Dataset Information

Generation of late Mesozoic felsic volcanic rocks in the Hailar Basin, northeastern China in response to overprinting of multiple tectonic regimes.

ABSTRACT: We performed zircon U-Pb age dating and geochemical analyses of late Mesozoic felsic volcanic rocks in the Hailar Basin, NE China, with the aim of eclucidating their emplacement ages, origin and geodynamic significance. The volcanic rocks consist of dacites, rhyolites and rhyolitic tuffs. Laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb dating results suggest that the rocks were erupted during the Late Jurassic-Early Cretaceous (161-117?Ma). They belong to the high-K calc-alkaline series and can be divided into two groups. Group I rocks are metaluminous to weakly peraluminous, contain low concentrations of heavy rare earth elements (HREEs) and high field strength elements (HFSEs), and have low zircon saturation temperatures (average 786?°C), all of which indicate an I-type affinity. In contrast, Group II rocks have higher HREE and HFSE concentrations and zircon saturation temperatures (average 918?°C), suggesting an A-type affinity. All the felsic volcanic rocks have positive ?_Hf(t) values of 1.43-12.32 with two-stage model ages of 1110-401?Ma. Our data indicate that the I-type felsic volcanic rocks formed from magmas generated by partial melting of a dominantly juvenile mica-bearing K-rich basaltic lower crust, whereas the A-type felsic volcanic rocks originated from the partial melting of a dry mafic-intermediate middle-lower crust that was dehydrated but not melt depleted. Based on the present results and previous research, we propose that the Late Jurassic I- and A-type felsic volcanic rocks in the Hailar Basin were formed in a post-collisional environment related to break-off of the subducted oceanic slab of the Mongol-Okhotsk Ocean and the subsequent gravitational collapse of the orogenically-thickened crust after closure of the ocean. In contrast, the Early Cretaceous I- and A-type felsic volcanic rocks were erupted in an extensional setting related to rollback of the subducted Paleo-Pacific Plate.

SUBMITTER: Ji Z

PROVIDER: S-EPMC6825236 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Generation of late Mesozoic felsic volcanic rocks in the Hailar Basin, northeastern China in response to overprinting of multiple tectonic regimes.

Ji Zheng Z Meng Qi-An QA Wan Chuan-Biao CB Zhu De-Feng DF Ge Wen-Chun WC Zhang Yan-Long YL Yang Hao H Dong Yu Y Jing Yan Y

Scientific reports 20191101 1

We performed zircon U-Pb age dating and geochemical analyses of late Mesozoic felsic volcanic rocks in the Hailar Basin, NE China, with the aim of eclucidating their emplacement ages, origin and geodynamic significance. The volcanic rocks consist of dacites, rhyolites and rhyolitic tuffs. Laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb dating results suggest that the rocks were erupted during the Late Jurassic-Early Cretaceous (161-117 Ma). They belong to the high-K calc- ...[more]

PMID: 31676817

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Project description:Volcanic rocks along the Panama Canal present a world-class opportunity to examine the relationship between arc magmatism, tectonic forcing, wet and dry magmas, and volcanic structures. Major and trace element geochemistry of Canal volcanic rocks indicate a significant petrologic transition at 21-25 Ma. Oligocene Bas Obispo Fm. rocks have large negative Nb-Ta anomalies, low HREE, fluid mobile element enrichments, a THI of 0.88, and a H2Ocalc of >3 wt. %. In contrast, the Miocene Pedro Miguel and Late Basalt Fm. exhibit reduced Nb-Ta anomalies, flattened REE curves, depleted fluid mobile elements, a THI of 1.45, a H2Ocalc of <1 wt. %, and plot in mid-ocean ridge/back-arc basin fields. Geochemical modeling of Miocene rocks indicates 0.5-0.1 kbar crystallization depths of hot (1100-1190°C) magmas in which most compositional diversity can be explained by fractional crystallization (F = 0.5). However, the most silicic lavas (Las Cascadas Fm.) require an additional mechanism, and assimilation-fractional-crystallization can reproduce observed compositions at reasonable melt fractions. The Canal volcanic rocks, therefore, change from hydrous basaltic pyroclastic deposits typical of mantle-wedge-derived magmas, to hot, dry bi-modal magmatism at the Oligocene-Miocene boundary. We suggest the primary reason for the change is onset of arc perpendicular extension localized to central Panama. High-resolution mapping along the Panama Canal has revealed a sequence of inward dipping maar-diatreme pyroclastic pipes, large basaltic sills, and bedded silicic ignimbrites and tuff deposits. These volcanic bodies intrude into the sedimentary Canal Basin and are cut by normal and subsequently strike-slip faults. Such pyroclastic pipes and basaltic sills are most common in extensional arc and large igneous province environments. Overall, the change in volcanic edifice form and geochemistry are related to onset of arc perpendicular extension, and are consistent with the idea that Panama arc crust fractured during collision with South America forming the observed Canal extensional zone.

Dataset Information

Generation of late Mesozoic felsic volcanic rocks in the Hailar Basin, northeastern China in response to overprinting of multiple tectonic regimes.

Publications

Generation of late Mesozoic felsic volcanic rocks in the Hailar Basin, northeastern China in response to overprinting of multiple tectonic regimes.

Similar Datasets

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