Tectonic evolution of the Western Kunlun orogenic belt in northern Qinghai-Tibet Plateau: Evidence from zircon SHRIMP and LA-ICP-MS U-Pb geochronology

Abstract

The Western Kunlun Range in northern Qinghai-Tibet Plateau is composed of the North Kunlun Terrane, the South Kunlun Terrane and the Karakorum-Tianshuihai Terrane. Here we report zircon SHRIMP and LA-ICP-MS U-Pb ages of some metamorphic and igneous rocks and field observations in order to provide a better understanding of their Precambrian and Palaeozoic-early Mesozoic tectonic evolution. Based on these data we draw the following conclusions: (1) The paragneisses in the North Kunlun Terrane are likely of late Mesoproterozoic age rather than Palaeoproterozoic age as previously thought, representing tectonothermal episodes at 1.0-0.9 Ga and ~0.8 Ga.(2) The North Kunlun Terrane was an orogenic belt accreted to the southern margin of Tarim during late Mesoproterozoic to early Neoproterozoic, the two episodes of metamorphisms correspond to the assemblage and breakup of Rodinia respectively. (3) The Bulunkuole Group in western South Kunlun Terrane, which was considered to be the Palaeoproterozoic basement of the South Kunlun Terrane by previous studies, is now subdivided into the late Neoproterzoic to early Palaeozoic paragneisses (khondalite) and the early Mesozoic metamorphic volcano-sedimentary series; the paragneisses were thrust onto the metamorphic volcano-sedimentary series from south to north, with two main teconothermal episodes (i.e., Caledonian, 460-400 Ma, and Hercynian-Indosinian, 340-200 Ma), and have been documented by zircon U-Pb ages. (4) In the eastern part of the South Kunlun Terrane, a gneissic granodiorite pluton, which intruded the khondalite, was crystallized at ca. 505 Ma and metamorphosed at ca. 240 Ma. In combination with geochronology data of the paragneiss, we suggest that the South Kunlun Terrane was a Caledonian accretionary orogenic belt and overprinted by late Paleozoic to early Mesozoic arc magmatism.

Geological characteristics and age of the Dahongliutan Fe-ore deposit in the Western Kunlun orogenic belt, Xinjiang, northwestern China

“…Therefore, the Paleoproterozoic rocks in either the North Kunlun or the Tianshuihai terranes, or both of them, are likely the detrital sources for the Tianshuihai metasedimentary rocks.Regarding the zircon age population of 2076-1644 Ma (small peaks: ca. 2051 and 1835 Ma), a few metamorphic ages of 1900 ± 12 Ma (gneissic granite) (Zhang et al, 2003c(Zhang et al, , 2007 and 2016 ± 39 Ma (meta-volcanic rocks) have been reported in the North Kunlun and Tianshuihai terranes. The 2000-1830 Ma metamorphic event have been widely recognized in the North Kunlun terrane (Wang, 2011).…”

“…The protoliths to the Precambrian metamorphic rocks had undergone amphibolite facies metamorphism in the Neoproterozoic (ca. 1.0-0.9 and 0.8 Ga) (Matte et al, 1996;Yuan et al, 2002Yuan et al, , 2003Xiao et al, 2003;Zhang et al, 2003aZhang et al, , 2007. The basement is overlain by a low-grade metamorphosed Upper Neoproterozoic (Sinian; ca.…”

“…From north to south, the belt is subdivided into the North Kunlun, South Kunlun, Tianshuihai and Karakorum terranes separated by the Oytag-Kudi suture, Mazar-Kangxiwar suture and Hongshanhu-Qiaoertianshan suture, respectively (Fig. 1b) (Pan, 1996;Jiang et al, 2002;Pan et al, 2004;Zhang et al, 2007).…”

“…For example, Xiao et al (2005) and Liu et al (2015) favoured Tianshuihai to be the western extension of the Songpan-Ganzi block which collided with the South Kunlun terrane in the Early Mesozoic. However, Yuan et al (2003) and Zhang et al (2007) proposed that Tianshuihai was part of the South Kunlun terrane. Many large-scale sedimentary-metamorphic Fe deposits have been discovered in the Precambrian strata of the Tianshuihai terrane, notably the Zankan, Yelike, Laobing and Mokaer magnetite deposits in the Bulunkuole Group (Fig.…”

“…The protoliths of the Bulunkuole metamorphic rocks can be recognized as a suite of volcaniclastic and sedimentary carbonate sequence (Huang, 2014). The depositional age of the Bulunkuole Group remains controversial: (1) Inherited zircon ages of 600-2200 Ma from two gneiss samples nearby Taxkorgan suggest that the deposition of the Bulunkuole Group occurred between Neoproterozoic and Early Paleozoic (Zhang et al, 2007); (2) Zircon U-Pb ages of 2130-2700 Ma have been reported on the metamorphic rocks comparable to those of the Bulunkuole Group, in western Pamir syntaxis (Wang, 2008); (3) U-Pb zircon age of 2481 ± 14 Ma has been reported from volcanic rocks in the Bulunkuole Group located west of Taxkorgan ; (4) U-Pb zircon dating of biotite quartz schist, felsic schist and plagioclase amphibole schist from Zankan, Yelike, Laobing and Zankandong Fe deposits show that the Bulunkuole Group was formed at 510-540 Ma and metamorphosed at 463-480 Ma (Yan et al, 2012;Huang, 2014). The greenschist to amphibolitefacies metamorphosed Saitula Group (Fig.…”