Intra-continental back-arc basin inversion and Late Carboniferous magmatism in Eastern Tianshan, NW China: Constraints from the Shaquanzi magmatic suite

Geoscience Frontiers

卷:8

Yi Zheng¹  Hongjun Jiang²  Huayong Chen²  Wanjian Lu²  Jinsheng Han²  Zhixiong Tan³  Gang Deng³ 

[1] Department of Earth Sciences, Sun Yat-sen University, Guangzhou 510472, China;

[2] Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;

[3] No. 6 Geological Party, Xinjiang Bureau of Geology and Mineral Exploration, Hami 839000, China;

关键词: Shaquanzi igneous rocks;    Geochronology;    Geochemistry;    Intra-continental back-arc basin;    Yamansu belt;    Eastern Tianshan Mountains;   

DOI  :  10.1016/j.gsf.2017.01.008

来源: DOAJ

【 摘 要 】

The Yamansu belt, an important tectonic component of Eastern Tianshan Mountains, of the Central Asian Orogenic Belt, NW China hosts many Fe–(Cu) deposit. In this study, we present new zircon U-Pb geochronology and geochemical data of the volcanic rocks of Shaquanzi Formation and diorite intrusions in the Yamansu belt. The Shaquanzi Formation comprises mainly basalt, andesite/andesitic tuff, rhyolite and sub-volcanic diabase with local diorite intrusions. The volcanic rocks and diorites contain ca. 315–305 Ma and ca. 298 Ma zircons respectively. These rocks show calc-alkaline affinity with enrichment in large-ion lithophile elements (LILEs), light rare-earth elements (LREEs), and depletion in high field strength elements (HFSEs) in primitive mantle normalized multi-element diagrams, which resemble typical back-arc basin rocks. They show depleted mantle signature with εNd(t) ranging from +3.1 to +5.6 for basalt; +2.1 to +4.7 for andesite; −0.2 to +1.5 for rhyolite and the εHf(t) ranges from −0.1 to +13.0 for andesites; +5.8 to +10.7 for andesitic tuffs. We suggest that the Shaquanzi Formation basalt might have originated from a depleted, metasomatized lithospheric mantle source mixed with minor (3–5%) subduction-derived materials, whereas the andesite and rhyolite could be fractional crystallization products of the basaltic magma. The Shaquanzi Formation volcanic rocks could have formed in an intra-continental back-arc basin setting, probably via the southward subduction of the Kangguer Ocean beneath the Middle Tianshan Massif. The Yamansu mineralization belt might have undergone a continental arc to back-arc basin transition during the Late Carboniferous and the intra-continental back-arc basin might have closed in the Early Permian, marked by the emplacement of dioritic magma in the Shaquanzi belt.

【 授权许可】

Unknown