A Carbonatite Complex on the Aegean Island of Anafi?

On Thursday, the 31 August 2000, the applicant of this proposal (E. HEJL) has discovered a carbonatitic dyke in the southwestern part of the Aegean island of Anafi. Subsequent field inves-tigations during September 2001 have revealed huge quantities of carbonatite rocks on that island, which most probably are of igneous origin. Up to 4 km2 of Anafi seem to be occupied by several types of carbonatite, including sövite, rauhaugite and silicocarbonatites. Anafi could be one of the biggest carbonatite occurrences of Europe (in area and volume) and probably belongs to the 50 largest carbonatite occurrences of the world. At the present state of investigation, the igneous nature of the carbonate rocks is supported by intrusive outcrop situations, by typical magmatic breccias and/or agglomerates, by the presence of unalterated plutonic xenoliths and by magmatic textures and structures at the thin-section scale. The submitted research program could help to elucidate the following questions: 1. What is the true extent of the carbonatites ? How can they be distinguished and delimited from marbles in ambiguous cases ? 2. Is there any petrogenetical relationship between the carbonatites and the associated silicate intrusive rocks ? If yes, can we find arguments for consanguinity ? 3. Which chronology of magmatism can be established by field observations and by geochronological dating ? 4. From which depth and from which source rocks have the melts and xenoliths been derived ? 5. How does the carbonatite complex of Anafi fit into the orogenic development of the Hellenides ? The planed investigations include field work and interpretation of satellite images, microscopic observation of thin sections, geochemical analysis by x-ray fluorescence and by electron microprobe, Ar-Ar dating of micas and mass spectrometry of Sr isotopes. A whole post-doc postion for one year (Dr. Jaromir LEICHMANN) would be very usefull for sample preparation and chemical analysis.

In course of this project, a first evidence of young volcanism was found on the Aegean island of Anafi. This island is situated 20 km to the east of the island of Thera, which belongs to the volcanic archipelago of Santorini. In contrast to Santorini`s violent volcanism in pre-historical and historical times, the island of Anafi was supposed to be not a volcanic centre, despite of the fact that it is situated along the South Aegean active volcanic arc. Anafi`s volcanism comprises magmatic intrusions (rhyolithes) along tectonic fissures, and tuff beds in young sediments. Volcanic activity was triggered by tectonic extension and deep circulation of meteoric waters. The eruptions were accompanied with phreatic explosions. Tectonic compression terminated the volcanic activity and prevented the formation of a larger volcano. Aboundant water supply during the volcanic period gave rise to a strong hydrothermal alteration of the volcanites and their country rocks. These alterations produced deposits of ochre and red chalk, that have been mined in ancient times. These natural pigments display close chemical and mineralogical similarities to those of some Bronze Age wall paintings of Thera. Most probably, Theran paintings were produced with pigments from Anafi.