Petrogenesis and geodynamic significance of the Ganhe Formation lavas, eastern Great Xing'an Range, China: Evidence from geochemistry and geochronology

Abstract

Mesozoic volcanic rocks are widespread throughout the Great Xing'an Range of northeastern China. However, there has been limited investigation into the age and petrogenesis of the Mesozoic volcanics in the eastern Great Xing'an Range. According to our research, the volcanic rocks of the Dayangshu Basin, eastern Great Xing'an Range are composed mainly of trachybasalt, basaltic andesite, and basaltic trachyandesite, with minor intermediate-basic pyroclastic rocks. In this study, the geochemistry and geochronology of the Mesozoic volcanic rocks are presented in order to discuss the petrogenesis and tectonic setting of the Ganhe Formation in the Dayangshu Basin. Zircon U-Pb dating by laser ablation inductively coupled plasma-mass spectrometry indicates that the Mesozoic lavas formed during the late Early Cretaceous (114.3-108.8 Ma). This suite of rocks exhibits a range of geochemical signatures indicating subduction-related genesis, including: (i) calcalkaline to high-K calc-alkaline major element compositions; (ii) enrichment of large ion lithophile elements (e.g. Rb, Ba, K) and light rare earth elements (LREEs/HREEs =7.33-9.85); and (iii) weak depletion in high field strength elements (e.g. Nb, Ta, Ti). Furthermore, Sr-Nd-Pb isotopic data yield initial 87 Sr/ 86 Sr values of 0.70450-0.70463, positive ε Nd (t) values of +1.8 to +3.3, and a mantle-derived lead isotope composition. Combined with the regional tectonic evolution, the results of this study suggest that the Ganhe Group lavas are derived from decompression melting of a metasomatized (enriched) lithospheric mantle, related to asthenospheric upwelling, which resulted from lithospheric mantle delamination and produced extension of the continental margin following the subduction of the Paleo-Pacific Plate.

Petrogenesis and tectonic implications of Early Cretaceous volcanic rocks from the Shanghulin Basin within the north‐western Great Xing'an Range, NE China: Constraints from geochronology and geochemistry

“…The mechanism that caused such a widespread extensional environment during the Early Cretaceous remains controversial. Two main models have been proposed: (a) post‐orogenic lithospheric extension related to the closure of the Mongol–Okhotsk Ocean (Fan et al, ; Gou et al, ; Gou, Sun, Ren, et al, ; Sun, Ren, et al, ; Wang et al, ; Ying et al, ) and (b) subduction of the Palaeo‐Pacific Plate and subsequent lithospheric delamination (Dong et al, ; Gu et al, ; Wu et al, ; Zhang, Zhou, et al, , Zhang et al, ). The Great Xing'an Range has been previously considered to be controlled only by the rollback of the Palaeo‐Pacific Plate, whereas some researchers suggest it was constrained by both of the Mongol–Okhotsk and Pacific regimes in recent years (Tang et al, ; Wang et al, ; Xu et al, ).…”

Zircon U–Pb geochronology and Sr–Nd–Pb–Hf isotopic constraints on the timing and origin of the Early Cretaceous igneous rocks in the Yongxin gold deposit in the Lesser Xing'an Range, NE China

“…The Jiufenghua Formation rocks are mainly composed of sandstone, pebbly sandstone, tuff sandstone, and mudstone intercalated with volcanic breccia and basalt. The Ganhe Formation rocks consist of basalt, basaltic andesite, and trachyandesite and likely formed during 123 to 82 Ma (Gu et al, ; Y. F. Li et al, ). The Fuminghe Formation rocks contain dacite, rhyolite, and rhyolitic tuff, and these rocks have been dated to form during 108 to 98 Ma (Y. F. Li et al, ; Z. C. Zhang, Mao, et al, ).…”

“…are mainly composed of sandstone, pebbly sandstone, tuff sandstone, and mudstone intercalated with volcanic breccia and basalt. The Ganhe Formation rocks consist of basalt, basaltic andesite, and trachyandesite and likely formed during 123 to 82 Ma (Gu et al, 2016;Y. F. Li et al, 2013).…”

Chronology and Geochemistry of Early Cretaceous Magmatism in the Northwestern Erguna Block, Northeast China

“…The extensional environment in the Early Cretaceous period is currently being debated, and the main points of views are as follows: (1) it was related to the post-closure extensional environment of the Paleo-Asian Ocean; (2) it was linked to the extensional environment of the Paleo-Pacific Ocean [13,50]; and (3) it was associated with the post-closure extensional environment of the Mongol-Okhotsk Ocean [14,37,38]. Northeast China was mainly under the dual influence of the Paleo-Asian Ocean and the Mongol-Okhotsk Ocean during the Late Permian-Early Triassic period [15,34], while the Paleo-Asian Ocean closed along the Solonker-Xar Moron River-Changchun-Yanji suture zone in the Late Permian-Early Triassic period, forming a large-scale magmatic belt trending nearly east-west on the Songnen Massif [18].…”