Datowanie cyrkonów z anortozytów : misja niemożliwa?

Despite the low content of Zr element (<100 ppm) in the anorthosites from the Suwałki Massif and Sejny Intrusion, it was necessary to undertake U-Pb age investigation on zircons. It was a technical challenge, which required a modification of typical separation procedures. In anorthosites associated with Fe-Ti ores, zircon is rich in Fe-Ti oxide inclusions and it often ends up in the magnetic fraction. The drillcore samples were selected from four different drillings located in the Suwałki Massif and nearby Sejny Intrusion, where a dominant rock type is anorthosites. In these rocks, zircon crystallizes as a late phase, which is reflected by its interstitial morphology. The samples were collected from depth intervals spanning multiple sections of the core, therefore a large number of U-Pb SHRIMP measurements (n = 50-97) has been performed for each sample. Age results, presented as a weighted average (Mean age), range from ~1510Ma (Jezioro Szlinokiemskie IG 1) to ~1505 Ma (Sejny IG 2). The SHRIMP data provided evidence of a distinct magma composi¬tion reflected by diversity of zircon chemical composition. The later evolution of Fe-Ti oxides is recorded as zircon lamellae being an effect of the subsolidus Zr precipitation from the ilmenite network at 1482 Ma.

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Opracowanie rekordu ze środków MNiSW, umowa nr POPUL/SP/0154/2024/02 w ramach programu "Społeczna odpowiedzialność nauki II" - moduł: Popularyzacja nauki (2025).