Abstract
AbstractCarbonatites are rare but worldwide occurring igneous rocks and their genesis remains enigmatic. Field studies show a close spatial but controversially debated genetic relationship with alkaline silicate rocks, and petrological and experimental studies indicate liquid immiscibility from mantle-derived magmas being one viable model for the generation of carbonatites. However, unaltered carbonatitic melts are rare and the composition of primary carbonate liquids and their silicate conjugates is poorly constrained. Here we show an example of primary Ca-carbonatitic melt formed by liquid immiscibility from a phonolitic magma of the Laacher See volcano (Eifel, Germany). The conjugate blebs of carbonate-silicate liquids are found in hauyne-hosted melt inclusions. The Ca-carbonatite melts are moderately alkali-rich and contain high F and Cl at elevated SiO2 and Al2O3 concentrations. Such carbonatite liquids are viable parental magmas to the globally dominating intrusive Ca-carbonatite complexes and may provide the missing link to extrusive Na-carbonatitic magmas.
Publisher
Springer Science and Business Media LLC
Subject
General Physics and Astronomy,General Biochemistry, Genetics and Molecular Biology,General Chemistry,Multidisciplinary
Reference70 articles.
1. Le Maitre, R. et al. (eds). Igneous Rocks: A Classification and Glossary of Terms: Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks 2nd edn (Cambridge University Press, 2002).
2. Woolley, A. R. & Kjarsgaard, B. A. Paragenetic types of carbonatites as indicated by the diversity and relative abundances of associated silicate rocks: evidence from a global database. Can. Mineral. 46, 741–752 (2008).
3. Bell, K. Radiogenic isotope constraints on relationships between carbonatites and associated silicate rocks—a brief review. J. Petrol. 39, 1987–1996 (1998).
4. Gittins, J. & Harmer, R. E. Myth and reality in the carbonate - silicate rock ‘association’. Period. Mineral. 72, 19–26 (2003).
5. Mitchell, R. H. Carbonatites and carbonatites and carbonatites. Can. Mineral. 43, 2049–2068 (2005).