Pseudotachylyte

Pseudotachylyte (sometimes written as pseudotachylite) is an extremely fine-grained to glassy, dark, cohesive rock occurring as veins[1] that form through frictional melting and subsequent quenching during earthquakes,[2] large-scale landslides, and impacts events.

[4] Pseudotachylyte was first documented by Shand in the Vredefort Impact Structure and was named due to its close resemblance to tachylyte, a basaltic glass.

[5] Though pseudotachylyte is reported to have a glassy appearance, they are extremely susceptible to alteration and are thus rarely found to be entirely composed of glass.

[14] A melt origin for pseudotachylyte was controversial for some time,[15] with some researchers favouring extreme comminution for their generation (crush-origin).

[18] The high viscosity of these melt patches raises the fault's coefficient of friction, hindering sliding.

[20] Once sliding is stopped, the quenching of the melt layer welds the fault shut and restores its strength to that of the unfaulted surrounding rock.

[25] E-Type (endogenic) pseudotachylytes are formed via frictional melting of the target rock due to high-speed slip caused by the collapse of the crater margin.

Structural analysis of impact-related deformation in the collar rocks of the Vredefort Dome, South Africa.