龙门山中北段重磁场特征与深部构造的关系

利用平均重力场与深部地壳测深资料估算了龙门山及邻区莫霍面的深度变化,表明龙门山地区正处于莫霍面由东南向西北的陡降带上。均衡重力异常计算结果显示该区为正异常。对航磁异常的向上延拓反映出茂汶杂岩体是“无根”的。此外还应用角度平均径向能谱法反演了该区深部磁性基岩的顶面与底面深度。结果表明,龙门山地区上地壳是由若干块体拼合而成的,川西拗陷带内的磁性界面呈现出向龙门山地腹下插的格局。

THE RELATION OF GRAVITY AND AEROMAGNETIC FIELD AND DEEP STRUCTURE IN MIDDLE-NORTHERN LONGMENSHAN MOUNTAINS

Based on the correlation analysis of average gravity field and deep seismic sounding data,the depth of Moho discontinuity was estimated in Longmenshan Mountain area. The result shows thatMoho discontinuity is deeper in northwest than in southeast and Longmenshan Mountains are just situ-ated in the steep dipping belt. The isostasy anomaly was calculated and positive anomaly was found inthe area. Upward continuating of aeromagnetic anomaly indicate that Maowen melange has no "root".The depth of the top and bottom of deep magnetic basement were calculated with the technique of aver-age angular raadial energy spectrum. The latter is equivalent to Curie depth. It is considered that uppercrust is pieced together by several smaller blocks and the blocks in west depressed area of Sichuan Basinshow the subduction tendency to Longmenshan Mountains.