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TitleOrigin of large-volume pseudotachylite in terrestrial impact structures
AuthorRiller, U; Lieger, D; Gibson, R L; Grieve, R A F; Stöffler, D
SourceGeology vol. 38, no. 7, 2010 p. 619-622,
Alt SeriesEarth Sciences Sector, Contribution Series 20100103
PublisherGeological Society of America
Mediapaper; on-line; digital
File formatpdf
AreaSudbury; Vredefort; Canada; South Africa
Lat/Long WENS-81.0000 -80.5000 47.0000 46.7500
Lat/Long WENS 27.7500 27.7500 -27.0000 -27.5000
Subjectsextraterrestrial geology; mineralogy; craters; meteorite craters; pseudotachylites; Sudbury Basin; Vredefort impact structure
Illustrationslocation maps; plots
Released2010 07 01
AbstractLarge-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.

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