НЕЗВИЧНІ ПЕРВИННІ ВКЛЮЧЕННЯ СО2-ФЛЮЇДУ І ВОДНОГО РОЗЧИНУ В КВАРЦІ КАМЕРНИХ ПЕГМАТИТІВ ВОЛИНІ (ГЕНЕТИЧНІ АСПЕКТИ)

Abstract

We studied quartz from chamber pegmatites of the Korostenskyi pluton, in particular from pegmatite body No. 348 of the Vyshniakivska section of the pegmatite field. In particular, two morion crystals were studied, the peripheral part of which is composed of colourless lategeneration quartz 2–3 mm thick. Previously, only numerous inclusions of tubular CO2-fluid were detected in late quartz. During the latest research, we found atypical primary inclusions of CO2-fluid with “reticulated” organic matter on the surface of the inclusions, as well as rarer inclusions of an aqueous solution (G ~ 20 %). Inclusions have the shape of negative crystals or are irregular, size from 2–3 μm to 1 mm and are located directly in contact with the morion faces. The spectra of organic matter recorded mass numbers corresponding to hydrogen, nitrogen, methane, ethane, and other hydrocarbons, among which there are higher (heavy) homologues of hydrocarbons (mass numbers in the range of 80–115). The difference in the conditions for the formation of tubular and unusual primary inclusions is due to the normal growth rate of the quartz faces to which bubbles of CO2-fluid have adhered. At a low rate of quartz growth, they were not repelled by layers of face growth, and the fluid was conserved in the form of inclusions that are not typical for the investigated type of quartz. PTparameters of conservation of inclusions are as follows: T = 210–230 °С, Р = ~ 14 MPa; the depth of pegmatite during this period was about 1.4 km. Chamber pegmatites of Volyn are almost the only pegmatites in the world, at the final stage of which endogenous formation the mineral-forming medium contained a gas or liquid CO2-fluid phase along with the aqueous solution. Liquid CO2-fluid corresponds to products of degassing of basic magma, which entered the chamber pegmatites in the form of fluid flows. In a short time, they completed the endogenous stage of chamber pegmatite formation. It is fixed by primary and secondary inclusions of heterogeneous origin (aqueous solution + CO2-fluid) in quartz, beryl, and topaz crystals