Very-low-grade phyllosilicates in the Aravis massif (Haute-Savoie, France) and the di-trioctahedral substitution in chlorite
<p>Very-low-grade mineral veins investigated in the impure limestone massif of the Aravis (Haute-Savoie, France) yielded a rich mineral assemblage typified by dolomite, calcite, quartz, illitic mica, fluorite and three types of chlorite. The vein network extends over more than 5 km and was pro...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-10-01
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| Series: | European Journal of Mineralogy |
| Online Access: | https://ejm.copernicus.org/articles/35/831/2023/ejm-35-831-2023.pdf |
| Summary: | <p>Very-low-grade mineral veins investigated in the impure limestone massif of
the Aravis (Haute-Savoie, France) yielded a rich mineral assemblage typified
by dolomite, calcite, quartz, illitic mica, fluorite and three types of
chlorite. The vein network extends over more than 5 km and was
probably emplaced around peak burial of the limestone (<span class="inline-formula">∼7</span> km
depth, 190 <span class="inline-formula"><sup>∘</sup></span>C). The mineralogy has been investigated with electron
microscopy, mass spectrometry and X-ray diffraction, with emphasis on
chlorite types. The first chlorite type is a chamosite often interlayered
with illitic mica. The second type is a Mg-rich, Al-depleted cookeite. The
third type is a Li-rich sudoite. Presence of the three chlorite types shows
limited solubility between di-trioctahedral chlorite phase components
(sudoite and cookeite) and with tri-trioctahedral chlorite (chamosite).
Departure of the Li-rich sudoite and Mg-rich cookeite from the ideal
end-member compositions suggests solid solutions towards a Li-sudoite
component. The associated illitic mica does not contain Li in significant
proportion but shows pyrophyllitic and di-trioctahedral substitution,
without a Tschermak component. These results call for systematic studies of
the Li content of chlorite and for better modelling of di-trioctahedral
substitution in chlorite and mica.</p> |
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| ISSN: | 0935-1221 1617-4011 |