EVOLUTION OF THE MESOZOIC-CENOZOIC MAGMATISM OF THE SONG DA RIFT AND ITS CONTOURING STRUCTURES

The paper deals with studying the peculiarities of the manifestation, composition, and evolution of the Mesozoic-Cenozoic magmatism of the S ong Da zone in the south of the Indocinian mobile belt. This zone is a complex rifting structure. By composition and lateral-zonation charac ter, the Song Da Permian-Triassic ultramafic-mafic magmatism is close to the early-stage magmatism in continental rifts. The next stages of the evolution of this region were involved with the formation of subal kaline basalt-trachyrhyolite associations in Jurassic-Cretaceous and C retaceous superimposed trenches and Paleogene ultrapotassic alkaline c omplexes of ultramafic-mafic and alkali-salic rocks, related to mantle -crust magmatic processes at the stages of the late activation of the Song Da zone and its contouring structures. The formation proceeded un der the conditions of the sufficiently thick and mantle crust. Along w ith the geodynamic peculiarities, the petrologic aspects of the format ion of the regional Mesozoic and Cenozoic magmatic associations are co nsidered.