Tectonic transition from the Paleo-Asian Ocean to the Paleo-Pacific Ocean in central Jilin (NE China): Constraints from the early Mesozoic high-Mg andesites

Highlights

• The central Jilin area exposed a set of Early Triassic continental island arc HMAs.

• The JYS was formed related to the westward subduction of the PPO in the Triassic.

• Tectonic transition from the PAO to PPO occurred in the Late Permian-Late Triassic.

Abstract

The Jilin–Yanji Suture is situated at the convergent margin between the North China Craton and Jiamusi-Khanka Massif, playing as a key hinge to link up the tectonic transition from the Paleo-Asian Ocean to the Paleo-Pacific Ocean. However, many parameters of this suture, e.g. the timing of its emplacement, tectonic setting and precise location remain controversial. For addressing these issues, we focused on the high-Mg andesites within the Seluohe Group which is a typical subduction-related volcanic association along the Jilin–Yanji Suture. Seven chlorite schist and six andesite samples were collected for petrological, geochemical and geochronological analyses. The geochemical results indicate the protoliths of chlorite schists and the andesite samples are high-Mg andesites, and their magma source was produced by the metasomatized mantle wedge by subducted slab-derived fluids in a continental island arc setting. Eight high-Mg andesites give the crystallization ages of 249 ± 3 Ma–246 ± 4 Ma, with a weighted mean age of 247 ± 1 Ma (MSWD = 0.27) yielded by 69 youngest zircons, indicative of an Early Triassic age. Based on our new results and the field investigation, we propose that the Seluohe Group is a set of Early Triassic volcanic-sedimentary association with continental island arc affinity related to the south-westward subduction of the Heilongjiang Ocean, rather than a Mesoproterozoic sequence or Late Permian accretionary complex as previously considered. Integrated with previous studies on the regional tectonic evolution, we suggest the Jilin-Yanji Suture belongs to the southern extension of the Jilin-Heilongjiang high-pressure metamorphic belt, which records the final collision between the Jiamusi-Khanka Massif and North China Craton during the Triassic caused by the subduction of the Paleo-Pacific Ocean, and the Late Permian-Late Triassic is a key period of tectonic transition from the Paleo-Asian Ocean to the Paleo-Pacific Ocean in the eastern edge of Eurasia.

Introduction

High-Mg andesites (HMAs) are characterised by higher contents of MgO (>5%), Ni and Cr, lower contents of Al₂O₃ (<16%) and CaO (<10%) and lower FeO^T/MgO (<1.5) ratios than other andesites exposed in the modern island or continental arc areas (Kelemen et al., 2007, Tatsumi, 1982, Tatsumi, 2001). Another definition of HMAs is the andesites with SiO₂ contents of 54–65 wt% and Mg^# > 45 (Mg^# = 100 × atomic Mg/(Mg + Fe²⁺); Kelemen, 1995). Various proposals have been made regarding that the partial melting of peridotite in a hydrous environment could produce high-MgO andesitic melts (Kushiro, 1969, Kushiro, 1974, Mysen and Boettcher, 1975) and HMAs form an important component of island arc magmatism, which is mainly exposed in the convergent margin between the oceanic plate and continental plate (Deng et al., 2010, Deng et al., 2015, Hirose, 1997, Kay, 1978, Kelemen et al., 2007, Saunders et al., 1987, Schiano et al., 1995, Tang and Wang, 2010, Tatsumi, 1982, Tatsumi, 2001, Wang et al., 2020, Bloomer and Hawkins, 1987, Li et al., 2007b). Consequently, HMAs can provide vital constraints on the mechanisms of oceanic plate subduction, especially on the timing and geodynamic setting (Kamei et al., 2004, Schiano et al., 1995, Shiraki et al., 1980, Tang and Wang, 2010, Tatsumi, 2006, Yogodzinski et al., 2001, Deng et al., 2015, Ishizuka et al., 2014).

The superposition and transition between the Paleo–Asian Ocean (PAO) and Paleo–Pacific Ocean (PPO) tectonic domains are hot topics in recent years (Han and Zhou, 2020, Li et al., 2021, Li et al., 2022, Tang et al., 2016, Tang et al., 2018, Zhu et al., 2021, Liang et al., 2021, Zhou et al., 2009, Zhou et al., 2013, Zhou et al., 2020, Bi et al., 2017, Wang et al., 2016). However, due to the lack of an optimal hinge to link up the two domains, some significant issues of tectonic superposition and transition, e.g., the timing and location of the termination of PAO, the initial time and subduction mode of the PPO, and the transition of driving force from the PAO to PPO, are still poorly constrained (Yang et al., 2015, Li et al., 2021, Li et al., 2022, Wang et al., 2017, Pei et al., 2008, Su, 1996, Tang, 1989, Zhou et al., 2009, Zhou et al., 2010a, Zhou et al., 2010b, Zhou et al., 2013, Zhou et al., 2020, Li, 2006, Bi et al., 2017, Yu et al., 2012). Recently, the Jilin–Yanji Suture (JYS) has been proposed to represent the collision between the JKM and NCC (Fig. 1a, b; Zhou et al., 2013, 2020). Its emplacement process can cover the gap of the tectonic transition from the closure of the PAO and onset of westward subduction of the PPO. Despite numerous efforts on the JYS, its tectonic affinity remains controversial. The JYS was traditionally defined as the eastern extension of the South Tianshan–Solonker–Xar Moron–Changchun Suture between the Altaids and Manchurides and formed by the closure of the PAO during the Late Permian (Xu et al., 2013, Wu et al., 2007a, Li, 2006, Li et al., 2014, Xiao et al., 2003). On the contrary, some recent studies have considered the JYS to represent the southern extension of the Jilin–Heilongjiang high-pressure metamorphic belt (J–H HP belt) and was caused by the collision between the JKM and NCC related to the subduction of PPO in the Triassic (Zhou and Li, 2017, Zhou et al., 2009, 2013, 2020).

Fortunately, we found a suit of HMAs in the Seluohe Group along the JYS (Fig. 1b). These HMAs can provide crucial insights into the affinity of JYS. Therefore, we report a combined study of the precise petrological, geochemical, and geochronological data of these HMAs, aiming to better understand their formation age, petrogenesis and tectonic setting. Our new results will provide not only important evidence for the tectonic affinity of the JYS but also further insights into the tectonic transition from the PAO to the PPO.