西藏米拉山地区化探异常特征与找矿预测

水系沉积物地球化学异常分析在勘查找矿方面一直发挥着重要作用。采用中位数+2倍绝对中位差和C-A分形法，对米拉山地区1：5万水系沉积物Cu元素及由R型因子分析确定的Cu+Au+Ag组合元素进行了异常分析，确定了阈值。结果显示C-A分形法能更好地识别异常下限，且C-A分形模型确定的Cu元素异常比Cu+Au+Ag组合元素能更有效地反映米拉山地区与铜矿相关的化学异常特征。进而对Cu元素进行了S-A多重分形滤波处理，筛选出背景场和异常场，为圈定异常区提供更精准的依据。借助S-A分形模型和中位数方法划分了甲类异常2处（驱龙、甲玛）、乙类异常3处（达布、拉抗俄、程巴）、丙类异常2处（普雄、甲布纳）。甲类异常区包含冈底斯最大的2个斑岩铜矿，异常强，具有四级浓度分带，异常面积最大，外围找矿潜力巨大。乙类异常区包含3个大中型铜矿，都具有四级浓度分带，具有很好的找矿潜力。丙类异常区目前尚未发现铜矿，但值得进一步开展地质工作，查明成矿潜力。

Geochemical anomaly characteristics and mineral potential mapping in Milashan area of Tibet

The analysis of geochemical anomalies derived from stream sediment geochemical data is a fundamental task in mineral prospecting.In this study, median+2 median absolute deviations(median+2MAD)and concentration-area(C-A)were applied to analyze geochemical anomaly delineation of Cu and Cu+Au+Ag association from factor analysis of stream sediment geochemical data in Milashan area of Tibet.The results show that the C-A fractal method is a favorable means for identifying the anomaly.Cu anomaly provides more information than Cu+Au+Ag associated anomaly.Furthermore, the S-A analysis was used to decompose the Cu element and distinguish the background from anomaly components, which provides a more accurate basis for delineating the anomalous area.Six anomalous areas have been classified into classes A(Qulong and Jiama), B(Dabu, Lakange and Chengba)and C(Puxiong and Jiabuna).Class A anomalous areas containing two largest porphyry copper deposits in the Gangdise belt are characterized by great anomalous intensity and largest anomalous area, and have great potential for periphery prospecting.Class B prospective areas contain three large and medium-sized copper deposits.Particularly, the Chengba anomalous area has similar anomalous intensity to Qulong and Jiama anomalous areas and thus has good prospecting potential.Copper deposits have not been discovered in Class C anomalous areas, but it deserves exploration work for identifying the mineral potential.