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dc.contributor.authorBroom-Fendley, SL
dc.contributor.authorBrady, AE
dc.contributor.authorHorstwood, MSA
dc.contributor.authorWoolley, A
dc.contributor.authorMtegha, J
dc.contributor.authorWall, F
dc.contributor.authorGunn, AG
dc.date.accessioned2017-05-31T06:53:39Z
dc.date.issued2017-06-02
dc.description.abstractSongwe Hill, Malawi, is one of the least studied carbonatites but has now become particularly important as it hosts a relatively large rare earth deposit. The results of new mapping, petrography, geochemistry and geochronology indicate that the 0.8 km diameter Songwe Hill is distinct from the other Chilwa Alkaline Province carbonatites in that it intruded the side of the much larger (4 x 6 km) and slightly older (134.6 ± 4.4 Ma) Mauze nepheline syenite and then evolved through three different carbonatite compositions (C1–C3). Early C1 carbonatite is scarce and is composed of medium–coarse-grained calcite carbonatite containing zircons with a U–Pb age of 132.9 ± 6.7 Ma. It is similar to magmatic carbonatite in other carbonatite complexes at Chilwa Island and Tundulu in the Chilwa Alkaline Province and others worldwide. The fine-grained calcite carbonatite (C2) is the most abundant stage at Songwe Hill, followed by a more REE- and Sr-rich ferroan calcite carbonatite (C3). Both stages C2 and C3 display evidence of extensive (carbo)-hydrothermal overprinting that has produced apatite enriched in HREE (<2000 ppm Y) and, in C3, synchysite-(Ce). The final stages comprise HREE-rich apatite fluorite veins and Mn-Fe-rich veins. Widespread brecciation and incorporation of fenite into carbonatite, brittle fracturing, rounded clasts and a fenite carapace at the top of the hill indicate a shallow level of emplacement into the crust. This shallow intrusion level acted as a reservoir for multiple stages of carbonatite-derived fluid and HREE-enriched apatite mineralisation as well as LREE-enriched synchysite-(Ce). The close proximity and similar age of the large Mauze nepheline syenite suggests it may have acted as a heat source driving a hydrothermal system that has differentiated Songwe Hill from other Chilwa carbonatites.en_GB
dc.description.sponsorshipThanks are due to A. Lemon, A. Zabula, C. Mcheka, I. Nkukumila (Mkango Resources Ltd.), É. Deady (BGS) and P. Armitage (Paul Armitage Consulting Ltd.) for logistical support and enthusiastic discussions in the field. This contribution benefitted from reviews by Jindřich Kynický and Ray Macdonald, as well as anonymous reviewers, who we thank for their time and insightful comments. This work was funded by a NERC BGS studentship to SBF (NEE/J50318/1; S208), the NERC SoS RARE consortium (NE/M011429/1) and by Mkango Resources Ltd. AGG publishes with the permission of the Executive Director of the British Geological Survey (NERC).en_GB
dc.identifier.citationPublished online 2 June 2017en_GB
dc.identifier.urihttp://hdl.handle.net/10871/27735
dc.language.isoenen_GB
dc.publisherElsevier for Geological Society of Africaen_GB
dc.rights© 2017 The Authors. Published by Elsevier Ltd. Open Access funded by Natural Environment Research Council. Under a Creative Commons license: https://creativecommons.org/licenses/by/4.0/
dc.subjectSongwe Hillen_GB
dc.subjectcarbonatiteen_GB
dc.subjectChilwa Alkaline Provinceen_GB
dc.subjectREEen_GB
dc.subjectU-Pb datingen_GB
dc.subjectHREEen_GB
dc.subjectapatiteen_GB
dc.titleGeology, geochemistry and geochronology of the Songwe Hill carbonatite, Malawien_GB
dc.typeArticleen_GB
dc.identifier.issn1464-343X
dc.descriptionThis is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.
dc.identifier.journalJournal of African Earth Sciencesen_GB
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/


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© 2017 The Authors. Published by Elsevier Ltd. Open Access funded by Natural Environment Research Council. Under a Creative Commons license: https://creativecommons.org/licenses/by/4.0/
Except where otherwise noted, this item's licence is described as © 2017 The Authors. Published by Elsevier Ltd. Open Access funded by Natural Environment Research Council. Under a Creative Commons license: https://creativecommons.org/licenses/by/4.0/