The Paleozoic effusives related to the extension and formation of the S«ng §µ structure were produced mainly in the alkalic and subalkalic fields. The mafic rocks play the main role with a subsidiary amount of rhyolite, trachyte and transitional types. The mafic effusives are distinguished by high- and low-Ti character. High-Ti (TiO₂ > 1%) type is richer in highly incompatible elements as well as light rare earth elements and is also higher in FeO and Zr/Y, Nb/Y ratios than the accompanying low-Ti type (TiO₂ < 1%) that is interpreted as the result of melting from fertile asthenospheric material with involvement of mafic veins such as clinopyroxenite and amphibolite, etc.. On the other the side, the low-Ti type may be the product of melting of the fertile and enriched asthenospheric material mixed with refractory and depleted lithospheric mantle when the asthenosphere rose following the lithospheric extension and the erosion of the base of the lithospheric mantle. We suggest that such the mantle-lithosphere interaction dynamics should eventually lead to progressive melting to form the volcanic rocks without the necessity of the presence of a mantle plume.