Bergartsforandring

Bergartsforandring, or rock-type alteration, is a geological process in which the mineralogy, texture, and chemical composition of a rock are changed after its initial formation. This change can occur under a range of conditions and by several mechanisms, including metamorphism, diagenesis, hydrothermal alteration, and weathering.

Mechanisms of bergartsforandring include metamorphism, where elevated temperature and pressure drive recrystallization and the formation of new mineral assemblages. Hydrothermal alteration involves circulating fluids that add or remove elements, causing metasomatism and distinctive mineralogical changes such as chloritization, sericitization, or potassic alteration. Diagenetic alteration occurs during burial and diagenesis at lower temperatures, including cementation, dissolution, and recrystallization of minerals. Weathering represents near-surface chemical and physical modification driven by atmospheric conditions and biological activity.

Types and patterns of forandring are diverse. Metamorphic rock alterations include regional and contact metamorphism. Ore-related alterations form characteristic halos around mineral deposits, while diagenetic and weathering processes produce surface rind changes and alterations in porosity and strength. Common indicators of bergartsforandring are new mineral phases, color changes, changes in grain size, and modifications to rock strength or texture.

Significance in geology lies in reconstructing geological history, identifying past fluid pathways, and guiding mineral exploration and engineering. Investigations combine petrography, geochemical analysis, mineralogical studies, and field mapping, often supplemented by remote sensing. Understanding bergartsforandring helps interpret tectonic settings, predict subsurface conditions, and assess the stability and economic potential of rock bodies.