Zircon U–Pb and garnet Lu–Hf geochronology of eclogites from the Lhasa Block, Tibet

Tracing the Transhimalayan magmatic belt and the Lhasa block southward using zircon U–Pb, Lu–Hf isotopic and geochemical data: Cretaceous – Cenozoic granitoids in the Tengchong block, Yunnan, China

“…We therefore suggest that the late Cretaceous -early Cenozoic, paired I-and S-type, Transhimalayan magmatic belt in southern Tibet can be traced at least as far as the Tengchong block. The South -Central Lhasa block boundary is characterized by Permian UHP metamorphic rocks that most likely originated during backarc closure and subsequent collision between the South and Central Lhasa Blocks (Cheng et al, 2012). Similar rocks have yet to be documented in the western Tengchong block, further research is thus needed to refine this rather simple, first order palaeogeographic model.…”

Pseudosection modelling and garnet Lu–Hf geochronology of HP amphibole schists constrain the closure of an ocean basin between the northern and southern Lhasa blocks, central Tibet

“…The Sumdo eclogite, which has typical normal mid‐ocean ridge basalt (N‐MORB) geochemical signatures, and the Carboniferous–Permian island‐arc volcanism across the northern Lhasa block (Yang et al., ) indicate that the oceanic crust subducted to the north beneath the northern Lhasa block c . 266–227 Ma (e.g., Chen et al., ; Cheng et al., ; Dong et al., ; Yang et al., ; Zeng et al., ; Zhang et al., ). Glaucophane blueschist enclosed in Permian limestone and quartzite has been identified from the Pangna village (Figure ), which is ~80 km west of Sumdo (Liu & Liu, ).…”

“…273 Ma to c . 230 Ma (Cheng et al., , ; Weller et al., ; Yang et al., ; Zeng, Jing, Gao, & Chen, ). A diachronous subduction model, i.e., different slices that had distinct P–T histories and underwent ultra‐high/high pressure (UHP/HP) metamorphism at different times, has been proposed (Cheng et al., ).…”

Post-peak metamorphic evolution of the Sumdo eclogite from the Lhasa terrane of southeast Tibet

“…Multichronometric studies, including U-Pb, Lu-Hf, Sm-Nd and Ar-Ar, of the eclogites from other localities in the Lhasa terrane, suggest a large time span of over ~35 Myr for the peak eclogite-facies metamorphism Cheng et al, 2012. Thus, it remains unclear when the high-pressure metamorphism occurred, whether multiple high-pressure metamorphic events are responsible for the spread in ages, and whether the age difference of ~65 million years implies a prolonged subduction or reflects differences in the timing of eclogite-facies metamorphism in distinct slices.…”

“…The Lhasa terrane is thus essential for revealing the origin and evolutionary history of the Himalayan-Tibetan orogen. The recent discovery of the Carboniferous ophiolite suite and the Permian (ultra)high pressure eclogite Cheng et al, 2012 in the Sumdo complex of the Lhasa terrane, indicates the existence of a Paleo-Tethys suture in the central Lhasa that divides the Lhasa terrane into northern and southern blocks.…”