Fluid inclusions in minerals of the exoand endocontact zone of the Lovozero alkaline massif
New data on the distribution, morphology and composition of fluid inclusions in nepheline and quartz from endocontact (nepheline syenites) and exocontact (fenites and fenitized gneiss) of the Lovozero alkaline massif have been obtained. The results of the fluid inclusions study showed that the fluid responsible for the metasomatic transformation of the host Archaean gneiss is characterized by a heterogeneous composition and is significantly enriched with high-density CH 4 (up to 0.24 g/cm 3 ). The solutions included in the fluid are essentially aqueous-chloride and low-saline (0.5-3.06 wt. % NaCl-eq.). Experiments on the homogenization of fluid inclusions allowed us to establish that the formation of the fenitization zone occurred at temperatures above 400 ° C. As the temperature of the metasomatic process decreased, the composition of the fluid gradually shifted from substantially gaseous (the ratio of CH 4 and H 2 O is 90:10) to substantially aqueous (the ratio of CH 4 and H 2 O is 10:90). With a decrease in the fenitization degree of gneiss, the density of CH 4 in the gas component of the fluid decreases from 0.24 to 0.03 g/cm 3 .