Expandable layer silicates associated with hydrothermal talc deposits of Murphy, North Carolina

Corrensite and other mixed-layer chlorites occur in the insoluble residues from the Murphy Marble. They are found in an ordered arrangement around one of the eight zones in the Murphy Marble. The envelope, 60 m wide, is centered on the mottled zone in the upper part of the marble formation. The progression of the layer silicates is: vermiculite --> vermiculite-smectite --> smectite --> smectite-chlorite --> corrensite + chlorite --> chlorite. In addition, quartz, plagioclase, and muscovite may occur. The mottled zone appears to have been a conduit of the hydrothermal fluids which have altered the silicates in the marbles; isotopic data supports this hypothesis. The altered carbonate rock is depleted in heavy isotopes. A genetic connection, between the talc bodies and the hydrothermal plumbing system, is indicated by an increase in the amount of expanding and contracting layers in the mixed-layer minerals of the mottled zone near the orebody.--Modified journal abstract.