The Amba Dongar carbonatite-alkalic complex is a subvolcanic diatreme with a ring dike of sovite. Country rocks are sandstones contained > 99 % SiO2. The fenitization of sandstone around ring dike of sovite is on distance up to 300 m. Fenites consist of pyroxene, quartz, potash feldspar and albite. The fluid inclusions in quartz and pyroxene were investigated. Pyroxene is the earliest mineral. Three types of inclusions are observed in it: 1- solid, 2- primary polyphase, 3- secondary gas-liquid. Polyphase inclusions consist of a liquid, gas and mineral phase. The temperature of homogenization of inclusions varies within 334-423º C, it probably corresponds for first stage of rock formation. The quartz forms xenomorphic grains. It hes two types of inclusions primary and secondary. The temperature of homogenization of primary inclusions is 130º C, it reflects a final stage of fenite formation.