Tectonics, fluid migration, and fluid pressure in a deformed forearc basin, Cook Inlet, Alaska

摘要

Faulting controls fluid migration within transpressive fault-propagation folds in the Cook Inlet forearc basin of south-central Alaska. Na-Ca-Cl brine migrates out of Mesozoic rocks through reverse and oblique-slip faults into the cores of anticlines, where the fluid spreads laterally outward into lower Tertiary strata by flow through cross faults and permeable beds. Precipitation of zeolite and carbonate cement and veins reduces the permeability of folded bedding and faults. Zeolite minerals are formed by chemical reactions between Na-Ca-Cl brine and sedimentary rocks. Carbonate minerals are precipitated when Na-HCO₃ connate fluid in the Tertiary section reacts with rocks during diagenesis, and by mixing of migrated Na-Ca-Cl brine with the Na-HCO₃ pore fluid. Carbonate cement is also precipitated by fluctuations in PCO₂ during faulting and jointing.