Nguyen Ba Dai’s scientific contributions

Determining thresholds are very useful and efficacious in hydrothermal alteration mapping because of their association with mineral deposits. Thus, quantifying the degree of association can serve as a reliable and definitive way of separating highly to less altered zones. This can be achieved through the application of the knowledge of the threshold values. The aim of the study is to propose a new and more effective method for defining thresholds from spatial profiles in thematic images. To achieve this, band ratio technique and threshold mapping of the study area were carried out. The band ratio method was used to delineate clay alteration by dividing band 5 on band 7. Ten (10) profiles each were generated within the study area and the maximum and minimum threshold values were determined. The results showed a close agreement and consistency between the Original Research Article Gajere et al.; AJOGER, 1(1): 1-11, 2018; Article no.AJOGER.41113 2 thresholds values derived from spatial profiling method with the values computed from other established method of threshold determination. It is also important to note that known gold mineralization points in the study area were observed to occur within the highly clay altered zones. Therefore, this study have shown that spatial profiling technique can be regarded as a valid and plausible method for determining threshold values in thematic images.