Geochronology and geochemistry of the Carboniferous Ulann Tolgoi granite complex from northern Inner Mongolia, China: Petrogenesis and tectonic implications for the Uliastai continental margin

Abstract

This study presents zircon U–Pb ages and geochemical and Sr–Nd isotopic data for acid granites from the Uliastai continental margin, which is located in the Ulaan Tolgoi area of the south‐eastern Central Asian Orogenic Belt (CAOB). Although most samples have similar calc‐alkaline (K2O/Na2O = 0.55–1.70, average of 1.35) and peraluminous (A/CNK = 1.02–1.20 and A/NK = 1.09–1.87) characteristics, the granodiorites, monzogranites, and alkali feldspar granites exhibit distinct light rare earth element (LREE)/heavy REE (HREE) anomalies, including negative Nb, P, Ti, Sr, and Ba anomalies and negative εNd(t) values. These characteristics indicate that this complex massif comprises lower Early Carboniferous subduction‐related calc‐alkaline granodiorites (348 ± 1 Ma); an upper Early Carboniferous syn‐collisional segment characterized by S‐type, high‐K, calc‐alkaline, and peraluminous monzonitic granites (334 ± 1 Ma); and Late Carboniferous post‐orogenic extensional A2‐type peraluminous alkali feldspar granites (317 ± 1 Ma). Previous studies performed on coeval volcanic rocks and Early Palaeozoic granites in the same area have demonstrated that the Early Carboniferous granodiorites have the same geochemical characteristics as volcanic arc granites (VAGs), thus indicating that the northward subduction of the Hegenshan Ocean may have continued through the Early Carboniferous. The monzogranite and alkali feldspar granites, in conjunction with the Late Carboniferous lagged arc volcanic rocks observed in this area, suggest a syn‐collisional to post‐collisional setting. The new data presented in this study provide constraints on the timing of the transition from island‐arc magmatism to post‐collisional extension‐related magmatism in this region during the later stage of the Early Carboniferous.

Evolution of the Paleo–Asian Ocean in south‐eastern Inner Mongolia, China: Evidence from zircon U–Pb ages, Hf isotopes data and specific deformation of the Linxi and Sunjiafen formations

“…The 1248–1000, 925–840 Ma age populations are similar to the ages of Xilin Gol Complex, Inner Mongolia (Xu et al, 1996; Hao & Xu, 1997; Shi et al, 2003; Zhu et al, 2004). The 1552–1285 Ma age populations are similar to the ages of volcanic rocks in the Yingchengzi Formation in the northern Songliao Basin and granites in the north of North‐eastern China (Gao et al, 2008; Li et al, 2011; Zhang, Chen, et al, 2008).…”

Geochronology, Mineralogy, and Geochemistry of the Tonsteins from the Permo–Carboniferous Benxi Formation, Ordos Basin, North China Craton

“…Some studies have demonstrated that IMPU is the origin of pyroclastic rocks in the eastern NCC (Zhang et al, 2007;Wang et al, 2020). The tonstein samples in this study have distinct negative Eu anomalies; however, pyroclastic rocks in the eastern NCC display weak negative Eu anomalies (Zhou et al, 2001(Zhou et al, , 2018Zhao et al, 2019;Wang et al, 2020). In parallel, the tonsteins in the Benxi Formation have no similar negative ε Hf (t) values compared to rocks from the magmatic arc in the IMPU (Fig.…”

“…This research also can infer the same conclusion, which also can suggest the distribution area of (Winchester and Floyd, 1977); (c, d) Zr/TiO 2 vs. Al 2 O 3 /TiO 2 and Nb/Yb vs. Al 2 O 3 /TiO 2 diagrams for the tonsteins. Colored fields represent late Carboniferous to early Permian volcanic rocks from the North China craton (Su et al, 2012;Zhao et al, 2017;Liu et al, 2018;Tian et al, 2018;Zhou et al, 2018;Cai et al, 2020;Hu et al, 2020). Taylor and McLennan (1985).…”

Petrogenesis and tectonic setting of Late Devonian high-Mg andesites in the Beishan orogen, NW China

“…The HMAs that have arc-like geochemical affinities in an intra-continental setting might be attributed to the inheritance of a previous subduction event in a metasomatized mantle source (Gao et al 2004;Gan et al 2020). Many similar cases can be found in a number of orogenic belts in western China, such as the upper Plioceneupper Pleistocene volcanic rocks in Tengchong (Zhao & Chen, 1992), the Permian basalt in the Santanghu basin in Xinjiang (Zhou et al 2006), the lower Permian volcanic rocks in the Western Junggar (Li et al 2016) and the Lower Carboniferous volcanic rocks in Inner Mongolia (Zhou et al 2018). Since the HNX Ocean in the Dundunshan area was likely closed during late Middle Devonian time, we suggest that the Dundunshan HMAs were formed in a post-collision extensional setting (Fig.…”