kidealue

Kidealue is a term used in mineralogy and geology to describe a geologic zone characterized by an elevated abundance of crystalline mineral phases. The term is derived from the Finnish words kide, meaning crystal, and alue, meaning area or region, reflecting its origins in Finnish geological literature. In formal usage, a kidealue refers to a portion of a rock body where crystal growth has been relatively unimpeded, resulting in well-formed crystals and a coarse-grained texture. The concept is regional and not standardized across all geological traditions, and its precise definition can vary between laboratories.

A kidealue is not a distinct lithologic unit but rather a zoning feature within igneous or metamorphic rocks. It commonly occurs where cooling rates are slow, fluids are available, and chemical conditions favor nucleation and growth of crystals. In hydrothermal settings, kidealue may align with vein systems or vein arrays where mineral parcels crystallize from circulating solutions.

Formation and characteristics: Factors that create a kidealue include steady heat flow, diffusion-controlled crystallization, and low deformation. The size of the zone can range from meters to tens of meters and it often contrasts with adjacent, more fine-grained zones. The crystals within a kidealue tend to be coarser and better formed than in surrounding rock.

Importance: Recognizing a kidealue helps petrologists interpret a rock’s thermal history and crystallization environment. It can influence ore texture in mining districts, affect rock strength and porosity, and guide sampling strategies in field geology. Related topics include crystal habit, mineral zoning, and hydrothermal mineral deposits.