E3S Web Conf.
Volume 98, 201916th International Symposium on Water-Rock Interaction (WRI-16) and 13th International Symposium on Applied Isotope Geochemistry (1st IAGC International Conference)
|Number of page(s)||4|
|Section||Geological Evolution of Water-Rock System: Mechanisms, Processes, Factors, Stages. The Session Dedicated to Stepan Shvartsev’s Memory|
|Published online||07 June 2019|
Interaction of B-rich supercritical magmatic fluids with granite: first report of dumortierite in Larderello, Italy
Istituto di Geoscienze e Georisorse, CNR, via Moruzzi 1, 56124 Pisa, Italy
* Corresponding author: firstname.lastname@example.org
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°C, P = 42 ±3 MPa at 2.9 km depth in well Venelle 2. All 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.
© The Authors, published by EDP Sciences, 2019
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