1:250 000 Toza Kangri and Tuohepingco Sheets in Xizang

The recent advances in the geological survey of the 1:250 000 Toza Kangri and Tuohepingco Sheets in Xizang are generalized as follows. (1) Eight group-scale, twenty-four formation-scale and several informal (litho)stratigraphic units and mappable units are designated or redelimited. (2) The Devonian strata in the Yaxi'ergou region are assigned to the Shouxinghu and Lazhuglung Formations. (3) The formerly Devonian Yaxi'er Group in the northern part of the Wanquan River are redivided and incorporated into the Lower Triassic strata Wanquanhe Group in the light of fossil data available. (4) There is an angular unconformable contact between the Lower Cretaceous Tielongtan Group and the Upper Jurassic Sumxico Group. (5) The Neogene Kangtog Formation lies with an angular unconformity upon the underlying strata, and there exists an angular unconformable contact between the first and second members of the Kangtog Formation. (6) The formerly pre-Devonian Amugang Group is redivided into the Carboniferous-Permian strata in the Qingtang region. (7) The main characteristics of the Horbaco Group rocks are ascertained. (8) The Triassic Xiaocaka Group is confirmed to be overlain with an angular unconformity upon the underlying strata. (9) abundant fossils are collected from the Sandaohu Jurassic measured stratigraphic section. The recent progress in petrology includes:(1) the mapping of abundant basic dikes and acidic stocks (veins) in the Tuohepingco region; (2) knowledge of the oceanic-island environment for the formation of the Zhanjin Formation volcanic rocks during the Early Permian; (3) absence of the Cenozoic volcanic rocks in the Tuohepingco region, and (4) discovery of the Cenozoic alkaline volcanic rocks in the area north of the Tianhui Lake with a younger age than that of the Yulinshan volcanic rocks. Tectonically, the Orbaco-Bairabco fault is interpreted as a boundary fault between the Karakorum landmass and Qiangtang landmass. In addition, a large-sized placer gold deposit is explored as well.