Zn Isotope Study On The End-guadalupian Mass Extinction In The Permian

The end-Guadalupian mass extinction(the GLB event),occurred at Middle-Late Permian transition,has been considered as a global event.However,the extent,bio-selectivity,level,temporal constrain,and mechanism of this event are far beyond consistency.Thus,it is important for us to find a new geochemical proxy to analyze the GLB event.Zinc is an essential micronutrient element to organisms,which widely involves in a variety of bio-processes and plays a vital role in biological life.Zn isotope fractionation in the carbonate rocks and sea water can hardly be influenced by temperature and thus the carbonate preserves the original Zn isotope information of the surface seawater.In this study,we studied the Zn isotope from the GSSP section of basal Lopingian at Penglaitan in Laibin,Guangxi,South China,and the main objectives are to reveal the paleoclimatic and paleoenvironmental impact on bio-evolution during the late Guadalupian extinction,and to discuss the mechanism of the end-Guadalupian mass extinction.The results show two significant Zn isotopic negative excursions around the GLB.The first phase of ~0.46 ‰ negative excursion begins with the transition from Jinogondolella xuanhanensis conodont zone to J.granti conodont zone at most,corresponding to the extinction interval of corals and brachiopods.The second phase of excursion begins with the top of J.granti conodont zone with value down to ~0.4 ‰,corresponding to the extinction interval of fusulinids,conodonts and ammonites.It should be noted that the changes of Zn isotopic composition are temporally agreement with the GLB event.Considering of the paleoenvironment background at that time,the first phase of extinction might be related to the volcanism of Emeishan large igneous province,and the second one might be related to the high amplitude regression on global scale.In sum,Zn isotope data may provide a useful constraint on the mechanism of the end-Guadalupian mass extinction.