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Newly discovered early Palaeozoic intraplate volcanic rocks within the southern Kunlun Orogen provide an opportunity to examine the middle to late Silurian tectonic setting of this area. This study presents new whole-rock geochemical and zircon U–Pb geochronological and Lu–Hf isotope data for the Silurian volcanic rocks of the Wanbaogou area, South Kunlun Belt. These volcanic rocks are split into trachytic and basaltic groups based on field observations and petrographic and geochemical data. Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb dating of zircons from four samples from this area yields similar ages of 428.2 ± 3.4, 426.4 ± 4.2, 426.1 ± 3.2, and 424.5 ± 3.2 Ma, indicating this volcanic complex formed during the middle to late Silurian. The basalts in this area have high Nb/La ratios, generally positive εHf(t) values and hump-shaped ocean island basalt (OIB)-like intraplate compositions that are free of negative Nb, Ta, and Ti anomalies, indicating the magmas that formed these units underwent at most only slight crustal contamination. In comparison, the trachytes have incompatible trace element concentrations that are higher than the concentrations found in typical arc-type magmas. The melting of the underplated young basaltic crust is a more likely explanation for the formation of the trachytes. These igneous rocks are all of within-plate affinity, were derived either from the asthenospheric mantle or from a mantle plume, and underwent some crustal contamination prior to their emplacement. Combining these data with the results of previous research on the Kunlun high to ultrahigh-pressure (UHP) belt and contemporaneous volcanic and intrusive rocks elsewhere in this region suggests that the Silurian volcanic rocks of the Wanbaogou area formed in a post-orogenic setting as a response to the final closure of the Proto-Tethys Ocean and the transition from Proto- to Paleo-Tethyan tectonic regimes within the East Kunlun Orogen. The geology of this region indicates that middle–late Silurian post-orogenic extension was not just limited to the Wanbaogou area but probably extended across the entire EKO. [ABSTRACT FROM AUTHOR]

The Silurian volcanic rocks of the Prague Basin represent within-plate, transitional alkali to tholeiitic basalts, which erupted in a continental rift setting through the thick Cadomian crust of the Teplá-Barrandian Unit (Bohemian Massif). Despite the variable, often intense alteration resulting in post-magmatic replacement of the basalt mass due to carbonatization, the geochemical signatures of Silurian basalts are still sufficiently preserved to constrain primary magmatic processes and geotectonic setting. The studied interval of Silurian volcanic activity ranges from Wenlock (Homerian, ~431 Ma) to late Ludlow (Gorstian, ~425 Ma) with a distinct peak at the Wenlock/Ludlow boundary (~428 Ma). Trace-element characteristics unambiguously indicate partial melting of a garnet peridotite mantle source. Wenlock basalts are similar to alkaline OIB with depleted radiogenic Nd signature compared to Ludlow basalts, which are rather tholeiitic, EMORB-like with enriched radiogenic Nd signature. The correlation of petrogenetically significant trace-element ratios with Nd isotopic compositions points to a mixing of partial melts of an isotopically heterogeneous, possibly two-component mantle source during the Wenlock-Ludlow melting. Lava eruptions were accompanied by intrusions of doleritic basalt and meimechite sills. The latter represent olivine-rich cumulates of basaltic magmas of probably predominantly Ludlow age. Meimechites with dolerites and, to a lesser extent, some lavas were subject to alteration due to wall-rock-fluid interaction. The trigger for the Wenlock-to-Ludlow (431-425 Ma) extension and related volcanism in the Prague Basin is related to far-field forces, namely slab-pull regime due to progressive closure of the Iapetus Ocean. The main stage of the Baltica-Laurentia collision then caused the Prague Basin rift failure at ca. 425 Ma that has never reached an oceanic stage. [ABSTRACT FROM AUTHOR]