Resolving impact volatilization and condensation from target rock mixing and hydrothermal overprinting within the Chicxulub impact structure  

作　　者：Thomas Déhais Stepan M.Chernonozhkin Pim Kaskes Sietze J.de Graaff Vinciane Debaille Frank Vanhaecke Philippe Claeys Steven Goderis 

机构地区：[1]Analytical,Environmental and Geo-Chemistry,Vrije Universiteit Brussel,Brussels,Belgium [2]Laboratoire G-Time,UniversitécLibre de Bruxelles,Brussels,Belgium [3]Department of Chemistry,Atomic&Mass Spectrometry,Ghent University,Ghent,Belgium

出　　处：《Geoscience Frontiers》2022年第5期16-31,共16页地学前缘（英文版）

基　　金：supported by the Research Foundation Flanders(FWO;project G0A6517N);the Belgian Federal Science Policy Office(BELSPO;project Chicxulub),the Excellence of Science Program(EoS project ET-HoME ID30442502);the VUB Strategic Research Program;the personal PhD fellowship awarded(projects11E6619N,11E6621N);the Fonds de la Recherche Scientifique(FRS-FNRS)for support;the FWO EoS project ET-HoME;funding for the acquisition of the MC-ICP-MS instrumentation(ZW15-02–G0H6216N);support from FWO under the form of the aforementioned EoS project and BOF-UGent;provided by IODPICDP Expedition 364,which was jointly funded by the International Ocean Discovery Program and the International Continental Scientific Drilling Program,with contributions and logistical support from the Yucatán State Government and the National Autonomous University of Mexico。

摘　　要：This work presents isotopic data for the non-traditional isotope systems Fe,Cu,and Zn on a set of Chicxulub impactites and target lithologies with the aim of better documenting the dynamic processes taking place during hypervelocity impact events,as well as those affecting impact structures during the post-impact phase.The focus lies on material from the recent IODP-ICDP Expedition 364 Hole M0077A drill core obtained from the offshore Chicxulub peak ring.Two ejecta blanket samples from the UNAM 5 and 7 cores were used to compare the crater lithologies with those outside of the impact structure.The datasets of bulk Fe,Cu,and Zn isotope ratios are coupled with petrographic observations and bulk major and trace element compositions to disentangle equilibrium isotope fractionation effects from kinetic processes.The observed Fe and Cu isotopic signatures,with δ^(56/54)Fe ranging from0.95‰to 0.58‰and δ^(65/63)Cu from0.73‰to 0.14‰,mostly reflect felsic,mafic,and carbonate target lithology mixing and secondary sulfide mineral formation,the latter associated to the extensive and long-lived(>105 years)hydrothermal system within Chicxulub structure.On the other hand,the stable Zn isotope ratios provide evidence for volatility-governed isotopic fractionation.The heavier Zn isotopic compositions observed for the uppermost part of the impactite sequence and a metamorphic clast(δ^(66/64)Zn of up to 0.80‰and 0.87‰,respectively)relative to most basement lithologies and impact melt rock units indicate partial vaporization of Zn,comparable to what has been observed for Cretaceous-Paleogene boundary layer sediments around the world,as well as for tektites from various strewn fields.In contrast to previous work,our data indicate that an isotopically light Zn reservoir(δ^(66/64)Zn down to0.49‰),of which the existence has previously been suggested based on mass balance considerations,may reside within the upper impact melt rock(UIM)unit.This observation is restricted to a few UIM samples only and cannot be extended to

关 键 词：Chicxulub impact structure Non-traditional stable isotopes Impact volatilization Impact condensation Hydrothermal alteration Target lithology mixing 

分 类 号：P542[天文地球—构造地质学]