Structural analysis and implicit 3D modelling of high-grade host rocks to the Venetia kimberlite diatremes, Central Zone, Limpopo Belt, South Africa

Abstract The Beit Bridge Complex of the Central Zone (CZ) of the Limpopo Belt hosts the 519 ± 6 Ma Venetia kimberlite diatremes. Deformed shelf- or platform-type supracrustal sequences include the Mount Dowe, Malala Drift and Gumbu Groups, comprising quartzofeldspathic units, biotite-bearing gneiss, quartzite, metapelite, metacalcsilicate and ortho- and para-amphibolite. Previous studies define tectonometamorphic events at 3.3–3.1 Ga, 2.7–2.5 Ga and 2.04 Ga. Detailed structural mapping over 10 years highlights four deformation events at Venetia. Rules-based implicit 3D modelling in Leapfrog Geo™ provides an unprecedented insight into CZ ductile deformation and sheath folding. D 1 juxtaposed gneisses against metasediments. D 2 produced a pervasive axial planar foliation (S 2 ) to isoclinal F 2 folds. Sheared lithological contacts and S 2 were refolded into regional, open, predominantly southward-verging, E–W trending F 3 folds. Intrusion of a hornblendite protolith occurred at high angles to incipient S 2 . Constrictional-prolate D 4 shows moderately NE-plunging azimuths defined by elongated hornblendite lenses, andalusite crystals in metapelite, crenulations in fuchsitic quartzite and sheath folding. D 4 overlaps with a: 1) 2.03–2.01 Ga regional M 3 metamorphic overprint; b) transpressional deformation at 2.2–1.9 Ga and c) 2.03 Ga transpressional, dextral shearing and thrusting around the CZ and d) formation of the Avoca, Bellavue and Baklykraal sheath folds and parallel lineations.