EOARCHEAN TO PALEOPROTEROZOIC CRUST HISTORY IN THE YAKUTIAN DIAMOND PROVINCE: EVIDENCE FROM U-Th-Pb (LA-ICP-MS) AND Lu-Hf DATING OF ZIRCONS FROM CRUSTAL XENOLITHS IN KIMBERLITE PIPES
V.S. Shatsky1,2,3, A.L. Ragozin1,2, Q. Wang4
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3Vinogradov Institute of Geochemistry, Siberian Branch Russian Academy of Sciences, Irkutsk, Russia
4School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
Keywords: Lower crust, kimberlite, U-Th-Pb dating of zircons, Hf isotopes, protolith age, conditions of metamorphism, tectonothermal events
Abstract
Radiometric dating of zircon grains from crustal xenoliths in kimberlites of the Yakutian diamond province show that most of the Daldyn and Markha terranes were formed in Paleoarchean but preserve some fragments of Eaoachean and possibly even Hadean crust recycled in several tectonothermal events. The oldest zircons were crystallized about 3.2 Ga and recrystallized during later activity stages of 2.9, 2.8-2.7, and 1.9 Ga, whereby they gained radiogenic hafnium produced by 176Lu decay in the rock. The degrees crust rework and the tectonothermal stages varied across the Anabar tectonic province. The earliest events of 3.2 and 2.9 Ga left record in zircons from kimberlites in the Nakyn field, while the signatures of the 2.7 Ga activity are best pronounced in zircons from kimberlites sampled in the Upper Muna and Nakyn fields. On the other hand, zircons from lower crustal mafic granulite xenoliths in the Daldyn and Alakit-Markha kimberlites lack traces of the earliest crust history and only evidence of the last 1.9 Ga event, which remained mute in xenolith samples from the Upper Muna field. Zircons from felsic granulite and metadiorite xenoliths in the Udachnaya kimberlite, which represent middle and upper crust, show a peak at 2.6 Ga besides that of 1.9 Ga. The synthesized available data support several previous inferences: vertical and lateral heterogeneity of the crust in the Yakutian diamond province; absence of linkage between the crust recycling degree and major collisional zones of the Siberian craton; absence of the separate Markha terrane. Correlation of age peaks corresponding to thermal events in the crust history of the Anabar tectonic province with those of large igneous provinces allows a hypothesis that the revealed tectonothermal events may be related with the activity of superplumes.
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