Mathematics – Logic
Scientific paper
Apr 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987gecoa..51..945t&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 51, Issue 4, pp.945-957
Mathematics
Logic
5
Scientific paper
Stability relationships between Al-goethite, Al-hematite, boehmite and gibbsite are presented in terms of water activity [H 2 O], temperature ( T ), grain size and bulk-composition in the system Fe 2 O 3 -Al 2 O 3 -H 2 O at a total pressure of 1 bar. Al-goethite and Al-hematite are treated as ideal solid solutions, the former of the end-members FeOOH (goethite) and AlOOH (diaspore) and the latter of the end-members Fe 2 O 3 (hematite) and Al 2 O 3 (corundum). Using log K sp provided by the literature for the various phases involved, the common associations observed in laterites, bauxites and ferricretes do not have stability fields over geologically reasonable intervals of [H 2 O] and T . Consequently a new internally consistent set of log K sp values is proposed and used, and allows such associations to have actual stability fields in the appropriate diagrams. The new log K sp values used in the calculations are such that the solubilities of the end members are greater than those commonly listed. This is in agreement with natural observations which show that such minerals, are generally poorly crystallized and of very small size. The assumption of an ideal solid solution in aluminous goethite and aluminous hematite combined with the new log K sp values leads to prediction of composition limits for these two minerals which agree well with observed values. The fact that an ideal solid solution must extend continuously from one end-member to the other is masked by the appearance of other stability fields ( e.g. gibbsite or boehmite) which cross and overlap a part of the solid solution stability fields of AlOOH-FeOOH and Fe 2 O 3 -Al 2 O 3 .
Tardy Yves
Trolard Fabienne
No associations
LandOfFree
The stabilities of gibbsite, boehmite, aluminous goethites and aluminous hematites in bauxites, ferricretes and laterites as a function of water activity, temperature and particle size does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The stabilities of gibbsite, boehmite, aluminous goethites and aluminous hematites in bauxites, ferricretes and laterites as a function of water activity, temperature and particle size, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The stabilities of gibbsite, boehmite, aluminous goethites and aluminous hematites in bauxites, ferricretes and laterites as a function of water activity, temperature and particle size will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1347996