Fluidní inkluze v oválných zirkonech těžké frakce kvarcitu z Květničky u Tišnova (svratecká klenba moravika)

Roč.13,(2006)

Zdeněk Dolníček Karel Malý

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Abstrakt
Inclusions within oval zircons selected from heavy mineral concentrate of Devonian quartz metaconglomerate from Květnička Hill near Tišnov (Svratka Dome) have been studied by means of inclusion petrography and cryometry. Two types of inclusions were distinguished – melt and fluid. Melt inclusions contain silicate glass±vapour±crystalline solids±fluid. Highly variable degree of recrystallization of glass phase has been observed within melt inclusions. Two subtypes of fluid inclusions were found: high-density CO2-H2O-NaCl and low-density CO2. Taken together, oval zircons from the studied rock sample seem to be genetically heterogeneous assemblage. Zircons containing strongly recrystallized melt inclusions associated with high-density fluid inclusions may originate in pegmatites or plutonic rocks because the trapping pressures would range in the units of kbars at geologically relevant model temperatures. Those containing essentially glassy melt inclusions in assemblage with low-density fluid inclusion are believed to originate in volcanic environment, with respect to low internal pressures ~200 bars at ~1000 °C.

Klíčová slova:
Moravicum; Old Red; heavy minerals; zircon; fluid inclusions; genesis
Reference

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