Article Dans Une Revue Minerals Année : 2024

Lithium, Phosphorus, Fluorine-Rich Intrusions and the Phosphate Sequence at Segura (Portugal): A Comparison with other Hyper-Differentiated Magmas

Michel Cathelineau
Marie-Christine Boiron
Andreï Lecomte
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Ivo Martins
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Ícaro Dias da Silva
António Mateus

Résumé

Near the Segura pluton, hyper-differentiated magmas enriched in F, P and Li migrated through shallowly dipping fractures, sub-perpendicular to the schistosity of the host Neoproterozoic to Lower-Cambrian metasedimentary series, to form two swarms of low-plunging aplite-pegmatite dykes. The enrichment factors for F, P and Li compared with peraluminous granites are of the order of 1.5 to 5 are linked to the extraction of supercritical fluids enriched in fluxing elements from the melt crystallising feldspars. With magmatic differentiation, increased P and Li activity yielded the crystallisation of primary amblygonite-montebrasite series, and Fe-Mn phosphates. The high activity of sodium during the formation of albite-topaz assemblage in pegmatites led to the replacement of the primary phosphates by lacroixite. The influx of external, post-magmatic and Ca-Sr-rich hydrothermal fluids replaced the initial Li-Na phosphates with phosphates of the goyazitecrandallite series, and was followed by massive formation of apatite. Dykes emplacement in metasediments took place close to the main injection site of the muscovite granite, which is offcentre from that of the Cabeza de Araya monzogranite, plausibly during a major compression event that favoured the ascent of hyper-differentiated melts to which the muscovite-rich granite is related.

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hal-04786145 , version 1 (15-11-2024)

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Michel Cathelineau, Marie-Christine Boiron, Andreï Lecomte, Ivo Martins, Ícaro Dias da Silva, et al.. Lithium, Phosphorus, Fluorine-Rich Intrusions and the Phosphate Sequence at Segura (Portugal): A Comparison with other Hyper-Differentiated Magmas. Minerals, 2024, 14 (3), pp.287. ⟨10.3390/min14030287⟩. ⟨hal-04786145⟩
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