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

The crystal chemistry of three ulvöspinels 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 Å 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.