Identifying late Carboniferous sanukitoids in Hala’alate Mountain, Northwest China: new constraint on the closing time of remnant ocean basin in West Junggar

Abstract

Volcanic rocks in the Hala'alate and Aladeyikesai formations, which are composed of basaltic andesite and pyroxene andesite, are widespread in Hala'alate Mountain, West Junggar, Northwest China. These rocks (plagioclase + clinopyroxene/olivine) formed in the late Carboniferous and show a remarkable geochemical affinity with typical sanukitoids with oversaturated SiO 2 (52.9-56.9 wt.%) and high MgO (3.47-6.88 wt.%, Mg # >48) contents. They also exhibit a narrow range of Sr-Nd-Pb isotopes within ( 87 Sr/ 86 Sr) i = 0.7037-0.7041, εNd(t) = 4.4-6.2, 206 Pb/ 204 Pb = 18.22-18.41, 207 Pb/ 204 Pb = 15.48-15.52, 208 Pb/ 204 Pb = 37.99-38.30. Hala'alate Formation volcanic rocks are similar to the sanukitoids of Karamay, with high Sr (633.5-970.1 ppm), Ba (268.7-796.3 ppm), and Sr/Y (61.34-84.28), formed by partial melting of the mantle metasomatized by slab-derived adakitic melts. In contrast, Aladeyikesai Formation volcanic rocks show some affinity with sanukitoids of the Hatu area and the Setouchi Volcanic Belt, with low Sr (442.2-508.7 ppm), Ba (199.2-485.1 ppm), and Sr/Y (25.03-30.28), generated by the partial melting of subducting sediments. Identification of late Carboniferous sanukitoids in Hala'alate Mountain provides important constraints on the closing time of the remnant ocean basin in West Junggar, and implies that multistage subduction-accretionary orogeny plays a crucial role in the evolution and growth of the continental crust in the Central Asian Orogenic Belt. ARTICLE HISTORY

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

“…Moreover, the Late Carboniferous–Early Permian mafic dikes, intermediate–felsic stocks, and basic volcanic rocks, which are located on both sides of the Darbut fault, were reported with typical features of sanukitoids in Setouchi volcanic belt of SW Japan ( ca . 322–291 Ma; Duan, Li, Zhi, & Wang, , in press; Li et al, ; Ma et al, ; Tang et al, ; Yin et al, , 2015). Additionally, the Late Carboniferous Hatu tholeiites ( ca .…”

“…The first subduction–accretionary finished at the Early Carboniferous and then developed into intracontinental post‐collisional evolution. The second subduction–accretionary occurred in the southern West Junggar region at the Late Carboniferous to early Early Permian and formed sanukitoid arc volcanic rocks in Hala'alate Mountain (Li et al, ). Meanwhile, during the formation of granitic magma, dioritic intrusions/dikes showing geochemical affinity with adakites and sanukitoids intruded upward along the regional faults into Early Carboniferous and/or Middle Devonian strata (Duan et al, ; Duan, Li, Zhi, & Wang, , in press; Ma et al, ; Shen et al, ; Tang et al, , 2010; Yin et al, ; Yin et al, ; Yin et al, ; Zhang et al, and this study), and some have experienced strong magma mixing between mantle‐ and crustal‐derived melts during their ascent and emplacement (Chao et al, ; Kang, Li, Zhang, Zhang, & Wang, ).…”

“…572–332 Ma) have been reported in this region, demonstrating a complex accretionary history of the Palaeo‐Asian Ocean (e.g., Gu, Li, Zhang, Tong, & Wang, ; Xu et al, ; Yang et al, ; Yang et al, ; Yang, Li, et al, ). Also, the Late Palaeozoic volcanic rocks exclusively outcrop in the Barleik mountains and Karamay region, consisting mainly of Devonian to Carboniferous basalt, andesitic basalt, andesite, felsic tuff, and tuffite (Geng et al, ; Geng, Sun, Yuan, Zhao, & Xiao, ; Li et al, ; Tang et al, ; Xiang et al, ), and some of which show a remarkable geochemical affinity with typical sanukitoids (Li et al, ). In addition to the ophiolitic mélanges and volcanic rocks, the other attractive geological feature in the southern West Junggar is the extensive distribution of Late Palaeozoic granitic batholiths and dioritic stocks (Figure b).…”

“…They are generally classified as A-and I-type granitoids, adakites, sanukitoids, and charnockites and characterized by their short emplacement time (mainly concentrated in Late Carboniferous to Early Permian; e.g., Chen et al, 2010;Duan et al, 2015a;Duan, Li, Zhi, & Wang, 2018, in press;Han, Ji, Song, Chen, & Zhang, 2006;Geng et al, 2009;Gao et al, 2014;Tang et al, 2009;Tang et al, 2010;Yin et al, 2010;Yin et al, 2015;Yin et al, 2016;Zhang, Wan, Jiao, & Zhang, 2006;Zhou et al, 2008 and unpublished data; Figure 1b). However, the petrogenesis and tectonic environments of the Late Carboniferous to Early Permian magmatism are still controversial for the region, with two major competing viewpoints being proposed, that is, post-collisional environment since the Early Carboniferous (e.g., Chen et al, 2010;Chen & Arakawa, 2005;Gao et al, 2014;Han et al, 2006;Liu et al, 2017;Su, Tang, Hou, & Liu, 2006) and subduction-related island arc environment (e.g., Geng et al, 2009;Li et al, 2017;Shen et al, 2009;Tang et al, 2009;Tang et al, 2010;Xiao et al, 2008;Xiao & Santosh, 2014;Yin et al, 2010;Yin et al, 2015;Yin et al, 2016;Zhang et al, 2006), which, to a great extent, restricts the further discussion of the tectonic evolution in the West Junggar.…”

Tectonics, magmatism, and mineralization of Circum–Balkash–Junggar area in the Central Asian Orogenic Belt

“…Both the lithologies and deformation features of the Tarbagatay Complex, together with zircon ages, suggest an accretionary origin generally with a top-to-the-south tectonic vergence, suggesting a N-dipping subduction beneath the Zharma-Saur arc, likely started in the Late Devonian and lasted until the middle Permian. Li et al (2017a) report the geochemical and isotopic analyses of late Carboniferous volcanic rocks in the Hala'alate and Aladeyikesai formations, which are composed of basaltic andesite and pyroxene andesite and widespread in Hala'alate Mountain, West Junggar, NW China. The authors found that the Hala'alate Formation volcanic rocks are similar to the sanukitoids of Karamay, formed by partial melting of the mantle metasomatized by slab-derived adakitic melts.…”