Lateral change of sources for the Cretaceous-Paleogene magmatism of the Tian Shan

The Southern and Northern-Central Tian Shan are sharply different in the character of the evolution of Cretaceous-Paleogene magmatism. The Southern Tian Shan comprises a picrobasalt-trachybasalt-basanite-phonotephrite-phonolite volcanic series, which was formed over a considerable time interval from 122 to 46 Ma, whereas the Northern-Central Tian Shan hosts a foidite-basanite-trachybasalt-basaltbasaltic andesite volcanic association, which erupted within a rather narrow time interval between 61 and 53 Ma. The entire volcanic series of the former region was derived from a shallow garnet-free mantle source. The volcanic assemblage of the latter region included basanites and foidites derived from a deep garnet-bearing mantle source, whereas trachybasalt, basalt, and basaltic andesite melts were generated in the lower crust. It is supposed that the change of sources and different evolutionary trends of Cretaceous-Paleogene magmatism in the Southern and Northern-Central Tian Shan were caused by the activation of the heterogeneous lithosphere beneath the converging shores of the Late Paleozoic Turkestan paleoocean.