Rainbow Vent Field

The Rainbow hydrothermal vent field is a system of ultramafic-hosted hydrothermal vents located at 36°14'N on the Mid-Atlantic Ridge (MAR). It was discovered in 1994 from temperature readings of ten high-temperature black smokers at a depth of approximately 2.3 kilometres (1.4 mi), where fluids can exceed 365 °C (689 °F). The site is shallower and larger in area than many other vent fields along the Azores section of the MAR with an area of 1.5 square kilometres (370 acres). Located 370 km (229.91 mi) southeast of Faial Island, it is a popular geochemical sampling and modeling site due to close proximity to the Azores and definitive representation of serpentinization from hydrothermal circulation and synthesis. Vent geology, biology, and fluid content make Rainbow comparable to other hot hydrothermal vents of the Azores such as Lucky Strike and Menez Gwen. However; chlorinity, metal concentration, and pH distinguish it from neighboring vent fields. As a hot, ultramafic-hosted vent field, pH levels of fluids are extremely low with much H2 and CH4 generated from water interactions with mafic igneous rocks. Though not actively considered for development, Rainbow lies within the MoMAR (Monitoring of the Mid Atlantic Ridge) survey area for a marine observatory.

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