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Origin of large-volume pseudotachylite in terrestrial impact structures

Ulrich Riller, Daniel Lieger, Roger L. Gibson, Richard A. F. Grieve and Dieter Stoeffler
Origin of large-volume pseudotachylite in terrestrial impact structures
Geology (Boulder) (July 2010) 38 (7): 619-622


Large-volume pseudotachylite bodies in impact structures are dike like and consist of angular and rounded wall-rock fragments enveloped by a microcrystalline and sporadically glassy matrix that crystallized from a melt. Knowledge of the formation of pseudotachylite bodies is important for understanding mechanics of complex crater formation. Most current hypotheses of pseudotachylite formation inherently assume that fragmentation and melt generation occur during a single process. Based on the structure of pseudotachylite bodies at Sudbury (Canada) and Vredefort (South Africa), we show that these processes differ in time and space. We demonstrate that the centimeter- to kilometer-scale bodies are effectively fragment- and melt-filled tension fractures that formed by differential rotation of target rock during cratering. Highly variable pseudotachylite characteristics can be accounted for by a single process, i.e., drainage of initially superheated impact melt into tension fractures of the crater floor.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 38
Serial Issue: 7
Title: Origin of large-volume pseudotachylite in terrestrial impact structures
Affiliation: McMaster University, School of Geography and Earth Sciences & Origins Institute, Hamilton, ON, Canada
Pages: 619-622
Published: 201007
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 27
Accession Number: 2010-064227
Categories: Igneous and metamorphic petrologyStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., geol. sketch maps
N46°25'00" - N46°49'60", W81°40'00" - W80°45'00"
S26°00'00" - S26°00'00", E27°00'00" - E27°00'00"
Secondary Affiliation: Humboldt-Universitaet zu Berlin, DEU, Federal Republic of GermanyUniversity of the Witwatersrand, ZAF, South AfricaNatural Resources Canada, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201035
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