Petrogenesis of Late Silurian volcanism in SW Yunnan (China) and implications for the tectonic reconstruction of northern Gondwana

Tectonic Evolution and Paleoposition of the Baoshan and Lincang Blocks of West Yunnan During the Paleozoic

“…In addition, the Silurian collision‐related high‐pressure metamorphic rocks akin to those in the Longmu Co‐Shuang Suture Zone (Zhang et al, 2014) and the angular unconformity between the Devonian and the Ordovician‐Silurian strata in the BSB and SMB (BGMRYP, 1980, 1981, 1990) are absent. These features do not favor the proposition that the Changning‐Menglian Proto‐Tethys Ocean had been closed in the Silurian‐Devonian and then reopened to form the Paleo‐Tethys Ocean in the Late Devonian but, rather, should be attributed to the results of the tectonic evolution of a single ocean developing from the Ordovician to the Carboniferous. The identification of some Paleozoic continental arc magmatic rocks emplaced at ~430–280 Ma in the western SMB (Hennig et al, 2009; Lehmann et al, 2013; Liu, Bi, et al, 2018; Mao et al, 2012; Nie et al, 2016) indicates the development of a long‐active subduction zone along the western margin of the SMB. This in turn reveals the existence of a similar ocean basin between the SMB and LCB to the CMO developing from the Early Paleozoic to the Late Paleozoic rather than a Late Paleozoic back‐arc ocean basin (e.g., Liu et al, 1993; Metcalfe, 2009, 2013, 2017; Sone & Metcalfe, 2008).…”

“…Meanwhile, intro‐oceanic subduction also induced back‐arc extension, which led to the formation of a new spreading ridge on the suprasubduction zone and oceanic basin that is an important component of the wide Paleo‐Tethys (the Changning‐Menglian Paleo‐Tethys Ocean). From a consideration of ~430–420 Ma Dazhonghe and Dapingzhang arc‐like volcanics (Lehmann et al, 2013; Liu, Bi, et al, 2018; Mao et al, 2012; Wang, Wang, et al, 2018), an alternative continental arc had been also present along the western margin of the SMB in the Silurian (Figure 9c). During Middle Devonian‐Early Permian times, a new ocean/rift basin between the LCB and BSB could have developed by transform faults at least since the Late Devonian (Figure 9d), which resulted in the variation of detrital sources in the LCB during Devonian to Early Permian times as discussed above.…”

“…Meanwhile, introoceanic subduction also induced back-arc extension, which led to the formation of a new spreading ridge on the suprasubduction zone and oceanic basin that is an important component of the wide Paleo-Tethys (the Changning-Menglian Paleo-Tethys Ocean). From a consideration of~430-420 Ma Dazhonghe and Dapingzhang arc-like volcanics (Lehmann et al, 2013;Liu, Bi, et al, 2018;Mao et al, 2012;, an alternative continental arc had been also present along the western margin of the SMB in the Silurian (Figure 9c). 4.…”

“…3. The identification of some Paleozoic continental arc magmatic rocks emplaced at~430-280 Ma in the western SMB (Hennig et al, 2009;Lehmann et al, 2013;Liu, Bi, et al, 2018;Mao et al, 2012;Nie et al, 2016) indicates the development of a long-active subduction zone along the western margin of the SMB. This in turn reveals the existence of a similar ocean basin between the SMB and LCB to the CMO developing from the Early Paleozoic to the Late Paleozoic rather than a Late Paleozoic back-arc ocean basin (e.g., Liu et al, 1993;Metcalfe, 2009Metcalfe, , 2013Metcalfe, , 2017Sone & Metcalfe, 2008).…”

Revisiting the tectonic evolution of the Triassic Palaeo-Tethys convergence zone in northern Thailand inferred from detrital zircon U–Pb ages

“…The Palaeozoic zircons originated from Ordovician to earliest Devonian igneous rock along the western margin of the Indochina Block (northern Thailand, Lao PDR to SW China), and around the Kham Duc complex and the Kontum Massif in the collision zone (central Vietnam), and Carboniferous igneous rocks of the Phetchabun Volcanic Belt. During this period, igneous rocks were generated in an active continental margin tectonic setting within the western Indochina Block (Qian et al 2015;Liu et al 2019). In addition, magmatism occurred in an active continental margin adjacent to a subduction zone along the South China Block (Nakano et al 2013), and was caused by the initiation of subduction and subsequent microcontinent collision (Faure et al 2018;Nguyen et al 2019).…”