Pressure-temperature-time path of Paleoproterozoic khondalites from Claudio shear zone (southern Sao Francisco craton, Brazil): Links with khondalite belt of the North China craton

摘要

The dextral Claudio shear zone (CSZ) corresponds to a NE-SW geological suture that separates the Archean Campo Belo/Bonfim and Divin6polis metamorphic complexes in southern Sao Francisco craton (SFC). The CSZ comprises sillimanite-cordierite-garnet-biotite gneisses (also known as khondalitic paragneisses) associated with graphite-rich metasedimentary rocks. The temperature and pressure conditions of khondalite metamorphic peak are 850-950 degrees C and 10-11 kbar, recorded by the reaction of biotite breakdown Bt + Sil + Qz +/- Pl -> Grt + Kfs + Melt. The post-peak stage temperature and pressure conditions are 750-830 degrees C and 4.5-5.3 kbar, recognized by the melt consumption reaction Grt + Sil + Melt -> Crd + Bt + Fe-oxide. Monazite U-Th-Pb geochronology reveals an average age of 2011 +/- 20 Ma for the metamorphic peak and an average age of 1910 +/- 20 Ma for the post-peak stage. The dataset obtained in this work is very similar in terms of P and T evolution to the Wulashan Complex from North China Craton (NCC). The khondalitic rocks of both CSZ and Wulashan Complex were subjected to a clockwise P-T-t path granulite facies metamorphism accompanied by partial melting events when SFC and NCC were probably connected during Paleoproterozoic.