首页|Early crustal evolution of the eastern Yangtze Block: Evidence from detrital zircon U-Pb ages and Hf isotopic composition of the Neoproterozoic Huashan Group in the Dahongshan area
Early crustal evolution of the eastern Yangtze Block: Evidence from detrital zircon U-Pb ages and Hf isotopic composition of the Neoproterozoic Huashan Group in the Dahongshan area
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NSTL
Elsevier
The Yangtze Block is separated into the eastern Yangtze Block (EYB) and western Yangtze Block (WYB) by the Chongqing-Huaying line (CHL). An integrated study of detrital zircon Lu-Hf isotopes and U-Pb ages from two sandstones in the Huashan Group together with previous studies reveals six major tectonothermal events in the EYB occurring at about 2.87 Ga, 2.67 Ga, 2.5 Ga, 2.0 Ga, 1.84 Ga and 0.8 Ga. Combined with paleogeographic map, this study reveals distinct detrital zircon U-Pb ages and Hf isotopic characteristics in the western EYB and eastern EYB. The former has most zircon U-Pb ages grouped at about 2.0 Ga, 2.67 Ga and 2.87 Ga with sporadic 2.5 Ga ages. The similar to 2.5 Ga zircons show negative to slightly positive epsilon(Hf)(t) values. However, the latter has significant ages grouped at similar to 2.0 Ga and similar to 2.5 Ga with negligible 2.67 Ga and older zircon ages. The similar to 2.5 Ga zircons show negative to high positive epsilon(Hf)(t) values. The Early Neoarchean (2.7-2.6 Ga) was a significant period for production of mature continental crust in the western EYB and the majority of crustal materials were extracted from the depleted mantle until then. Zircon Hf isotopic compositions indicate that the Late Neoarchean to Early Paleoproterozoic event (similar to 2.5 Ga) involved both reworking of old crust and juvenile crust growth. With previous studies of sedimentary facies, lithochemical compositions, zircon morphology and zircon Hf isotopes, it is proposed that there are unexposed similar to 2.5 Ga basement rocks in the EYB. During the 2.2-1.8 Ga, subduction processes, collisional and post-collisional events were recorded in the north and west of the EYB, which can be correlated to the assembly and breakup of the supercontinent Columbia. Two changes in epsilon(Hf)(t) value at similar to 840 Ma and similar to 790 Ma have been found from detrital zircons in the northern margin of the EYB, which probably represent arc-continent collision and contine
NSTL
Elsevier
