A multi-analytical study of the crystal structure of unusual Ti–Zr–Cr-rich Andradite from the Maronia skarn, Rhodope massif, western Thrace, Greece
Unusual Ti–Cr–Zr-rich garnet crystals from high-temperature melilitic skarn of the Maronia area, western Thrace, Greece, were investigated by electron-microprobe analysis, powder and single-crystal X-ray diffraction, IR, Raman and Mössbauer spectroscopy. Chemical data showed that the garnets contain...
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Published in: | Mineralogy and petrology Vol. 95; no. 1-2; pp. 113 - 124 |
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Main Authors: | , , , , , |
Format: | Journal Article |
Language: | English |
Published: |
Vienna
Springer Vienna
2009
Springer Nature B.V |
Subjects: | |
Online Access: | Get full text |
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Summary: | Unusual Ti–Cr–Zr-rich garnet crystals from high-temperature melilitic skarn of the Maronia area, western Thrace, Greece, were investigated by electron-microprobe analysis, powder and single-crystal X-ray diffraction, IR, Raman and Mössbauer spectroscopy. Chemical data showed that the garnets contain up to 8 wt.% TiO
2
, 8 wt.% Cr
2
O
3
and 4 wt.% ZrO
2
, representing a solid solution of andradite (Ca
3
Fe
3+
2
Si
3
O
12
≈46 mol%), uvarovite (Ca
3
Cr
2
Si
3
O
12
≈23 mol%), grossular (Ca
3
Al
2
Si
3
O
12
≈10 mol%), schorlomite (Ca
3
Ti
2
[Si,(Fe
3+
,Al
3+
)
2
]O
12
≈15 mol%), and kimzeyite (Ca
3
Zr
2
[Si,Al
2
]
3
O
12
≈6 mol%). The Mössbauer analysis showed that the total Fe is ferric, preferentially located at the octahedral site and to a smaller extent at the tetrahedral site. Single-crystal XRD analysis, Raman and IR spectroscopy verified substitution of Si mainly by Al
3+
, Fe
3+
and Ti
4+
. Cr
3+
and Zr
4+
are found at the octahedral site along with Fe
3+
, Al
3+
and Ti
4+
. The measured H
2
O content is 0.20 wt.%. The analytical data suggest that the structural formula of the Maronia garnet can be given as: (Ca
2.99
Mg
0.03
)
Σ=3.02
(Fe
3+
0.67
Cr
0.54
Al
0.33
Ti
0.29
Zr
0.15
)
Σ=1.98
(Si
2.42
Ti
0.24
Fe
0.18
Al
0.14
)
Σ=2.98
O
12
OH
0.11
. Ti-rich garnets are not common and their crystal chemistry is still under investigation. The present work presents new evidence that will enable the elucidation of the structural chemistry of Ti- and Cr-rich garnets. |
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ISSN: | 0930-0708 1438-1168 |
DOI: | 10.1007/s00710-008-0023-4 |