Fluid flow in cataclastic thrust fault zones in sandstones, Sub-Andean Zone, southern Bolivia

Выпуск 340
Автор(ы):Labaume P., Moretti I., Sheppard S.M.F.
Издание:Journal Tectonophysics, 2001 г., 32 стр.
Fluid flow in cataclastic thrust fault zones in sandstones, Sub-Andean Zone, southern Bolivia

The Bolivian Sub-Andean Zone (SAZ) corresponds to a Neogene thrust system that affects an about 10-km thick Palaeozoic to Neogene siliciclastic succession. The analysis of macro and microstructures and cement distribution in thrust fault zones shows that they are sealed by quartz at depths > 3 km, due to local silica transfer by pressure-solution/precipitation activated at temperatures >70–90 C. At shallower depths, faults have remained open and could be preferential drains for lateral flow of carbonate-bearing fluids, as shown by the occurrence of carbonate cements in fractures and their host-sandstone. Due to decreasing burial, resulting from foothill erosion during fault activity, critically buried fault segments can be affected by nonquartz-sealed structures that post-date initial quartz-sealed structures. The integration of textural, fluid inclusion and isotopic data shows that carbonates precipitated at shallow depth ( < 3 km), low temperature ( < 80 C) and relatively late during the thrusting history. Isotopic data also show that precipitation occurred from the mixing of gravity-driven meteoric water with deeper formation water bearing carbonate carbon derived from the maturation of hydrocarbon source rocks (Silurian and Devonian shales). The combined microstructural and isotopic analyses indicate that: (i) fluid flow in fault zones often occurred with successive pulses derived from different or evolving sources and probably related to episodic fault activity, and (ii) at a largescale, the faults have a low transverse permeability and they separate thrust sheets with different fluid histories. 

МеткиBolivia, Carbon isotopes, Cataclasis, Cement, Fault zone, Fluid flow, Oxygen isotopes, Sub-Andean Zone, Анды, Боливия, Изотопия, Песчаники
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