Geodynamic significance of the A-type granites in the Sawuer region in west Junggar, Xinjiang: Rock geochemistry and SHRIMP zircon age evidence

Abstract

Sawuer region is located in west Junggar, Jimunai County of Altay district and Hefeng County of Tacheng district, Xinjiang. The region is along the north margin of Kazakstan-Junggar plate. The intrusions (mainly acid) are widespread. Qiaqihai and Kuoyitasi intrusions are important in the region, with the characteristics of A-type granite. Further investigations indicate that they belong to A2-type granite that formed in extension tectonic setting of post collision. The REE chondrite-normalized patterns of the intrusions show LREE enrichment and the δ Eu values are lower. The Nd, Sr, Pb isotope compositions of the intrusions indicate a mantle source, while the low δ 18 O valuesresulted from the isotope exchange between intrusion and meteoric water. According to SHRIMP U-Pb age analysis results, the crystallization age of Qiaqihai intrusion is 290.7 ± 9.3 Ma (1σ ), and that of Kuoyitasi intrusion is 297.9 ± 4.6 Ma (1σ ), corresponding to the beginning of early Permian. The A2-type granites indicate that the region was in the extension period of the post-collisional stage at the beginning of early Permian in the Sawuer region. The A-type granites in the Sawuer region in west Junggar discovered from this work is analogous to the A-type granites found in east Junggar of the Ulungur alkali granites belt. The confirmation of post-collisional A-type granites of early Permian in the Sawuer region provides new evidence for the regional vertical continental crust growth in early Permian. The former proposed Ulungur alkali granites belt can extend from east Ulungur through west Ulungur and to Zhaisang in Kazakstan westwards.

Late Paleozoic paleogeographic reconstruction of Western Central Asia based upon paleomagnetic data and its geodynamic implications

“…Synthesis of geochronological data from magmatic Late Paleozoic rocks of West Junggar, after Kwon et al (1989), Jin and Shen (1993), Qi et al (1993), Shen et al (1993), Li et al (2004), Chen and Arakawa (2005), Han et al (2006), Su et al (2006), Zhou et al (2006), Song et al (2007), Wang and Zhu (2007), Zhou et al (2008), An and Zhu (2009), Geng et al (2009), Tang et al (2009) and Yin et al (2010. Table 4.…”

New 40Ar/39Ar age constraints on the Late Palaeozoic tectonic evolution of the western Tianshan (Xinjiang, northwestern China), with emphasis on Permian fluid ingress

“…Bimodal magmatic and volcanic rocks with an alkaline signature of mainly Permian age are widespread throughout the Chinese Tianshan (Allen et al 1993;Chen et al 2000;Hu et al 2000;Mao et al 2005;Gao et al 2006;Zhou et al 2006;Charvet et al 2007;Wang et al 2008a, this issue). The intrusive rocks are quartz diorite, quartz syenite, granodiorite, monzonite, and K-feldspar granite plutons, as well as abundant dykes (Mao et al 2005).…”

The a-Type Kerkini Granitic Complex in North Greece: Geochronology and Geodynamic Implications

“…Eby 1992, Wu et al 2002, Zhou 2006) although a clear distinction between rift-related and post-collisional A-type granites is not well documented. A rift responsible for several magmatic events in the broader area has been sug gested by many researchers (cf.…”