Formation conditions and REY enrichment of the 2060 Ma phosphorus mineralization at Schiel (South Africa): geochemical and geochronological constraints

Journal article


Publication Details

Author(s): Graupner T, Klemd R, Henjes-Kunst F, Goldmann S, Behnsen H, Gerdes A, Dohrmann R, Barton JM, Opperman R
Journal: Mineralium Deposita
Publication year: 2018
Volume: 53
Journal issue: 8
Pages range: 1117-1142
ISSN: 0026-4598
Language: English


Abstract

Rocks of the rare-earth element (REY)-enriched apatite deposit in the eastern part of the Schiel Alkaline Complex (SAC; Southern Marginal Zone, Limpopo Belt) were studied for their whole-rock and mineral chemistry, REY mineral distribution and geochronology. Apart from phoscorite (sensu lato), pyroxenite and various syenitic rock types with quite variable apatite contents display P-REY enrichments. Field observations, mineralogical composition as well as major and trace element chemistry of soils make it possible to constrain the distribution of the hidden P-REY-rich rock types in the apatite deposit. Uranium-lead ages of zircon from phoscorite (sensu lato) and syenite are in the range of 2.06–2.05 Ga. Samarium-neodymium (εNd(t) −8.6 to −6.0) and in part Rb-Sr (87Sr/86Sr(t) 0.70819–0.70859) isotope data for whole-rock samples and mineral separates indicate an origin from an isotopically enriched and slightly variable source. Fluorapatite, early allanite and titanite are the main REY carriers at Schiel. Fluorapatite dominates the REY budget of pyroxenite and phoscorite, whereas early allanite hosts most of the REY in syenite. Three apatite types are distinguished based on their occurrence in the rocks, REYtotal contents and colouration in cathodoluminescence microscopy. Magmatic apatite in pyroxenite and in phoscorite (sensu lato) as well as early stage type I/II apatite in syenitic rocks have moderate to high REYtotal abundances (up to 3.2 wt%) with the mineral enriched in light REE. Early ferriallanite-(Ce) is strongly enriched in light REE and shows very high REYtotal values (13.7–26.4 wt%), while late allanite has lower REYtotalconcentrations (6.9–14.9 wt%). Titanite is abundant in most syenitic rocks (REYtotal 1.7–6.4 wt%); chevkinite-(Ce) occurs locally and contributes to an REY enrichment in contact aureoles between syenite and different lithologies. Apatite-enriched rocks in the SAC in part contain significantly higher REYtotal concentrations in apatite grains compared to those in apatite-mineralized pyroxenite, phoscorite and carbonatite from Phalaborwa.


FAU Authors / FAU Editors

Behnsen, Helge
Professur für Geochemie und Lagerstättenkunde
Klemd, Reiner Prof. Dr.
Professur für Geochemie und Lagerstättenkunde


External institutions with authors

Bundesanstalt für Geowissenschaften und Rohstoffe (BGR)
Goethe-Universität Frankfurt am Main
University of Fort Hare


How to cite

APA:
Graupner, T., Klemd, R., Henjes-Kunst, F., Goldmann, S., Behnsen, H., Gerdes, A.,... Opperman, R. (2018). Formation conditions and REY enrichment of the 2060 Ma phosphorus mineralization at Schiel (South Africa): geochemical and geochronological constraints. Mineralium Deposita, 53(8), 1117-1142. https://dx.doi.org/10.1007/s00126-018-0791-7

MLA:
Graupner, Torsten, et al. "Formation conditions and REY enrichment of the 2060 Ma phosphorus mineralization at Schiel (South Africa): geochemical and geochronological constraints." Mineralium Deposita 53.8 (2018): 1117-1142.

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Last updated on 2019-20-05 at 20:23