|
|
|
Azuara
under construction
|
|
Rubielos de la Cérida
under construction
|
|
|
|
|
Impact melt page
Melt rocks in impact structures may result from shock melting and from frictional melting in strong dynamic metamorphism (pseudotachylites). For the formation of total rock melts, shock pressures in excess of roughly 60 GPa (600 kbar) are required.
According to the IUGS Subcommission on the Systematics of Metamorphic Rocks, Study Group for Impactites, impact melt rocks are crystalline, semihyaline or hyaline rocks which have solidified from shock-produced impact melt und which contain variable amounts of clastic debris.
On this page, we show and describe impact melt rocks and pseudotachylites from different impact structures (Ries, Rochechouart, Dellen, Sääksjärvi, Lappajärvi, Mien, Vredefort, Charlevoix) with special emphasis on the impact melt rocks from the Azuara and Rubielos de la Cérida impact structures (Spain).
Pseudotachylites
A tachylite is a black volcanic glass formed by the chilling of basaltic magmas. Early geologists in Vredefort identified something like it and called it pseudotachylite. According to the IUGS Subcommission on the Systematics of Metamorphic Rocks, Study Group for Impactites, a pseudotachylite is a dike-like breccia which formed by frictional melting in the basement of impact structures and which may contain unshocked and shocked mineral and lithic clasts in a fine-grained aphanatic matrix.
[nach oben] |
