Paleoproterozoic Demala Group complex in the Zayu area, Tibet

A medium and high grade metamorphic series is exposed in the Zayu area, Tibet. It consists of schist, gneiss and granulitite （leptynite） with amphibolite and marble. On the basis of petrological, geochemical and isotope geological studies and characteristics of protoliths combined with the integrated comparison and analysis of structure strata events, two lithostratigraphic units the Mosetong and Shedu formation complexes have been newly established, which are called by a joint name the Demala Group complex. According to its Sm Nd ageof 2 264～2 145 Ma, it is considered to be Paleoproterozoic in age. The rocks of this group complex very closely resemble khondalite formed 2 300～2 100 Ma ago in Madras of India and Sri Lanka, so it is possibly a sequence of neritic deposits on the northern margin of the nucleus of Gondwana.