One of the metamorphic rocks in the Nain ophiolitic mclange is
skarn which is fonned during the contact metamorphism of intrusive
tonalites with their neighboring limestones and carbonate parts of banded
cherts. Minerals of these skarns consist of carbonate (calcite). clinopyroxene
(diopside). garnet (grossular-andradite). wollastonite, sphene and epidote.
Also tonalites contain quartz, plagioclase (albite). alkali feldspar
(orthoclase). garnet (almandine-spessartine) and prchnite, Based on mineral
assemblages ofNain skarns as well as geothennometry of feldspars existing
in relevant granites and also applications of different calibrations of garnet·
clinopyroxene geothennometer. the Nain skams fonn at temperatures of
about 440 to 650 °C al low pressure during a contact metamorphism which
has occurred at hornblende hornfels to pyroxene hornfels facies.