The Stratigraphic Sequence And Tectono-paleogeography Of Yanbian Group In Western Part Of South China Block

Yanbian group was in the western part of Yangtze block, South China, outcropping in the middle part of the Kang-Dian region. It's a volcanic-sedimentary succession which is overlying the Kangding Complex. The researches of the Yanbian group can provide very important clues for the tectonic evolution of Yangtze continent during Rodinia breaking up. The researches about Kang-Dian region till now are primarily around the tectonic property studies of middle Neoproterozoic magmatism. We discuss the geological characteristics and tectonic property of the Yanbian group, proceed with the clastic rock in Yanbian group. which have very important significance in the studies of the position of Yangtze continent during Rodinia dissamble.According to the detailed fieldwork and lab analysis, we obtained a few conclusions as follows:1. Base on the detailed fieldwork, structural analysis and isotope age, the stratigraphic sequence of Yanbian group was redefined. It's respectively zhagu, Xiaoping and yumen formation from the bottom up.2. According to the previous data, sedimentary structures-observed during fieldwork and researches on the stratigraphic sequence characteristics of Yanbian group, analyzed the sedimentary facies of Yanbian group. It's a deep-see debris flow and turbidite system. It's a clastic rock system,of which grain size becomes gradually smaller upwards.3. With the studies of petrological characteristics, the petrophysic feature and statistic analysis on petrogenetic minerals of clasolite from Yanbian group, analyzed the source direction. Its provenance was volcanic arc.4. Geochemical analysis of the detrital rocks from Yanbian group were done, and the major element, trace element and REE tectonic setting identification diagrams show us that the tectonic setting is active continental margin, which is associated with continental-arc.As a result, with the fieldwork and lab data the stratigraphic sequence of Yanbian group is redefined. The tectonic setting is associated with continental margin and continental arc. The proto-type basin of Yanbian group may was arc-back basin. The western part of Yangtze block was located in continental arc-active continental margin. It has very significance in the tectonic evolution of Yangtze continent during Rodinia break up.