Structural investigations of natural and synthetic chlorite minerals by X-ray diffraction, Mossbauer spectroscopy and solid-state nuclear magnetic resonance

• The structures of one synthetic and two natural chlorites of the chlinochlore type were explored using X-ray diffraction, magic-angle spinning nuclear magnetic resonance (NMR) and Mossbauer spectroscopy. Rietveld refinements indicated that all structures are of the trioctahedral ordered IIb polytype. Mossbauer spectra provided the ratio Fe-II/Fe-III but gave no evidence for the presence of Fe-III in the brucite-like sheet. We also report unit-cell parameters, Mossbauer isomeric shifts, Si-29 NMR chemical shifts as well as Al-27 isotropic shifts and quadrupolar coupling parameters. Very broad Si-29 NMR peaks from the natural samples prevented us from obtaining accurate information on the Si-Al ordering in the tetrahedral sheets; the limitations of Si-29 NMR as applied to natural chlorites are discussed. High-resolution 3QMAS NMR resolved the Al-27 signal of the M4 octahedral site in the brucite-like sheet from the other three Al signals of crystallographically inequivalent octahedral positions.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geology (hsv//eng)

Nyckelord

Al-27 NMR

cation distributions

chlorite

layered mineral

mineral structure

Mossbauer spectroscopy

Si-29 NMR

XRD

Chemistry

Kemi

Mineralogy

Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics

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