Petrogenetic links between lepidolite-subtype aplite-pegmatite, aplite veins and associated granites at Segura (central Portugal)

The occurrence of amblygonite-montebrasite, lepidolite, cassiterite, columbite-(Fe), columbite-(Mn) and microlite suggests that lepidolite-subtype granitic aplite-pegmatite veins are highly differentiated. Montebrasite shows a heterogeneous Na distribution and secondary lacroixite was identified in some montebrasite areas enriched in Na. Unusual Mn > Fe cassiterite is zoned, with the alternating darker zones being strongly pleochroic, oscillatory zoned, and containing more Nb and Ta than the lighter zones. Inclusions of muscovite, apatite, tapiolite-(Fe), ixiolite and microlite are present both in lighter and darker zones of cassiterite. It shows exsolutions of columbite-(Fe), columbite-(Mn,Fe) and columbite-(Mn), particularly in darker zones.