| As with most geochemical signatures CAI values will manifest as a geochemical halo. A halo signature occurs toward the periphery of the hydrocarbon seepage area. This is due to the limited amount of calcium available to form an apical carbonate anomaly over the seepage area. Excess CO2 and the formation of organic acids due to soil fauna metabolic processes will prevent the formation of CaCO3 and keep it from precipitating over parts of the seepage area. This is why halos form such diverse shapes.
The use of CAI as a hydrocarbon exploration tool relies on the accumulation of bacterial end-products in pore fluids which result in the precipitation of carbonate minerals. These end products affect pore water pH, Eh, and ionic strength. | |
