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Melt and fluid inclusions were studied in the minerals of Cenozoic olivine melanephelinites from the Chukchi Peninsula, Russia.The rock contain several generations of olivine phenocrysts varying in composition at mg=0.88～0.77.The phenocrysts bear fluid and melt inclusions recording various stages of melt crystallization in volcanic conduits and shallow magma chambers.Primary fluid inclusions are CO_2-dominated with a density of up to O.93 g/cm~3.All fluid inclusions are partially leaked,which is indicated by haloes of tiny fluid bubbles around large fluid inclusions in minerals.Melt inclusions contain various daughter crystals,which were completely resorbed in thermometric experiments at about 1230℃.Assuming that this temperature corresponds to the entrapment conditions of the CO_2 fluid inclusions,the minimum pressure of the beginning of magma degassing is estimated as 800MPa.Variations in the compositions of homogenized silicate melt inclusions indicate that olivine was the earliest crystalline phase followed by clinopyroxene,nepheline and orthoclase.This sequence is in agreement with the mineralogy of the rocks.The melts are strongly enriched in incompatible trace elements and volatiles(in addition to CO_2,high C1,F,and S contents were detected).There are some differences between the compositions of melts trapped in minerals from different samples.Variations in SiO_2,FeO,and incompatible element contents are probably related to melt generations at various levels in a homogeneous mantle reservoir.
Melt and fluid inclusions were studied in the minerals of Cenozoic olivine melanephelinites from the Chukchi Peninsula, Russia. The rock contains several generations of olivine phenocrysts varying in composition at mg = 0.88 ~ 0.77. The phenocrysts bear fluid and melt inclusions recording various stages of melt. crystallization in volcanic conduits and shallow magma chambers. Primary fluid inclusions are CO_2-dominated with a density of up to O.93 g / cm ~ 3. All fluid inclusions are partially leaked, which is indicated by haloes of tiny fluid bubbles around large fluid inclusions in minerals.Melt inclusions contain various daughter crystals, which were completely resorbed in thermometric experiments at about 1230 ° C. Assuming that this temperature corresponds to the entrapment conditions of the CO_2 fluid inclusions, the minimum pressure of the beginning of magma degassing is estimated as 800MPa. Variations in the compositions of homogenized silicate melt inclusions indicate that olivine was the earli est crystalline phase followed by clinopyroxene, nepheline and orthoclase.This sequence is in agreement with the mineralogy of the rocks.The melts are strongly enriched in incompatible trace elements and volatiles (in addition to CO_2, high C1, F, and S contents were detected There are some differences between the compositions of melts trapped in minerals from different samples. Variations in SiO_2, FeO, and incompatible element contents are likely related to melt generations at various levels in a homogeneous mantle reservoir.