Detrital zircon U-Pb age and Hf isotope constrains on the generation and reworking of Precambrian continental crust in the Cathaysia Block, South China: A synthesis

The South China Block, consisting of the Yangtze and the Cathaysia blocks, is one of the largest Precambrian blocks in eastern Asia. However, the early history of the Cathaysia Block is poorly understood due largely to intensive and extensive reworking by Phanerozoic polyphase orogenesis and magmatism which strongly overprinted and obscured much of the Precambrian geological record. In this paper, we use the detrital zircon U-Pb age and Hf isotope datasets as an alternative approach to delineate the early history of the Cathaysia Block. Compilation of published 4041 Precambrian detrital zircon ages from a number of (meta)sedimentary samples and river sands exhibits a broad age spectrum, with three major peaks at similar to 2485 Ma, similar to 1853 Ma and similar to 970 Ma (counting for similar to 10%, similar to 16% and similar to 24% of all analyses, respectively), and four subordinate peaks at similar to 1426 Ma, similar to 1074 Ma, similar to 780 Ma and similar to 588 Ma. Five of seven detrital zircon age peaks are broadly coincident with the crystallisation ages of similar to 1.89-1.83 Ga, similar to 1.43 Ga, similar to 1.0-0.98 Ga and similar to 0.82-0.72 Ga for known igneous rocks exposed in Cathaysia, whereas, igneous rocks with ages of similar to 2.49 Ga and similar to 0.59 Ga have not yet been found. The Hf isotopic data from 1085 detrital zircons yield Hf model ages (TENT) between similar to 4.19 Ga and similar to 0.81 Ga, and the calculated epsilon Hf(t) values between -40.2 and 14.4. The Archean detrital zircons are exclusively oval in shape with complicated internal textures, indicating that they were sourced by long distance transportations and strong abrasion from an exotic Archean continent. In contrast, the majority of detrital zircons in age between similar to 1.9 and similar to 0.8 Ga are euhedral to subhedral crystals, indicative of local derivation by short distance transportations from their sources. The oldest crustal basement rocks in Cathaysia were most likely formed by generation of juvenile crust and reworking of recycled Archean components in Late Paleoproterozoic at similar to 1.9-1.8 Ga, rather than in the Archean as previously speculated. Reworking and recycling of the continental crust are likely the dominant processes for the crustal evolution of Cathaysia during the Mesoproterozoic to Neoproterozoic time, with an intervenient period of significant generation of juvenile crust at similar to 1.0 Ga. Precambrian crustal evolutions of the Cathaysia Block are genetically related to the supercontinent cycles. By comparing detrital zircon data from Cathaysia with those for other continents, and integrating multiple lines of geological evidence, we interpret the Cathaysia Block as an orogenic belt located between East Antarctica, Laurentia and Australia during the assembly of supercontinent Columbia/Nuna at similar to 1.9-1.8 Ga. The Cathaysia Block amalgamated with the Yangtze Block to form the united South China Block during the Sibao Orogeny at similar to 1.0-0.89 Ga. The Laurentia-Cathaysia-Yangtze-Australia-East Antarctica connection gives the best solution to the paleo-position of Cathaysia in supercontinent Rodinia. The significant amount of similar to 0.6-0.55 Ga detrital zircons in Cathaysia and West Yangtze have exclusively high crustal incubation time of >300 Ma, indicating crystallisation from magmas generated dominantly by crustal reworking. This detrital zircon population compares well with the similar-aged zircon populations from a number of Gondwana-derived terranes including Tethyan Himalaya, High Himalaya, Qiangtang and Indochina. The united South China-Indochina continent was likely once an integral part of Gondwanaland, connected to northern India by a Pan-African collisional orogen. (C) 2014 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.