Discovery of eclogite and its geological significance in Qiangtang area, central Tibet

Eclogite is first discovered from Qiangtang area, central Tibet, which occurs as a lens in the high-pressure metamorphic belt comprising glaucophane-muscovite schist and garnet-muscovite schist, along the south margin of Lungmu Co-Shuanghu Paleo-Tethys suture. A glaucophane 40Ar/39 Ar age of 220 Ma and a phengite 40Ar/39Ar age of 221.9 Ma have been obtained from blueschists associated with eclogite. The rock consists of garnet, omphacite, amphibole, phengite, and rutile, etc, and the jadeite content in omphacite ranges from 32.7% to 38.95%. It is estimated that the temperature of the eclogite is <500°C and pressure varies in the range of 1.56–2.35 GPa. The discovery of Qiangtang ecologite further supports that there is a suture zone of Indo-Chinese epoch in central Qiangtang area, and is very important for discssing the evolution of the paleo-ocean and paleo-plate tectonics in this area.