Spilit-Brekzie

Spilit-Breccia

Tegau, Thuringian Slate Mountains
Spilit-Brekzie
Image: IGW

What is written on the plate:

Spilit-Breccia

Volcanic eruptions occurring under shallow marine cover result in fragmentation of the lavas. Basalt melts partially solidify as glass and react with seawater: olivine and pyroxene are converted to the green minerals chlorite and actinolite. The plagioclases absorb sodium and release calcium. The released calcium is deposited as carbonate between lava fragments and in bubble cavities precipitated.

Görkwitz Formation, Upper Devonian, Tegau, Thuringian Slate Mountains, ca. 370 Ma

Spilit-Breccia

Location: Tegau, Thuringian Slate Mountains

Age: ca. 370 million years

Tegau, Thüringisches Schiefergebirge
Tegau, Thüringisches Schiefergebirge
Image: Google Maps

Spilite breccia is a rock consisting of a combination of spilite and breccia. However, to provide a description of spilite breccia, it is necessary to consider information about spilite and breccia separately.

Spilite is a volcanic rock consisting mainly of basaltic composition. It is formed by the rapid cooling of basaltic lava at the Earth's surface. Spilite is usually fine-grained and has a dark color that can range from dark gray to black. It contains various minerals such as plagioclase feldspar, pyroxene, olivine, and possibly magnetite. The composition and properties of spilite may vary depending on the geological region.

Breccia, on the other hand, is a sedimentary rock composed of angular rock debris cemented by a fine-grained groundmass. These rock debris can have different sizes and compositions. The formation of breccias usually occurs near the site where the crushing of the parent material took place. There are several types of breccias, including sedimentary, volcanic, diagenetic, tectonic, and impact breccias.

Spilite breccia is thus a rock that has the characteristics and composition of both spilite and breccia. It consists of angular rock debris cemented in a fine-grained matrix of spilite. The exact composition and appearance of spilite breccia may vary from case to case, depending on the specific properties of the spilite and breccia involved in the formation of the rock.

Location of the rock spilite breccia near the village Tegau
Location of the rock spilite breccia near the village Tegau
Image: Thomas Voigt