We establish various results on the large level limit of projective quantum representations of surface mapping class groups obtained by quantizing moduli spaces of flat SU(n)-bundle. Working with the metaplectic correction, we proved that these projective representations lift to asymptotic representations. We show that the operators in these representations are Fourier integral operators and determine explicitly their canonical relations and symbols. We deduce from these facts the Egorov property and the asymptotic unitarity, two results already proved by J.E. Andersen. Furthermore we show under a transversality assumption that the characters of these representations have an asymptotic expansion. The leading order term of this expansion agrees with the formula derived heuristically by E. Witten in "Quantum field theory and the Jones polynomial".

34 pages, minor corrections and references modified