca5(PO4)3(OH), and the synthetic salt Cu3(PO4)2 · 2H2O have been used to construct a model for the formation of suites of Zn(II) and Cu(II) phosphate minerals found in the oxidation zone of base metal orebodies. The distributions and modes of occurrence of many natural assemblages of these minerals are readily explained by the model. Particular attention has been focused on deposits at Broken Hill, Zambia, and Saginaw Hill, Arizona, USA.

Keywords

stability constantsphosphate mineralslibethenitepseudomalachitecornetitetarbuttitespenceritescholzite
Type
Mineral Chemistry
Information
Mineralogical Magazine , Volume 50 , Issue 355 , March 1986 , pp. 33 - 39
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1986

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Footnotes

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Author for correspondence

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