REE minerals as geochemical proxies of late-tertiary alkalic silicate ± carbonatite intrusions in Carpathian Back-Arc

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Marco E. Ciriotti
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REE minerals as geochemical proxies of late-tertiary alkalic silicate ± carbonatite intrusions in Carpathian Back-Arc

Messaggio da Marco E. Ciriotti » mer 31 mar, 2021 14:56

▪ Hurai, V., Huraiová, M., Konečný, P. (2021): REE Minerals as Geochemical Proxies of Late-Tertiary Alkalic Silicate ± Carbonatite Intrusions Beneath Carpathian Back-Arc Basin. Minerals, 11, 369.

The accessory mineral assemblage (AMA) of igneous cumulate xenoliths in volcanoclastic deposits and lava flows in the Carpathian back-arc basin testifies to the composition of intrusive complexes sampled by Upper Miocene-Pliocene basalt volcanoes. The magmatic reservoir beneath Pinciná maar is composed of gabbro, moderately alkalic to alkali-calcic syenite, and calcic orthopyroxene granite (pincinite). The intrusive complex beneath the wider area around Fiľakovo and Hajnáčka maars contains mafic cumulates, alkalic syenite, carbonatite, and calc-alkalic granite. Both reservoirs originated during the basaltic magma underplating, differentiation, and interaction with the surrounding mantle and crust. The AMA of syenites is characterized by yttrialite-Y, britholite-Y, britholite-Ce, chevkinite-Ce, monazite-Ce, and rhabdophane(?). Baddeleyite and REE-zirconolite are typical of alkalic syenite associated with carbonatite. Pyrochlore, columbite-Mn, and Ca-niobates occur in calc-alkalic granites with strong peralkalic affinity. Nb-rutile, niobian ilmenite, and fergusonite-Y are crystallized from mildly alkalic syenite and calc-alkalic granite. Zircons with increased Hf/Zr and Th/U ratios occur in all felsic-to-intermediate rock-types. If rock fragments are absent in the volcanic ejecta, the composition of the sub-volcanic reservoir can be reconstructed from the specific AMA and zircon xenocrysts–xenolith relics disintegrated during the basaltic magma fragmentation and explosion.
Marco E. Ciriotti

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