Publication details
Compositional variations of zirconolite from the Evate apatite deposit (Mozambique) as an indicator of magmatic-hydrothermal conditions during post-orogenic collapse of Gondwana
| Authors | |
|---|---|
| Year of publication | 2018 |
| Type | Article in Periodical |
| Magazine / Source | Mineralogy and Petrology |
| MU Faculty or unit | |
| Citation | |
| Web | http://dx.doi.org/10.1007/s00710-017-0538-7 |
| Doi | http://dx.doi.org/10.1007/s00710-017-0538-7 |
| Field | Geology and mineralogy |
| Keywords | Zirconolite · Carbonatite · Evate · Mozambique · Gondwana |
| Description | Zirconolite is documented from the Evate apatite- magnetite-carbonate deposit in the circular Monapo Klippe (eastern Mozambique)—a relic of Neoproterozoic nappe thrusted over the Mesoproterozoic basement of the Nampula block. Zirconolite enriched in rare earth elements— REE = Y + Lu+La–Yb (up to 24.11 wt% REE2O3, 0.596 apfu REE) creates thin rims around spinel and magnetite grains, whereas zirconolite enriched in U and Th (up to 18.88 wt% ThO2 + UO2, 0.293 apfu Th + U) replace the Late Ediacaran (~ 590 Ma) zircon and baddeleyite along contacts with pyrrhotite and magnetite. Both types of zirconolite contain locally increased Nb and Ta concentrations (up to 7.58 wt% Nb2O5 + Ta2O5, 0.202 apfu Nb + Ta). Other types of zirconolite from Evate are dominated by the common CaZrTi2O7 end member, but the aforementioned “synthetic” REEZrTiFe3+O7 accompanied by another ‘synthetic’ (U,Th) ZrFe3 + 2O7 component are also abundant. The nonradiogenic Pb-corrected age of the early zirconolite corresponded to 485 ± 9 Ma, within uncertainty limit identical with the 493 ± 10 Ma age of the associated uranothorianite. The variegated chemical composition of zirconolites reflects the complex history of the Evate deposit. Compositional and substitution trends of the REE-zirconolite overlaps that genetically linked with carbonatites, syenites and mafic igneous rocks, whereas the U,Th-zirconolite is reminiscent of hydrothermal-metasomatic deposits. The predominance of trivalent iron in zirconolite most likely reflects strongly oxidizing parental fluids that percolated during episodic Late Ordovician to Late Cambrian rifting of Gondwana. |