Detrital zircon U–Pb ages and Hf isotopic composition of the Ordovician Duguer quartz schist, central Tibetan Plateau: constraints on tectonic affinity and sedimentary source regions

Abstract

AbstractMany previous studies have investigated the late Palaeozoic ophiolites, migmatites and high-pressure metamorphic belts of the Tibetan Plateau, whereas the early Palaeozoic evolution of the regions is relatively poorly understood. Lower Palaeozoic strata, including the Duguer quartz schist, occur in the Himalaya, Lhasa and South Qiangtang terranes of the Tibetan Plateau. In this study, we report the depositional age and sedimentary provenance of the Duguer quartz schist of the central South Qiangtang terrane, which enables us to interpret the tectonic affinity of the terrane. We obtained U–Pb ages, trace-element compositions and Hf isotopic data from zircons from the Duguer quartz schist. A total of 162 U–Pb analyses of detrital zircons from the schist yielded two pronounced age peaks at c. 600 Ma and c. 960 Ma. These results indicate that the provenance of the Duguer quartz schist is India Gondwana or the terranes that share an affinity with India Gondwana in the Tibetan Plateau, which include the South Qiangtang and Himalaya terranes. Detrital zircon crystals show large variations in Hf isotope compositions, with εHf(t), TDM and TDMC values of −52.5 to 13.2, 900–3300 Ma and 1010–4240 Ma, respectively. This suggests that the source area for the Duguer quartz schist included Precambrian rocks and, more specifically, Pan-African and Grenville–Jinning crustal material. During Pan-African and Grenville–Jinning events, crustal recycling and the addition of mantle material occurred in the source regions of the quartz schist, when the South Qiangtang, Lhasa and Himalaya terranes were all part of the northern margin of Gondwana.