| Abstract: | Lancangjiang plate junction consisting of the Paleozoic and pre|Paleozoic underwent multiple tectonism and was overlain by sedimentary cover which resulted in rare reservation and scattered exposure of the Paleozoic and pre|Paleozoic. Meanwhile, Strong deformation and metamorphism result in difficulty in correlating various strata, in determining stratigraphical age and in distinguishing contact character. Therefore, Arguments for formation and evolution of the plate junction have not been convinced. This study advances some new conceptions.Whether or not the Lancangjiang Ocean existed in Late Paleozoic? There are controversies over differing opinions. Our basin research of the Qamdo block indicates no sufficient evidence for existence of the Lancangjiang Ocean in Late Paleozoic. Firstly, commonly, people think the Lancangjiang Ocean to be opened in Devonian to Middle Carboniferous , to be closed in Late Carboniferous to Late Permian and to be collided to orogeny in Triassic. However, along Qamdo—Jitang—Dengba zone, only Kargong Group and Machala Formation are exposed in Jitang and Shalong—Dengba regions, respectively. Both Kargong Group and Machala Formation consist of clastic rock intercalated with coal|bearing series in the lower and carbonate rock intercalated with a small amount of clastic rock, without abyssal deposits. Secondly, island arc volcanite resulting from collision other than ophiolite suite has been discovered along the Lancangjiang in the Qamdo block. In view of the above|mentioned facts, we make an approach to evolution of the Lancangjiang plate junction by correlation with the Jinshajiang plate junction. |
