The Northern Qaidam Basin The Tanjianshan Group Volcanic Rocks In Combination And Formation Environment

The paper mostly study volcanic rocks of Tanjianshangroup in the north of Chaidamu basin,Qinghai province. The rocks have been systemly studied according to petrology, petrochemistry, geochemistry of rare earth and microelement, isotopic age. We infer diagenetic environment of rocks in base of them.There are the rocks in the north of Chaidamu basin here and there. Most of rocks are deterioration. There are some carbonating rocks. Most of rocks are basic and acidic. The ages of Tanjianshangroup rocks were formed in 408-5 1 8Ma.They belong to Ordovician and Silurian period according to isotopic ages. In term of regional geology, rock character, isotopic age. We newly set off Tanjianshangroup. The name of Tanjianshangroup is abolished. That is to say, Ordovician period O_1-2^h, Ordovician period O₃^c>, Ordovician period O₃^y. The rocks have characters of rift valley and volcanic arc according to rock association, petrochemistry, geochemistry of rare earth and microelement. Consequently, We infer diagenetic environment of rocks. They have suffered several stages of forming rift valley, stable rift valley and arc.