Mantle peridotites are one of the most important rock units of
Jandaq ophiolite that are affected by numerous,phases of dynamic and static
serpentinization, and metamorphism. The main part of mantle peridotites is
lherzolite. This ophiolitic association is covered by Paleozoic metamorphic
rocks that are schist and marble. All olivines are changed to serpentine. Most
of orthopyroxenes are bastitized and some of clinopyroxenes are changed to
tremolite by metamorphism. Clinopyroxenes are the most resistant mineral
against the metamorphism and alteration. Most of spinels are magnetitized,
but in some cases the inner parts are fresh. Composition of chromian-spinels
are the same in all mantle peridotites with CrN "" 0.46. Gabbros that intruded
the peridotites are rodingitized. Peridotites of Jandaq ophiolite are abyssal
peridotites that belong to spinel lherzolite facies. Crystallization temperature
of pyroxenes in Iherzolites ranges from 1041 to I 178 DC. One of the most
characteristics of these peridotites is absence of chromitite that relates to
lherzolitic system of mantle, low degree of partial melting, low activity of
mantle in continual ascending melt production, and low Cr content of
pyroxenes.