Paquette J. L., Le Pennec Jean-Luc. (2012). 3.8 Ga zircons sampled by Neogene ignimbrite eruptions in Central Anatolia. Geology, 40 (3), p. 239-242. ISSN 0091-7613.
Titre du document
3.8 Ga zircons sampled by Neogene ignimbrite eruptions in Central Anatolia
Dating the oldest terrestrial rocks and minerals allows constraining the age and formation conditions of the ancient basement of our present-day continents. The oldest terranes, with ages ranging from 3.8 Ga to 4.0 Ga, have been identified in Canada, while Australian zircon crystals dated at 4.4 Ga represent the oldest dated minerals on Earth. The exceptional resistance of zircon grains to repeated geological cycles has allowed dating 3.3-3.9 Ga crystals in several Archean cratons worldwide. Identifying new, scarce but essential witnesses to this primitive Earth is still a challenging goal. Ignimbrites are silicic pyroclastic deposits produced by large-scale explosive eruptions. During magma residence and ascent, basement enclaves may be scavenged and mixed with the rhyolitic magma. Here we show that an ignimbrite eruption from Central Anatolia (Turkey) dated at 5.4 Ma has sampled Proterozoic and Archean zircons ranging from 2.3 Ga to 3.8 Ga in age. This is the first documented occurrence of Early Archean zircon crystals sampled by a recent volcanic event. These Central Anatolian zircon grains are among the oldest discovered on Earth and imply the presence at depth of remnants of an Early Archean basement that was hitherto unknown in Eurasia.
