Ważne i użyteczne fakty dotyczące inkluzji fluidalnych w minerałach w kontekście rozpoznawania systemów naftowych
Abstract
Important and useful facts on fluid inclusions in minerals in the context recognition of hydrocarbon systems.
A b s t r a c t. Samples of minerals, solid bitumen and rocks from different localities and different basins have been an object of mineralogical, petrographic and geochemical analyses. Their microfissures (microfractures) are often filled with fluids forming “fluid inclusions” (FI). Such inclusions are small portions of palaeofluids that existed in the basin during the mineral formation, which may be a significant record from the geological past. Analytical procedures comprised several stages: preparation of thin and thick sections, microscopic evaluation of the material (organic matter, minerals, inclusions), FI microthermometric determinations, geochemical analyses, and auxiliary studies. General microscopic observations were conducted using a polarization microscope, cold cathode, and the special heating- freezing stage. Fluid inclusions in minerals were studied aiming at the characterization of fluids that fill these micro-volumes in crystals. The undertaken analytical steps have led to determination of the fluids trapped in inclusions as brine and/or hydrocarbons (based on fluorescence abilities). Furthermore, they have resulted in the measurement of the homogenization temperatures of inclusions (values positive for, e.g., oil, negative for methane, pure or with admixtures), and determinations of the eutectic and ice-melting temperatures of the aqueous inclusions. Thermometric studies in the heating mode generally lead to determination of temperatures of mineral crystallization since it has been assumed that the homogenization temperature of the primary aqueous inclusions represents a minimum temperature of fluid trapping during mineral precipitation. Complementary analyses, as the Raman spectrum analysis and studies on the organic matter, lead to the interpretation of the results richer, clearer and meaningful for the hydrocarbon systems context, what has been proved on some examples.
A b s t r a c t. Samples of minerals, solid bitumen and rocks from different localities and different basins have been an object of mineralogical, petrographic and geochemical analyses. Their microfissures (microfractures) are often filled with fluids forming “fluid inclusions” (FI). Such inclusions are small portions of palaeofluids that existed in the basin during the mineral formation, which may be a significant record from the geological past. Analytical procedures comprised several stages: preparation of thin and thick sections, microscopic evaluation of the material (organic matter, minerals, inclusions), FI microthermometric determinations, geochemical analyses, and auxiliary studies. General microscopic observations were conducted using a polarization microscope, cold cathode, and the special heating- freezing stage. Fluid inclusions in minerals were studied aiming at the characterization of fluids that fill these micro-volumes in crystals. The undertaken analytical steps have led to determination of the fluids trapped in inclusions as brine and/or hydrocarbons (based on fluorescence abilities). Furthermore, they have resulted in the measurement of the homogenization temperatures of inclusions (values positive for, e.g., oil, negative for methane, pure or with admixtures), and determinations of the eutectic and ice-melting temperatures of the aqueous inclusions. Thermometric studies in the heating mode generally lead to determination of temperatures of mineral crystallization since it has been assumed that the homogenization temperature of the primary aqueous inclusions represents a minimum temperature of fluid trapping during mineral precipitation. Complementary analyses, as the Raman spectrum analysis and studies on the organic matter, lead to the interpretation of the results richer, clearer and meaningful for the hydrocarbon systems context, what has been proved on some examples.