This paper describes the mineralogy and petrology of an albite pegmatite dike cropping out close to Malga Garbella, Rabbi Valley, Trento province, Italy. The pegmatite is hosted by high-grade metamorphic rocks of the crystalline basement of the Tonale-Ultimo Unit, Austroalpine domain. The dike, now almost completely exploited, was 10 m long and 1 m thick. The internal structure of the pegmatite cannot be reconstructed, but from the available specimens it is possible to infer that a blocky albite unit and masses of quartz (quartz cores) formed the main units of the dike. The pegmatite, composed mainly of primary albite (Ab96-Ab100), also contains primary chrysoberyl, almandine, schorl, and muscovite as common accessory minerals, while beryl, zircon, monazite-(Ce), and uraninite represent rare minerals. Secondary uranium-bearing minerals were also detected. The primary phosphate association is given by graftonite + sarcopside + (minor) triphylite masses, and wolfeite was found alone at the contact between albite and quartz. The secondary phosphate association was formed in both a non-oxidized paragenesis and an oxidized and metasomatized one. The petrological processes leading to the crystallization of the secondary phosphates are complex and include: (1) hydration and Ca, Mg, and Mn leaching, mainly of graftonite; (2) hydration and oxidation of Fe; (3) destabilization of albite. The age of magmatic crystallization of the Malga Garbella pegmatite, measured using monazite-(Ce), is 257 ± 3 Ma, consistent with the Brissago (Canton Ticino, Switzerland) phosphate-bearing pegmatite.
The chrysoberyl-And phosphate-bearing Albite pegmatite of Malga garbella, val di rabbi, Trento province, Italy / P. Vignola, M. Zucali, N. Rotiroti, G. Marotta, A. Risplendente, A. Pavese, M. Boscardin, V. Mattioli, G. Bertoldi. - In: CANADIAN MINERALOGIST. - ISSN 0008-4476. - 56:4(2018), pp. 411-424.
|Titolo:||The chrysoberyl-And phosphate-bearing Albite pegmatite of Malga garbella, val di rabbi, Trento province, Italy|
VIGNOLA, PIETRO (Corresponding)
|Parole Chiave:||Albite pegmatite; Anatectic pegmatite; Austroalpine domain; Chrysoberyl; Italy.; Malga Garbella; Phosphates; Trento; Triassic; Geochemistry and Petrology|
|Settore Scientifico Disciplinare:||Settore GEO/06 - Mineralogia|
Settore GEO/03 - Geologia Strutturale
Settore GEO/08 - Geochimica e Vulcanologia
|Data di pubblicazione:||2018|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.3749/canmin.1700058|
|Appare nelle tipologie:||01 - Articolo su periodico|