Telescoping ore targets by geochemical exploration at multiple scales in Eastern Yunnan Pt geochemical province, southwestern China

Platinum has been one of the highly needed mineral resources in China. The geochemical exploration at two survey scales was applied in telescoping ore targets for the first time in Eastern Yunnan Pt geochemical province that was delineated using Pt data from flood plain sediments with extra-low sampling density. Our study was based on the delineations and assessments of both regional and local Pt anomalies using the Pt data by analyzing with C-OES the composite samples with two sampling densities. The composite samples were obtained by recomposing at two sampling densities the original stream sediment samples collected by the National Geochemical Mapping Project. Semi-variograms were used to quantitatively describe the variability of Pt anomalies and further analyze the factors controlling the variability. Pt resource potentials of both the regional Pt anomalies and the local Pt anomalies in the study area were estimated based on the geochemical block methods, respectively. It comes to the conclusions as follows. (1) From the regional to local Pt anomaly, the factors controlling their variability from the deep seated faults-basalts turn into the basalts-branch faults, which suggest that Semi-variograms could identify the geological factors controlling the variability of the Pt anomalies identified by the Pt data from the stream sediments with different sampling densities. (2) There exist two types of Pt anomalies in the study area. One is those displaying at sampling densities, and its average Pt concentration significantly increases with sampling density increasing. The other is getting weaker and/or disappears with sampling density increasing. This shows that TOTGEMS could gradually eliminate non-ore anomalies and keep ore anomalies. (3) The average Pt concentration of the local Pt anomaly blocks delineated using Pt data from stream sediments with sampling density of one composite per 16 km2 is twice as much as that of the regional Pt anomaly blocks delineated using Pt data from stream sediments with sampling density of one composite per 64 km2. The Pt resource amount of the local Pt anomaly blocks is 60% of the regional anomaly blocks, but the area of the former is just 35% of the latter, which suggests that the Pt resource amount is mainly concentrated in its local anomalies, and that TOTGEMS has a good exploration function that efficiently approaches ore targets.