LREE rich perovskite in antiskarn reactions - REE transfer from pyroxenites to carbonatites?

We study three ultrabasic-alkaline carbonatite complexes (UACCs: Afrikanda, Vuorijarvi, Kovdor) from the Kola Alkaline Province to focus on the comparison of REE contents from pyroxenites and carbonatites and the fate of perovskite. Pyroxenites and carbonatites have large REE variations and similar contents in all three complexes. Afrikanda and Vuorijarvi pyroxenites and carbonatites have higher REE contents compared to all Kovdor rocks. Despite their comparable LREE contents, pyroxenites and carbonatites have different REE-carrier minerals. In most studied pyroxenites, perovskite is the main REE-bearing mineral and its abundance controls the LREE enrichment of the whole rock. When perovskite is absent or in low abundance, apatite is the main REE carrier. Instead, in carbonatites and phoscorites, apatite and calcite control REE contents. REE‑carbonates - found in several carbonatite samples - do not play a substantial role in the overall REE budget because of their very low abundance and tiny grain sizes. We found large LREE variations at very low local scales (< 1 mm) in several thin sections. These large variations are related to carbonatite infiltration and associated antiskarn reactions. Perovskite near calcite is replaced by titanite that has much lower LREE contents. Most LREE released from the breakdown of perovskite were probably dissolved in the carbonatite melt because apatite and calcite that crystallized from this melt are highly enriched in LREE. Newly formed apatites and calcites show large LREE variations that probably are controlled by local factors (e.g. variations of Si, Ca, Mg activities). Y/Ho ratios are strongly fractionated in most minerals and often show large variations at local scales (mm) in these antiskarn reactions. The potential of REE remobilization from such perovskite replacement reactions is very high as perovskite contributes about 70% to the REE budget for these three UACCs. Therefore, more attention should be given to perovskite replacement reactions and its role for LREE enrichment of carbonatite melts.