Geochemistry and geochronology of OIB-type, Early Jurassic magmatism in the Zhangguangcai range, NE China, as a result of continental back-arc extension

Abstract

The Zhangguangcai Range in the Xing’an Mongolian Orogenic Belt, NE China, contains Early Jurassic (c. 188 Ma) Dabaizigou (DBZG) porphyritic dolerite. Compared with other island-arc mafic rocks, the DBZG dolerite is characterized by high trace-element contents, relatively weak Nb and Ta enrichments, and no Zr, Hf or Ti depletions, similar to OIB-type rocks. Analysed rocks have (87Sr/86Sr)i ratios of 0.7033–0.7044, relatively uniform positive ɛNd(t) values of 2.3–3.2 and positive ɛHf(t) values of 8.5–17.1. Trace-element and isotopic modelling indicates that the DBZG mafic rocks were generated by partial melting of asthenospheric mantle under garnet- to spinel-facies conditions. The occurrence of OIB-like mafic intrusion suggests significant upwelling of the asthenosphere in response to lithospheric attenuation caused by continental rifting. These processes occurred in an incipient continental back-arc environment in the upper plate of a palaeo-Pacific slab subducting W–NW beneath East Asia.

Geodynamic Evolution of Flat‐Slab Subduction of Paleo‐Pacific Plate: Constraints From Jurassic Adakitic Lavas in the Hailar Basin, NE China

“…The subduction of the Paleo‐Pacific Plate beneath the NE China continental margin is generally considered to have started by the Early Jurassic, as recorded by an Early Jurassic continental arc and back‐arc system in the EHJP (Wu et al, ; Yu et al, ; Xu et al, ; Wang, Ge, et al, ; Feng et al, ). The ~200‐km‐wide continental arc consists of the Early Jurassic calc‐alkaline mafic intrusions, I‐type granitoids, and their eruptive counterparts.…”

A comprehensive re‐look into Jurassic‐Cretaceous Neotethyan active margin in Iran: Evidence of deep mantle flow into subduction magma factory and formation of transitional basalts

“…The orange OIB field is from Hofmann (2003). Other OIB fields include specific provinces of Hawaii and Okete (Briggs & McDonough, 1990 and references therein), Dabaizigou (Feng et al, 2021) and Armenia (Rolland et al, 2009). Mantle array is from H. F. Zhang et al (2005).…”

Subduction zone processes and crustal growth mechanisms at Pacific Rim convergent margins: modern and ancient analogues

“…Feng et al (2018) present new U–Pb zircon geochronology, whole-rock geochemistry and Sr–Nd–Hf isotopic data from an Early Jurassic diorite pluton, which is intrusive into the crystalline basement in the NE end of the North China Craton (see green box with number 9 in Fig. 1).…”

“…Wu et al 2019), particularly in the North China Block; in the development of extensive magmatic belts and associated mineralization zones (Deng et al 2017); and in the formation of margin-parallel transform-transcurrent fault systems and kinematically and temporally related terrestrial sedimentary basins (Zhang et al 2017(Zhang et al , 2019b. Changing slab geometries, widths and slab rollback rates, and the amount and compositions of subducted sediments affected the melt evolution and formation of different types of magmatism and mineralization in the continental upper plate (Dilek & Altunkaynak, 2009;Jamali et al 2010;Conticelli et al 2015;Deng et al 2017;Feng et al 2018;Niu X et al 2019;Schellart, 2020). Thus, ESE China (Fig.…”

“…The authors introduce the late Cretaceous -Eocene tectonics of the Western US Cordillera (Dilek & Moores, 1999) as a more recent analogue for the Mesozoic tectonics of SE China. Feng et al (2018) present new U-Pb zircon geochronology, whole-rock geochemistry and Sr-Nd-Hf isotopic data from an Early Jurassic diorite pluton, which is intrusive into the crystalline basement in the NE end of the North China Craton (see green box with number 9 in Fig. 1).…”