Composition of impact melt particles and the effects of post‐impact alteration in suevitic rocks at the Yaxcopoil‐1 drill core, Chicxulub crater, Mexico

Abstract Petrographical and chemical analysis of melt particles and alteration minerals of the about 100 m‐thick suevitic sequence at the Chicxulub Yax‐1 drill core was performed. The aim of this study is to determine the composition of the impact melt, the variation between different types of melt particles, and the effects of post‐impact hydrothermal alteration. We demonstrate that the compositional variation between melt particles of the suevitic rocks is the result of both incomplete homogenization of the target lithologies during impact and subsequent post‐impact hydrothermal alteration. Most melt particles are andesitic in composition. Clinopyroxene‐rich melt particles possess lower SiO2 and higher CaO contents. These are interpreted by mixing of melts from the silicate basement with overlying carbonate rocks. Multi‐stage post‐impact hydrothermal alteration involved significant mass transfer of most major elements and caused further compositional heterogeneity between melt particles. Following backwash of seawater into the crater, palagonitization of glassy melt particles likely caused depletion of SiO2, Al2O3, CaO, Na2O, and enrichment of K2O and FeOtot during an early alteration stage. Since glass is very susceptible to fluid‐rock interaction, the state of primary crystallization of the melt particles had a significant influence on the intensity of the post‐impact hydrothermal mass transfer and was more pronounced in glassy melt particles than in well‐crystallized particles. In contrast to other occurrences of Chicxulub impactites, the Yax‐1 suevitic rocks show strong potassium metasomatism with hydrothermal K‐feldspar formation and whole rock K20 enrichment, especially in the lower unit of the suevitic sequence. A late stage of hydrothermal alteration is characterized by precipitation of silica, analcime, and Na‐bearing Mg‐rich smectite, among other minerals. This indicates a general evolution from a silica‐undersaturated fluid at relatively high potassium activities at an early stage toward a silica‐oversaturated fluid at relatively high sodium activities at later stages in the course of fluid rock interaction.

[1]  V. Lüders,et al.  Fluid inclusion evidence for impact‐related hydrothermal fluid and hydrocarbon migration in Creataceous sediments of the ICDP‐Chicxulub drill core Yax‐1 , 2004 .

[2]  A. Wittmann,et al.  Origin and emplacement of the impact formations at Chicxulub, Mexico, as revealed by the ICDP deep drilling at Yaxcopoil‐1 and by numerical modeling , 2004 .

[3]  D. Kring,et al.  Hydrothermal alteration in the core of the Yaxcopoil‐1 borehole, Chicxulub impact structure, Mexico , 2004 .

[4]  A. Wittmann,et al.  Geochemistry of drill core samples from Yaxcopoil‐1, Chicxulub impact crater, Mexico , 2004 .

[5]  A. Wittmann,et al.  Impact‐related dike breccia lithologies in the ICDP drill core Yaxcopoil‐1, Chicxulub impact structure, Mexico , 2004 .

[6]  D. Stöffler,et al.  The suevite of drill hole Yucatàn 6 in the Chicxulub impact crater , 2003 .

[7]  A. Wittmann,et al.  The ICDP Drill Core Yaxcopoil-1, Chicxulub Impact Crater, Mexico: Shock Metamorphism of the Impactite Units (794 894 m) , 2003 .

[8]  J. Morgan,et al.  Investigating a 65-Ma Old smoking gun: Deep drilling of the Chicxulub impact structure , 2003 .

[9]  A. Wittmann,et al.  Hydrothermal Alteration of the Impactites at the ICDP Drill Site Yax-1 (Chicxulub Crater) , 2003 .

[10]  H. Newsom,et al.  Hydrothermal alteration at the Lonar Lake impact structure, India: Implications for impact cratering on Mars , 2003 .

[11]  D. Kring,et al.  Preliminary Results on the Post-Impact Hydrothermal Alteration in the Yaxcopoil-1 Hole, Chicxulub Impact Structure, Mexico , 2003 .

[12]  A. Wittmann,et al.  Properties, Classification, and Genetic Interpretation of the Allochthonous Impact Formations of the ICDP Chicxulub Drill Core YAX-1 , 2003 .

[13]  P. Schulte,et al.  Fe-rich and K-rich mafic spherules from slumped and channelized Chicxulub ejecta deposits in the northern La Sierrita area, NE Mexico , 2003 .

[14]  B. Dressler,et al.  Chicxulub YAX-1 Impact Breccias: Whence They Come? , 2003 .

[15]  T. Hansteen,et al.  Trace element mobility during sub-seafloor alteration of basaltic glass from Ocean Drilling Program site 953 (off Gran Canaria) , 2002 .

[16]  H. Schmincke,et al.  Palagonite – a review , 2002 .

[17]  M. Warner,et al.  Geophysical constraints on the size and structure of the Chicxulub impact crater , 2002 .

