Lötschberg Base Tunnel (south section), Westlich Raron, Valais, Switzerlandi

Regional Level Types
Lötschberg Base Tunnel (south section)	Tunnel
Westlich Raron	District
Valais	Canton
Switzerland	Country

The Lötschberg Base Tunnel (LBT) is a 34.57-km-long railway base tunnel on the BLS AG's Lötschberg line cutting through the Bernese Alps some 400 m below the existing Lötschberg railway tunnel (opened in 1913). It was opened on June 15, 2007, as part of the NRLA (New Railway Link through the Alps) project. The LBT runs between the South portal near Sankt German, Raron (Valais), and the North portal at Tellenfeld, Frutigen (Bern). Currently from south to north a third of the tunnel is double track, a third is single track with the second bore in place but not equipped, and a third is only a single track tunnel with the parallel exploration adit providing the emergency egress.

Interesting minerals were found during tunneling in the first half of the 2000s and particularly in the Valais section.
In its south section, the Valais section, the tunnel starting from the South portal penetrates the autochthonous Mesozoic cover, with sequences of sedimentary rocks of Upper Triassic and Jurassic (Lias, Dogger, and Malm) age; the Late Variscan Baltschider granodiorite and Central Aar (aka Bietschhorn) granite; sedimentary rocks and conglomerates of the Ferden Carboniferous zone; the so-called "Altkristallin" consisting of pre-Variscan gneisses, schists and amphibolites, which have experienced a complex polymetamorphic evolution; Mesozoic rocks (limestones) of the so-called Jungfraukeil (Jungfrau wedge); the the Late Variscan Gastern granite.

Typical minerals in the Alpine fissures inside Mesozoic limestones are calcite, dolomite, ankerite, celestine, baryte, pyrite, and galena. The fissures in granite and gneisses are characterised by the presence of quartz, adularia, clinochlore, albite, calcite, dolomite, fluorite, fluorapophyllite-(K), titanite, fluorapatite, rutile, anatase, pyrrhotite, pyrite, chalcopyrite, sphalerite, molybdenite and galena. The fissures in amphibolites are typically filled with epidote, amphibole (byssolite), and calcite.

Some fissures have yielded very remarkable crystals, as a fresh pyrrhotite floater measuring 12.7 cm in length (the largest pyrrhotite crystal ever found in Switzerland) and a limpid calcite crystal, 30 cm long and less than 0.5 cm thick, overgrown by numerous crystals of fluorapophyllite-(K).

Fossils

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References