Latite

Latite nicol parallei

Latite nicol incrociati

Latite is a type of igneous rock that is intermediate in composition between andesite and dacite. It is characterized by a mineral assemblage that typically includes plagioclase feldspar, alkali feldspar, quartz, biotite, hornblende, and sometimes pyroxene. Latites are often porphyritic, with large crystals (phenocrysts) of plagioclase and alkali feldspar set in a finer-grained matrix (groundmass).

Formation and Occurrence

Latite forms through the cooling and solidification of magma that is intermediate in composition. This magma can originate in a variety of tectonic settings, including continental arcs and post-collisional environments. The intermediate composition of latite magma is typically a result of the mixing of mafic and felsic magmas, or through the partial melting of a mixed source rock.

Latites are found in various geological settings around the world, often associated with volcanic arcs and in areas of continental crust extension. They can occur as lava flows, domes, and as components of composite volcanoes.

Mineralogy and Petrology

The mineralogy of latite is intermediate between that of andesite and dacite, reflecting its intermediate silica content. The most common minerals found in latite include:

• Plagioclase feldspar: Usually oligoclase or andesine in composition.
• Alkali feldspar: Often sanidine or orthoclase.
• Quartz: Present in varying amounts, but less than in dacite.
• Biotite: A common mafic mineral in latite.
• Hornblende: Also a common mafic mineral, sometimes accompanied by pyroxene.

Phenocrysts of plagioclase and alkali feldspar are common, often set in a matrix that may be fine-grained or glassy. The presence of quartz can vary, but it is typically less abundant than in more felsic rocks like dacite.

Geochemistry

Latites are characterized by an intermediate silica content, generally ranging from 57% to 63%. They also have intermediate levels of alkalis (Na_2O + K_2O), calcium, iron, and magnesium. The intermediate composition reflects the mixing processes or partial melting events that generated the magma from which latites form.

Economic Importance

While not as widely known for their economic importance as some other igneous rocks, latites can host mineral deposits, particularly where they are associated with volcanic arcs and hydrothermal systems. They may contain deposits of copper, gold, and other metals.

Environmental and Cultural Significance

Latites, like other volcanic rocks, can significantly influence the landscapes and ecosystems where they occur. Their weathering contributes to soil formation, and their physical characteristics can influence topography and hydrology.

In some cultures, latite and other volcanic rocks have been used as construction materials due to their durability and abundance.

See Also

• Igneous rock
• Volcanology
• Petrology
• Mineralogy