澜沧老厂多金属矿床成矿模型AMT响应分析

AMT Response Analysis of Metallogenic Model of Polymetallic Deposits in Laochang,Lancang

针对澜沧老厂矿区的复杂成矿背景,根据已知地质资料建立地球物理模型,开展模型AMT二维正演及AMT二维反演参数影响研究。通过分析二维正演响应,确定了纯地形条件下,高峰地形与低阻高相位的对应关系;地球物理模型条件下能粗略的将地下电阻率分布趋势反应出来。通过对比研究二维反演参数,确定了老厂矿区最佳反演参数选择方案:极化模式选择TE+TM组合模式比单独使用TE和TM模式能更好的反应围岩的分界面,异常体的形态、规模和埋深;选择靠近异常体的围岩电阻率500Ω·m作为反演的初始背景电阻率效果最好;拉格朗日乘子τ值为3时,反演的结果和实际最相符。确定澜沧老厂矿区的AMT异常特征的最佳反演参数,将为进一步开展深部地球物理勘查工作提供参考依据。

According to the complex metallogenic background of the Laochang mining area in Lancang,the geophysical model is established based on the known geological data.The AMT two-dimensional forward modeling of the model and the influence of AMT two-dimensional inversion parameters are carried out.By analyzing the two-dimensional forward response,the corresponding relationship between the peak terrain and the low resistance and high phase under the condition of pure terrain is determined.Under the condition of geophysical model,the distribution trend of underground resistance can be roughly reflected.Through the comparative study of two-dimensional inversion parameters,the selection scheme of the best inversion parameters in Laochang mining area is determined.The polarization mode selection TE(TM)combined mode is better than that of the TE and TM mode alone,and the morphology,scale and depth of the abnormal body can be improved.The surrounding rock resistance 500Ω·m close to the abnormal body is selected as the initial background resistance of inversion,and the effect is the best.When the Lagrangian multiplier value is 3,the inversion results are in good agreement with the actual results.Determining the best inversion parameters for the characteristics of AMT anomalies in Laochang mining area of Lancang will provide a basis for further deep geophysical exploration.