Natural and synthetic re-equilibration textures of fluid inclusions in quartz (Marmarosh Diamonds): Evidence for refilling under conditions of compressive loading
Vityk, Maxim O.; Dudok, Igor V.; Bodnar, Robert J.
European Journal of Mineralogy Volume 7 Number 5 (1995), p. 1071 - 1088
published: Oct 5, 1995
manuscript accepted: May 9, 1995
manuscript received: Oct 25, 1994
ArtNo. ESP147050705004, Price: 29.00 €
Abstract Hydrocarbon inclusions in quartz crystals (Marmarosh Diamonds) from calcite-quartz fissures in flysch deposits of the Ukrainian Folded Carpathians display unusual morphological features (scal’oped textures) that have been related to post-trapping re-equilibration. Tectonic models for the evolution of the region are consistent with P-T paths that would generate internal overpressures in the inclusions during uplift. However, based on a comparison of laboratory produced fluid inclusion re-equilibration textures with textures in natural hydrocarbon inclusions in Marmarosh Diamonds, we have concluded that the latter were produced by leakage and refilling under conditions of compressive loading. Multi-stage laboratory re-equilibration of natural hydrocarbon inclusions in Marmarosh Diamonds under conditions of internal underpressure (compressional loading) at 500°C and 2, 3, 4, and 5 kbar of confining pressure shows that inclusion density remains relatively constant up to about 3 kbar internal underpressure (4 kbar of confining pressure). In most inclusions that have been re-equilibrated in the laboratory, fluid density increased after re-equilibration at about 4 kbar underpressure (5 kbar of confining pressure) as a result of a decrease in inclusion volume due to plastic deformation.