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Granitic plutons constitute a major portion of the Phanerozoic continental crust of Mexico, with the great majority (ca. 90%) associated to the Laramide Late-Cretaceous–Eocene orogeny and the eastward subduction of the Pacific Ocean plates, as well as to magmatic arcs essentially built since the early Mesozoic at the western margin of North America. Exposed mainly as a wide (up to 300 km) and over 3000 km long batholithic belt at the Mexican Pacific margin from Baja California to Chiapas, granitoids conform large intrusive complexes and hundreds of smaller plutons, the age of which vary from ca. 1400 Ma (Mesoproterozoic) to ca. 10 Ma (late Miocene). In many cases uplift and erosion have revealed the deep roots of the batholiths, whereas in other places many intrusions were emplaced in upper crustal environments, as suggested by the extremely variable cooling rates of > 200 °C/Ma (very shallow) to 1–10 °C/Ma (very deep). Lithologies and isotopic data indicate unambiguously the central participation of the local lower crust in the genesis of the batholiths and plutons, imprinting on them marked petrologic, geochemical and structural zoning across the Paleozoic paleomargins and through the present NW-trending Mexican continental edge according to the lithospheric component involved: Laurentia in the northern and northwestern regions of Mexico, accreted Mesozoic terranes in western Mexico, and Oaxaquia (Gondwana) in eastern and southern Mexico. Major problems related to the evolution of the Mexican main granitoids are outlined in time slices for the Proterozoic, Paleozoic, Permo-Triassic, Jurassic, Early Cretaceous, Late Cretaceous–Paleogene and Neogene, which represent in Mexico major epochs of crustal growth and continental recycling, mainly associated not only with Pacific–North America convergence, but also with extensional and transpressional events that altogether marked, not only the lithological and structural evolution of most of the country, but also its extraordinary mineral wealth. Finally, some preliminary comparisons (differences and similarities) are made between the Mexican batholiths and other plutonic complexes in Central Asia (Lhasa Terrane) and Japan.

We present LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) U–Pb detrital and igneous zircon data of poly-deformed metamorphic and igneous rocks of the Ayu area, southern Mexico. These rocks were previously inferred to be part of the Late Paleozoic Acatlan Complex, but new age data indicate that they formed in the Mesozoic and should be placed in the newly designated Ayu Complex. The Ayu Complex comprises polydeformed metasedimentary rocks (Chazumba Lithodeme) of a turbidite-like protolith that are intercalated with boudinaged ortho-amphibolites with transitional arc- to MORB tholeiitic geochemistry. In the south, the metasedimentary sequence is affected by a ca. 171 Ma partial melting which formed the Magdalena Migmatite. Migmatization was accompanied by 171–168 Ma intrusions of granodioritic, dioritic, and granitic dikes and sheets as well as pegmatite bodies, which are characterized by inherited zircon populations of ca. 260–290, 320–360, 420–480, 880–990, and 1080–1250 Ma that are also found in the Chazumba Lithodeme. U–Pb (detrital zircon) dating of seven metasedimentary samples from the migmatized and unmigmatized Chazumba Lithodeme yielded youngest detrital zircons and clusters of 192, 198, 214, 250, 266, and 291 Ma, and are interpreted to reflect the Late Triassic–Middle Jurassic deposition of turbiditic rocks. The transitional arc–tholeiitic geochemistry of the Chazumba amphibolites is consistent with turbidite sedimentation in a back-arc environment along a rifted passive margin, close to a contemporaneous magmatic arc. Inferred flattening of the subduction zone led to subduction erosion during the Early–Middle Jurassic and underthrusting of the Chazumba Lithodeme to depths equivalent to amphibolite facies metamorphism. Steepening of the subducting slab and diachronous rifting within the Gulf of Mexico contributed to extensional tectonics recorded on the Mexican mainland and facilitated the tectonic exhumation of the Chazumba Lithodeme by normal faulting along the reactivated Providencia shear zone during the Middle–Late Jurassic. More generally, the documentation of arc-back arc assemblages in the Ayu Complex requires deposition adjacent to a subducting ocean, and thus supports a Pangea-A reconstruction that was synchronous with the breakup of Pangea.