Gas Concentrations in Minerals with Reference to the Problem of the Genesis of Hydrocarbon Gases in Rocks of the Khibiny and Lovozero Complexes

摘要

The bulk concentations and distributions of hydrocarbon gases (HCG) in fluid inclusions were determined in 38 rock samples and 122 monomineralic fractions from the Khibiny and Lovozero complexes, in order to get better insight into the genetic mechanism and conditions of the origin of very high (for igneous rocks) concentrations of these gases and to achieve a more reliable way of interpreting such important tracers of various geochemical processes as isotopes of noble gases. The concentrations of methane, the predominant component of the gas phase in the rocks and minerals, vary from 0.04 to 120.1 cm~3/kg. The principal mineral concentrators of the gases are sodalite, nepheline, and K-Na feldspar. The decrease in the average gas concentrations in the main rock-forming minerals from nepheline to feldspar and aegirine and variations in the duration and intensity of postmagmatic alterations of these minerals, as well as by variations in the physicochemical parameters of these processes. The leading mechanism producing hydrocarbons was the Fischer-Tropsch synthesis, per-haps, from juvenile carbon dioxide and hydrogen, which in turn, was provided by iron oxidation and hydration during the origin of aegirine, magnetite, cancrinite, and zeolites during the epimagmatic evolutionary stages of agpatic complexes.