准噶尔盆地南缘玛纳斯背斜的构造分析与构造建模

Structural Analysis and Structural Modeling of Manasi Anticline in the Southern Margin of the Junggar Basin

玛纳斯背斜位于准噶尔盆地南缘山前第二排构造带,是三排构造带中变形最强烈的,地表出露了典型的断层相关褶皱现象。本文从过玛纳斯背斜地震剖面的构造分析入手,通过运用断层相关褶皱的构造几何分析方法,以地表、钻井数据、相邻地震剖面的对比为约束,建立与实际剖面相吻合的构造几何模型,并通过正演平衡地质剖面制作,再现玛纳斯背斜几何变形的运动学过程。分析表明玛纳斯背斜为三个构造三角楔的叠加变形,构造三角楔底、顶逆冲断层均派生次级反向逆冲断层,与对应的主断层形成突发构造变形样式。从垂向上看,玛纳斯背斜由下至上可划分为三套构造形变层:下部构造形变层—来自于深部的滑脱面(J2x以下)形成的低幅度断层转折褶皱;中部构造形变层—由胜金口组(K1sh)底部滑脱面控制的反向逆冲断层与底部逆冲断层形成的多级构造三角楔的叠加构造;上部构造形变层—由安集海河组(E2-3a)滑脱面控制的浅部大规模逆冲推覆构造。

The Manasi Anticline located in the second row of tectonic belt in piedmont of the southern Junggar Basin,has the most intensest deformation of three rows of tectonic belts,with typical fault-related folding phenomenon exposed on the surface.Starting with the geometric analysis of the 2-D seismic profile through the Manasi Anticline constrained by the comparison of the surface and drilling data,along with the adjacent seismic profiles,establishing a reasonable structural geometric model of the Manasi Anticline.Then,through the forward balance geological profile production,reconstructing the kinematic process of the Manasi Anticline geometric deformation.The analysis shows the Manasi Anticline is a superposed deformation of three triangular wedges and derived secondary reverse thrust fault on their bottoms and tops thrust faults,forming a pop-up structural—deformation style corresponding to the main fault.From the vertical perspective, the Manasi Anticline from the down top can be divided into three tectonic deformation layers. The lower tectonic deformation layer:detachment(J2 x) from the deep formed the low-amplitude fault bend folds.The middle tectonic deformation layer,a superposed structure of the multilevel tectonic triangular wedge formed by the reverse and bottom thrust fault and controlled by the Shengjinkou formation(K1 sh)bottom detachment.The upper tectonic deformation layer, a shallow large-scale thrust-nappe structures controlled by the Anjihaihe formation(E2-3 a)detachment.