First occurrence of titanomagnetites from the websterite dykes within Balmuccia peridotite (Ivrea-Verbano zone): crystal chemistry and structural refinement

Abstract

Periodico di Mineralogia (2011), 80, 1 (Special Issue), 19-26 - DOI: 10.2451/2011PM0002 Special Issue in memory of Sergio Lucchesi First occurrence of titanomagnetites from the websterite dykes within Balmuccia peridotite (Ivrea-Verbano zone): crystal chemistry and structural refinement Davide Lenaz* and Francesco Princivalle Dipartimento di Geoscienze, Universita di Trieste, Italy *Corresponding author: lenaz@units.it Abstract The crystal chemistry of three ulvospinels from the websteritic dykes within the Balmuccia peridotites has been investigated by means of X-ray single crystal diffraction and electron microprobe. They are very similar each other with cell edge about 8.43 A and oxygen positional parameter between 0.2565 and 0.2570. Ti content is about 0.32 a.p.f.u. As they are embedded in a glass with syenite composition it is supposed they quenched during the rapid cooling of a melt pervading the websteritic dykes. This is the first finding of similar spinels in the studied area. Key words : Balmuccia peridotite; websterite dykes; ulvospinel; crystal chemistry; structural refinement.