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(revised 07/22/2004)

Comments and Questions

1. What would cause corrosion of some minerals in one portion of the pegmatite while in other areas of the same pegmatite minerals show little or no corrosion?

2. White overgrowths on amazonite - albite or microcline?

3. Vapour saturation in pegmatite - when does it take place and what is the evidence?

4. Pegmatite crystallization - an open or closed system? Can it be open to influx of metamorphic/meteoric fluid from external sources, and at what stage? What is the evidence of pegmatite becoming open to the influx from external system(s)?

5. To what extent is replacement a valid late-stage process within pegmatites? If it is, in particular for "albitization" (replacement of K-spar by albite), then what is the disposition of the K that must be displaced by the Na?

6. A series of questions that pertain to the fractionation trends among the (Mn,Fe)(Nb,Ta) oxides in pegmatites. In general, these oxides exhibit increasing Mn/Fe and Ta/Nb with progressive fractionation. Comments on several factors ­ including solubility with temperature, effects of co-crystallizing phases, and the selectivity of the Nb and Ta oxide structures ­ that might influence this trend.

You can submit questions and comments in electronic formats only to

Dr. David London
University of Oklahoma
School Geology & Geophysics
100 E Boyd St, Rm 810 SEC
Norman, OK 73019-0628

Telephone: (405) 325-3253
Facsimile: (405) 325-3140
E-Mail: dlondon@ou.edu

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