Hi Mustafa, I suggest you to have a look on chapter 15 in F. Spear's book (Metamorphic Phase Equilibria and P-T-t Paths), Monograph, Mineralogical Society of America, 1993. Cheers, hassina Hassina Mouri Senior Lecturer Department of Earth Sciences University of Pretoria Pretoria 0002 Republic of South Africa Tel (office): (+27 12) 4 20 24 56 Tel (Cell): (+27 12) 8 26 36 26 43 Fax: (+27 12) 3 62 52 19