Calcite U-Pb Geochronology Revealing Late Ediacaran-Early Paleozoic Hydrothermal Alteration in the Stenian-Tonian Carbonate of Northeastern North China Craton

Two calcite LA-ICP-MS U-Pb ages of 534±26 Ma(MSWD=5.9)and 456±43 Ma(MSWD=3.8)were obtained from the Nanfen Formation,Xihe Group in the southern Liaoning Prov-ince,northeastern China,which significantly postdate the theoretical depositional age of sampling hori-zon.This means they represent timing of post-depositional hydrothermal event possibly induced by syn-chronous far-field magmatism in the South Qinling.Occurrence of common Pb enriched muddy compo-nents coupled with input of"mantle"-like common Pb could account for the relatively low U contents and high common Pb contents in the dated muddy carbonates.We recommend that micro-domains of carbonates are prescreened by rapid in situ carbonate U-Pb geochronology to demonstrate whether they are of primary or secondary origin before utilizing them for chemostratigraphic study.