期刊
GONDWANA RESEARCH
卷 71, 期 -, 页码 49-75出版社
ELSEVIER
DOI: 10.1016/j.gr.2019.01.013
关键词
West Junggar; Junggar Basin; Ridge subduction; Geochemistry
资金
- National Natural Science Foundation of China [41702138, 41702198]
- Fundamental Research Funds for the Central Universities [18CX02012A, 17CX02001A]
- Key Laboratory of Tectonics and Petroleum Resources [TPR-2016-08]
- Strategic Priority Research Program of the Chinese Academy of Sciences [XDA14010301]
- Shandong Provincial Natural Science Foundation, China [ZR2017BD008]
The northwestern margin of the Junggar Basin is a transition zone between the Zaire-Hala'alate mountains and the Junggar Basin in West Junggar, which developed a large amount of volcanic rocks in the late Carboniferous. An investigation of the tectonic evolution of this area will be helpful for understanding the accretionary process of West Junggar. Here, we selected well-preserved drill core samples of andesite and andesitic tuff for detailed petrogenesis and geochemical studies, while high-quality seismic and resistivity prospecting cross-sections were also used to reveal the tectonic setting. Zircon U-Pb dating results of three andesite and andesitic tuff samples show that these rocks were erupted at ca. 312 Ma. The results of the geochemical and isotopic analyses of seven samples are characterized by relatively high MgO (1.84-5.52 wt%), Cr (26.19-246.61 ppm), Ni (16.53-82.85 ppm) contents. Ba/La (14.19-218.48) ratios, and high positive epsilon Hf-(t) (+ 4.8 to + 14.2) values, but low TiO2 (0.68-1.25 wt%) contents, FeOT/MgO (1.18-2.81), Sr/Y (5.63-27.40), and Th/Yb (0.19-2.18) ratios, which are similar to the Bieluagaxi sanukitoids of West Junggar. LREEs are enriched in all samples, while Nb and Ta are significantly depleted. All the evidence suggests the volcanics were most likely derived from partial melting of oceanic slab that was contaminated by the overlying mantle wedge during the magma ascent. The seismic and resistivity cross-sections show apparent southeastward-vergent imbricate thrust fault systems, implying northwestward subduction in the late Carboniferous. Together with previous studies and our geochemical and geophysical data, we suggest that the formation of these late Carboniferous volcanic rocks is probably related to a northwestward ridge subduction process. (C) 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
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