In this preprint we deal with convergence rates for a Tikhonov-like regularization approach for linear and non-linear ill-posed problems in Banach spaces. Therefore we deal with so-called distance functions which quantify the violation of a (non-linear) reference source condition. Under validity of this
reference source condition we derive convergence rates which are optimal in a Hilbert space situation. In the linear case we additionally present error bounds and convergence rates which base on the decay rate of the distance functions when the reference source condition is violated.