Sample localities
We investigated four semi-pelitic to pelitic paragneiss samples (AGC 221, 415, 417, 419), from different outcrops along the Matsanjeni River. Samples AGC 221 (S26°49.236’ E31°23.660’), 417 (S26°49.429’ E31°23.618’), and 419 (S26°49.441’ E31°23.681’) are exposed at the border with the eastern Mahamba orthogneiss, whereas AGC 415 (S26°49.236’ E31°26.034’) occurs near a metasemipelitic tectonic lens in the centre. Except for the different amount of leucosome (AGC 417 and AGC 419 contain a higher amount of leucosome and represent the neosome, while AGC 221 and AGC 415 were identified as melanosome) and for the different sample locations (AGC 221, 417, 419 were collected 3-4 km west of AGC 415) all four rocks are of the same general rock type and from the same geological sequence.