CHEMICAL WEATHERING OF TRAPROCK MATERIALS UNDER SUBARCTIC CONDITIONS

Abstract

We present data that shed some light on the role of chemical weathering in the erosion of traprock in the Subarctic. This rock type was chosen with a purpose, namely for two reasons: first, all known copper-nickel deposits in the region (which are prospected for by various methods, including geochemical methods) are associated with intrusive traprock facies; second, a study of the weathering of mafic rocks in the subarctic zone would yield results that could be compared with the large body of published data on weathering in middle and tropical latitudes. Comparative analysis of data on the weathering of mafic rocks in the different climatic zones revealed that the process of soil generation in the subarctic zone is quite similar to that in middle and low latitudes. This fact suggests that the generation of the clayey fraction of eluvium under subarctic conditions involves an essentially chemical mechanism. Chemical weathering is dominant in the breakdown of sulfide-containing rocks, and the rate of decomposition depends on the overall sulfur content. The breakdown of ores rich in sulfides in the subarctic zone gives rise to pronounced secondary geochemical anomalies, which can be effectively prospected for by looking for haloes and dispersion flows.