Tonalite

Tonalite is an igneous rocks ( plutonic ) with a composition similar to that of granite.

Mineral composition and rock description

Tonalites are mostly dark gray to light. This depends on the number of bright and dark minerals in the rock. The tonalite is however significantly more basic than the granite and contains no alkali feldspar. Tonalites contain quartz, plagioclase, hornblende, biotite and rare augite. They are medium - to coarse -grained. Moreover ancillary they contain allanite, apatite, zircon, titanite, and magnetite.

Formation

Tonalites occur in granite and granodiorite batholith next in intrusive magmas. You can anatexis, by remelting, also arise.

Naming and deposits

The name of the rock goes back to the Tonale Pass in northwestern Italy and was introduced by this type locality by Gerhard vom Rath 1864 in the lithology. It lies on the Periadriatic seam ( also Insubric line, a major South European geological fault line). It is a leucocratic ( light gray) with abundant biotite tonalite, which occurs in the eastern part of the Adamellomassivs and goes back to a massive intrusion of the Tertiary period.

Tonalites form at subduction zones and in significant measure on the Pacific coast of America, but also in the south of Norway. In Germany there are few occurrences: Im Fichtelgebirge there is an occurrence of tonalite, the so-called Redwitziten from Seußen and Wölsau at Marktredwitz. Furthermore, tonalite - occurrence is in Märker forest for large -Bieberau and the Bavarian Forest.

Use

Use find Tonalite in masonry, to brick, facade panels, floor and stair coverings and road than gravel and pavement. This stone was preferably used in Germany in the 1950/1960er years as grave stone. Tonalites can be polished and frost resistant.