EarthRef.org Reference Database (ERR) -- Hart & Staudigel 1978

Times of vein mineral deposition in ocean crust have been determined both Rb-Sr isochron ages of vein smectites and by comparison of 87Sr/86Sr ratios of vein calcites with the known variations of seawater 87Sr/86Sr ratio with time. Results from drill sites 105, 332B and 418A, Atlantic Ocean, which have basement formation ages of 155 m.y., 3.5 m.y., and 110 m.y., respectively, show that vein deposition is essentially complete within 5-10 m.y. after formation of a basaltic crust. This provides direct evidence that hydrothermal circulation of seawater through the oceanic curst is an important process for only 5-10 m.y. after crust formation. Times of vein mineral deposition in ocean crust have been determined both Rb-Sr isochron ages of vein smectites and by comparison of 87Sr/86Sr ratios of vein calcites with the known variations of seawater 87Sr/86Sr ratio with time. Results from drill sites 105, 332B and 418A, Atlantic Ocean, which have basement formation ages of 155 m.y., 3.5 m.y., and 110 m.y., respectively, show that vein deposition is essentially complete within 5-10 m.y. after formation of a basaltic crust. This provides direct evidence that hydrothermal circulation of seawater through the oceanic curst is an important process for only 5-10 m.y. after crust formation.