Geothermal Springs of the West Florida Continental Shelf: Evidence for Dolomitization and Radionuclide Enrichment

Authors

Kent A. Fanning, University of South FloridaFollow
Robert H. Byrne, University of South FloridaFollow
Jabe A. Breland II, University of South Florida
Peter R. Betzer, University of South Florida
Willard S. Moore, University of South Carolina
Robert J. Elsinger, University of South Carolina
Thomas E. Pyle, Office of Naval Research

Document Type

Article

Publication Date

1981

Digital Object Identifier (DOI)

https://doi.org/10.1016/0012-821X(81)90188-6

Abstract

On the sea bed of the West Florida continental shelf about 45 km SSW of Ft. Myers, Florida, an 85-km² area has been discovered in which six thermal springs discharge warm, chemically altered seawater from vents and seepage zones. The spring water apparently originates in the subsurface ocean around the Florida Platform and penetrates the highly porous strata of the platform about 500–1000 meters below sea level. It percolates toward the interior of the platform and is geothermally heated to about 40°C en route. Then it rises along more vertical flow channels and is discharged in warm submarine springs.

Beneath the platform, several chemical processes alter the percolating seawater. One process seems to be a secondary dolomitization of the limestone of the platform because, in the discharging seawater, magnesium is lower by 2.7 mmole/kg and calcium higher by 3.6 mmole/kg than in normal seawater with the same chlorinity. Other reactions within the sediments of the platform enrich the spring effluents 1000-fold in²²⁶Ra, 10,000-fold in²²²Rn, and 90-fold in²²⁸Ra compared to the seawater surrounding the platform. Thus, the springs may be important sources of radionuclides for the Gulf of Mexico. The percolating seawater also loses all of its oxygen and nitrate to reduction processes, loses most of its phosphate and 40% of its²³⁸U, and roughly quadruples its silica content.

Coastal carbonate platforms are fairly common geological features. Thus, processes like those beneath the West Florida Shelf may function on a world-wide basis to play an important role in the diagenesis of carbonate sediments.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Earth and Planetary Science Letters, v. 52, issue 2, p. 345-354

Scholar Commons Citation

Fanning, Kent A.; Byrne, Robert H.; Breland, Jabe A. II; Betzer, Peter R.; Moore, Willard S.; Elsinger, Robert J.; and Pyle, Thomas E., "Geothermal Springs of the West Florida Continental Shelf: Evidence for Dolomitization and Radionuclide Enrichment" (1981). Marine Science Faculty Publications. 1665.
https://digitalcommons.usf.edu/msc_facpub/1665