Properties of impact-related pseudotachylite and associated shocked zircon and monazite in the upper levels of a large impact basin : a case study from the Vredefort impact structure

dc.contributor.authorKovaleva, Elizaveta
dc.contributor.authorDixon, Roger D.
dc.date.accessioned2021-07-01T09:59:16Z
dc.date.available2021-07-01T09:59:16Z
dc.date.issued2020-11-25
dc.description.abstractThe Vredefort impact structure in South Africa is deeply eroded to its lowermost levels. However, granophyre (impact melt) dykes in such structures preserve clasts of supracrustal rocks, transported down from the uppermost levels of the initial structure. Studying these clasts is the only way to understand the properties of already eroded impactites. One such lithic clast from the Vredefort impact structure contains a thin pseudotachylite vein and is shown to be derived from the near-surface environment of the impact crater. Traditionally, impact pseudotachylites are referred to as in situ melt rocks with the same chemical and isotopic composition as their host rocks. The composition of the sampled pseudotachylite vein is not identical to its host rock, as shown by the micro-X-ray fluorescence ( XRF) and energy-dispersive X-ray (EDX) spectrometry mapping. Mapping shows that the melt transfer and material mixing within pseudotachylites may have commonly occurred at the upper levels of the structure. The vein is spatially related to shocked zircon and monazite crystals in the sample. Granular zircons with small granules are concentrated within and around the vein (not farther than 6–7 mm from the vein). Zircons with planar fractures and shock microtwins occur farther from the vein (6–12 mm). Zircons with microtwins (65 /{112}) are also found inside the vein, and twinned monazite (180 /[101]) is found very close to the vein. These spatial relationships point to elevated shock pressure and shear stress, concentrated along the vein’s plane during impact.en_ZA
dc.description.departmentGeologyen_ZA
dc.description.librarianam2021en_ZA
dc.description.sponsorshipThe National Research Foundation (NRF) and the Directorate for Research Development, University of the Free State, 2019–2020.en_ZA
dc.description.urihttp://www.mdpi.com/journal/mineralsen_ZA
dc.identifier.citationKovaleva, E. & Dixon, R. 2020, 'Properties of impact-related pseudotachylite and associated shocked zircon and monazite in the upper levels of a large impact basin : a case study from the Vredefort impact structure', Minerals, vol. 10, art. 1053, pp. 1-22.en_ZA
dc.identifier.issn2075-163X
dc.identifier.other10.3390/min10121053
dc.identifier.urihttp://hdl.handle.net/2263/80674
dc.language.isoenen_ZA
dc.publisherMDPIen_ZA
dc.rights© 2020 by the authors. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.en_ZA
dc.subjectGranular zirconen_ZA
dc.subjectShocked monaziteen_ZA
dc.subjectShock microtwinsen_ZA
dc.subjectPseudotachyliteen_ZA
dc.subjectGranophyreen_ZA
dc.subjectSouth Africa (SA)en_ZA
dc.titleProperties of impact-related pseudotachylite and associated shocked zircon and monazite in the upper levels of a large impact basin : a case study from the Vredefort impact structureen_ZA
dc.typeArticleen_ZA

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