LREE redistribution during hydrothermal alteration at the Okorusu carbonatite complex, Namibia

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Marco E. Ciriotti
Messaggi: 26570
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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LREE redistribution during hydrothermal alteration at the Okorusu carbonatite complex, Namibia

Messaggio da Marco E. Ciriotti » dom 18 ago, 2019 11:26

Prossima pubblicazione.

Referenza:
▪ Cangelosi, D., Broom-Fendley, S., Banks, D., Morgan, D., Yardley, B. (2020): LREE redistribution during hydrothermal alteration at the Okorusu carbonatite complex, Namibia. Mineralogical Magazine, 84, (in press).

Abstract:
The Cretaceous Okorusu carbonatite, Namibia, includes diopside-bearing and pegmatitic calcite carbonatites, both exhibiting hydrothermally altered mineral assemblages. In unaltered carbonatite, REE, Sr and Ba are largely hosted by calcite and fluorapatite. However, in hydrothermally altered carbonatites, small (< 50 μm) parisite-(Ce) grains are the dominant REE host, while Ba and Sr are hosted in baryte, celestine, strontianite and witherite. Hydrothermal calcite has a much lower trace element content than the original, magmatic calcite. Despite the low REE contents of the hydrothermal calcite, the REE patterns are similar to those of parisite-(Ce), and magmatic minerals and mafic rocks associated with the carbonatites. These similarities suggest that hydrothermal alteration remobilised REE from magmatic minerals, predominantly calcite, without significant fractionation or addition from an external source. Ba and Sr released during alteration were mainly reprecipitated as sulfates. The breakdown of magmatic pyrite into Fe-hydroxide is inferred to be the main source of sulfate. The behaviour of sulfur suggests that the hydrothermal fluid was somewhat oxidising and it may have been part of a geothermal circulation system. Late hydrothermal massive fluorite replaced the calcite carbonatites at Okorusu and resulted in extensive chemical change, suggesting continued magmatic contributions to the fluid system.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 26570
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: LREE redistribution during hydrothermal alteration at the Okorusu carbonatite complex, Namibia

Messaggio da Marco E. Ciriotti » gio 26 mar, 2020 17:29

Pubblicazione effettuata.

Referenza:
▪ Cangelosi, D., Broom-Fendley, S., Banks, D., Morgan, D., Yardley, B. (2020): LREE redistribution during hydrothermal alteration at the Okorusu carbonatite complex, Namibia. Mineralogical Magazine, 84, 49-64.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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