Chun-Kit Lai

Tethysian Metallogenesis of the Major Metalliferous Minerals in Mainland SE Asia and Sanjiang Region in SW China: Implications for Exploration

and its adjacent mainland SE Asia comprises a complex collage of microcontinents including the Indochina, Sibumasu and West Myanmar Terranes(Zhong,1998; Metcalfe,2002). Within these microcontinents,there are a number of suture zones that represent the remnants of the three Tethyan Oceans (Paleo–Tethys, Meso–Tethys and Ceno–Tethys) and their branches or oceanic backarc basins that once existed in this region(Li et al.,2004; Metcalfe,2013).

Age and geochemistry of the Carboniferous-Permian magmatism and Fe-Ti-V oxide metallogeny in the Eastern Tianshan Orogen, NW China: evidence from the Yaxi mafic-ultramafic complex

ABSTRACT The Eastern Tianshan Orogen (Xinjiang, NW China) in the Central Asian Orogenic Belt (CAOB) is featured by its many Carboniferous-Triassic mafic-ultramafic intrusions and associated magmatic Fe-Ti-V oxide mineralization. In this study, we present the first systematic data comparison on the age and whole-rock geochemistry of the ore-forming mafic-ultramafic complexes at Yaxi, Niumaoquan, Xiangshanxi, and Weiya. Our new age dating on the Yaxi complex indicates that the mineralized gabbro (zircon SHRIMP U-Pb dated 297.3 ± 4.9 Ma) formed in the latest Carboniferous-Early Permian, similar to the diorite (LA-ICP-MS zircon U-Pb dated 308.3 ± 8.6 Ma) and granodiorite (LA-ICP-MS zircon U-Pb dated 304.9 ± 1.7 Ma). The Yaxi complex is the oldest late Palaeozoic mafic-ultramafic intrusion reported so far in the Eastern Tianshan. The mineralized gabbro at Yaxi contains higher average Fe2O3T (20.83 wt.%), TiO2 (5.91 wt.%), and V (523 ppm) contents than its ore-barren counterpart (7.45 wt.%, 0.99 wt.%, and 133 ppm, respectively). These Eastern Tianshan mafic rocks are mildly large ion lithophile element (LILE) enriched and high field-strength element (HFSE) depleted, and with LREE/HREE enrichment (Yaxi: (La/Yb)N = 2.7 ~ 5.37) and subtle positive Eu anomalies (Yaxi: Eu/Eu* = 0.94 to 3.31). This suggests that the Eastern Tianshan mafic-ultramafic magmas were likely derived from an arc/subduction-modified magma source. The E-W trending crustal-scale faults (e.g. the Aqikkuduk fault) may have acted as magma conduits and controlled the magma emplacement. The spatial-temporal distribution of the Eastern Tianshan Fe-Ti-V ore-forming mafic-ultramafic complexes and their petrologic and geochemical features suggest that the latest Carboniferous-Early Permian magmatic phase was likely emplaced in a collision-related compression setting following the Junggar Ocean closure, whereas the late Early Permian phase may have been related to a post-collisional orogenic setting. Graphical Abstract