Three-phased Middle Permian–Mesozoic magmatism in the Great Xing'an Range: implications for episodic southern subduction of the Mongol–Okhotsk Ocean

Abstract

The Erguna Massif is located in the southwestern portion of the Great Xing'an Range and is adjacent to the Mongol–Okhotsk suture zone. It has not to be determined whether the tectonic evolutionary processes of the Erguna Massif belong to the Mongol–Okhotsk tectonic regime during the Middle Permian–Mesozoic. In this study, a suite of rocks comprising Mesozoic S-type monzogranite (LA–ICP–MS U–Pb zircon age of 248 ± 1.2 Ma), highly fractionated I-type rhyolite (204 ± 1.1 Ma), gabbro (196 ± 1.9 Ma), A2-type volcanic rocks (190 ± 0.9 Ma), A1-type trachydacite (167 ± 0.8 Ma), and Early Cretaceous A1-type alkaline rhyolite are newly identified and geochemically studied. The rhyolite, gabbro, trachydacite, and alkaline rhyolite whole-rock Sr–Nd isotope analyses got the values of initial 87Sr/86Sr ratios ranging from 0.7044 to 0.7058 and εNd(t) values of −0.68–+2.73. These samples show εHf(t) values ranging from +5.3 to +11.2 and TDM2 ranging from 0.48 Ga to 0.90 Ga. The 248 Ma monzogranites were produced by the partial melting of greywackes. The 204 Ma rhyolites were derived from the partial melting of lower mafic crust. The 196 Ma gabbros originated from the partial melting of an enriched mantle metasomatized by subduction-slab released fluids. The 190 Ma volcanic rocks, 167 Ma trachydacite, and Early Cretaceous alkaline rhyolite were mainly formed by the partial melting of the basaltic rocks. They all show enrichment in the large ion lithophile elements (e.g., Rb, Ba, and K) and depletions in the high field strength elements (e.g., Nb, Ta, and Ti), suggesting they formed in an active continental margin setting. The features of these igneous rocks indicate the southward subduction of the Mongol-Okhotsk ocean plate. Based on compiled age data, three phases of middle Mesozoic magmatism were identified in the Erguna Massif at ca. 275–225 Ma, 215–165 Ma, and 150–110 Ma. In addition, three similar magmatic phases were found in the Xing'an Massif. However, a hysteresis about ca. 15–20 Ma exists between the two massifs. These magmatic rocks may record the three stages of the southward subduction of the Mongol–Okhotsk oceanic plate, and two periods of slab rollback occurred during the Middle Permian to Early Cretaceous.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5459285

Spatial–temporal influence of the Mongol–Okhotsk and Palaeo–Pacific tectonic systems in NE China: Evidence from geochronological and geochemical data of felsic rocks in the east‐Central Jilin Province and southern Great Xing'an Range

“…An angular unconformity between the lower Cretaceous and the lower geological body in Tuquan area, southern GXAR (Song et al, 2022), 150–135 Ma unconformity event in Zhangjiakou, northern NCC (Zhang et al, 2008) represent the closure of MOO and extension began from the early Cretaceous. Alkaline rock, bimodal volcanic rocks, faulted coal‐bearing basin in GXAR also reflect an extensional environment (Yang et al, 2022). All of the evidence suggests that the rhyolite may have formed in an extensional post‐orogenic setting.…”

“…An angular unconformity between the lower Cretaceous and the lower geological body in Tuquan area, southern GXAR(Song et al, 2022), 150-135 Ma unconformity event in Zhangjiakou, northern NCC represent the closure of MOO and extension began from the early Cretaceous. Alkaline rock, bimodal volcanic rocks, faulted coal-bearing basin in GXAR also reflect an extensional environment(Yang et al, 2022). All of the evidence suggests that the rhyolite may have formed in an extensional post-orogenic setting.5.3.3 | Tectonic evolution of NE China in the late MesozoicBased on the chronological and geochemical data of the samples collected from the two areas in NE China (Shancheng and Wushijazi), we conclude that the granites and the rhyolites in each area formed under different tectonic settings with different magma sources.…”

40Ar/39Ar Dating and In Situ Trace Element Geochemistry of Quartz and Mica in the Weilasituo Deposit in Inner Mongolia, China: Implications for Li–Polymetallic Metallogenesis

“…5 Ma,[112]), and Taipinggou Mo deposit (130 Ma,[115]). Recent studies have shown that the GXR was affected only by the Paleo-Pacific Ocean during the Early Cretaceous and was in an extensional environment [116].…”