Fine structure of the lithosphere beneath the Well SK-2 and its adjacent: Revealed by deep seismic reflection profile

In order to reveal the fine structure of the lithosphere adjacent to Well SK-2, a deep seismic reflection profile crossing Well SK-2 was laid out in the Songliao Basin (SB), with the trend north to south. Data acquisition was featured in the shooting technique of multi-scale explosive source and data reception by large offset with smaller trace distance in key area. Besides, processing flow of high fidelity and amplitude-preservation was undertaken to get the pre-stack migrated seismic reflection profile with high resolution and high signal-to-noise ratio. As the result, the profile shows strong reflections from settled layers alternate with and weak reflections of igneous rock beneath T-4 reflector, and two residuals of upper Paleozoic stratums are distinguished out, one is beneath Well SK-2 (TWT, 3. 5 similar to 4 s), the other is beneath the Renmin-Yong'an Terrace (CDP, 3500 similar to 4500, TWT, 3. 5 similar to 4 s). Some paralleled seismic patterns dipping north can be observed in the middle and lower crust, as well as some strong but short lenticular reflectors are observed beneath Zhonghe Fault Depression, and the overall contour of these lenticular reflectors is like a mushroom cloud, we interpret this phenomenon as the hot material from downward in the lithosphere extension environment. The Moho in the north part shows strong near-horizontal continuous reflection, while the Moho in the Xujiaweizi Fault Depression in the south shows weak reflection. Three types of upper mantle reflections are distinguished on the deep seismic profile, including inclined mantle reflections, near-horizontal mantle reflections and super-deep reflections in the mantle. It is inferred that they are the early subduction relics, bottom of early thickened crust and the present lithosphere-asthenosphere boundary (LAB). Based on the latest results of deep seismic profile detecting crossing Well SK-2, this paper study structure features preserved in the lithosphere of Songnen Massif with tectonic superposition of Palo-Asia Ocean regime, Mongol-Okhotsk regime and Palo-Pacific regime, thus providing a new perspective for the discussion of the formation cause, tectonic background and dynamic factors of Songliao Basin.