Sedimentary Provenance And Tectonic Evolution Of Neoproterozoic To Early Paleozoic Sedimentary Rocks In The South Wuyi Area

To investgate the basement tectonic framework of the Cathaysia Block,the representative Neoproterozoic to Early Paleozoic steata in different sections of South Wuyi area along the southern Nanping–Ninghua–Ganzhou tectonic belt was selected for U-Pb dating and geochemical analysis,so as to identify the source of sediments and tectonic setting.Integrated petrology,geochronology and geochemistry show that the Neoproterozoic-Early Paleozoic strata in South Wuyi area are mainly composed of metafeldspathic quartz sandstones and metasiltstones,among which Huanglian and Lintian Formations are intercalated by siliceous rocks.The U-Pb geochronology data of 910 groups are obtained from 13 samples,which mainly have three peaks of ca.745 Ma,ca.988 Ma and ca.2476 Ma,which represent the three important tectonothermal events in the source area of sediments.Among them,ca.745 Ma event is coeval with the arc magmatic rocks in Nanping-Ninghua–Ganzhou tectonic belt,which mainly reflect the arc magmatism in this period.ca.988 Ma event is the most intense one in the source area,corresponding to the global Grenville orogeny,the detrital zircons come from the magmatic rocks of the Cathaysia Block or adjacent area.ca.2476 Ma event corresponds to global paleo-continental-core growth,indicating that the global tectonic event also recorded in the source area of South Wuyi sedimentary rocks,which is conducive to the global comparative study of the Cathaysia Block.It is worth mentioning that several zircons of more than ca.2800 Ma are also obtained in this study,indicating that the Cathaysia Block has Archean basement or accepts a more ancient material supplyment.In this study,the samples of Nanhua to Cambrian strata in different areas along the Nanping–Ninghua–Ganzhou tectonic belt show that they have low CIA(52.6–77.4)and high ICV(0.84–1.42)values,suggesting weak chemical weathering and low clastic maturity.Their relatively low Th/U(4.12–6.81)and Rb/Sr(0.68–5.97)ratios reflect a simple recycling history.The contents of Sc,Cr,Co,and Ni in most of the metamorphic sandstone samples are relatively low,and the ratios of K / Rb,La / Sc,Th / Sc,Co / Th,and other elements are similar to the sediments from the felsic source area.The backarc basin setting of Nanhua to Cambrian system,which should be formed on the active continental margin,is distinguished by geochronology and geochemical discrimination diagrams.The geochemical features,in combination with detrital zircon age distributions,indicate that the Nanhua to Cambrian strata are probably deposited in a back-arc basin.These evidences suggest that the Cathaysia Block is assembled by multiple terranes during the Neoproterozoic to the early Paleozoic.