Fluid inclusions in granulite-facies metapelites of the Hercynian ancient lower crust of the Serre,Calabria, Southern Italy |
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Authors: | Petra Herms Volker Schenk |
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Institution: | (1) Mineralogisch-petrographisches Institut, Universität Kiel, Olshausenstrasse 40, W-2300 Kiel, Federal Republic of Germany |
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Abstract: | Investigations of fluid inclusions in granulitefacies metapelites of southern Calabria enable characterization of the fluid composition of these lower crustal rocks, and constrain the petrologically deduced retrograde P-T path characterized by isothermal uplift prior to isobaric cooling in middle crustal levels. Fluid inclusions in cordierite, garnet and sillimanite have a CO2-rich composition. Inclusions in cordierite rarely contain minor amounts of N2 and H2O, and in garnets some CO2–CH4–N2 inclusions have been analyzed by Raman microprobe. Quartz reveals the most complex fluid melusion compositions (1) CO2-rich, (2) CO2–CH4–N2, (3) CH4–N2, (4) H2O–MgCl2–CaCl2–NaCl, (5) H2O–NaCl and (6) H2O–CO2. The earliest fluid inclusions after peak metamorphism are rich in CO2 with minor amounts of N2 and H2O. An early CO2–(H2O–N2) fluid composition has been confirmed by detection of CO2, H2O and N2 in the channels of the cordierite structure. Most of the early CO2-rich fluid inclusions were modified during the uplift from the lower to the middle crustal level, resulting in a density decrease with CO2 still dominant. The subsequent isobaric cooling led to further modifications of the fluid inclusions. High-density inclusions around implosion textures or scattered amongst lower-density ones must have formed during this cooling episode. Aqueous inclusions in quartz are mostly formed late and are consistent with trapping during retrograde rehydration.This project has been supported by the DFG as contribution to the special program Continental Lower Crust |
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