Differential weathering of feldspar and pyroxene in an arctic‐alpine environment

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AbstractThe relative relief of adjacent plagioclase and pyroxene minerals was accurately measured on a recently‐exhumed outcrop of gabbroic rocks in Leirdalen, southern Norway. Above the level of the former soil surface the feldspars protrude above the pyroxenes whereas below that level the pyroxenes are higher. Differential relief declines with increasing depth of burial down to 80 cm. On exposed surfaces the mean loss of pyroxene relative to feldspar is 103 cm3 m−2 of rock surface. With burial down to 50 cm in an arctic‐alpine Brown Soil the mean loss of feldspar relative to pyroxene is 179 cm3 m−2. These figures represent minimum amounts of weathering over about 9000 years. The results confirm the importance of chemical weathering in arctic‐alpine environments and the techniques may provide useful physical measures of degree of weathering for use in rate studies and relative‐dating.