faultvein

Faultvein is a mineral-filled fracture that develops along geological faults. In many crustal settings a fault acts as a conduit for hydrothermal fluids; when these fluids ascend, depressurize, or cool, they precipitate minerals within open spaces created by fault-related rock displacement. The resulting vein often follows the fault plane or cuts across it, and its geometry records the deformation history of the host rocks.

Formation and textures: Fluid sources include metamorphic dehydration, magmatic intrusions, or basinal waters. Permeable fault zones, fractures, slickensides, and dilation spaces concentrate fluids. Mineralization occurs as vein quartz, calcite, dolomite, fluorite, and sulfide minerals such as pyrite, galena, and sphalerite, with occasional native gold or silver. Vein fills may be crystalline, drusy, crustiform, banded, or crosscut by later generations of veins; multiple episodes of mineralization can be preserved in a single fault zone.

Geologic and economic context: Fault veins are characteristic of ore deposits formed by hydrothermal activity, especially epithermal and mesothermal systems. They host metals including gold, silver, lead, zinc, and copper. Economic value depends on metal content, vein width, and continuity. Exploration emphasizes structural mapping, alteration halos, and drilling to establish grade, geometry, and continuity. Mining can be complicated by fault movement, variable permeability, and water inflow.

See also: vein deposit, hydrothermal ore deposit, and fault-related mineralization.