Sedimentary Characteristics Of The Cambrian Clastic Rocks In Southern Part Of South China And Their Geotectonic Implications

The Cambrian in southern part of South China is a large and thickness clastic system, which is located in the southeast of South China ancient land. By sorting the regional rock characteristics and depositional environment should provide some important guides for the Yangtze block in the construction of the Cambrian ancient geological. The topics of this study focus on studying characteristics of Damingshan, Dayaoshan and Daguishan Cambrian sedimentary facies, paleocurrent, rock geochemistry and detrital zircon age spectrum characteristics and combined with the same period of formation development characteristics, determine the margin of the Yangtze ancient sedimentary environments and prototype basin characteristics.In this study five results can be explore by field and laboratory experimental works.The stratigraphic sequence of the Cambrian grain size in the south-east Guangxi show thicker to upper part and thinner to north part, from a chert, carbonaceous shale rock assemblage dominated by the gradual upward into sandstone, pebbly sandstone dominated the clastic sequence.Based on previous data, lithology, paleontology, and sedimentary textures and structures co ard into sandstone, The sediments of Guangxi can be grouped into two sedimentary fades:turbidite facies and abyssal facies. From the bottom upward, the sedimentary facies changed from turbidite facies to abyssal facies,This showed typical characteristics of progressive sequence. This set of clastic rocks of the ancient flow of the overall point north, indicating sediment spread from south to north direction.According to analysis of samples of thin sheets for identification and the use of sandstone framework grain analysis and the source direction, combined with rock features, that the Cambrian in southeastern Guangxi provenance tectonic attributes to re-cycle the main belt, both the volcanic arc, characteristics of Precambrian basement uplift.In the Cambrian clastic rock geochemical analysis, including major elements, trace elements and rare earth element tectonic discrimination diagrams show that the tectonic environment in which they are for the active continental margin, is the re-cycle continental collision orogenic belt.LA-ICPMS detrital zircon dating and age, pedigree analysis showed that this clastic rocks source should Gondwana, and the source area near the northern margin of India (now low and high Himalayan belt) and Arabian-Nubian massif.