Interaction of B-rich supercritical magmatic fluids with granite: first report of dumortierite in a geothermal field, Larderello, Italy
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Keywords

boron
dumortierite
supercritical magmatic fluids
granite
geothermal field
larderello

How to Cite

Puxeddu, M. . (2022). Interaction of B-rich supercritical magmatic fluids with granite: first report of dumortierite in a geothermal field, Larderello, Italy. South Florida Journal of Development, 3(3), 3162–3169. https://doi.org/10.46932/sfjdv3n3-009

Abstract

In a peraluminous two-mica monzogranite cored at 4.5 km depth in well Radicondoli 29, dumortierite occurs together with andalusite, Li-rich tourmaline, fluorite and fluorapatite. The average composition is SiO2: 30.9, Al2O3: 58.6, FeO: 0.44, MgO: 0.47, CaO: 0.02, F: 0.15. Dumortierite crystallized from supercritical magmatic fluids at T =520-620°C, P = 100 ± 30 MPa. Synthetic fluid inclusions yielded T = 510 ± 10 MPa, P = 42 ± 3 MPa at 2.9 km depth in well Venelle 2. Al data suggest present day T = 450-550°C, P = 40-80 MPa. The supercritical magmatic fluids were hypersaline brines with ~ 30 wt % LiCl and up to 2.4 wt % F, extreme contents that can be found only in pegmatites, aplites and leucogranites. Larderello granites derived from partial melting of a lower crust made up of interlayered metasediments and amphibolites. Extensive melting took place in the lower crust during the last 10 Ma owing to extensional tectonics, lithosphere thinning, roll back or break down of the west merging Adria plate and swelling of the asthenosphere below the western side of the Apennines.

https://doi.org/10.46932/sfjdv3n3-009
Full Text (PDF)