Spatial and temporal distributions of the late Mesozoic volcanic successions and their controlling effects on the Changling fault depression of the Songliao Basin, northeast China.

Volcanic successions, including their spatial, temporal, tectonic, and geochemical attributes, were identified based on well data, 2D and 3D seismic data, U-Pb isotopic ages, and major and trace element data from the Changling fault depression of the Songliao Basin in northeastern China. Three eruption cycles developed in the Changling fault depression: K1h (Huoshiling Formation) (124-118 Ma), K1yc1 (first member of the Yingcheng Formation) (115-106 Ma), and K1yc3 (third member of the Yingcheng Formation) (106-102 Ma). These three eruption cycles comprised seven eruption stages. The volcanic successions in every eruption cycle were bimodal and evolved from basic to acidic. The magma of the basic and intermediate rocks in these cycles was derived from partial melting of the asthenosphere. In K1yc1 and K1yc3, partial melting of the newly formed basic rocks in the lower crust formed the high-SiO2 acidic magma. In addition, fractional crystallization of basic magma formed the small-scale intermediate-acidic magma. In K1h, the most likely origin of the acidic magma was fractional crystallization of basic magma. During the early stage of the fault depression, the volcanic rocks of K1h were controlled primarily by the boundary fault activity. In K1yc1 and K1yc3, basic-intermediate rocks were distributed widely along syngenetic faults, and acidic rocks were concentrated in areas where the syngenetic faults had their largest amplitudes. Multiple cycles and stages of the volcanic successions were controlled by magmatic evolution, and the spatial distribution was controlled by basin tectonics. [ABSTRACT FROM AUTHOR]