关键词: 花岗岩, 压力计, Q-Ab-Or-H2O相图

Abstract:

       This paper briefly and critically discusses several common geobarometers applied  to granitic systems, especially
the specific  rock  types, and  their  limitation and error analysis. The Al-in-hornblende barometer can be applied  to calc-alkaline granites and  is  suitable  for  low-pressure mineralized granitic pluton. The Fe-rich orthopyroxene-fayalite-quartz assemblage barometer can be used  to calculate  the crystallization pressure condition of  rapakivi granites, and  the crystallization pressure of coexisting alkali  feldspar, plagioclase and quartz can be obtained via projecting onto  the Q-Ab-Or-H2O phase diagram  for granites. The hydrostatic pressure of  fluid  inclusion  in granites can be acquired by  thermodynamic state equations or    raman spectroscopy. Some  indicative minerals  like magmatic epidote  sometimes can constrain  the  lower pressure  limit. Moreover, the pseudosection calculated by THERMOCALC   eventually can define  the pressure scope  for a specific coexisting mineral assemblage and specific pressure and temperature.

Key words:  granite, geobarometry, Q-Ab-Or-H2O phase diagram