地球化学异常再现性与可对比性

不同密度采样是否可以获得稳定的和可追索的地球化学模式是检验采样是否具有代表性，分析技术是否成熟的重要依据。笔者选择新疆哈密大南湖地区约6400km^2面积，进行了从超低密度(1个样／100km^2)，甚低密度(1个样／25km^2)直到低密度(1个样／4km^2)地球化学采样，对比了3种密度地球化学采样所获得的地球化学数据和异常分布模式。得出如下结论：超低密度、甚低密度、低密度地球化学调查获得的元素含量平均值和背景值非常接近；超低密度、甚低密度、低密度调查所圈定的地球化学省在形态上和变化趋势上非常相似，浓集中心的位置重合，表明不同调查阶段可获得稳定的和可追索的地球化学模式；采样密度越大数据离散程度越高，即最小值更小，最大值更大，表明元素分布的局部不均匀性，正是这种局部的不均匀性才能通过加密采样刻画出地球化学模式的细节变化，为逐步追踪矿化体奠定了基础；超低密度和甚低密度采样可以有效圈定矿集区所形成的大规模地球化学异常，低密度地球化学调查不仅可以圈定矿集区异常，同时可以圈定分散矿化的小规模局部异常。

Reproducibility and Comparison of geochemical anomalies

The wide-spaced sampling method is widely used to delineate large-scale geochemical patterns. However, the premise is that the large-scale anomalies must be reproducible in the follow-up surveys. A study area of 6400 km2 in Xinjiang was surveyed to investigate the reproducibility of geochemical anomalies delineated by different sampling densities, i.e. 1 sample/ 100 km2, 1 sample/25 km2 and 1 sample/4 km2. The results show that (1) the background values and average values obtained by different sampling densities are very consistent, (2) the large-scale geochemical patterns are very similar and reproducible by different sampling densities,(3)the values are more scattered as the sampling spacing becomes smaller, and (4) ultra-low (1 sample/ 100 km2) and very low-density (1 sample/25 km2) sampling can only delineate large-scale geochemical anomalies, but low-density sampling (1 sample/4 km2) can delineate both large-scale anomalies and small ones.