Mordberg,L.E., Stanley,C.J. and Antonov,A.V.(2008): Polystage apatite recrystallization and svanbergite formation during weathering in an acid karstic environment. Mineralogical Magazine, 72(1), 95-99.

『酸性カルスト環境の風化での多段階の燐灰石の再結晶化とスバンベルグ石の生成』


Abstract
 A Devonian weathering profile was developed near the contact of Riphean dolostone containing disseminated carbonate-fluorapatite and intensively pyritized black shales. samples from the profile were investigated by XRF, SEM, electron microprobe and ion microprobe. Rock-forming minerals are apatite, diaspore, chlorite and kaolinite, while accessory minerals are svanbergite, anatase, pyrite and zircon.
 Primary marine carbonate-fluorapatite is represented by extremely weathered crystals concentrated near the footwall. Dissolution of apatite and pyrite provided an acidic environment that is expressed in the formation of S-rich apatite and svanbergite. The environment allowed Ti migration which formed anatase in weathered apatite grains. Coupled substitution Na+ + S6+ = Ca2+ + P5+ is suggested in S-rich apatite. A large volume of dissolved carbonate rocks was a source of Sr necessary for svanbergite formation. Apatite of the third generation formed at the final stage of weathering is represented by small (10-30μm) very well shaped crystals.

Keywords: weathering; sulphate-apatite; anatase; svanbergite; Devonian』

Introduction
Geological setting and mineralogy
Material and methods
Results and discussion
Conclusions
Acknowledgements
References


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