Petrogenesis of the southern Qiangtang mafic dykes, Tibet: Link to a late Paleozoic mantle plume on the northern margin of Gondwana?

Abstract

This study presents 13 new U-Pb zircon ages obtained by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) together with whole-rock geochemical, Sr-Nd isotopic and zircon Hf isotopic data for a mafic dike swarm in the southern Qiangtang area of Tibet. These data provide the basis for a new model of the late Paleozoic evolution of the Tethys. Combined with the results of previous zircon U-Pb dating, the magmatic zircon grains extracted from mafic dikes yield latest Carboniferous to Early Permian ages (317–279 Ma). The geochemistry of the southern Qiangtang mafic rocks indicates the presence of low-Ti (QLT) and high-Ti (QHT) suites. The magmas that formed the QLT suite underwent higher degrees of partial melting (>5%) and display evidence of crustal contamination, whereas the QHT suite was derived from magmas generated by low-degree (1%–5%) partial melting of a garnet-bearing mantle source, with a greater extent of fractional crystallization than the QLT suite, and no evidence of crustal contamination. We propose that the QHT and QLT suites may have been derived from magmas from different parts of a single mantle plume. The formation of the southern Qiangtang mafic dikes (latest Carboniferous to Early Permian; 317–279 Ma) may have been related to the northward drift of the Cimmerian continent from the northern Gondwana margin, which resulted in the opening of the Meso-Tethys Ocean.

The Early Permian Woniusi Flood Basalts from the Baoshan Terrane, SW China: Petrogenesis and Geodynamic Implications

“…Unlike the Woniusi, Selong and Panjal basalts, the Qiangtang mafic dykes and flood basalts were probably derived from a sub-lithospheric mantle source . Differently, the Qiangtang low-Ti mafic dykes have undergone continental crustal assimilation en route to the surface (Wang et al, 2019). Thus, all these basaltic rocks in the Himalaya could have genetically been related to a Permian upwelling mantle plume.…”

“…During this time a series of intra-plate, basaltic rocks were emplaced within the Tethyan Himalaya domains of Pakistan, India and China and they are considered to be parts of a Large Igneous Provine (LIP) associated with the breakup of Gondwana (Ernst and Buchan, 2001;Zhu et al, 2010;Liao et al, 2015;Shellnutt et al, 2015;Xu et al, 2016;Zhang and Zhang, 2017;Wang et al, 2019). The Panjal Traps, Abor, Nar-Tsum, Bhote Kosi, and Selong volcanic groups and Qiangtang mafic dykes and flood basalts are amongst the many occurrences of the Late Carboniferous to Early Permian basaltic rocks within the Himalaya (Bhat et al, 1981;Garzanti et al, 1999;Chauvet et al, 2008;Zhu et al 2010;Ali et al 2012;Zhai et al 2013;Shellnutt et al, 2014Shellnutt et al, , 2015Xu et al, 2016;Zhang and Zhang, 2017;Liu et al, 2018;Wang et al, 2019). Recent studies have also documented large volumes of Late Carboniferous to Early Permian flood basalts and mafic dykes in the Jinji (Wang et al, 2004;Ali et al, 2013;Liao et al, 2015) and Shidian (Huang et al, 2012;Ali et al, 2013) areas in the Baoshan terrane, SW China.…”

“…The formation of continental LIPs has also significant implications for continental growth, rifting and breakup (Wang et al, 2008;Bryan and Ferrari, 2013). Previous work suggests the extensive Late Carboniferous to Early Permian basaltic rocks throughout the Himalaya are likely the volcanic expressions of passive lithosphere extension on the northern margin of East Gondwana whereas others suggest they could be the products of basaltic magmatism induced by mantle plume activity (Chauvet et al, 2008;Zhu et al, 2010;Zhai et al, 2013;Shellnutt et al, 2014Shellnutt et al, , 2015Liao et al, 2015;Xu et al, 2016;Zhang and Zhang, 2017;Wang et al, 2019). Consequently, the origin and tectonic implications of this magmatism remain unclear.…”

Early Carboniferous Back‐Arc Rifting‐Related Magmatism in Southern Tibet: Implications for the History of the Lhasa Terrane Separation From Gondwana

“…Generalized space‐time diagram that shows the basement rocks, sedimentary covers, tectonic, and magmatic history of the Lhasa and Qiangtang terranes (after Zhu et al, 2013). The age data are from Ji et al (2012), Dong, Zhang, Geng, et al (2010), Dong, Zhang, and Santosh (2010), Dong et al (2014), Lin et al (2013), L. Ma, Keer, et al (2019), X. X. Ma et al (2020), Zhu et al (2009, 2012), Hu et al (2005), M. Wang et al (2015), M. Wang, Li, et al (2019), Pullen et al (2011), H. R. Zhang, Yang, et al (2016), and Zhai et al (2018). …”

“…The age data are from Ji et al (2012), Dong, Zhang, Geng, et al (2010), Dong, Zhang, and Santosh (2010), Dong et al (2014), Lin et al (2013), L. Ma, Keer, et al (2019), X. X. Ma et al (2020), Zhu et al (2009Zhu et al ( , 2012, Hu et al (2005), M. Wang et al (2015), M. Wang, Li, et al (2019), Pullen et al (2011), H. R. Zhang, Yang, et al (2016), andZhai et al (2018). 4m-4o).…”