1. New shock microstructures in titanite (CaTiSiO5) from the peak ring of the Chicxulub impact structure, Mexico
- Author
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Timms, NE, Pearce, MA, Erickson, TM, Cavosie, AJ, Rae, ASP, Wheeler, J, Wittmann, A, Ferriere, L, Poelchau, MH, Tomioka, N, Collins, GS, Gulick, SPS, Rasmussen, C, Morgan, JV, Chenot, E, Christeson, GL, Claeys, P, Cockell, CS, Coolen, MJL, Gebhardt, C, Goto, K, Green, S, Jones, H, Kring, DA, Lofi, J, Lowery, CM, Ocampo-Torres, R, Perez-Cruz, L, Pickersgill, AE, Rebolledo-Vieyra, M, Riller, U, Sato, H, Smit, J, Tikoo, SM, Urrutia-Fucugauchi, J, Whalen, MT, Xiao, L, Yamaguchi, KE, Curtin University [Perth], Planning and Transport Research Centre (PATREC), Australian Resources Research Centre, Kensington, NASA Johnson Space Center (JSC), NASA, Department of Earth Science and Technology [Imperial College London], Imperial College London, University of Liverpool, Arizona State University [Tempe] (ASU), Natural History Museum [Vienna] (NHM), Albert-Ludwigs-Universität Freiburg, Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Department of Earth Science and Engineering [Imperial College London], University of Texas at Austin [Austin], Géosciences Montpellier, Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA)-Université de Montpellier (UM)-Institut national des sciences de l'Univers (INSU - CNRS), Institut de chimie et procédés pour l'énergie, l'environnement et la santé (ICPEES), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Earth and Ocean Sciences, LeRoy Eyring Center for Solid State Science, Department of Geology, University of Freiburg [Freiburg], DGS, Jackson School of Geosciences, Institute of Geophysics [Austin] (IG), Analytical, Environmental & Geo-Chemistry, Earth System Sciences, Chemistry, and Natural Environment Research Council (NERC)
- Subjects
Geochemistry & Geophysics ,PLASTIC-DEFORMATION ,010504 meteorology & atmospheric sciences ,EBSD ,Shock metamorphism ,Metamorphism ,Titanite ,U-PB ,Titanite, Shock metamorphism, Mechanical twinning, Dislocation slip system, Meteorite impact, EBSD ,Mechanical twinning ,Slip (materials science) ,engineering.material ,010502 geochemistry & geophysics ,01 natural sciences ,Geochemistry and Petrology ,ELECTRON-BACKSCATTER DIFFRACTION ,HIGH-PRESSURE ,Meteorite impact ,Planar deformation features ,0402 Geochemistry ,[CHIM]Chemical Sciences ,Petrology ,ZIRCON ,0105 earth and related environmental sciences ,Science & Technology ,Energy ,Mineralogy ,Dislocation slip system ,Baddeleyite ,MONAZITE ,Geophysics ,0403 Geology ,[SDU]Sciences of the Universe [physics] ,13. Climate action ,Physical Sciences ,[SDE]Environmental Sciences ,PHASE-TRANSITION ,REIDITE ,engineering ,VREDEFORT ,Deformation bands ,ORIENTATION ,Geology ,[SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy ,Zircon - Abstract
© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. Accessory mineral geochronometers such as apatite, baddeleyite, monazite, xenotime and zircon are increasingly being recognized for their ability to preserve diagnostic microstructural evidence of hypervelocity-impact processes. To date, little is known about the response of titanite to shock metamorphism, even though it is a widespread accessory phase and a U–Pb geochronometer. Here we report two new mechanical twin modes in titanite within shocked granitoid from the Chicxulub impact structure, Mexico. Titanite grains in the newly acquired core from the International Ocean Discovery Program Hole M0077A preserve multiple sets of polysynthetic twins, most commonly with composition planes (K 1 ) = ~ { 1 ¯ 11 } , and shear direction (η 1 ) = < 110 > , and less commonly with the mode K 1 = {130}, η 1 = ~ . In some grains, {130} deformation bands have formed concurrently with the deformation twins, indicating dislocation slip with Burgers vector b = < 341 > can be active during impact metamorphism. Titanite twins in the modes described here have not been reported from endogenically deformed rocks; we, therefore, propose this newly identified twin form as a result of shock deformation. Formation conditions of the twins have not been experimentally calibrated, and are here empirically constrained by the presence of planar deformation features in quartz (12 ± 5 and ~ 17 ± 5 GPa) and the absence of shock twins in zircon (< 20 GPa). While the lower threshold of titanite twin formation remains poorly constrained, identification of these twins highlight the utility of titanite as a shock indicator over the pressure range between 12 and 17 GPa. Given the challenges to find diagnostic indicators of shock metamorphism to identify both ancient and recent impact evidence on Earth, microstructural analysis of titanite is here demonstrated to provide a new tool for recognizing impact deformation in rocks where other impact evidence may be erased, altered, or did not manifest due to generally low (< 20 GPa) shock pressure.
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- 2019
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