EPISODIC CIRCULATION OF REACTIVE FLUIDS ALONG FAULTS From travertine- to basin-scale study on the Colorado Plateau natural example (USA)
This work aims to characterise fluid flow along faults in time and space. Multi-disciplinary and multi-scale investigations of a natural analogue have been carried out in the Colorado Plateau area (Utak, USA), from fieldwork to numerical modeling. The study of Quaternary travertine calibrated the near-surface mineralization and their relationship with the faults. Stable Isotope measurements and U/Th datings of travertine veins revealed episodic cycles of CO2-fluid circulation and related calcium carbonate precipitation (travertine). These cycles may be linked with seasonal or climatic cycles (annual and centennial) and also with seismic cycles of millennial duration. Based on the obtained data, escaping CO2 volumes from the fault zone, with time have been calibrated. Chemical bleaching of the outcropping sandstones, linked with fluids paleo-circulation at depth, has been characterized at basin scale. Two main circulation events have been distinguished: a first circulation contemporaneous to maximum burial and a second along-reservoirs and faults circulation that could be linked with later regional tectonic events, contemporaneous of Colorado Plateau rusing. Pulses of different fluids (such as brines, fluids enriched in hydrocarbons or CO2) are linked in time and space with the last circulation.