Extreme fractionation in a granite-pegmatite system documented by quartz chemistry: The case study of Tres Arroyos (Central Iberian Zone, Spain)

A continuous fractionation trend from the monzogranite up to the most fractionated aplite-pegmatites is inferred from geochemical modelling by applying the Rayleigh equation for fractional crystallization. Fractionation rates over 50% are needed to obtain the marginal granite and the barren aplite-pegmatites compositions, and over 99% for the most evolved dykes. No pattern in the chemical variation of the trace elements in quartz from different layers in the layered aplite-pegmatites has been found, suggesting the lack of internal fractionation processes, most probably due to the rapid crystallization of the pegmatitic melt, intruded into a colder country rock.