磁法广泛应用于探测金伯利岩,金伯利岩常常含有作为副矿物的磁铁矿。未风化的金伯利岩通常产生明显的磁异常。但风化的金伯利岩则不同,根据风化程度,风化的金伯利岩大大失去了磁性,实际上变为无磁性。风化似乎阻碍了用磁性探测,但这样的金伯利岩当风化程度和范围相当大时,在磁性围岩成为磁法探测的极好目标。风化的金伯利岩和围岩之间的磁化反差变成负的。这样的风化金伯利岩在磁场图上表现的图像与正的磁化反差的正常图像是相反的。在印度南部安得拉邦沃杰勒格鲁尔地区,一个已知的高度风化的金伯利岩上进行了试验性地面磁测,得出了明显的磁响应。特征是在岩筒的正上方为平稳而宽广的梯度,在其两侧,在岩筒的北边和南边分别为“高”和“低”的闭合圈。将岩筒近似为垂直的有多边形截面的圆柱并赋予负的磁化进行了模拟。计算和观测的磁等值图表现出良好的相关关系。此项工作表明,把负的磁化赋予风化金伯利岩的方法对于探测金伯利岩是快速有效的。 Magnetic methods are widely used to detect kimberlites, which often contain magnetites as accessory minerals. Unweathered kimberlite usually produces significant magnetic anomalies. However, the weathered kimberlites are different and, depending on the degree of weathering, weathered kimberlites greatly lose their magnetism and in fact become non-magnetic. Weathering seems to be an impediment to magnetic detection, but such kimberlites are an excellent target for magnetic detection when magnetic weathering is high when the degree and extent of weathering is considerable. The magnetization contrast between the weathered kimberlite and the surrounding rock becomes negative. Such weathered kimberlite images on magnetic field maps are the opposite of normal images with positive magnetization contrasts. Experimental ground magnetometry was conducted on a well-known, highly weathering kimberlite in the Vogelegerur region of Andhra Pradesh in southern India, yielding a significant magnetic response. It is characterized by a smooth and broad gradient directly above the rock cylinder, on both sides of which are “high” and “low” closed rings on the north and south sides of the rock cylinder, respectively. The rock can is approximated as a vertical cylinder with polygonal cross-section and a negative magnetization is simulated. The calculated and observed magnetic equivalent plots show a good correlation. This work shows that the method of imparting negative magnetization to weathered kimberlite is fast and effective for kimberlite detection.