Geochemistry of high‐Nb basalt‐andesite in the Erguna Massif (NE China) and implications for the early Cretaceous back‐arc extension

Abstract

This paper presents new zircon laser ablation-inductively coupled plasma-mass spectrometry U-Pb age and whole-rock geochemical data for the high-Nb basalts-andesites (HNBs) from the Meiletu Formation in NE China. In comparison with common arc basalts and Nb-enriched basalts, the Meiletu HNBs (140 Ma) show high TiO 2 (1.7-3.2 wt.%), P 2 O 5 (0.7-1.7 wt.%), Nb (14.6-34.0 ppm), and Zr (314-600 ppm) contents, and high (Nb/Th) PM (0.26-0.91), (Nb/La) PM (0.22-0.36), Nb/U (8.2-24.8) ratios. They show strongly light rare earth element (REE) enriched chondrite-normalized REE patterns with unusually high total REE contents [(TREE)cn = 978-1802]. Unlike adakite-associated HNBs derived from a mantle wedge metasomatized by adakites, the Meiletu HNBs were derived from low degree (<2%) partial melting of the garnet peridotite at considerable depth (>80 km). The Meiletu HNBs were generated in an intracontinental back-arc extension setting. Combined with previous geological observations, it is argued that Early Cretaceous tectonics of the Erguna Massif is dominated by the Mongol-Okhotsk oceanic slab-rollback and back-arc extension. KEYWORDS back-arc extension, Erguna Massif, high-Nb basalt, Mongol-Okhotsk Ocean, Nb-enriched basalt

Geochemistry of Khandadharpahar-Thakuranipahar metabasites from the western Singhbhum Craton, eastern India: implications for subduction-zone tectonics and mantle-wedge metasomatism

“…However, the REE and multi-element patterns deviate from the usual OIB, Enriched mid-ocean ridge basalts (E-MORB) and Normal mid-ocean ridge basalts (N-MORB) patterns (Figure 4B). These characteristics are analogous to those of Precambrian and Phanerozoic NEB (Aguillon-Robles et al, 2001;Castillo, 2008;Hollings, 2002;Liu et al, 2017Liu et al, , 2018Sajona et al, 1996;Wang et al, 2013).…”

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

“…Hf isotopic data for the Mesozoic crust‐derived rocks in the HB and northern GXR are from Li, Ding, et al, , Li et al, ), Tang et al (, ), Hu et al (), Zhou et al (), Dong et al (, ), Ji et al (), Gou et al (), and Ji et al (). Hf isotopic data for the Mesozoic mantle‐derived rocks in the HB and northern GXR are from Tang et al (), Wang, Tang, et al (), Liu et al (), Gou et al (), and Zhang et al ().…”

Petrogenesis and tectonic implications of Late Mesozoic volcanic rocks in the northern and central Great Xing'an Range, NE China: Constraints from geochronology and geochemistry

“…It is generally accepted that NE China and the entire eastern CAOB were under an extensional environment during the Late Jurassic–Early Cretaceous (Liu et al, 2019; Mao et al, 2020; Tang et al, 2019). The widespread metamorphic core complexes combined with the occurrence of bimodal rock suites (Zhang et al, 2007; Zhang, Yang, Wu, & Liu, 2006), A‐type granites, alkaline rhyolites (Ge, Wu, Zhou, & Abdel Rahman, 2005), and extensional basins (Wang et al, 2011) in the NCGXR also indicate a Late Jurassic–Early Cretaceous extensional setting.…”

“…Tang et al (2019) summarized geochronological and Hf–Nd isotope data for Mesozoic intermediate‐felsic igneous rocks within the central GXR and adjacent areas, but the geodynamic setting of the Mesozoic intermediate igneous rocks has not been discussed. Additionally, Liu et al (2019) discussed the petrogenesis, geodynamic processes, and tectonic setting of the Late Mesozoic mafic rocks of the EB. However, systematic data on the intermediate‐mafic Late Mesozoic igneous rocks in the NCGXR are still scarce, which hampers the effort to understand the petrogenesis and geodynamic setting of large‐scale volcanism in this region.…”