  We study the production of primordial magnetic fields in inflationary models
in type IIB string theory where the role of the inflaton is played by a Kahler
modulus. We consider various possibilities to realise the Standard Model
degrees of freedom in this setting and explicitly determine the time dependence
of the inflaton coupling to the Maxwell term in the models. Using this we
determine the strength and scale dependence of the magnetic fields generated
during inflation. The usual "strong coupling problem" for primordial
magnetogesis manifests itself by cycle sizes approaching the string scale, this
appears in a certain class of fibre inflation models where the standard model
is realised by wrapping D7-branes on cycles in the geometric regime.
