Cation distribution in a Fe-bearing K-feldspar from Itrongay,Madagascar. A combined neutron- and X-ray single crystal diffractionstudy
We determined the cation distribution and ordering of Si, Al and Fe on the tetrahedral sites of a monoclinic low-sanidine from Itrongay, Madagascar, by combined neutron- and X-ray single-crystal diffraction. The cation distribution was determined by means of a simultaneous refinement using neutron- and X-ray data, as well as by combining scattering densities obtained from separate refinements with chemical data from a microprobe experiment. The two methods give the same results and show that Fe is fully ordered on T1, whereas Al shows a high degree of disorder. Based on this and previously published temperature-dependent X-ray data, we conclude that it is preferential ordering of Fe on T1 even at high temperature, rather than a high diffusion kinetics of Fe, which causes this asymmetry in ordering behavior between Al and Fe. The preferential ordering of Fe3+ relative to Al3+ in T1 is consistent with its 25 percent larger ionic radius.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. Office of Basic EnergySciences
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 888754
- Report Number(s):
- LBNL-57466; R&D Project: A58189; BnR: KC0204016; TRN: US200622%%123
- Journal Information:
- Schweizaerische Mineralogische und Petrographische Mitteilungen, Vol. 84, Issue 3; Related Information: Journal Publication Date: 2004
- Country of Publication:
- United States
- Language:
- English
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