Acta Geological Sinica
Gulu hot spring is located on the west bank of Sangqu river,Gulu town,Nagqu county of Tibet.The elevation is about 4700～4750 m a.s.l.. It is still intensely activing. Consisted mainly by geyserite,the sinter formed a medium scale hot spring type Cs-deposit. It is the result of collision of Indian and Eurasian plates. On the basis of investigating the characteristics of the geology and geomorphology,this paper divided the sinter into,south and north areas,5 suites. Suite 1 is located in the south area and under the big geyserite platform. It cut across the Sangqu river and reaches its east bank and formes the fluvioglacial platform of the Penultimate Glacial Period (Paran Glacial Period ). Suite 2 consists of the big geyserite platform of the south area.Consists of conglomerate cemented by sinter,Suite 3 located under geyserite platform of the north area and cut across the Sangqu river and reaches the east bank too. Which Consists of the fluvioglacial platform of the Last Glaciation (Laqu Glacil Period)of the late Late Pleistocene. Suite 4 Consists of the geyserite platform of the north area and is divided into,south and north,two small parts separated by a small ditch. Everyone of the two parts consisted by several geyserite pyramids. Suite 5 consists of the geyserite pyramids that modern activing. According to nine U-series dates from Gulu geyserite and the characteristics of the geology and geomorphology,this paper divided Gulu Cs-deposit into five stages. Stage 1,although We have not get the dates temporarily,according to the position of geomorphology and stratigrphic sequence,which can be inferred that it is deposit after Ningzhong glacial period,maybe the early-middle stage of the largest International period (about 0.5～0.4 Ma).Stage 2 is 0.38～0.25 Ma BP. It is correspond from the late stage of the largest International period to the early stage of Paran glacial period. Stage 3 is about 0.22 Ma BP which is the early stage of Paran glacial period. Stage 4 is 108.6～17.2 ka BP that is formed from late stage of the Last Glaciation to the Laqu glacial period. Stage 5 is from 5.3 ka BP,to the present. From early to late stage,the content of SiO2 gradually falls,while contents of Cs rise. The reason is that impurity components are not expelled from crystals with the falling degree of SiO2 ordering.