Stolemberg

The summit of Stolemberg is a magnificent example of a klippe composed of Zermatt-Saas ophiolitic metabasalt, resting on the Monte Rosa bedrock.

On the slopes leading up to the summit, one initially observes the typical micaschists of Monte Rosa, with an Alpine character, along with some white aplitic gneisses. On a plateau (at an altitude of 3,043 m), a number of metabasic lenses are found within the Monte Rosa gneisses, which exhibit an almost horizontal structure. A little further on, as you climb, you can see the contact between the Monte Rosa gneisses and the Zermatt-Saas meta-ophiolites (altitude 3,068 m). Extensive reaction zones of amphibole, talc and chlorite develop between the gneisses and the serpentinites (the path can be slippery). The Stolemberg metatholiolites consist mainly of banded amphibolites containing albite, with garnet relics, derived from former eclogites. Some eclogite remnants, which escaped the subsequent retrogression, consist of omphacite, garnet and amphibole. Walking along the contact, as this is folded, one encounters several lenses of Monte Rosa gneiss and meta-ophiolite. There are therefore several repetitions of the two units.