| Autor: |
Stijn Glorie, Andrei Izmer, Frank Vanhaecke, Tom Andersen, F.I. Zhimulev, J. De Grave, Mikhail Buslov, Diana Plavsa |
| Přispěvatelé: |
Glorie, S, Zhimulev, FI, Buslov, MM, Andersen, T, Plavsa, Diana, Izmer, A, Vanhaecke, F, De Grave, J |
| Rok vydání: |
2015 |
| Předmět: |
|
| Zdroj: |
Gondwana Research. 27:424-438 |
| ISSN: |
1342-937X |
| DOI: |
10.1016/j.gr.2013.10.012 |
| Popis: |
The Kokchetav subduction-collision zone is located in the western part of the ancestral Central Asian Orogenic Belt. This zone is built up by the Precambrian Kokchetav microcontinent which includes a HP-UHP metamorphic belt, and the North Kokchetav tectonic zone (NKTZ) which represents an accretionary complex between the Kokchetav microcontinent and the adjacent Stepnyak island-arc. The entire region is widely intruded by Palaeozoic granitoids which were emplaced after the collision of the Stepnyak island-arc with the Kokchetav microcontinent. We present zircon U-Pb ages and Lu-Hf systematics in zircon to better characterize the tectonic evolution of the Kokchetav subduction-collision zone.The Lu-Hf results indicate that the Kokchetav basement rocks are derived from late Neoarchaean - early Palaeoproterozoic (~. 2.5. Ga) crust. For the granite-gneiss basement of the Kokchetav microcontinent, early Mesoproterozoic (Grenville-age, ~. 1.17-1.14. Ga) zircon U-Pb crystallization ages were obtained. For the NKTZ, two main age-components were recognized: (1) an oldest Mesoproterozoic age-component (~. 1.20-1.05. Ga) similar as for the Kokchetav microcontinental zircons, and (2) a younger Early Cambrian (540-520. Ma) or Late Cambrian - Early Ordovician (~. 490-480. Ma) age-component. Th/U ratios (. 0.1) and are typical of a magmatic protolith. The distinction between both zircon types is supported by characteristic cathodoluminescence images. These results confirm previous observations, indicating early Palaeozoic high-grade metamorphism (~. 540-520. Ma) and collisional deformation (~. 490-480. Ma) of the Mesoproterozoic Kokchetav zone as a result of subduction-accretion and collision of the Stepnyak island-arc to the Kokchetav microcontinent. For two additional samples of the Balkashin granitic complex Early Devonian (~. 415-395. Ma) zircon crystallization ages (magmatic Th/U ratios) were obtained. The occurrence of a Mesozoic xenocryst within these leucogranites may indicate that they were emplaced in a continental-arc setting. Refereed/Peer-reviewed |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect