塔里木盆地中央高磁异常带成因: 来自地震反射剖面的新证据

根据钻井资料及构造分析, 对塔东地区二维地震资料和塔中地区三维地震资料进行系统解释, 在该地区震旦系之下识别出断坳二元结构的陆内裂谷, 该裂谷由4个断陷沿纬向形成一个裂谷带, 其平面分布形态与高磁异常范围极为吻合。结合构造与地层发育特征认为: 裂谷期断陷中发育典型陆内双峰式火山岩, 是航磁异常带上磁力高的直接表现; 高磁异常带轴线与断陷的边界断层位置吻合, 异常源具有垂直向下的通道, 与基底断裂及深部岩浆上涌有关。正演计算验证了南华纪裂谷带模型的磁异常结果。高磁异常带东段为裂谷成因, 向中部、西部裂谷作用逐渐减弱直至消失, 至巴楚段高磁异常主要由二叠纪玄武岩造成, 异常带西段则属于塔南古陆块。

Genesis of High Aeromagnetic Anomaly Zone in Central Tarim Basin: New Evidence from Seismic Profiles

Based on a comprehensive analysis of borehole and structural features, the authors interpreted 2D seismic data in East Tarim and 3D seismic data in Central Tarim area. Under the layer of Sinian, a sag-depression dual structure intracontinental rift was identified. The rift zone consists of 4 east-west sags, and its plane distribution is consistent with the hige aeromagnetic anomaly zone. The structural and stratigraphic analysis shows that there are bimodal volcanic rock in a typical intracontinental syn-rift sags, and it is the direct reflection of the high aeromagnetic anomaly; the boundary faults of 4 sags are consistent with axial trace of high aeromagnetic anomaly zone, from which it can be inferred that the anomaly source has a vertical downward channel, and it relates to basement faults and upwelling of hypomagma. Further research involving calculation of the magnetic anomaly confirmed the Nanhua rift zone model. The east segment of high aeromagnetic anomaly zone is formed by rift zone, while it weakened until disappears to the middle and west; high aeromagnetic anomaly in Bachu segment is mainly caused by Permian basalt and the west segment belongs to North Tarim landmass.