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Spectroscopic data on coexisting prehnite-pumpellyite and epidote-pumpellyite

1995; Mineralogical Association of Canada; Volume: 33; Issue: 1 Linguagem: Inglês

1499-1276

Gilberto Artioli, Simona Quartieri, A. Deriu,

Geochemistry and Geologic Mapping

X-ray absorption spectra in the Fe K near-edge region (XANES) and 57 Fe Mossbauer spectra were collected on two Fe-rich pumpellyite specimens from low-grade metamorphosed spilitic rocks from the Keweenaw Peninsula, northern Michigan, and on prehnite and epidote coexisting with pumpellyite. Spectroscopic data for prehnite, presented for the first time, are discussed in light of the pseudosymmetry of its structure. The data clearly show the prevailing role of Fe (super 3+) in the crystal chemistry of the paragenetically associated Ca-silicates. This is in agreement with the overall oxidizing conditions typical of the low-grade metamorphic environment and the mineral assemblages characteristic of alteration zones in basaltic rocks as described by petrological analyses.