Serpentinitic veins consisting of associated chrysotile and well crystallized lizardite were extensively sampled in the Monte Fico quarries, Elba Island, Italy. The veins are mostly formed of euhedral lizardite-1T. After optical, IR and X-ray characterization, the specimens were studied by transmission electron microscopy. TEM provides evidence for the occurrence of chrysotile, polygonal serpentine and lizardite, with microstructural relations pointing to a continuous recrystallization from chrysotile to polygonal serpentine and to lizardite. No major fault structure occurs in lizardite. Chemical data indicate the existence of a compositional gap between lizardite [mean composition (Mg2.79Fe2+ 0.09 Fe3+ 0.07Al0.07)Σ=3.02(Si 1.91Al0.09)Σ=2.00 O5 (OH)3.90] and chrysotile [mean composition (Mg2.80Fe0.11Al0.06) Σ=2.97Si2.00 O5 (OH)4] with lizardite systematically enriched in aluminum and iron with respect to chrysotile. Therefore, the two minerals should no longer be considered as polymorphs.
|Titolo:||Contrasting chemical compositions in associated lizardite and chrysotile in veins from Elba, Italy|
|Appare nelle tipologie:||1.1 Articolo in rivista|