陕西凤太矿集区深部铅锌矿产资源潜力及地球物理找矿方向

随着近20年的铅锌矿业开发,陕西凤太矿集区各大中型矿山将面临资源枯竭的困境。甘肃西成矿集区近年通过物探方法寻找到郭家沟隐伏铅锌矿体,表明物探方法对于深部找矿意义重大。从地质和地球物理角度综合研究,以凤太矿集区古岔河向斜为界,总结了南、北两侧的铅硐山—东塘子、银硐梁、八方山—二里河等大型铅锌矿床,手搬崖、峰崖、黑崖、银母寺等中型铅锌矿床以及多处小型矿床和矿点的铅锌矿体产出特征、形态特征及其赋存特征、控矿因素、物探识别标志。以银母寺铅锌矿床深部广域电磁法异常验证见到含铜矿化体,杨家湾铜矿点深部瞬变电磁法异常验证见到铜矿体,及二里河铅锌矿床深部短偏移距瞬变电磁法推断出寻找铅锌矿较好地段等3种地球物理方法技术的深部找矿实例,结合铅锌矿的空间分布规律,认为矿集区内铅硐山—水柏沟背斜西段、尖端山—八方山背斜东段、银母寺—大黑沟背斜西段等已知矿床的深部延伸部位,及含矿背斜旁侧更次一级具有找矿潜力的隐伏背斜成矿有利新区(如铅硐山—水柏沟背斜西段两侧区域、银母寺—大黑沟背斜西段两侧区域、尖端山—八方山背斜两侧区域)为铅锌矿地球物理找矿方向。同时,综合比较各种物探方法在凤太矿集区中的应用,建议选用长剖面或面积性的广域电磁法开展深部找矿。     

广域电磁法近区高分辨率的研究

广域电磁法与其他人工场源电磁法相比较,其显著特点是近区分辨率反常的低于远区分辨率。本文对此进行了研究,是由于其感应测深的幅值受几何测深幅值控制所致。本文进一步对广域电磁法近区高分辨率的探讨,研究了近区电场虚分量多项式的作用,发现电场虚分量第三项具有高分辨率因子的存在。据此,推导出广域电磁法近区高分辨率的解析表达式。本文的结果,可使广域电磁法无需广域探测,只需在近区探测,不仅施工方便、合理和信噪比高,而且能比远区和过渡区获得更大的探测深度,更精细的分层能力,以此更灵敏发现良导金属矿体。     

基于小波有限元法的连续梁移动荷载识别

将待识别车载简化为移动荷载投影到小波空间;车载所作用的连续梁模型以小波尺度函数为插值函数,以小波有限元法为建模方法,并通过单元转换矩阵实现了小波空间向物理空间的变换;采用部分加速度信号作为测得动响应数据,据此积分求出速度与位移响应并用于识别移动荷载。识别方法则借助了动态规划法与正则化法,避免了时程分析中的振荡现象。仿真算例验证了小波有限元用于连续梁模型移动荷载识别的可行性,且单元数较少;识别过程中所用一阶Tikhonov正则化法具有平滑去噪能力。     

基于矢量位和标量位的广域电磁法三维有限元数值模拟

广域电磁法（WFEM）提出了一种适用于全域公式计算的视电阻率,从根本上突破了“远区”理论的束缚,有效扩展了人工源电磁法的观测范围和探测深度,提高了野外数据的观测精度和效率。考虑到地下介质是三维的,从基于库仑规范的矢量位和标量位角度出发研究了广域电磁法三维有限元数值模拟方法。该方法克服了直接根据麦克斯韦方程组求取电磁场分布时出现的“伪解现象”和模型边界不连续的问题,避免了较为复杂的棱边有限元正演模拟。其中背景场使用准解析法求解,二次场使用有限元法求解,克服了局部激发场源的奇异性问题。在模型算例中,利用均匀介质解析解验证了方法的正确性和较高的计算精度;在此基础上,设计棱柱体模型,利用提出的正演算法对比分析了广域电磁法与可控源音频大地电磁法（CSAMT）对典型三维目标体的探测能力,结果表明在相同的条件下,广域电磁法能够更准确地反映地下目标体信息,且具有更高的分辨能力。     

Application of pseudo-random frequency domain electromagnetic method in mining areas with strong interferences

Due to the strong electromagnetic interferences and human interference, traditional electromagnetic methods cannot obtain high quality resistivity data of mineral deposits in Chinese mines. The wide field electromagnetic method (WFEM), in which the pseudo-random signal is taken as the transmitter source, can extract high quality resistivity data in areas with sever interference by only measuring the electric field component. We use the WFEM to extract the resistivity information of the Dongguashan mine in southeast China. Compared with the audio magnetotelluric (AMT) method, and the controlled source audio-frequency magnetotelluric (CSAMT) method, the WFEM can obtain data with higher quality and simpler operations. The inversion results indicate that the WFEM can accurately identify the location of the main ore-body, which can be used for deep mine exploration in areas with strong interference.     

Distributed wide field electromagnetic method based on high-order 2n sequence pseudo random signal

To make three-dimensional electromagnetic exploration achievable, the distributed wide field electro- magnetic method (WFEM) based on the high-order 2ⁿ sequence pseudo-random signal is proposed and realized. In this method, only one set of high-order pseudo-random waveforms, which contains all target frequencies, is needed. Based on high-order sequence pseudo-random signal construction algorithm, the waveform can be customized according to different exploration tasks. And the receivers are independent with each other and dynamically adjust the acquisition parameters according to different requirements. A field test in the deep iron ore of Qihe?Yucheng showed that the distributed WFEM based on high-order pseudo-random signal realizes the high-efficiency acquisition of massive electromagnetic data in quite a short time. Compared with traditional controlled-source electromagnetic methods, the distributed WFEM is much more efficient. Distributed WFEM can be applied to the large scale and high-resolution exploration for deep resources and minerals.