Initial chronology of a recently discovered hydrothermal field at 14°45′N, Mid-Atlantic Ridge

Abstract

Two expeditions of the ‘Sevmorgeologija’ association (1991–1994) led to the discovery of two new hydrothermal sites on the Mid Atlantic Ridge (MAR), south of the 15°20′ North Fracture Zone, one around 14°45′N and the other around 14°42′N. The northern one, between 14°45′ and 14°45.3′N has been studied in detail. About 12 mounds have been mapped and 3 of them have been sampled using a large hydraulic grab sampler. The largest one is about 200 m long and 200 m wide. When progressively moving up on the slope of an uplifted block of the rift valley floor, the sulphide samples have revealed ages ranging from about 10 ka to 60 ka. The ages were obtained using the 230Th/234U dating method used for chronological studies of diverse hydrothermal fields. The general picture of this lateral location of the samples of different ages provides evidence of a shift in the focus of hydrothermal activity with time. Moreover, there were rejuvenation stages of hydrothermal activity, including black and white smokers.