Repeated tabular injection of high-level alkaline granites in the eastern Bushveld, South Africa

Field observations, petrography and magnetic susceptibility fabrics are use d to characterize the structure and evolution of the Nebo granite, forming part of the Bushveld Complex, in South Africa. The Nebo granite is the domi nant component of the Lebowa granite suite, the largest known anorogenic gr anitoid complex. It is a composite tabular intrusion, comprising alkali fel dspar granites and syenogranites. There are seven main petrographic units, defined by differences in modal content, crystallization sequence, magmatic water content. magnetic susceptibility and magnetic fabric. Each unit was emplaced independently and fed by vertical dykes. Anisotropy of magnetic su sceptibility used to map magmatic Fabrics within the granite shows that the y are dominantly controlled by alignment of early-crystallizing magnetite a nd are similar in outcrop and pluton scale. Magnetic foliations and lineati ons are horizontal, reflecting vertical host-rock compression and horizonta l magma flow during emplacement. Space was created by magma pressure which resulted in roof uplift and floor depression: displacements were accommodat ed by normal and reverse faulting and flexural-slip along bedding planes in host-ruck metasediments.