Non-destructive spectroscopic and petrochemical investigations of Paleoarchean spherule layers from the ICDP Drill Core BARB5, Barberton Mountain Land, South Africa

Autor(en)
Jörg Fritz, Roald Tagle, Luisa Ashworth, Ralf Thomas Schmitt, Axel Hofmann, Béatrice Luais, Phillip D. Harris, Desirée Hoehnel, Seda Özdemir, Tanja Mohr-Westheide, Christian Koeberl
Abstrakt

A Paleoarchean impact spherule-bearing interval of the 763 m long International Continental Scientific Drilling Program (ICDP) drill core BARB5 from the lower Mapepe Formation of the Fig Tree Group, Barberton Mountain Land (South Africa) was investigated using nondestructive analytical techniques. The results of visual observation, infrared (IR) spectroscopic imaging, and micro-X-ray fluorescence (μXRF) of drill cores are presented. Petrographic and sedimentary features, as well as major and trace element compositions of lithologies from the micrometer to kilometer-scale, assisted in the localization and characterization of eight spherule-bearing intervals between 512.6 and 510.5 m depth. The spherule layers occur in a strongly deformed section between 517 and 503 m, and the rocks in the core above and below are clearly less disturbed. The μXRF element maps show that spherule layers have similar petrographic and geochemical characteristics but differences in (1) sorting of two types of spherules and (2) occurrence of primary minerals (Ni-Cr spinel and zircon). We favor a single impact scenario followed by postimpact reworking, and subsequent alteration. The spherule layers are Al

2O

3-rich and can be distinguished from the Al

2O

3-poor marine sediments by distinct Al-OH absorption features in the short wave infrared (SWIR) region of the electromagnetic spectrum. Infrared images can cover tens to hundreds of square meters of lithologies and, thus, may be used to search for Al-OH-rich spherule layers in Al

2O

3-poor sediments, such as Eoarchean metasediments, where the textural characteristics of the spherule layers are obscured by metamorphism.

Organisation(en)
Department für Lithosphärenforschung
Externe Organisation(en)
Saalbau Weltraum Projekt, Museum für Naturkunde Berlin - Leibniz-Institut für Evolutions- und Biodiversitätsforschung, GeoSpectral Imaging, University of Johannesburg (UJ), Bruker Nano GmbH, Centre National De La Recherche Scientifique (CNRS)
Journal
Meteoritics and Planetary Science
Band
51
Seiten
2441–2458
Anzahl der Seiten
18
ISSN
1086-9379
DOI
https://doi.org/10.1111/maps.12736
Publikationsdatum
12-2016
Peer-reviewed
Ja
ÖFOS 2012
105105 Geochemie
Schlagwörter
ASJC Scopus Sachgebiete
Geophysics, Space and Planetary Science
Sustainable Development Goals
SDG 15 – Leben an Land
Link zum Portal
https://ucrisportal.univie.ac.at/de/publications/aba3d98a-d94c-4110-ab03-ad74bce735e7