Volatiles During the Crystallization of Olivine from Meimechites of the Guli Pluton, Maimecha-Kotui Province: Pyrolysis-Free Gas Chromatography–Mass Spectrometry Data

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The volatile content of syngenetic 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 (GC–MS). The melt inclusions in olivine were fine-crystallized. According to scanning electron microscope study, daughter phases in them 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 transparent 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 its heterogeneous trapping, i.e. heterogeneity of mineral-forming environment. During olivine crystallization, the volatiles were predominantly represented by hydrocarbons (83.0 rel. %), nitrogenated (7.2 rel. %) and sulfonated (3.4 rel. %) compounds, as well as H 2 O (5.9 rel. %) and CO 2 (0.3 rel. %). The hydrocarbons and sulfonated compounds include the relatively high amount of halogenated compounds (4.0 rel. %). The species diversity of the volatile components amounted 201 chemical compounds. The hydrocarbons were dominated by oxygenated components (74.5 rel. %), which include 34.0 rel. % alcohols and 9.9 rel. % ethers, 11.4 rel. % aldehydes, 6.8 rel. % ketones, and 12.2 rel. % carboxylic acids. Aliphatic and cyclic hydrocarbons accounted for only 4.6 and 3.7 rel. %, respectively. Olivine crystallized at relatively reducing conditions at H/(H + O) = 0.87. The comparison of the obtained data with data on olivine from olivinites of the Krestovskaya intrusion showed that meimechites cannot be the parental magma for olivinites of alkaline-ultrabasic carbonatite massifs.

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