Volcanogenic-sedimentary rocks

VOLCANOGENIC-SEDIMENTARY ROCKS (EN: volcanogenic-sedimentary rocks; DE: vulkano-sedimentare Gesteine; FR: roches volcano-sédimentaires; ES: rocas volcano-sedimentarias; RU: вулканогенно-осадочные породы) are the rocks, which are consisting of the volcanic and sedimentary material. These rocks are sub-divided into volcanogenic-clastic and chemogenic. The major volcanic component of the volcanogenic-clastic rocks is the pyroclastic material of the explosive eruptions of the volcanoes, which is formed as the result of the crushing, by the volcanic explosions, of the liquid lava, and of the rocks, which are forming the volcano.

Depending on the quantity of the volcanic material, they distinguish among the cemented volcanogenic-clastic rocks: the volcanic tuffs, which are almost entirely consisting of the pyroclastic material, the tuffites with the content of the latter of more than 50%, and the pyroclastic-sedimentary rocks (tuffs-sandstones, tuffs-gravelites, tuffs-conglomerates, and others) with the prevalence of the sedimentary components. According to the size of the debris, they sub-divide the tuffs and tuffites into pelitic (less than 0.01 millimetres), aleuritic (0.01-0.1 millimetres), psammitic (0.1-2 millimetres), and psephitic (2-200 millimetres and more). The material, which is removed by the hot water sources, and by the steam-gas jets, and which is being extracted during the leaching of the volcanic rocks, while precipitating within the seas and on the dry land, forms the chemogenic volcanogenic-sedimentary rocks, as the examples of which there serve many jaspers, depositions of sulfur, certain ores of iron, and of manganese, the phosphorites, and so on.