内蒙古巴彦塔拉-明安图地区地球化学数据分形和混合筛分定量分析及稀有金属找矿预测

Quantitative analysis of fractal and mixed distribution with geochemical data from the Bayantala-Mingantu Region,Inner Mongolia,and implications for rare metal prospecting prediction

为了探讨分形和混合筛分定量分析工具在化探数据分析中的作用,利用C-A分形(质量分数-面积)和混合筛分方法对内蒙古巴彦塔拉-明安图地区1325个土壤样品中钨(W)、铌(Nb)、铜(Cu)和铋(Bi)元素化探数据进行定量分析。结果表明:C-A分形显示其拟合直线为三段式,呈多重分形特征;混合筛分显示其服从包含两个对数正态分布的混合分布。依据分形拐点和混合分布估计的异常阀值圈定化探异常。对比两种方法获得的化探异常,发现混合筛分的W-Bi-(Cu)综合异常与已知的主要矿床或矿点吻合程度较高,表明该方法在该地区铌(钽)钨等稀有金属找矿预测工作中可能具有良好的应用效果。在综合异常的基础上,结合地质成矿条件圈定3个稀有金属找矿预测靶区。

In order to study the role of fractal and mixed distribution quantitative analysis in geochemical exploration,W,Nb,Cu,and Bi elemental data of 1 325 soil samples from the Bayantala-Mingantu area,Inner Mongolia were quantitatively analyzed by means of multi-fractal(C-A fractal) and multimodal distribution(mixed distribution) methods. Results showed that the C-A fractal analysis got a fitting line of three-step with multifractal characteristics. The mixed distribution analysis indicated that it followed a mixed distribution containing two lognormal distributions. Geochemical anomalies were delineated according to the anomalous threshold estimated by C-A fractal inflection point and mixed distribution. By comparing the geochemical anomalies obtained by these two methods,it was found that the W-Bi-(Cu)geochemical comprehensive anomalies highlighted by mixed distribution were in good agreement with the known major ore deposits or occurrences of rare metals. This indicated that multimodal distribution(mixed distribution)method might have a good application effect in the prospecting prediction of rare metals,such as Nb(Ta)and W in this area. On the basis of comprehensive anomalies and combined with geological metallogenic conditions,three prospecting and prediction target areas for rare metals were delineated.