Crystal chemistry of lizardite-1T from Northen Apennines Ophiolites (Italy)

This study investigates the crystal chemical features of six lizardite-1T crystals sampled in four ophiolitic outcrops (Pompeano, Sassomorello, Varana, and Santa Scolastica) in the Modena Apennines (Italy).Notwithstanding the extensive contributions already present in literature, this is the first study dealing with lizardites from Modena ophiolites. As evidenced by one of our samples, the whole rock composition affects lizardite composition, which results to be sensible to the overprint of secondary, metasomatic events. In our study, particular attention was devoted to the effects of octahedral Fe for Mg and of Si-1Al(Mg,Mn,Fe)2+-1 (Al,Cr,Fe)3+ exchange mechanisms on the structure. Our results suggest that Fe for Mg substitution induces an increase in the octahedral M-O4 length, and a decrease in the octahedral site distortion. Both these effects are also observed to influence unit-cell parameter c. The effect of the Si-1 Al(Mg,Mn,Fe)2+-1(Al,Cr,Fe)3+ substitution is a decrease in the M-O1 distance and a concomitant increase in the T-O1 distance.