区域化探异常(老资料)评价、评序方法讨论

对区域化探老资料及成矿区(带)的化探资料圈出的异常进行评价、分类、评序是一项紧迫工作。笔者用谢学锦和邵跃的异常评价方法思路提出了新的异常评序方法。方法是:先计算出异常的各种地球化学参数;每个异常按元素规格化面金属量NAP值从大至小依次排队,写出每个异常的多元素组合表达式;根据区域地球化学特征、区域地质矿产规律、成矿物质来源、控矿地质条件、已知矿区异常规律结合异常特征等对异常进行评价,对有找矿远景的异常进行矿种预测;按异常评价结论对异常进行分类;最后将各类异常中每一个异常的成矿元素及其前缘元素NAP值累加值作为异常评序参考值,按其值的大小序列进行排队,这样同类型矿床的异常就可以进行比较了。1981年至1982年对湖南省区域化探(老资料)中圈出来的132个异常评价、分类、评序取得较好的结果。经评序后已知大中型矿床的异常都排在每类的最前面,说明最前面的异常找矿规模也最大,其中排在前面的尚未见矿的异常一般是有找矿希望的异常。且这种序列与异常评价结论是一致的。异常评价后发现有七个异常的评价意见与新的储量资料相吻合。1983年至1984年在两个异常区钻探打到相应的工业矿体,说明这种异常评价、评序方法是可行的。

A METHOD FOR EVALUATING AND RANKING REGIONAL GEOCHEMICAL ANOMALIES DELINEATED FROM THE FORMER DATA:A DISCUSSITON

The evaluation, classification and ranking of the anomalies delineated from the former regional geochemical prospecting data and geochemical data of meta llogenic province (belt) seem to be a pressing job. Following the line of thought of Xie Xuejin and Shao Yue for anomaly evaluation, the author has advanced a new method for the ranking of anomalies. Its process goes like this: first, vari ous geochemical parameters of the anomalies are evaluated; then the anomalies are arranged in decreasing order of normalized areal productivity (NAP) values, and the expression of multi-element association for each anomaly is worked out; based on such factors as regional geochemical charactersitics, regional geological and metallogenic regularities, ore-forming material sources, ore-governing geologi cal conditions, and regularity of anomalies in known ore districts, combined with the characteristics of anomalies, the evaluation is made for all the anomalies with the ore types predicted for promising anomalies; the anomalies are classi fied according to the results of anomaly evaluation; finally, the additive NAPvalues of the metallogenic elements and the frent elements in each anomaly ofvarious groups are taken as reference values for the ranking of anomalies, and these values are arranged in order. In this way, anomalies of the same type deposits can be compared with each other.During1981 and 1982, evaluation, classification, and ranking were conducted for 132 anomalies delineated from the former regional geochemical data of Hunan Province, which turned out to be quite encouraging. It is noticed after ranking that the anomalies of the known large-and medium-size deposits are all concentrated in the forefront part of every group, suggesting that the anomalies in the forefront part are of the greatest prospect in ore-searching, and that the anomalies falling in the front but seemingly connected with no ore deposits are likely to be promising in ore prospecting. Moreover, this sort of sequence proves to be consistent with the conclusion drawn from evalution of anomalies. The evaluation results of seven anomalies are found to be in conformity with the newly-obtained reserve data. In1983 and 1984, economic orebodies were discovered through drilling in two anomalous areas, implying that this method for evaluating and ranking anomalies is effective.