Garnet-Kyanite Bearing Pelitic and Associated Mafic Granulites along Jalsoor-Mercara Shear Zone: Evidence for Deep Burial and Later Uplift

Garnet-kyanite-sillimanite bearing pelitic and garnetiferous mafic granulites exposed at several places along the Jalsoor-Mercara and Bavali shear zones preserve evidences of deep burial of atleast 30 km. Estimation of P-T conditions of metamorphism of these granulites gives T of 725-800°C and P of 7 to 8.6 kb. Increase of pressure form core to rim in the garnet-kyanite assemblages and kyanite mantling garnet are the most significant aspects of these lithologies, suggesting long residence in the deep crust and possible thrust tectonics.

Moreover, fibrolitic sillimanite overgrowing kyanite in pelites and the developement of opx-calcic plag symplectites around garnet in the mafic rocks indicate decompression/uplift, subsequent to crustal thickening. This uplift could be part of a later event unrelated to the burial episode.

Significantly, syenite and anorthosite bodies of late Proterozoic age occur along these shear zones indicating that these lineaments were reactivated again in late Proterozoic times.