In the Guerrero-Morelos platform (Guerrero State, Mexico) the adakitic rocks of Early Tertiary age contain abundant hornblende-rich tonalite xenoliths. Zircon crystals have been concentrated from both adakites and xenoliths, and dated using in-situ U-Pb ion microprobe analyses. These analyses indicate the presence of inherited Grenvillian and early Triassic/late Permian crust ages, as well as a Paleocene age related with the adakite rock intrusion. This range of inherited ages is reported for the first time in the Guerrero-Morelos platform, suggesting that a continous Grenvillian crust exists be