Petrologische Anwendung der Inversionstemperatur-Bestimmung von Quarzen

Abstract

The determination of the high-low quartz inversion temperature applied to some petrologic problems.

The two modifications of quartz, high and low quartz, are in thermodynamic equilibrium at about 573°C (p=1 atm.). The exact temperature of this displacive inversion of secondary coordination depends on the chemistry of trace elements and on crystal-structural defects. Since the amount of substitutional and interstitial trace elements and the character of structural defects of natural quartzes depend on their conditions of formation, the determination of inversion temperatures can be used as a petrologic tool.

Generally, the inversion temperatures of authigenic sedimentary quartzes are lower than those of igneous rocks. The method suitable for the determination of the inversion temperatures of quartz crystals is the precision differential thermal analysis under standard conditions. We tried to apply this d.t.a.-method to the following petrologic problems: 1) The distinction of authigenic and hydrothermally formed quartzes in limestones. 2) The conditions of formation of quartz crystals found in brown coals. 3) The influence of contact metamorphism on surrounding sandstones. 4) Different generations of vein quartzes from the northern Black Forest. 5) Differences in inversion temperatures of microcrystalline quartzes.