摘要
化探异常下限合理确定是地球化学勘查的关键环节,直接影响到矿产勘查工作部署和找矿成效。文章选取青海省鄂拉山成矿带北延小河坝地区,运用传统计算法、累积频率法、C-A分形法、地质子区法以及趋势面分析法等,对该地区5幅1:5万水系沉积物化探数据中主要成矿元素进行了异常提取效果的对比研究。结果显示,传统计算法异常由于受k值固定取值的影响,存在元素异常下限偏高的情况;累频法异常只突出了数据的高值异常区,对于低值异常区的识别效果一般;C-A分形法效果整体接近于计算法,其下限值也较为接近,但是两者在不同元素异常下限值的数值差浮动较大,也就导致不同元素的异常图效果差异性较大;趋势面分析法可以较好的识别低值异常,保留强异常的同时弱化部分高值区的影响,但是趋势面法异常规模存在偏小情况;地质子区法更适合于每个元素,能较好的识别低值异常,在保留强异常的同时弱化部分高值区的影响,并且整体与已知矿床点的对应度最佳。利用地质子区法进行化探数据处理,可以有效解决小河坝地区由于地质体不同导致的背景区存在差异这一情况。异常中的高值区一般都是由一些矿致现象产生,可用本方法来对小河坝地区进行化探异常综合研究,并指导实际矿产勘查工作。
The reasonable determination of the geochemical anomaly is a key link of geochemical exploration, which directly affects the deployment and prospecting results of mineral exploration. This article selects Ngola mountain metallogenic belt in Qinghai province north Xiaoheba area, using the traditional calculation method, the cumulative frequency method, C-A fractal method, geological area method and trend surface analysis, etc. A comparative study was made on the abnormal extraction effects of the major oreforming elements in the geochemical data of 5 pictures 1 : 50000 stream sediment systems in this area. the results show that the abnormal threshold of individual elements is higher in the traditional calculation method, because of the influence of the fixed value of K value. The anomaly of the frequency method only highlights the high value anomaly area of the data, and the recognition effects of the low value abnormal area is general. The overall effect of C-A fractal method is slightly closer to the calculation method, and the abnormal thresholds of two methods are close too, but the difference of different element abnormal threshold values is large in both methods,which leads to the difference of both result of anomalies is large. The trend surface analysis method can better identify the low value anomalies, retaining the strong anomaly and weakening the influence of the high value area, but the trend surface method has a small scale. Geological subarea method is more suitable for each element, it can better identify low value anomaly, keeps strong anomalies and weakens the influence of some high value area, moreover, the correspondence between the whole anomalies and known mineral deposit is best. Using the geological area method for the geochemical data processing, which can effectively solve the Xiaoheba area due to different geological background area differences, the high value anomaly is usually produced by some mineralization phenomena, we can use this method to the integrated study of geochemical anomalies in Xiaohebaarea, and guide the actual work of mineral exploration.
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