Pizzo Paglia pegmatite dyke, Leggia Valley, Leggia, Grono, Moesa Region, Grisons, Switzerlandi

Regional Level Types
Pizzo Paglia pegmatite dyke	- not defined -
Leggia Valley	Valley
Leggia	Village
Grono	Municipality
Moesa Region	Region
Grisons	Canton
Switzerland	Country

LCT pegmatite dyke at 2385 m, discoverd in summer 2009.

The pegmatite body is both hosted in amphibolite rocks and migmatite gneiss of the Bellinzona-Dascio Zone, Southern Steep Belt of the Central Alps. The dyke outcrops for 20 m and can attain 3-4 m in thickness. The lower portion (lower end) of the dyke is concordant with the foliation of leucocratic migmatite gneiss. Here, the pegmatite reaches the maximum width (3-4 metres) due to the coalescence with a lateral pegmatite dyke. The border-wall zone of the pegmatite is coarse-grained (up to 10 cm) and consists of idiomorphic white perthitic K-feldspar, albite, large aggregates of silvery muscovite and subordinate brownish vitreous quartz masses. The core zone has giant texture (up to metre) and consists of huge euhedral perthitic K-feldspar projecting into large masses of brownish to smoky vitreous quartz. In the intermediate-core zone of the pegmatite large euhedral crystals of red almandine-spessartine crystal with trapezohedral habit occur. They are associated with sky-blue to greenish, vitreous, centimetre-sized hexagonal prisms of beryl, prisms of black schorl, and greyish millimetre-sized zircon. The upper portion (upper end) of the pegmatite, hosted by black amphibolite rock, narrows and reaches one metre in width. In this section the coarse-grained (centimetre-sized) texture is characterized by white perthitic K-feldspar, albite, and quartz. Centimetre-sized primary miarolitic cavities lined with albite, K-feldspar, quartz, and acicular prisms of black schorl also occur. This pegmatite portion hosts black centimetre-sized prisms of schorl which diffuse along the exocontacts and permeate the amphibolite.

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References