Инд. авторы:	Glorie S., Zhimulev F.I., Buslov M.M., Andersen T., Plavsa D., Izmer A., Vanhaecke F., De Grave J.
Заглавие:	Formation of the Kokchetav subduction-collision zone (northern Kazakhstan): Insights from zircon U-Pb and Lu-Hf isotope systematics
Библ. ссылка:	Glorie S., Zhimulev F.I., Buslov M.M., Andersen T., Plavsa D., Izmer A., Vanhaecke F., De Grave J. Formation of the Kokchetav subduction-collision zone (northern Kazakhstan): Insights from zircon U-Pb and Lu-Hf isotope systematics // Gondwana Research. - 2015. - Vol.27. - Iss. 1. - P.424-438. - ISSN 1342-937X. - EISSN 1878-0571.
Внешние системы:	DOI: 10.1016/j.gr.2013.10.012; SCOPUS: 2-s2.0-84911983361; WoS: 000345805800021;
Реферат:	eng: 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) are indicative of a metamorphic origin for both Early Cambrian and Late Cambrian - Early Ordovician zircon populations. The oscillatory zoned Mesoproterozoic zircons have higher 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. © 2013 International Association for Gondwana Research.
Ключевые слова:	Lu-Hf isotopes; Kazakhstan; Central Asian Orogenic Belt; Kokchetav subduction-collision zone; Zircon U-Pb geochronology;
Издано:	2015
Физ. характеристика:	с.424-438