Fluid Composition during Crystallization of Olivine from Meimechites of the Guli Pluton, Maimecha-Kotuiskaya Province: Gas Chromatography-Mass Spectrometry Data

The fluid composition from coeval melt and fluid inclusions in olivine phenocrysts (Fo_92–89) from meimechites of the Guli alkaline-ultrabasic carbonatite pluton was studied using gas chromatography-mass spectrometry. The melt inclusions in olivine were fine-crystallized. Daughter phases in inclusions by scanning electron microscopy were represented by diopside, phlogopite, ilmenite, Ti-bearing magnetite, titanite, nepheline, sodalite, and xenogenic chromite. According to Raman spectrometry, the fluid inclusions were low-density and contained magnesite and water. During heating experiments, after melting of the last colorless daughter phase in melt inclusions at about 1300°C, the volume of the gas phase coexisting with the melt varied from 1/4 to 2/3 of the inclusion volume, indicating a heterogeneous state of the trapped mineral-forming environment. During olivine crystallization, the fluid phase was predominantly composed of hydrocarbons (83.0 rel. %), nitrogenated (7.2 rel. %) and sulfonated (3.4 rel. %) compounds, as well as H₂O (5.9 rel. %) and CO₂ (0.3 rel. %). The hydrocarbons and sulfonated compounds contained a relatively high amount of halogenated compounds (4.0 rel. %). The species diversity of fluid components amounted to 201 chemical compounds. Among the hydrocarbons, oxygenated components prevailed (74.5 rel. %), consisting of 34.0 rel. % alcohols and 9.9 rel. % esters, 11.4 rel. % aldehydes, 6.8 rel. % ketones, 12.2 rel. % carboxylic acids. Aliphatic and cyclic hydrocarbons constituted only 4.6 and 3.7 rel. %, respectively. Olivine crystallization occurred under relatively reducing conditions at H/(H+O) = 0.87. A comparison of the obtained data with those from olivine in olivinites of the Krestovskaya intrusion, showed that meimechites could not be the parental magma for olivinites of alkaline-ultramafic carbonatite massifs.