Integration of Petrology with Aqueous Geochemistry in a Recent Mixing Zone, Southeastern Barbados, West Indies

Investigator(s):

John Humphrey (PI)

Sponsor:

Colorado School of Mines, CO 80401 3032733200

Start Date/Expiration Date

1992-01-01 to 1996-12-31 (amended 1996-06-17)

Awarded Amount to Date:

$125,058

Abstract: Late Pleistocene raised reef terraces on the island of Barbados provide an unparalleled setting to investigate early, near-surface diagenesis in carbonate rocks. Dolomite has been encountered in core samples from within the modern mixing zone in southeastern Barbados. This dolomite may be Recent in age and related to the modern water chemistry. We well further investigate this dolomite occurrence with additional core-drilling, lithologic, geochemical, and hydrogeochemical studies. Four boreholes will be drilled atop sea-cliffs along the windward southeastern coastline, in an area where there is significant meteoric phreatic discharge and a potentially thick mixing zone. Southeastern Barbados provides the ideal site to test the mixing versus marine models and to directly sample fresh, mixed, and normal marine pore waters in contact with carbonate sediments and rocks actively undergoing diagenesis. The mixing zone model has not received universal acceptance. It is therefore important to document the occurrence and geochemistry of the dolomite and pore fluids in question to test the validity of the model. This will be accomplished through minerologic, petrographic, trace element, stable isotope, strontium isotope, fluid inclusion, and absolute dating techniques. In collaboration with R. K. Stoessell, pore waters from the boreholes will be characterized by temperature, salinity, conductivity, pH, Eh, alkalinity, dissolved oxygen, dissolved hydrogen sulfide, major and minor elements and ions, saturation indices and stable isotopic compositions. Given the geologic/hydrologic setting of Barbados, the fluid/rock interactions responsible for dolomitization must necessarily be confined to either a normal seawater or mixed meteoric/marine model. This integrated petrologic and hydrogeochemical approach represents a comprehensive effort to answer important questions regarding the enigmatic process of early dolomitization, and will directly test the viability of each of these possible models.

NSF Org:

EAR - Division of Earth Sciences

Award Number:

9123842

Award Instrument:

Standard Grant

Program Manager:

John A. Maccini
EAR Division of Earth Sciences
GEO Directorate for Geosciences

NSF Program(s):

GEOLOGY & PALEONTOLOGY, GEOLOGY & PALEONTOLOGY

Field Application(s):

Geological Sciences, Other nsf.applications NEC

Program Element Code(s):

1571
, 1571