Abstract
Partially dolomitized carbonate rocks of the Middle East and North America host large hydrocarbon reserves. The origin of some of these dolomites has been attributed to a hydrothermal mechanism. The Benicassim area (Maestrat Basin, eastern Spain) constitutes an excellent field analogue for fault-controlled stratabound hydrothermal dolomitization: dolostone geobodies are well exposed and extend over several kilometres away from seismic-scale faults. This work investigates the main controls on the formation of stratabound versus massive dolomitization in carbonate sequences by means of two-dimensional (2D) reactive transport models applied to the Benicassim case study. Simulation results suggest that the dolomitization capacity of Mg-rich fluids reaches a maximum at temperatures around 100 degrees C and a minimum at 25 degrees C (studied temperature range: 25-150 degrees C). It takes of the order of hundreds of thousands to millions of years to completely dolomitize kilometre-long limestone sections, with solutions flowing laterally through strata at velocities of metres per year (m/a). Permeability differences of two orders of magnitude between layers are required to form stratabound dolomitization. The kilometrelong stratabound dolostone geobodies of Benicassim must have formed under a regime of lateral flux greater than metres per year over about a million years. As long-term dolomitization tends to produce massive dolostone bodies not seen at Benicassim, the dolomitizing process there must have been limited by the availability of fluid volume or the flow-driving mechanism. Reactive transport simulations have proven a useful tool to quantify aspects of the Benicassim genetic model of hydrothermal dolomitization.
Original language | English |
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Pages (from-to) | 41-54 |
Number of pages | 14 |
Journal | Petroleum Geoscience |
Volume | 20 |
Issue number | 1 |
Early online date | 27 Jan 2014 |
DOIs | |
Publication status | Published - Feb 2014 |
Keywords
- Mesozoic extensional tectonics
- lead-zinc deposits
- Iberian Chain
- hydrothermal Dolomites
- carbonate platforms
- crustal evolution
- reservoir quality
- fluid-inclusion
- Northern Spain
- origin