Elb- Granodiorite

Phaneritic rock composed of the crystals easily identified by naked eye: feldspar (grains with a milky white aspect), quartz (pale grey grains; the single grains are colourless but they appear grey in the rock because they are surrounded by the other coloured mineral grains), biotite (black grains with a shiny lustre). The rock sample comes from the Mt Capanne pluton, emplaced 6.9 Ma ago in western Elba (Tuscany) and belonging to the Tuscan Magmatic Province (Geol.F.Trips, Vol.5 No.2.1 (2013), DOI 10.3301/GFT.2013.03). See R8 rhyolite for further details on this magmatic province. This sample comes from the granodioritic-monzogranitic San Piero facies of the Mt Capanne pluton, that is quarried for its homogeneous texture.

Thin section description

The field of view is largely occupied by large plagioclase (Pl), alkali-feldspar (Afs) and plagioclase (Pl) crystals, that appear colourless in the PPL view but that can be identified looking also at the aspect seen in the XPL view. The Pl crystals are often twinned in the XPL view and may exhibit zoning; the quartz (Qz) crystals are clear in the PPL view while the Afs crystals show a slight clouding. The small crystals showing the light to dark brown pleochroism are biotite (Bt).

thin section PPL	thin section XPL