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Geoscience ›› 2022, Vol. 36 ›› Issue (03): 824-835.DOI: 10.19657/j.geoscience.1000-8527.2022.013

• Petrology • Previous Articles     Next Articles

Ancient Crust Remelting in Wenquan Area, Xinjiang: Evidence from the Age and Sr-Nd Isotopes of the Late Carboniferous Granite Porphyry Dykes

YANG Hanwen1,2(), WANG Jianzhong3,4(), ZHAO Jun4,5, DUAN Jun3, WANG Rongmin6, GAO Wenbin3, WEI Wenhao1, ZHENG Yanhe1   

  1. 1. Xi’an Center of Mineral Resources Survey, China Geological Survey, Xi’an, Shaanxi 710100, China
    2. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
    3. College of Earth Science and Land Resources, Chang’an University, Xi’an, Shaanxi 710054, China
    4. Northwest University of Political Science and Law, Xi’an, Shaanxi 710122, China
    5. Urumqi Center of Mineral Resources Survey, China Geological Survey, Urumqi, Xinjiang 830057, China
    6. Oilfield Business Development of Changqing Oilfield Branch, Xi’an, Shaanxi 710018, China
  • Received:2021-01-17 Revised:2022-04-30 Online:2022-06-10 Published:2022-07-19
  • Contact: WANG Jianzhong

Abstract:

Dyke swarms with complex lithology are distributed on the southern margin of the Alataw Mountains (some closely ore-related), providing a good window to understand the crustal growth process. Numerous intermediate-felsic dykes are exposed in the western section, which intruded the Upper Devonian Tuskuertau Formation. These dykes are dominated by diorite with minor granite porphyry and felsite. We carried out zircon U-Pb age and Sr-Nd dating on the granite porphyry dyke to reveal its formation age, magma source and tectonic setting. The zircon U-Pb dating yielded weighted average age of 310 Ma, indicating that the granite porphyry dykes were formed in the early Late Carboniferous. This age is very close to the eruption age (310 Ma) of the Shawan intraplate rhyolite formed under an extensional environment and the formation age of the Chahawusu batholith (313 Ma), which is the product of the latest magmatism in the western Alataw Mountains. The Sr-Nd isotopic compositions indicate that the dykes are featured by medium ISr (0.709,328-0.710,018) and negative εNd(t) (-3.92 to -2.33) values and older Nd model age (1,294-1,502 Ma), which are obviously different from those of coeval granitoids in the western Tianshan and northern Xinjiang. The latter has generally low ISr and highly positive εNd(t) values and younger Nd isotope model ages, and were likely derived from the mantle, and underwent magma underplating and ACF or magma mixing processes. After 310 Ma, the Alataw Mountains gradually entered a post-collision extension stage, which was in a vertical growth of continental crust. We conclude that the granite porphyry dykes were unlikely to be formed by mantle-derived magma underplating and evolution, and the magma source is the Precambrian basement rock with relatively high maturity. The dykes may have formed in a post-collision extensional setting.

Key words: granite porphyry, emplacement age, isotope composition, basement rock, Wenquan area

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