Variographic Trends of Gold in the Alluvial Sediments Associated with the Quartz Lodes of the Princesa Isabel Region, Paraiba, Brazil

Abstract

The gold bearing quartz lodes occur in the metasedimentary sequences pertaining to the Middle to Upper Proterozoic formations. The average gold concentration varies from 2.21 g/t to 10.71 g/t in the two main quartz lodes of the study area and is being mined at a small scale. An attempt has been made in this study to capture the structural characteristics of the gold assay values in the sediments associated with the gold bearing quartz veins with the objective of localising or detecting the presence of other quartz veins in the subsurface and to investigate the level of continuity in the distribution of the metal in the sediments. The metal occurs as disseminated traces in the sediments and the average concentration of gold is 9.44 ppb, with a variance of 841.49 and a coefficient of variation of 3.1. An omnidirectional variogram of the sediments was poorly structured but the directional variogram resulted in an acceptable model with a sample range of 7 m. The directional variographic analysis showed the presence of a well-defined structure and a systematic variation in the assay values. Continuity and spatial correlation between the sample gold assays can be detected in the variogram along the drainage patterns.