Combined petrography, noble gas, stable isotope and fluid inclusion chemistry of carbonatites from Uganda: Implications for the origin of the carbonatite melt in continental rift setting

Benkó, Zsolt; Molnár, Kinga; Magna, Tomáš; Rapprich, Vladislav; Palcsu, László; Pour, Ondřej; Čejková, Bohuslava; Futó, István; Czuppon, György

doi:10.1016/j.chemgeo.2021.120213

Cited by 7 publications

(13 citation statements)

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“…In the Sukulu carbonatites, the main silicate phase is phlogopite, but sample AC01C previously studied by Benkó et al (2021) also contains abundant (~7 vol. %) olivine phenocrysts (ESM 1; Fig.…”

Section: Sukulu and Tororo Carbonatite And Carbonatitic Pyroxenitementioning

confidence: 99%

Section: Sukulu and Tororo Carbonatitesmentioning

confidence: 99%

“…The Sukulu carbonatite (~24-26 Ma; Davies 1965;Bloomfield 1973) is represented by predominant calcite-dolomite carbonatite containing variable amounts of silicate minerals (olivine, phlogopite), magnetite, and apatite (Benkó et al 2021). In contrast, the Tororo calcite carbonatite (~16-32 Ma; Bell and Blenkinsop 1987) is characterized by the presence of clinopyroxene (aegirineaugite) and K-feldspar as the principal silicate mineral phases (Benkó et al 2021). Available Sr-Nd and noble gas (He-Ne) isotopic data suggest that the source of parental melts for both carbonatite bodies was a mixture of depleted and only slightly enriched mantle reservoirs (Bell and Blenkinsop 1987;Benkó et al 2021).…”

Section: Sukulu and Tororo Carbonatitesmentioning

confidence: 99%

“…In contrast, the Tororo calcite carbonatite (~16-32 Ma; Bell and Blenkinsop 1987) is characterized by the presence of clinopyroxene (aegirineaugite) and K-feldspar as the principal silicate mineral phases (Benkó et al 2021). Available Sr-Nd and noble gas (He-Ne) isotopic data suggest that the source of parental melts for both carbonatite bodies was a mixture of depleted and only slightly enriched mantle reservoirs (Bell and Blenkinsop 1987;Benkó et al 2021). Detailed fluid inclusion studies on both complexes (Benkó et al 2021) revealed the importance of late-stage hydrothermal circulation and common hydrothermal overprint of primary mineral phases.…”

Section: Sukulu and Tororo Carbonatitesmentioning

confidence: 99%

“…Available Sr-Nd and noble gas (He-Ne) isotopic data suggest that the source of parental melts for both carbonatite bodies was a mixture of depleted and only slightly enriched mantle reservoirs (Bell and Blenkinsop 1987;Benkó et al 2021). Detailed fluid inclusion studies on both complexes (Benkó et al 2021) revealed the importance of late-stage hydrothermal circulation and common hydrothermal overprint of primary mineral phases.…”

Section: Sukulu and Tororo Carbonatitesmentioning

confidence: 99%

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Petrogenesis of silica-rich carbonatites from continental rift settings: a missing link between carbonatites and carbonated silicate melts?

Ackerman¹,

Rapprich²,

Polák³

et al. 2021

J. Geosci.

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Four carbonatite bodies (Sukulu and Tororo -Uganda, Lemitar Mts. and Iron Hill -USA) from two intracontinental rift systems containing a prominent silicocarbonatite-carbonatite association were studied in detail in terms of petrography, major-/trace-element chemistry, and Sr-Nd-C-O isotope systematics to provide constraints on their petrogenesis and mutual relationship. The Sukulu and Tororo carbonatites (< 30 Ma) within the East African Rift System are characterized by the wide range of SiO 2 contents and presence of phlogopite ± olivine and aegirine-augite + K-feldspar, respectively. These different mineral parageneses correspond to the Mg-K-rich nature of the former and Na-Fe-K-rich composition of the latter. Overall, these signatures can be best explained by progressive fractionation of parental carbonated silicate melts and liquid immiscibility documented by the chemical variation of clinopyroxene and the presence of silicate-carbonate pockets. However, at Tororo, this process was likely accompanied by assimilation of local crustal lithologies to account for its different Sr-Nd isotopic signatures and Na-rich nature of carbonatites. Despite their spatial and temporal difference, the Lemitar Mts. and Iron Hill from the Cambro-Ordovician North American Rift resemble similar petrography and mineralogy as Sukulu and Tororo bodies, expressed by the presence of phlogopite and clinopyroxene + K-feldspar. We present a general model explaining the origin of silicocarbonatite-carbonatite association involving segregation of silicate and carbonate melts from parental carbonated silicate melts through a process of liquid immiscibility. Subsequent distinct evolutionary paths are related to differences in Si-Na-K-Fe-Mg and H 2 O-F contents, oxygen fugacity, and melt ascent efficiency, perhaps related to crustal assimilation. Therefore, we emphasize that relatively silica-rich carbonatites represent a crucial linkage between silicate and carbonate melts.

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Section: Sukulu and Tororo Carbonatite And Carbonatitic Pyroxenitementioning

confidence: 99%