Greenstone-hosted quartz-carbonate vein deposits typically occur along major faults in ancient greenstone belts composed of basalt, komatiite, and sedimentary rocks that have been metamorphosed to greenschist facies. They form simple to complex quartz-carbonate vein networks that contain gold deposited by hydrothermal fluids from 5-10 km depth. While most common in Archean terranes, significant deposits also exist in younger belts. Examples include the Sigma-Lamaque deposit in Quebec and the Giant Mine in the Northwest Territories.