Finding of ancient materials in Cathaysia and implica-tion for the formation of Precambrian crust
Finding of ancient materials in Cathaysia and implication for the formation of Precambrian crust

U-Pb dating for fifty-six detrital zircons from a paragneiss in Nanxiong area, northern Guangdong Province, indicates that the latest Neoproterozoic sediments in Cathaysia hinterland are composed of numerous Grenvillian and Neoarchaean clastic materials, as well as some Mesoproterozoic detritus. Minor Paleoarchaean (3.76 Ga) and Mesoarchaean (3.0–3.2 Ga) zircons, which are the oldest zircons in South China, also are firstly found in the sediments, suggesting that the Cathaysia Block may contain very old materials. The Hf isotope compositions of thirty-seven zircons reveal that these clastic materials have different origins. Minor zircons crystallized from magma generated from relatively juvenile crust, while the parental magma of most zircons was derived from ancient crust. Integration of U-Pb dating and Hf isotope analysis of these zircons suggests that the generation of juvenile crust in the Cathaysia block mainly occurred at 2.5–2.6 Ga. Mesoarchaean (3.0–3.3 Ga), late Paleoproterozoic (～1.8 Ga) and Paleoarchaean (～3.7 Ga) may also be important episodes of crustal growth. Grenvillian magmatism is extremely intense, but it mainly involved recycling of ancient crustal components with little formation of juvenile crust. The marked presence of ～2.1 Ga Hf model ages and the absence of the zircons with crystallization ages at ～2.1 Ga suggest that the parental magma of many zircons was probably derived from the mixed source consisting of Neoarchaean and late Paleoproterozoic materials. Supported by the National Natural Science Foundation of China (Grant Nos. 40221301, 40372087 and 40132010) and ARC Discovery and Linkage International grants