Labtium has been the laboratory providing analyses of precious metals for the geochemical mapping of Finland
In the geochemical exploration for the precious metals i.e.Au, Pd and Pt, we recommend aqua regia leach, followed by pre-concentration by Hg co-precipitation and analysis by GFAAS (Methods 520U and 521U; 5 g subsample). Ppb -level detection limits can be attained for Au and Pd giving meaningful anomaly contrasts. Alternatively a larger sample weight of 20 g can be used (Method 522U).
The methods are applicable to non-mineralised samples such as till, weathered bedrock, stream sediments, humus, rock.
The use of pathfinder elements in geochemical prospecting – particularly for gold is known to give more information of element dispersion in secondary environments and assist in the classification of the type of mineralization. *Nurmi et al. concluded that the most important elements in exploration for Precambrian mesothermal gold deposits are: Au, Te, Bi, As, Ag, W and Se. Labtium offers for gold exploration a unique package including Au, Bi, Sb, Se and Te (520U) with ultra low detection limits. This set can be complemented by methods 511P or 511PM.
Another option is a multi-element package using ICP-OES and ICP-MS-techniques (515PM). This package will give totally 42 elements including Au and Pd with trace level detection limits.
Note that these methods are not suitable for mineralised samples.
As geochemical methods have been optimised for analysis of large set of elements preferably with low detection limits, they have analytical limitations with very high element concentrations. Labtium’s laboratory has defined upper concentration level for each element. When this concentration is exceeded, a more suitable ore grade assay method should be used for checking the grades. For the analyses of precious metals the choice is to use classical Fire Assay method (704A/P).
*Nurmi P.A., Lestinen, P. and Niskavaara, H. (1991). Geochemical Characteristics of mesothermal gold deposits in Fennoscandian Shield and a comparison with selected Canadian and Australian deposits. Geological Survey of Finland,Bulletin 351,Espoo 1991