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amphibolite-facies conditions. This is supported by garnet-gneiss sample 76114C, which shows the primary assemblage garnet-plagioclase-biotite
± ilmenite. Using the DOMINO program, we derived peak metamorphic conditions of 710°C at 0.80-
0.85 GPa. Rutile inclusions in plagioclase point to a higher pressure stage before this upper amphibolite-facies event.
Somewhat different P-T conditions are mirrored by garnet mica schist 76111A, which bears the primary assemblage garnetbiotite-muscovite-plagioclase-quartz
± rutile, ilmenite. Based on garnet zoning, we derived a P-T path starting at 485°C and
0.6 GPa and reaching peak metamorphic conditions at 575-600°C and 1.0-1.3 GPa. These data point to burial followed by
high-temperature metamorphism during exhumation, i.e. a Barrovian, clockwise P-T path in the Proterozoic basement.
The low-grade metamorphic overprint led to the formation of the assemblage actinolite-albite-chlorite-epidote in metabasites.
Metapelites reveal the syn-tectonic assemblage stilpnomelane-phengite-chlorite-calcite, for which PT conditions of 300-
350°C at 0.6-0.7 GPa were calculated using the thermobarometer of Currie & van Staal (1999). The final metamorphic overprint
occurred under lower greenschist-facies conditions as indicated by the growth of post-tectonic biotite. The timing of
the low-grade metamorphic event is badly constrained. While Zhang et al. (1996) report a Paleozoic Rb-Sr whole rock isochronic
age of ≈422 Ma, we rather suppose a Triassic age as the metamorphic conditions are similar to those in the Mulanshan
(Zhou et al. 1993) and Zhangbaling (Ratschbacher et al. in prep.) areas in the Dabie-Sulu belt. Further geochronologic and
petrologic investigations are in progress.
Figure 1. Metamorphic evolution of the Douling complex
REFERENCES
Currie, K.L. & van Staal, C.R. 1999: The assemblage stilpnomelane–chlorite–phengitic mica: a geothermobarometer for
blueschist and associated greenschist terranes. J. metamorphic Geol. 17, 613-620
Ratschbacher, L., Hacker, B.R., Calvert, A., Webb, L.E., Grimmer, J.C., McWilliams, M., Ireland, T., Dong, S. & Hu, J. 2003:
Tectonics of the Qinling Belt (Central China): Tectonostratigraphy, geochronology, and deformation history.
Tectonophysics 366, 1-53.
Zhang, S., Wei, C., Zhao, Z. & Shen, J. 1996: Formation and metamorphic evolution of the Douling Complex from the East
Qinling Mountains. Science in China, series D 39 supplement, 80-86.
Zhou, G., Liu, Y.J., Eide, E.A., Liou, J.G. & Ernst, W.G. 1993: High-pressure / low-temperature metamorphism in northern
Hubei Province, central China. J. metamorphic Geol. 11, 561-574.
Symposium 2: Mineralogy-Petrology-Geochemistry