Journal
PRECAMBRIAN RESEARCH
Volume 374, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.precamres.2022.106626
Keywords
Neoproterozoic; S-type granites; Mafic dikes; Tectonic transition; Yili Block; Central Asian Orogenic Belt
Categories
Funding
- National Key Research and Development Program of China [2017YFC0601202]
- State Key Laboratory of Geological Processes and Mineral Resources [GPMR202117]
- State Key Laboratory for Mineral Deposits Research [2021-LAMD-K09]
- Fundamental Research Funds for the Central Universities [2652019044]
- Natural Environment Research Council [NE/P017452/1]
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This study provides systematic investigations on the petrology, geochemistry, and geochronology of the Yili Block in the Central Asian Orogenic Belt. The results reveal the tectono-magmatic history of the region, which underwent continuous collisional orogenesis and subsequent intraplate extensional setting during the early Neoproterozoic. Comparison with adjacent micro-continents suggests a common geodynamic evolution during the Neoproterozoic.
Understanding the tectonic evolution of the many micro-continents in the Central Asian Orogenic Belt is a complex and controversial issue. One such micro-continent, the Yili Block is characterized by Neoproterozoic magmatic rocks, which can provide important constraints on the tectono-magmatic history of the region. Herein, we present a systematic investigation of the petrology, whole-rock geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes on newly identified leucogranite intrusions and gabbroic dikes in the Wenquan district of the northern Yili Block. Two leucogranite samples yielded zircon U-Pb ages of 983 +/- 9 Ma and 905 +/- 9 Ma, respectively. Both of muscovite-bearing leucogranites have S-type affinities and show distinctive geochemical compositions similar to peraluminous granites. Furthermore, the leucogranites exhibit low Rb/Sr ratios (0.10-0.49) and elevated zircon epsilon Hf-(t) values (+3.04 - +13.59), indicating that they were derived from partial melting of supracrustal pelitic and mafic rocks. In contrast, one gabbroic dike sample yielded a zircon U-Pb age of 779 +/- 5 Ma. The gabbroic samples have distinctly high Th/Yb (1.10-1.68) and low Nb/La (0.37-0.46) ratios, with enrichment in large ion lithophile elements and depletion in Nb, Ta and Ti, implying that they were sourced from a metasomatic subcontinental lithospheric mantle. Integrated with other available data, we propose that the Yili Block underwent continuously collisional orogenesis during the early Neoproterozoic (ca. 983-780 Ma), with a subsequent tectonic shift from collisional to an intraplate extensional setting at ca. 779-776 Ma. A comparable magmatic evolution also occurred in adjacent micro-continents of the Kazakhstan region and northern Tarim Craton, indicating that these micro-continents may have shared a common Neoproterozoic geodynamic evolution.
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