Late Carboniferous adakitic porphyries in the Huangliangzi pluton, West Junggar (Xinjiang), NW China: Petrogenesis and their tectonic implications

Abstract

Late Carboniferous to Early Permian granitic rocks are widely distributed in the Western Junggar (Xinjiang, NW China), but their petrogenesis and tectonic contexts remain controversial. In this paper, we present new zircon U–Pb age, major element, trace element data for the Huangliangzi pluton from the southern West Junggar. The pluton mainly consists of granodiorite porphyry, biotite monzonitic granite porphyry, and quartz monzonite diorite porphyry. Laser‐ablation inductively‐coupled mass‐spectrometry (LA‐ICP‐MS) zircon U–Pb obtained the age of 321.7 ± 1.3 Ma, indicating the granodiorite porphyry was emplaced in the early Late Carboniferous, coeval with abundant magmatic rocks in the region. Geochemically, these rocks are moderately peraluminous high‐K calc‐alkalic and characterized by relatively high SiO2 (64.31–66.69 wt.%), Al2O3 (15.82–16.73 wt.%), and Sr (379–489 ppm) contents and low MgO (1.08–2.46 wt.%; Mg# = 39–55), Y (7.61–9.64 ppm), and Yb (0.95–1.23 ppm) contents, along with positive Eu anomalies (Eu/Eu* = 1.01–1.34) and high Sr/Y (47.7–57.1) ratios. These are compositional features of adakites that are commonly assumed to have been produced through partial melting of subducted oceanic crust. In addition, the adakitic rocks are relatively enriched in light rare‐earth elements (LREEs), large ion lithophile elements (LILEs: e.g., Rb, Ba, Sr, and K), and depleted in high‐field‐strength elements (HFSEs: e.g., Nb, Ta, and Ti) and are also characterized by high εNd(t) value and low initial (87Sr/86Sr)i ratio. The most plausible mechanism for the Huangliangzi adakitic porphyries is the partial melting of subducted oceanic crust interacting with a mantle wedge. Combined with the geological setting and previous studies, therefore, we suggest that the southern West Junggar was in a subduction‐dominated island‐arc setting in the early Late Carboniferous, and multistage subduction–accretionary orogeny may be the main mechanism for the difference between the north and the south subduction duration in the Western Junggar.

Granite Extraction Based on the SDGSAT-1 Satellite Thermal Infrared Spectrometer Imagery

“…The Hongshan and Karamay plutons were formed at about 330 Ma, characterized as quartz–alkali feldspar granites with high quartz and orthoclase content. In contrast, the Xiaerpu pluton was formed at about 298 Ma, representing a diorite–monzonite granite with a significant presence of ferromagnesian minerals [ 32 , 33 , 34 , 35 ]. The abundance of iron–magnesium minerals causes a relatively weak response in SDGSAT-1 TIS, leading to partial omission errors due to the low sensitivity of the sensor in the direction of longer wavelengths [ 22 ].…”

Tianshan Orogen along the Silk Road (Volume 3): Orogen links, geochemistry, geochronology, mineral deposits, and environments

“…These enclaves are formed of a mixture of mantle‐derived mafic magma and crust‐derived felsic mantle. The paper by Duan, Li, Yang et al ( ) describes the petrogenesis of Late Carboniferous adakitic porphyries in the Huangliangzi pluton of West Junggar. These porphyries were derived from partial melting of subducted oceanic crust interacting with a mantle wedge in an island arc setting.…”

Geochemical, Sr–Nd–Pb and zircon U–Pb–Hf isotopic constraints on the Late Carboniferous back-arc basin basalts from the Chengjisihanshan Formation in West Junggar, NW China

“…In the early to middle stage of Late Carboniferous time, as consumption of the Junggar oceanic lithosphere proceeded, subductionrelated intermediate-acid intrusive rocks were widely distributed in southern West Junggar, such as c. 322-312 Ma slab-derived adakitic rocks exposed in the Baogutu, Dulunhe and Huangliangzi regions (Zhang et al 2006;Shen et al 2009Shen et al , 2012Tang et al 2010;Duan et al 2015Duan et al , 2018b, and contemporaneous sanukitic dykes from the Bieluagaxi and Karamay regions (c. 321-315 Ma;Yin et al 2010;Duan et al 2019), as well as calc-alkaline I-type granitic stocks distributed on both sides of the Darbut Fault (c. 319-310 Ma; e.g. Tang et al 2012;Duan et al 2018a).…”