ProjectKruidfontein – The weakly eroded Kruidfontein phonolite-carbonatite volcano - a proxy sound into the interior of…
Basic data
Acronym:
Kruidfontein
Title:
The weakly eroded Kruidfontein phonolite-carbonatite volcano - a proxy sound into the interior of the Laacher See volcano
Duration:
14/11/2024 to 14/11/2025
Abstract / short description:
Carbonatites are relatively rare rocks (~610 occurrences world-wide). About 80 % of all carbonatite occurrences are spatially associated with diverse silicate rocks, whereby the genetic relationship between carbonatites and these silicate rocks is debated with different models. Only a minor proportion of carbonatites (50 occurrences) are extrusive; the associated silicate rocks are mostly nephelinites and phonolites, whereby phonolitic melts are assumed to be evolved from parental nephelinitic melts. However, their specific genetic relation to carbonatites is not clear. A good example for this controversity is the Quaternary Laacher See phonolitic volcano, which is part of the Eastern Eifel (Germany). Carbonatites at Laacher See are only known from xenoliths, which indicate a phonolite-carbonatite association at depth. In general, only surface pyroclastic deposits are exposed, while the feeding system, which may show a direct relationship between carbonatites and phonolites remain unexposed. A better understanding of the holistic structure of Laacher See (as a representative for carbonatite-phonolite complexes) would require a comparison with similar but shallow intrusions and feeding systems that are only slightly eroded to deeper intrusion levels. An ideal candidate for such a comparative study represents the so far poorly studied Kruidfontein Proterozoic phonolite–carbonatite volcano (South Africa).
This project will investigate the Kruidfontein carbonatite-phonolite complex, which preserves surface pyroclastic phonolitic facies that are penetrated by later phonolitic and carbonatitic intrusions at a subsurface level. The carbonatites at Kruidfontain, furthermore, reflect a highly evolved composition represented by fluorite-rich calcite carbonatites and pure fluorite veins. Our study will focus on (1) the eruption mechanism of the Kruidfontein volcano in comparison to the Laacher See volcano, (2) the age determination of Kruidfontein and its temporal assignment into regional magmatic events, and (3) the origin and role of fluorine in the carbonatites. For this purpose, the different lithologies of the Kruidfontein complex will be investigated by means of petrography (microscopy, µXRF, SEM), whole rock analyses (XRF, ICP-MS, CSA), mineral chemistry (EMPA), stable and radiogenic isotopy (IRMS, ICP-MS), and detailed fluid inclusion studies (micro-thermometry, Micro-Raman spectroscopy). Results will be compared with the information available from the Laacher See volcano, which will allow a better understanding of phonolite-carbonatite associations in general.
This project will investigate the Kruidfontein carbonatite-phonolite complex, which preserves surface pyroclastic phonolitic facies that are penetrated by later phonolitic and carbonatitic intrusions at a subsurface level. The carbonatites at Kruidfontain, furthermore, reflect a highly evolved composition represented by fluorite-rich calcite carbonatites and pure fluorite veins. Our study will focus on (1) the eruption mechanism of the Kruidfontein volcano in comparison to the Laacher See volcano, (2) the age determination of Kruidfontein and its temporal assignment into regional magmatic events, and (3) the origin and role of fluorine in the carbonatites. For this purpose, the different lithologies of the Kruidfontein complex will be investigated by means of petrography (microscopy, µXRF, SEM), whole rock analyses (XRF, ICP-MS, CSA), mineral chemistry (EMPA), stable and radiogenic isotopy (IRMS, ICP-MS), and detailed fluid inclusion studies (micro-thermometry, Micro-Raman spectroscopy). Results will be compared with the information available from the Laacher See volcano, which will allow a better understanding of phonolite-carbonatite associations in general.
Keywords:
Extrusive carbonatites
strato-volcano
alkaline silicate rock – carbonatite association
fluid inclusion geochemistry
fluorite deposit
Involved staff
Managers
Mineralogy and Geodynamics Research Area
Department of Geoscience, Faculty of Science
Department of Geoscience, Faculty of Science
Contact persons
Faculty of Science
University of Tübingen
University of Tübingen
Mineralogy and Geodynamics Research Area
Department of Geoscience, Faculty of Science
Department of Geoscience, Faculty of Science
Mineralogy and Geodynamics Research Area
Department of Geoscience, Faculty of Science
Department of Geoscience, Faculty of Science
Local organizational units
Department of Geoscience
Faculty of Science
University of Tübingen
University of Tübingen
Funders
Bonn, Nordrhein-Westfalen, Germany
Cooperations
Prag, Czechia