TY - JOUR
TI - Olivine–spinel diffusivity patterns in chromitites and dunites from the finero phlogopite-peridotite (Ivrea-Verbano Zone, Southern Alps): Implications for the thermal history of the massif
AU - Bussolesi, M.
AU - Grieco, G.
AU - Tzamos, E.
JO - Minerals
PY - 2019
VL - 9
TODO - 2
SP - null
PB - MDPI AG
SN - 2075-163X
TODO - 10.3390/min9020075
TODO - null
TODO - The study of Mg–Fe 2+ subsolidus exchange between olivine and spinel is a powerful tool to unravel the thermal history of ultramafic rocks. We have implemented such a study using olivine–spinel diffusivity patterns in fresh mineralogical samples from the Finero mafic-ultramafic Complex in the Ivrea-Verbano zone of Northern Italy. Our analytical suite includes chromitites and dunites of the Phlogopite-Peridotite Unit from the core of the Complex. Primary and re-equilibrated olivine and spinel compositions were derived from diffusivity curves calculated by fitting data via an exponential function. Resulting XMg (Mg/(Mg + Fe 2+ ) values were then used for geothermometry. Samples are found to demonstrate a maximum temperature of 849 ◦ C and a minimum temperature of 656 ◦ C; these temperatures coincide with the limits of elemental exchange in this mineralogic system. We were unable to identify primary olivine/spinel compositions related to the original formation of the dunite–chromitite suite during Early Permian metasomatic activity. Temperature of 849 ◦ C is ascribed to the Late Triassic re-heating event dated at 208 ± 2 Ma. Continuous cooling followed this event at rates of 10 −4 and 10 −2◦ C/yr until cessation of elemental exchange activity at ~656 ◦ C. A rapid cooling rate is associated with the uplift and subsequent decrease of geothermal gradient during the early stages of the opening of the Piemont ocean basin. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
ER -