Fig. 3

Microstructures of monazite in backscattered electron images (BSE). Numbers are single Th-U–Pb ages in Ma. Weighted averages with 2σ error are calculated from several analyses within a grain, and from several small grains analysed by a single measurement. a Large monazite (Mnz) with slightly embayed rims and patchy darker core zones, with Carboniferous ages. b Large monazite with patchy darker core zone. c Embayed large monazite with darker domains. d Carboniferous monazite in biotite (Bt) with tiny apatite (Ap) at the rim and formation of allanite (Aln), initial stage of corona structure. e Progressed stage of corona formation with broad apatite zones. Only some single ages are labelled for spread of data. f Late stage of corona formation with broad apatite and allanite rims and thin relic monazite. Sutured monazite grain boundaries signal dissolution. Compared to e, the relic monazite cores are older. g Large cluster of small monazite grains which are surrounded by allanite and biotite. h Details of monazite cluster arrangement in plagioclase (Pl), quartz (Qtz) and biotite (Bt), with allanite rims around all small monazite grains. (i, j) Small Carboniferous monazite surrounded by allanite coronas (not visible due to BSE contrast/brightness); with stable grain boundaries and no signs of possible fluid-mediated marginal dissolution-repricipitation