U-Pb geochronology and Hf-isotopes on detrital zircons of Lower Paleozoic strata from Hainan Island: New clues for the early crustal evolution of southeastern South China

摘要

Integrated in situ U-Pb dating and Hf-isotope analysis on detrital zircons from six sandstone samples from Hainan Island have been used to identify dastic sedimentary provenances, regional magmatic activity and crustal evolution processes. Four samples (2011XL-1,2011JB-1,09HN54 and 2011GB-1) are from previous mapped Silurian strata and the other two samples (2011TD-1 and 09HN39) belong to Ordovician and Cambrian strata, respectively. A total of 463 concordant U-Pb zircon analyses of the six samples define five major age populations: 2598-2320 Ma (a peak of 2480 Ma), 1944-1606 Ma (peak-1750 Ma), 1600-1406 Ma (peak-1502 Ma), 1288-902 Ma (peak-957 Ma), 470-427 Ma (peak-442 Ma) and two subordinate populations at 898-710 Ma (peak-730 Ma) and 618-513 Ma (peak-578 Ma). The combination of age peaks within the samples provide a record of igneous activity in the source region: the 2480 Ma peak is consistent with those ages reported for Neoarchean global continental growth; the 1944-1606 Ma population correlates with the time of assembly of the supercontinent Nuna (Columbia); the 1502 Ma peak with documented magmatic activity on Hainan Island; and the 1288-902 Ma and 898-710 Ma populations with global tectonothermal activity associated with assembly and breakup of Rodinia. Our data also reveal a 618-513 Ma population that may relate with the assembly of Gondwana. The distinctive age peak at 442 Ma indicates input from a region affected by the Kwangsian orogeny. The combined ages and Hf-isotope data for each population suggest that generation of juvenile crust occurred at 1900-1400 Ma, 940-740 Ma and 470-430 Ma. Most of the other age populations that display negative sHf(t) values suggest reworking of older crust. (C) 2014 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.