Palladium soil geochemistry, Baronskoye Pd–Au prospect, Sverdlovsk oblast, Russia

Abstract

A programme of B-horizon soil sampling coupled with low detection-limit, fire-assay/ICP-MS analysis for Pd, Au and Pt was carried out on the Baronskoye prospect in the Central Urals of Russia in 1999 and 2000. Of the three precious metals, Pd proved to be particularly effective in locating occurrences of very low-sulphide Pd-Au mineralization of inferred hydrothermal, shearzone type within pyroxenites and gabbros in fairly flat, thickly forested terrain. In contrast, potential pathfinder elements, such as Cu, Ni, Ag, As and Te, as determined by a separate aqua regia digestion/ ICP-MS analytical package, were found to be of little use.

At a threshold of 55 ppb Pd the soil-sampling results clearly defined a northwest-trending linear anomaly over the pyroxenite. Although usually only about 20 m wide, this Main Anomaly, with a maximum value of 447 ppb Pd, can be traced along strike for 900 m and is well supported by Au at the 20-130 ppb level and by Pt in the range 10-45 ppb. An intermittently developed Eastern Split Anomaly was identified about 20 m east of the Main Anomaly, and a potentially more important Northeastern Anomaly, about 320 m × 150 m, was found 200 m to the east of the northern end of the Main Anomaly and just inside the gabbro surrounding the pyroxenite. Testing of the three soil anomalies by diamond drilling in 2000 confirmed the presence of sporadic Pd-Au mineralization in the bedrock below all of them.