IFPEN project : study of paleocirculations in faults

The objective of the program is, through a multidisciplinary and multi-scale approach, to characterize the evolution over time and space of fluid flows along the faults of the Colorado Plateau (Utah). Near-surface mineralization and its relationship to faults are studied on recent travertine rocks. Isotopic analysis and U/Th dating of travertine veins reveal CO2-enriched fluid circulation and episodic carbonate precipitation cycles corresponding to seasonal or climatic cycles (annual and centennial) as well as cycles that are similar to seismic cycles of the order of a thousand years. This data is used to calibrate the volume of CO2 that leaked through the fault.

Paleo-circulation zones, observed as chemical bleaching of sandstones, are also studied at the basin scale. Two main episodes of fluid circulation along faults can be distinguished : a first circulation during burial and a second circulation through reservoirs and along faults, which is related to regional tectonic phenomena. The last circulation was divided into several pulses with the circulation of fluids of different natures (such as brines, fluids rich in hydrocarbons or CO2) over time and along the faults.

**References

Gratier, J.-P., Frery, E., Deschamps, P., Røyne, A., Renard, F., Dysthe, D. K., Ellouz-Zimmerman, N., and Hamelin, B. (2012) How travertine veins grow from top to bottom and lift the rocks above them : the effect of the force of crystallization, Geology, in press.