Geochronology and geochemistry of the Late Jurassic bimodal volcanic rocks from Hailisen area, central‐southern Great Xing'an Range, Northeast China

Abstract

Zircon U–Pb dating and whole‐rock geochemical analysis have been studied on the Late Jurassic volcanic rocks in the Hailisen area, Northeastern China, with the aim of constraining the tectonic evolution of the central‐southern Great Xing'an Range during the Late Jurassic. The volcanic rocks mainly consist of andesite from the Tamulangou Formation, and rhyolite and minor dacite from the Manketouebo Formation. The results of inductively coupled plasma‐mass spectrometry Zircon U–Pb dating for two andesites and one dacite indicate that they formed in the Late Jurassic (161–150 Ma). The mafic rocks are characteristic of low TiO2 (1.01–1.04 wt.%) and P2O5 (0.23–0.31 wt.%) contents, and high Al2O3 (17.19–20.18 wt.%) and CaO (6.69–7.45 wt.%) contents, and belong to the low‐K tholeiitic series. These mafic rocks are also characterized by moderately enriched light rare earth element (LREE) patterns and high abundances of Th, U, Zr, and Hf but negative Nb, Ta, and Ti anomalies. The felsic rocks are enriched in alkalis, Th, U, and LREEs; depleted in Ba, Sr, Nb, Ta, and Ti; and exhibit moderately LREE‐enriched patterns. These features indicate that the mafic volcanic rocks were likely formed by the partial melting of a lithospheric mantle that was metasomatized by subduction‐derived components, but the felsic rocks could derived by partial melting of a crustal source. The Tamulangou and Manketouebo formations have compositions of typical bimodal volcanism, an extensional environment, similar to a post‐orogenic setting, which might be related to the closure of Mongol–Okhotsk Ocean.