广域电磁法在胶西北金矿集中区深部探测中的应用研究

The application of wide field electromagnetic method to deep exploration in Jiaoxibei(northwest Shandong)gold concentration area

胶西北矿集区内的焦家与三山岛断裂带是著名的金矿成矿带,近年深部找矿成果显著,目前钻孔已揭露至4006 m,以往的物探方法深部探测效果不佳,亟需有效的深部探测地球物理技术。将广域电磁法应用于焦家—三山岛断裂带已知剖面,断面揭示两大断裂带形成的低阻带特征明显,真实反映了地下电性分布,视电阻率高阻、中低阻的分布反映了玲珑花岗岩体及变质岩体的展布;同时断面清晰展示了两大断裂在深度4 km附近交汇,剖面为研究焦家—三山岛断裂之间的断裂特征提供了依据。应用试验表明,广域电磁法探测深度大,抗干扰能力强,在胶西北岩浆岩分布区探测低阻断裂带具有较好的效果,是该区5000 m深度范围内很好的非震地球物理方法。

Jiaojia and Sanshandao fault zones are famous gold ore-forming zones in Jiaoxibei region.In recent years,the deep exploration results are remarkable.At present,the borehole has reached the depth of 4006 m.The previous geophysical exploration methods have poor deep exploration effect,so effective deep exploration geophysical technology is urgently needed.The wide field electromagnetic method is applied to the known section of Jiaojia and Sanshandao fault zones.The section reveals that the characteristics of the low resistance zone formed by the two major fault zones are obvious,which truly reflects the distribution of underground electricity;the distribution of apparent resistivity high resistance and low resistance reflects the distribution of Linglong granite body and metamorphic rock mass;meanwhile,the section clearly shows the intersection of the two major faults at a depth of 4 km.The section provides the basis for the fault characteristics between Sanshandao and Jiaojia faults.The application test shows that the wide area electromagnetic method has a large detection depth and strong anti-interference capability,and hence it is a good non-seismic geophysical method for detecting the low resistance fault zone in the magmatic rock distribution area of Jiaoxibei region.