Iron-containing weathering products of basalt in a cold, dry climate

Abstract Two different microenvironments for secondary iron mineral formation in a basaltic stone exposed to weathering in the cold, dry climate at the top of a nunatak in Greenland have been investigated. At the upper, exposed surface a red stained rind (varnish) has formed, and within a crack, a loose, reddish-brown material and a greenish coloured material were found. The weathering products were identified by 57 Fe Mossbauer spectroscopy, X-ray diffraction and infrared spectroscopy. The reddish stain on the exposed surface consists of hematite. In contrast, the reddish-brown material from the crack contains goethite and magnetite/maghemite, but no hematite could be detected. Nontronite is the main mineral in the greenish material. The conditions determining the neoformation of minerals in the two environments are briefly discussed.