1. Fluids derived from the compaction and
dewatering of shale have relatively low salinity,
similar to fluids derived from metamorphism of
shale to form slate and schist.
Fluid inclusions are trapped in mineral
crystals as the solid minerals grow.
The minimum temperature and salinity
of the fluid can be determined by
freezing and heating the inclusion.
Fluids that interacted with previously dry basement
rocks have high salinity. The fluids that form
economically important oil and gas reservoirs in
limestones represent mixing of low and high salinity
fluids. Vertical flow between these reservoirs occurred
along fault zones. Active faulting helps to pump fluids
vertically.