Oriented Goethite Inclusions in Metamorphic Garnet of Alumina Gneisses of the Orekhovo-Pavlograd Zone (Ukrainian Shield, Vasil'kovka Village Area)

摘要

Garnet traditionally attracts the attention of petrologists owing to its informativity, which is based on the often found internal compositional heteroge-neity that reflects thermodynamical and physical-chemical genesis conditions of the host rock [ 1 and others]. In recent years, it has been shown that specific types of mineral inclusions in garnet can be very infor-mative as well. Regularly oriented acicular inclusions of titaniferous mineral phases (ruthile, ilmenite, titan-ite) hold particular interest, because they indicate the formation of garnet at extreme pressures and temper-atures favorable for titanium to enter the garnet struc-ture. A decrease in pressure and temperature is considered as one of the possible ways how such inclusions appear: at such decreases, Ti is "ejected" from the garnet structure and forms independent phases within garnet grains [2, 3, and others].