PUMA
Istituto di Scienze Marine     
Ligi M., Bonatti E., Cuffaro M., Brunelli D. Post-Mesozoic Rapid Increase of Seawater Mg/Ca due to Enhanced Mantle-Seawater Interaction. In: scientific reports, vol. 3 article n. 2752. NATURE PUBLISHING GROUP, MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND, 2013.
 
 
Abstract
(English)
The seawater Mg/Ca ratio increased significantly from similar to 80 Ma to present, as suggested by studies of carbonate veins in oceanic basalts and of fluid inclusions in halite. We show here that reactions of mantle-derived peridotites with seawater along slow spreading mid-ocean ridges contributed to the post-Cretaceous Mg/Ca increase. These reactions can release to modern seawater up to 20% of the yearly Mg river input. However, no significant peridotite-seawater interaction and Mg-release to the ocean occur in fast spreading, East Pacific Rise-type ridges. The Mesozoic Pangean superocean implies a hot fast spreading ridge system. This prevented peridotite-seawater interaction and Mg release to the Mesozoic ocean, but favored hydrothermal Mg capture and Ca release by the basaltic crust, resulting in a low seawater Mg/Ca ratio. Continent dispersal and development of slow spreading ridges allowed Mg release to the ocean by peridotite-seawater reactions, contributing to the increase of the Mg/Ca ratio of post-Mesozoic seawater.
DOI: 10.1038/srep02752
Subject MID-ATLANTIC RIDGE; BENEATH MIDOCEAN RIDGES; CALCIUM-CARBONATE VEINS; SEA-FLOOR GENERATION; EAST PACIFIC RISE; FLUID INCLUSIONS; HYDROTHERMAL CIRCULATION; PHANEROZOIC SEAWATER; ISOTOPIC COMPOSITION; OCEANIC LITHOSPHERE


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