Chronology and geochemistry of the volcanic rocks in Woruo Mountain region, northern Qiangtang depression: Implications to the Late Triassic volcanic-sedimentary events

Abstract

A suite of sedimentary-volcaniclastic rocks intercalated with the volcanic rocks unconformably overlies the Triassic Xiaochaka Formation in the Woruo Mountain region, Qiangtang Basin, northern Tibet. The vitric tuff from the base of these strata gives a SHRIMP zircon U-Pb age of 216 ± 4.5 Ma, which represents the age of the Late Triassic volcanic-sedimentary events in the Woruo Mountain region, and is consistent with that of the formation of the volcanic rocks from the Nadi Kangri Formation in the Nadigangri-Shishui River zone. There is a striking similarity in geochemical signatures of the volcanic rocks from the Woruo Mountain region and its adjacent Nadigangri-Shishui River zone, indicating that all the volcanic rocks from theQiangtang region might have the same magmatic source and similar tectonic setting during the Late Triassic. The proper recognition of the Late Triassic large-scale volcanic eruption and volcanic-sedimentary events has important implications for the interpretation of the Late Triassic biotic extinction, climatic changes and regressive events in the eastern Tethyan domain, as well as the understanding of the initiation and nature, and sedimentary features of the Qiangtang Basin during the Late Triassic-Jurassic.

Sedimentary and tectonic evolution of the southern Qiangtang basin: Implications for the Lhasa‐Qiangtang collision timing

“…In particular, the youngest 220–210 Ma peak is typical of Upper Triassic strata of southern Qiangtang [ Gehrels et al , ]. Volcanic and granitoid rocks of this age are widely exposed in central and northern Qiangtang [ Fu et al , ; Li et al , ; J. Wang et al , ; Wu et al , ; Zhai et al , ], and yield similar ε Hf (t) values [ Li et al , ; Zhai et al , ] as those in upper Biluoco sandstones. Sandstone petrography and detrital‐zircon ages and Hf isotopic ratios thus converge to indicate the Paleozoic to Upper Triassic strata and igneous rocks of central Qiangtang area as the detrital source of the upper Biluoco Formation.…”

Tectonic evolution and high-pressure rock exhumation in the Qiangtang terrane, central Tibet

“…Upwards, the conglomerate grades into sandstone intercalated with siltstone, followed by ∼ 300 m of tuffaceous sand-and siltstone, rhyolite and limestone intercalations. One rhyolite layer was dated as 214 ± 4 Ma and actinolite from the underlying units gave an Ar-Ar age of 219.7 ± 6.5 Ma Wang et al, 2008a).…”

“…5. Numbers in parentheses refer to the following references: (1) ; (2) Zhai et al (2010); (3) Zhai et al (2013b); (4) Wang et al (2008a); (5) unpublished data; (6) Zhai et al (2009); (7) Zhao et al (2014); (8) Kapp et al (2003b); (9) Zhu (2005).…”

U–Pb zircon age, geochemical and Lu–Hf isotopic constraints of the Southern Gangma Co basalts in the Central Qiangtang, northern Tibet

“…A recent study suggests that the central Qiangtang is a key locality to investigate the evolution of the opening and closure of the Paleo-Tethys Ocean, specifically the Longmu Co-Shuanghu suture zone (LSLS), and has generated new evidence on the evolution of the Paleo-Tethys Ocean. The most important evidence includes: (1) the discovery of Paleozoic ophiolite (Hu et al, , 2014Li et al, 2008;Wang et al, 2008aWang et al, , 2008bWu, 2013;Wu et al, 2009;Zhai et al, 2010); (2) the identification of Carboniferous ophiolite and island arc magmatic rocks in the central Qiangtang block (Hu et al, 2013;Shi et al, 2009;Zhai et al, 2013a); and (3) a record of subduction and collision of the Paleo-Tethys Ocean in the Late Triassic has also been uncovered: for example, island arc volcanic rocks in the Qiangtang area (e.g., Hu et al, 2010;Wang et al, 2007Wang et al, , 2008aWang et al, , 2008bZhai et al, 2007;Zhai et al, 2013b). In addition, a Triassic highpressure metamorphic belt, trending from west to east for about 500 km, is present in the middle of the Qiangtang terrane, and is considered to record the closure of the Paleo-Tethys Ocean (e.g., Bao et al, 1999;Deng et al, 2000;Dong and Li, 2009;Hening, 1915;Kapp et al, 2000Kapp et al, , 2003Li et al, 2006Li et al, , 2008Pullen et al, 2008;Zhai et al, 2011a, b;Zhang et al, 2010).…”