[18]  B. Dressler,et al.  Terrestrial impact melt rocks and glasses , 2001 .

[19]  Pascal Lee,et al.  Impact‐induced hydrothermal activity within the Haughton impact structure, arctic Canada: Generation of a transient, warm, wet oasis , 2001 .

[20]  H. Melosh,et al.  Peak-ring formation in large impact craters: geophysical constraints from Chicxulub , 2000 .

[21]  A. Deutsch,et al.  Chicxulub impactites: Geochemical clues to the precursor rocks , 2000 .

[22]  E. González-Partida,et al.  Fluid Inclusions from Anhydrite Related to the Chicxulub Crater Impact Breccias, Yucatan, Mexico: Preliminary Report , 2000 .

[23]  H. Melosh,et al.  Hydrocode modeling of Chicxulub as an oblique impact event , 1999 .

[24]  J. Smit.  THE GLOBAL STRATIGRAPHY OF THE CRETACEOUS-TERTIARY BOUNDARY IMPACT EJECTA , 1999 .

[25]  C. Koeberl,et al.  Petrography and geochemistry of target rocks and impactites from the Ilyinets Crater, Ukraine , 1998 .

[26]  T. See,et al.  Compositional variation and mixing of impact melts on microscopic scales , 1998 .

[27]  C. Broman,et al.  IMPACT-RELATED HYDROTHERMAL ACTIVITY IN THE LOCKNE IMPACT STRUCTURE, JAMTLAND, SWEDEN , 1998 .

[28]  D. Ames,et al.  Dating of a regional hydrothermal system induced by the 1850 Ma Sudbury impact event , 1998 .

[29]  M. Pilkington,et al.  Size and morphology of the Chicxulub impact crater , 1997, Nature.

[30]  I. Gilmour,et al.  The Gardnos impact structure, Norway: Petrology and geochemistry of target rocks and impactites , 1997 .

[31]  L. Crossey,et al.  Post-impact hydrothermal alteration of the Manson impact structure , 1996 .

[32]  B. Bohor,et al.  Origin and diagenesis of K/T impact spherules—From Haiti to Wyoming and beyond , 1995 .

[33]  K. H. Wedepohl,et al.  The Composition of the Continental Crust , 1995 .

[34]  B. Schuraytz,et al.  Petrology of impact-melt rocks at the Chicxulub multiring basin, Yucatán, Mexico , 1994 .

[35]  J. Bishop,et al.  Roter Kamm impact crater, Namibia: Geochemistry of basement rocks and breccias , 1994 .

[36]  C. Koeberl,et al.  Geochemistry of impact glasses from the K/T boundary in Haiti - Relation to smectites and a new type of glass , 1992 .

[37]  W. Boynton,et al.  Petrogenesis of an augite-bearing melt rock in the Chicxulub structure and its relationship to K/T impact spherules in Haiti , 1992, Nature.

[38]  M. Pilkington,et al.  Chicxulub Crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatán Peninsula, Mexico , 1991 .

[39]  J. Zachos,et al.  Glass from the Cretaceous/Tertiary boundary in Haiti , 1991, Nature.

[40]  K. Keil,et al.  Alteration of basaltic glasses from north-central British Columbia, Canada , 1990 .

[41]  R. Grieve,et al.  Geochemistry of the melt and country rocks of the Lake St. Martin impact structure, Manitoba, Canada , 1990 .

[42]  W. Fyfe,et al.  Palagonitization of basaltic glass from DSDP Site 335, Leg 37; textures, chemical composition, and mechanism of formation , 1989 .

[43]  A. C. Olis.  Chemistry of Clays and Clay Minerals , 1989 .

[44]  M. McBride.  Chemistry of Clays and Clay Minerals , 1988 .

[45]  P. E. Brown,et al.  Fluid-inclusion evidence for impact heating at the Siljan Ring, Sweden , 1988 .

[46]  J. Schott,et al.  Fundamental processes controlling the first stage of alteration of a basalt glass by seawater: an experimental study between 200° and 320°C , 1987 .

[47]  W. Engelhardt,et al.  Origin of moldavites , 1987 .

[48]  R. W. Le Maitre,et al.  A Chemical Classification of Volcanic Rocks Based on the Total Alkali-Silica Diagram , 1986 .

[49]  S. Hart,et al.  Alteration of basaltic glass: Mechanisms and significance for the oceanic crust-seawater budget , 1983 .

[50]  C. Allen,et al.  Hydrothermally altered impact melt rock and breccia: Contributions to the soil of Mars , 1982 .

[51]  L. W. Alvarez,et al.  Extraterrestrial Cause for the Cretaceous-Tertiary Extinction , 1980, Science.

[52]  R. Grieve,et al.  Cratering processes: as interpreted from the occurrence of impact melts. , 1977 .