Geothermal convection: a mechanism for dolomitization at Enewetak Atoll?

Geothermal convection in carbonate platforms could drive massive dolomitiza tion by supplying mass transport of magnesium over long periods and at temp eratures high enough to overcome kinetic limitations. Reactive-transport si mulations based on Enewetak Atoll show dolomitization in a thin band at a p ermeability contrast near the base of the platform, which is consistent wit h field observations of dolomitized Eocene deposits. Dolomitization is pred icted at approximately 6% per My at temperatures of 45-60 degrees C, and co mplete dolomitization could be accomplished in similar to 16 My. Calcium en richment of pare fluids and upward transport of these fluids is established early, prior to 30 ky. (C) 2000 Elsevier Science B.V. All rights reserved.