Shand (1916) introduced the term pseudotachylite for an inclusion-rich black rock with a glassy, or cryptocrystalline, matrix that resembles the basaltic glass, tachylite (Fig 1). The pseudotachylite forms veins and networks in rocks of the Vredefort Ring, which is now considered to be the eroded remnant of the central uplift of one of the world's largest crypto-explosion structures (Dietz, 1961). The veins transgress all other structures and are not related to faults. The commonly rounded inclusions are mostly pieces of the host rock, and the matrix is close in composition to the host. Later work has shown the inclusions to contain shock-formed planar elements (Wilshire, 1971) as well as coesite and stishovite (Martini, 1978).
Anastamosing veins of pseudotachylite in shocked gneiss from the Manicouagan cryptoexplosion structure, Quebec. Scale is in centimeters.
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References
Dietz, R. S., 1961, The Vredefort Ring Structure: meteorite impact scar?, Jour. Geology 69, 499–516.
Maddock, R. H., 1983, Melt origin of fault-generated pseudotachylites demonstrated by textures, Geology 11, 105–108.
Martini, J. E. J., 1978, Coesite and stishovite in the Vredefort Dome, South Africa, Nature 272, 715–717.
Philpotts, A. R., 1964, Origin of pseudotachylites, Am. Jour. Sci. 262, 1008–1035.
Shand, S. J., 1916, The pseudotachylyte of Parys, Geol. Soc. London Quart. Jour. 72, 198–221.
Wenk, H. R., 1978, Are pseudotachylites products of fracture or fusion?, Geology 6, 507–511.
Wilshire, H. G., 1971, Jour. Geology 79, 195–206.
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Murtaugh, J.G. (1987). Pseudotachylites . In: Structural Geology and Tectonics. Encyclopedia of Earth Science. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-31080-0_85
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