Radium decay series dating of barite deposition in the Gulf of Mexico: Initial results
- and others
Barite deposits consisting of chimneys and crusts were recently documented and recovered by submersible from hydrocarbon seeps in the Gulf of Mexico offshore Louisiana at water depths of 510-670 m in the Garden Banks and Mississippi Canyon areas. This is the first discovery of barite deposits associated with cold hydrocarbon seeps. The outer part of the chimneys are dominated by barite whereas the inner part of the chimneys are dominated by barite with pyrite as accessory mineral. The crusts are about 5-8 cm thick and their surficial layers are composed of barite coexisting with carbonate whereas the lower part of the crusts consists of barite, carbonate, and pyrite. A program of radiometric dating by Ra decay series isotopes was initiated in order to derive a chronology of barite deposition in association with the hydrocarbon seeps. Chimneys and crusts were analyzed for NORM using a high purity intrinsic germanium gamma spectroscopy system. The deposits were found to contain {sup 226}Ra and {sup 228}Ra at concentrations comparable to those found in scale associated with oil production in the Gulf States Region (approximately 500 pCi/gm and 250 pCi/gm, respectively). The deposits were subjected to two separate age dating techniques. The primary technique utilized gamma spectroscopy for determination of {sup 210}Pb/{sup 226}Ra ratios. The second technique utilized gamma spectroscopy for determination of {sup 226}Th/{sup 228}Ra ratios. Ages as determined by {sup 210}Pb/{sup 226}Ra ranged from 2 years to 40 years. The {sup 228}Th/{sup 228}Ra methodology tended to validate the primary dating technique, although the useful range of dating for this method does not exceed 15 years. Sulfide-rich layers in the barite deposits tended to give anomalous and biased results when dated by the primary method. Both methodologies also appear valid for age dating scale deposits {le} 100 years old that are generated in oil production operations.
- Research Organization:
- US Department of Energy (USDOE), Washington DC (United States); Amoco Production Co., Houston, TX (United States); Conoco, Inc., Stamford, CT (United States)
- OSTI ID:
- 377214
- Report Number(s):
- CONF-9509296-; ON: DE96001221; TRN: 96:004054-0050
- Resource Relation:
- Conference: 2. international petroleum environmental conference: environmental issues and solutions in petroleum exploration, production, and refining, New Orleans, LA (United States), 25-27 Sep 1995; Other Information: PBD: 1995; Related Information: Is Part Of Environmental issues and solutions in petroleum exploration, production and refining; Sublette, K.L. [ed.]; PB: 1078 p.
- Country of Publication:
- United States
- Language:
- English
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