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Pseudotachylite vein hosted by a clast in the Vredefort Granophyre; characterization, origin and relevance

E. Kovaleva, M. S. Huber, F. Roelofse, M. Tredoux and H. Praekelt
Pseudotachylite vein hosted by a clast in the Vredefort Granophyre; characterization, origin and relevance
South African Journal of Geology (April 2018) 121 (1): 51-68

Abstract

A small, meta-granitic clast with a crosscutting microcrystalline vein was found enclosed within the Vredefort Granophyre. Semi-quantitative chemical analyses of the granophyre, granitic clast, and the vein were obtained in situ, demonstrating affinity to granitic composition for the vein. Microstructural and geochemical evidence is consistent with the vein representing pseudotachylite derived from granite. Within the granitic clast, evidence of high-grade metamorphism with preferential melting of biotite was observed. Brittle, ductile and shock deformation microstructures were found in quartz grains in the granite ground mass, including mosaicism, undulatory extinction, non-planar and curviplanar fractures and planar deformation features (PDFs) with crystallographic orientations {1121} and {2241} Similar deformation features were observed in quartz clasts within the vein. Pods of in situ pseudotachylitic material have been documented in foliated granite around the vein. The vein suggests that a generation of pseudotachylite was evolved and already solidified when the granophyre dyke intruded. Therefore, a minimum age of pseudotachylite emplacement is suggested by the presence of the pseudotachylite vein within the granophyre.


ISSN: 1012-0750
EISSN: 1996-8590
Serial Title: South African Journal of Geology
Serial Volume: 121
Serial Issue: 1
Title: Pseudotachylite vein hosted by a clast in the Vredefort Granophyre; characterization, origin and relevance
Affiliation: University of the Free State, Department of Geology, Bloemfontein, South Africa
Pages: 51-68
Published: 20180417
Text Language: English
Publisher: Bureau for Scientific Publications, Pretoria, South Africa
References: 80
Accession Number: 2018-050928
Categories: Igneous and metamorphic petrologyGeomorphology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch maps
S26°49'00" - S26°49'00", E27°25'00" - E27°25'00"
Country of Publication: South Africa
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, Copyright, Geological Society of South Africa. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201827
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