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| Titel |
Petrogenesis and tectonic implications of the Late Paleozoic igneous rocks from the Alataw area of North Yili Block, NW China |
| VerfasserIn |
Xiangsong Wang, Keda Cai, Min Sun, Wenjiao Xiao, Xiaoping Xia, Bo Wan, Zihe Bao, Yannan Wang |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250153563
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| Publikation (Nr.) |
 EGU/EGU2017-18561.pdf |
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| Zusammenfassung |
| Late Carboniferous to Early Permian is a critical period for the final amalgamation and tectonic evolution of the Central Asian Orogenic Belt (CAOB). However, the amalgamation time and processes have been a matter of debated. In order to reconstruct the termination processes of the subduction of the Junggar oceanic plate in the Chinese western Tianshan, a suite of magmatic rocks including tuff, rhyolite and granite from the North Yili Block are studied systematically. Our secondary ion mass spectrometry (SIMS) zircon U-Pb dating of the tuff, rhyolite and biotite granite showed that they were formed at 300.4±2.6 Ma, 298.6-302.6 Ma, and 287.5±1.2 Ma, respectively. Geochemically, the tuffs have relatively low SiO2 (65.8-71.5 wt.%) and Mg# (5.9-12.6) values, and exhibit arc affinity with significantly enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE) such as Nb, Ta and Ti. The whole-rock εNd(t) and zircon εHf(t) values range from +6.9 to +7.0 and +9.86 to +14.07 respectively, indicative of a juvenile basaltic lower crustal origin. In contrast, the rhyolites have higher SiO2 (72.7-74.0 wt.%) and K2O (3.86-4.53 wt.%) contents, high zircon δ18O (11.67-13.23 ‰) values and low whole-rock εNd(t) (+2.9 to +3.8) and zircon εHf(t) (+2.78 to +9.97) values, which show a significant involvement of sediments. The biotite granites have the highest SiO2 (74.7-75.5 wt.%) contents and high whole-rock εNd(t) (+7.7 to +8.8), zircon εHf(t) (+9.81 to +12.71) and low zircon δ18O (5.99-6.84 ‰) values suggest a juvenile basaltic lower crustal source. Moreover, the high zircon saturation temperatures (815-938℃) of the tuffs and rhyolites demonstrate a possible genetic link with a break-off tectonic scenario. On the contrast, the very low zircon saturation temperatures (723-735℃) of the biotite granites may suggest a hydrous partial melting of juvenile lower crust, whist the abundant water-fluxes might have been introduced by the later stage of large strike-slip shearing along the North Tianshan Fault. Therefore, the magmatic rocks from the North Yili Block are suggested to be a magmatic probe for tectonic switch during the termination of accretionary orogenesis, which may be related to the evolution of the Kazakhstan Orocline. |
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