深地震反射剖面揭示嫩江断裂带中段的深部几何形态与地壳形变

Deep structure geometry features of Nenjiang fault zone and crustal deformation revealed by deep seismic reflection profile

嫩江断裂带对探讨松辽盆地的演化、与大兴安岭的盆山耦合关系以及兴安地块与松嫩地块的归属问题具有重要研究意义。本文利用深地震反射剖面，揭示了嫩江断裂带中段的深部几何形态，表明它目前呈花状构造样式；它也并非松辽盆地内部的拆离断层，而是一条超壳断裂，控制了大兴安岭的物质东移和松辽盆地的中生代沉积；现今的嫩江断裂带同晚古生代兴安地块与松嫩地块拼合的嫩江构造拼贴带并没有继承性关系；莫霍面可能在后期的演化过程中扮演了滑脱层的作用，致使向西俯冲的地幔体向东位移。

Nenjiang fault zone, located in the Middle Northeast China, and the eastern margin of the Great Xing＇an Range, is the basin-controlling fault zone of the western margin of the depression of the Songliao Basin. Tectonically, it is the eastern part of the central Asian oceanic belt, and the boundary between the Xing＇an and Songnen blocks. The research of it will shed a light on the evolution of the Songliao Basin, the basin-range coupling relation between the Great Xing＇an Range and the Songliao Basin, and the nature of the Xing＇an and Songnen blocks. In this paper, by the new deep seismic reflection profile, we revealed the geometry features of the Nenjiang fault zone, which is a flower structure. The Nenjiang fault zone is not the detachment zone in the Inner Songliao Basin, but an ultra-crustal fault. It controls the east-moving of the crustal materials of the Great Xing＇an Range and the depression of the Songliao Basin in Mesozoic. The present Nenjiang fault zone is not the successor of the collision zone between Xing＇an and Songliao blocks in Late Paleozoic. Moho may act as a decollment surface to induce the east-slipping of the mantle subduction zone.