Age, lithology and structural evolution of the c. 3.53 Ga Theespruit Formation in the Tjakastad area, southwestern Barberton Greenstone Belt, South Africa, with implications for Archaean tectonics

Abstract A field and petrographic re-assessment of rocks from the Theespruit Formation near Tjakastad, southwestern Barberton Greenstone Belt, is combined with new zircon U–Pb ages and whole-rock Sm–Nd isotopic results to reveal several important inconsistencies with a previous thrust-accretion model for this area. It was found that faults previously interpreted as ‘thrusts’ are extensional, ‘thrust slices of basement orthogneiss’ are little deformed quartz-feldspar porphyries or sheared felsic volcaniclastic sedimentary rocks, and ‘sedimentary diamictites’ are felsic agglomerates. These observations, combined with consistent facing directions of bedding, the recognition of distinct stratig…