Hydrothermal Dolomitization in Paleozoic Carbonates - Enhanced Fluid
Flow and
Lavoie, Denis1, Guoxiang Chi2 (1) Geological Survey of
In
The Ordovician HTD cases occur in passive
margin to foreland basin carbonates. Hot saline fluids moved along Taconian extensional faults commonly rooted in crystalline
basement; these fluids were laterally forced into carbonate units when reaching
an effective seal. Coeval K-bentonite deposits
testify to major volcanic centres and hence high
geothermal gradients critical for enhancing deep-seated fluid convection. The
Lower Silurian peritidal ramp facies
is dissected by older faults that were reactivated at the late Early Silurian
onset of the Acadian foreland basin. The major reef complexes and pinnacles of
Upper Silurian to lowermost Devonian were positioned on the paleotopographic
highs of tilted extensional tectonic blocks. Lower Devonian outer shelf
carbonate facies were deposited in a faulted
depositional setting; these faults were in late Early Devonian, reactivated as
dextral strike slip. These faults were conduits for episodic high pressure
migration of high temperature saline fluids that resulted in local to regional
hydrothermal dolomitization. Enhanced fluid
convection was generated by high geothermal gradients that resulted from active
volcanism episodically recorded from the Early Silurian to the Early Devonian.
Lower Paleozoic tectono-magmatic
events created conditions for the hydrothermal alteration of carbonates. The
Ordovician and Devonian reservoirs host economic accumulations of hydrocarbons.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California